Biodiversity Net Gain (BNG) is an approach to development that aims to leave nature in a measurably better state than before. This is achieved through embedding the mitigation hierarchy into development design through the use of a biodiversity metric, highlighting impacts on, and opportunities for nature.
“Under the Environment Act 2021, all planning permissions granted in England (with a few exemptions) will have to deliver at least 10% biodiversity net gain from an as yet unconfirmed date, expected to be in November 2023. BNG will be measured using Defra’s biodiversity metric and habitats will need to be secured for at least 30 years.
This sits alongside: – a strengthened legal duty for public bodies to conserve and enhance biodiversity, – new biodiversity reporting requirements for local authorities, – mandatory spatial strategies for nature: Local Nature Recovery Strategies or ‘LNRS’.”
The live virtual event occurred on Wed 29 March 2023 and was aimed at professionals that will be working with BNG (such as planners, ecologists and conservationists), bringing together professionals from a range of sectors to discuss their experience and lessons learned from working with BNG.
The event was hosted by Dan Carpenter (Digital Ecology) and featured 4 speakers:
Biodiversity Net Gain – A Policy and Metric Update
Dr Nick White, Natural England
The presentation will update the audience on the forthcoming mandatory approach to biodiversity net gain, encompassing the latest Government policy announcements and what these mean for ecologists, developers, planners and land owners. It will also provide an update about the biodiversity metric that will be used for mandatory biodiversity net gain.
Delivering Biodiversity Net Gain for Infrastructure Projects
Dr Julia Baker CEnv MCIEEM, Mott MacDonald
To design Biodiversity Net Gain, Ecologists must balance the unit calculation of the Biodiversity Metric with the Metric’s trading rules, whilst ensuring the habitat creation and enhancement of a BNG design are feasible, will endure for at least 30 years and contribute towards conservation. This presentation explores this balance, with key considerations and pitfalls to avoid for BNG to genuinely deliver long-term and meaningful outcomes on the ground.
Biodiversity Net Gain: The Wiltshire Council Perspective
Rachel Jones, Wiltshire Council
Wiltshire Council have been moving from securing no net loss to net gain and offering solutions to developers to help deliver nature recovery across Wiltshire. Rachel Jones will discuss Wiltshire Council’s approach to Biodiversity Net Gain and how they have been offering solutions to developers to help deliver nature recovery across Wiltshire. These solutions include opportunities on our own land holding, working with wider landowners and farmers for strategic sites, and securing on-site enhancements on development sites. Wiltshire Council are also looking at how to combine solutions with wider community and environmental benefits and how to address the expected resourcing implications for the Council.
The Wildlife Trusts Habitat Banking Investment project aims to create new financing structures to meet near-term demand for BNG credits and prepare to accelerate delivery when national policy is implemented. Their partnership has developed a new model to enable Trusts to leverage private finance and secure biodiversity unit agreements with developers to secure strategic land and create new habitats, reducing current reliance on piecemeal grant funding and offset payments.
Earthworms are well-known ecosystem engineers, profoundly affecting soil processes. They are generally considered beneficial organisms that improve soil quality. But what happens when earthworms are introduced to ecosystems that have evolved with no or very different kinds of earthworms? Prof Katalin Szlávecz discusses the impacts of non-native earthworms in the Atlantic region of North America.
Katalin Szlávecz is a Research Professor in the Department of Earth and Planetary Sciences at Johns Hopkins University (USA). Katalin does research on soil biodiversity, earthworm ecology and soil ecosystem services. Her research focuses on human-modified landscapes, including secondary forests, crop fields, and the urban landscape.
Q&A with Prof Katalin Szlávecz
Can you recommend a book about the earthworm invasion of North America? There are three books that come to mind, but both of these are relatively old now. The first is a booklet by Cindy Hale and is a good starting point for beginners interested in the natural history and of invasive species and their identification. The second is edited by Paul Hendrix and contains a collection of scientific papers on the subject of invasive earthworms. The third option is the textbook by Clive Edwards covering the biology and ecology of earthworms.
Hale, C. M. (2013) Earthworms of the Great Lakes. Duluth: Kollath+Stensaas Publishing.
Hendrix, P. F. (Ed.) (2006). Biological Invasions Belowground: Earthworms as Invasive Species. Dordrecht: Springer.
Edwards, C. A. & Arancon, N. Q. (2022). Biology and Ecology of Earthworms (4th ed.). New York: Springer.
Could an earthworm predator, such as the New Zealand Flatworm (Arthurdendyus triangulatus), be used as a possible biological control agent for earthworms in North America? Our history is full of examples of failed attempts to control one invasive species by introducing a predator. Often, these predators are not specific in their diet, and end up decimating the native species. Examples include the African Cane Toad to Australia or the mongoose to the Caribbean Islands. We don’t know if New Zealand Flatworms would survive and we don’t know what the impact could be on native earthworms and other species. The few success stories using such methods have usually followed in-depth and long-term studies on the potential impacts of a non-native predator.
Are the non-native earthworm species a notifiable pest in the USA? Earthworms are not included in this category and the public is not asked to submit sightings of earthworms. Some government agencies, such as the U.S. Forest Service, U.S. Fish and Wildlife Service and Department of Natural Resources, have now started focusing on this more and funds systematic surveys to monitor the problem – so most of the data comes from researchers. A lot of the questions that we get are from gardeners regarding the Jumping Worms (genera Amynthasa and Metaphire). In the US we have a habit of mulching our flowerbeds, around trees, and even forest trails. This practice facilitates the spread of jumping worms causing concerns in gardeners. In some states, e.g. California and Minnesota, invasive earthworms are species of concern, and there are regulations in place in which it is illegal to transport them or soil into the state. Plants can be transported bare root only.
Is North America at risk of a third invasion? We don’t know if a third invasion is on the horizon or where it would come from if it was. Inspections at the border are now being done much more efficiently and there are now extremely strong restrictions regarding transport of soil into the US, even for scientific purposes.
Literature references
Chang C.-H., Snyder, B. A. & Szlávecz, K. (2016). Asian pheretimoid earthworms in North America north of Mexico: An illustrated key to the genera Amynthas, Metaphire, Pithemera, and Polypheretima (Clitellata: Megascolecidae). Zootaxa, 4179, 495-529. DOI: 10.11646/zootaxa.4179.3.7
Chang, C.-H., Johnston, M., Görres, J. H., Dávalos, A., McHugh, D. & Szlávecz, K (2017). Co-invasion of three Asian earthworms, Metaphire hilgendorfi, Amynthas agrestis and Amynthas tokioensis in the USA. Biological Invasions, 20, 843-848. DOI: 10.1007/s10530-017-1607-x
Chang, C.-H., Szlávecz, K. & Buyer, J. (2017). Amynthas agrestis invasion increases microbial biomass in Mid-Atlantic deciduous forests. Soil Biology and Biochemistry, 114,189-199. DOI: 10.1016/j.soilbio.2017.07.018
Chang, C.-H., Bartz, M. L., Brown, G., Callaham Jr., M.A., Cameron, E. K., Dávalos, A., Dobson, A., Görres, J. H., Herrick, B. M., Ikeda, H., James, S. W., Johnston, M. R., McCay, T. S., McHugh, D., Minamiya, Y., Nouri-Aiin, M., Novo, M., Ortiz-Pachar, J., Pinder, R. A., Ransom, T., Richardson, J. B., Snyder, B.A. & Szlávecz , K. (2021). The second wave of earthworm invasions in North America: Biology, environmental impacts, management and control of invasive “jumping worms”. Biol Invasions, 23, 3291–3322. DOI: 10.1007/s10530-021-02598-1
Csuzdi, C., Chang, C.-H., Pavlícek, T., Szederjesi, T., Esopi, D. & Szlávecz.,K. (2017). Molecular phylogeny and systematics of native North American lumbricid earthworms (Clitellata: Megadrili). PLoS ONE, 12 (8), e0181504. DOI: 10.1371/journal.pone.0181504
Ferlian, O, Eisenhauer, N, Aguirrebengoa, M, et al. (2018). Invasive earthworms erode soil biodiversity: A meta-analysis. J Anim Ecol., 87, 162–172. DOI: 10.1111/1365-2656.12746
Hendrix, P. F., Callaham Jr., M. A., Drake, J. M., Huang, C.-Y., James, S. W., Snyder, B. A. & Zhang, W. (2008) Pandora’s Box Contained Bait: The Global Problem of Introduced Earthworms. Annual Review of Ecology, Evolution, and Systematics, 39 (1), 593-613. DOI: 10.1146/annurev.ecolsys.39.110707.173426
Ma, Y., Filley, T. R., Johnston, C. T., Crow, S. E., Szlávecz , K. & McCormick, M. K. (2013). The combined controls of land use legacy and earthworm activity on soil organic matter chemistry and particle association during afforestation. Org. Geochem., 58, 56-68. DOI: 10.1016/j.orggeochem.2013.02.010
McCay, T.S., Brown, G., Callaham, M.A. Jr., Chang, C-H., Dávalos, A., Dobson, A., Görres, J.H., Herrick, B.M., James, S.W., Johnston, M.R., McHugh, D., Minteer, T., Moore, J.-D., Nouri-Aiin, M., Novo, M., Ortiz-Pachar, J., Pinder, R.A., Richardson, J.B., Snyder, B.A. & Szlávecz, K. (2020). Tools for monitoring and study of peregrine pheretimoid earthworms (Megascolecidae). Pedobiologia, 83, 150669. DOI: 10.1016/j.pedobi.2020.150669
McCormick, M. K., Parker, K., Szlávecz, K. & Whigham, D. (2013). Native and exotic earthworms affect orchid seed loss. AoB PLANTS, 5: plt018. DOI:10.1093/aobpla/plt018
Szlávecz, K., McCormick, M. K., Xia, L, Saunders, J., Morcol, T., Whigham, D., Filley, T. & Csuzdi, C. (2011). Ecosystem effects of non-native earthworms in Mid-Atlantic deciduous forests. Biological Invasions, 15, 1165-1182. DOI: 10.1007/s10530-011-9959-0
Szlávecz, K., Chang, C.-H., JL Burgess, J. L. & Csuzdi, C. (2014). Earthworms (Annelida: Clitellata) of Plummers Island, Maryland, USA, with description of a new species. Proc. Biol. Soc. Washington, 126, 312-322. DOI: 10.2988/0006-324X-126.4.312
Szlávecz, K., C-H Chang, C.-H., Bernard, M. J., Pitz, S. L., Xia, L., Ma, Y., McCormick, M. K., Filley, T., Yarwood, S. A. & Csuzdi, C. (2018).Litter quality, dispersal and invasion drive earthworm community dynamics and forest soil development. Oecologia,188(1), 237-250. DOI: 10.1007/s00442-018-4205-4
The Orinoco Llanos of Columbia and Venezuela were home to a mystery. These tropical wetlands are home to a landscape dominated by densely packed, regularly spaced mounds of soil. These Surales can be up to 5 m in diameter and 2 m tall and cover an area almost the size of Scotland! Rumsaïs Blatrix takes us on a journey to South America to discover how the mystery of the Surales was solved by his colleagues, Delphine Renard and Doyle McKey.
Rumsaïs Blatrix is an ecologist, mostly interested in species interactions. He works at two levels: 1. The mechanisms of interaction between individuals and their evolutionary significance (in particular deceptive pollination and ant-plant symbioses). 2. The consequences of interactions at the landscape scale (in particular the role of soil organisms in patterned landscapes).
Q&A with Rumsaïs Blatrix
How much do we know about the other species that rely on this earthworm-made habitat? It is very well known that the termite nests in termite savannahs act as ‘fertility islands’ and support species that you wouldn’t otherwise find. It’s possible that we could have a similar situation with the surales, but we haven’t undertaken any kind of census to evidence this. It would make a very interesting study.
Are there any threats to the surales landscape of the Orinoco Llanos? Historically this landscape was used for cattle ranching, which does not seem too destructive if it is not too intensive. The main threat facing this landscape is probably conversion to other types of agriculture, particularly for rice cultivation. This involves levelling the land and therefore destroying the mounds. Once levelled, this landscape provides the perfect conditions for cultivating rice.
Is there a specific number of worms per mound? We don’t know, but this is one of the things we are looking into this year. Doyle McKey is undertaking fieldwork in South America to investigate this question and more. Questions he will be looking at include ‘How many earthworms are in each mound?’, ‘Is the number constant between mounds, ‘Is there any behavioural relationship between the earthworms within a mound?’ and ‘How much soil do they move?’.
Literature references
Zangerlé, A., Renard, D., Iriarte, J., Suarez Jimenez, L. E., Adame Montoya, K. L., Juilleret, J. & McKey, D. (2016) The Surales, Self-Organized Earth-Mound Landscapes Made by Earthworms in a Seasonal Tropical Wetland. PLoS One, 11(5), e0154269. DOI: 10.1371/journal.pone.0154269
Mckey, D., Renard, D. & Blatrix, R. (2021). ‘The multiple roles of soil animals in the interpretation of archaeological soils and sediments in lowland tropical South America’, in Odonne, G., & Molino, J.-F. (Eds.). (2020). Methods in Historical Ecology: Insights from Amazonia (1st ed.). Routledge. pp. 121-129. DOI: 10.4324/9780429060175
Renard, D., Birk, J. J., Zangerlé, A., Lavelle, P., Glaser, B., Blatrix, R. & McKey, D. (2013). Ancient human agricultural practices can promote activities of contemporary non-human soil ecosystem engineers: A case study in coastal savannas of French Guiana. Soil Biology and Biochemistry, 62, 46-56. DOI: 10.1016/j.soilbio.2013.02.021
The morphology of earthworms is as obscure as their habitat, and this complicates our understanding of their evolutionary relationships and historical biogeography. Dr Daniel Marchán reviews different applications of genetic tools to shed light on these big questions, with an emphasis on the rare, endemic and threatened species.
Dr Daniel Fernandez Marchán is an earthworm researcher integrating the fields of molecular phylogenetics, morphology and ecological methods (as ecological niche modelling). His research is focused on the systematics of hormogastrid (Oligochaeta, Hormogastridae) and lumbricid earthworms (Oligochaeta, Lumbricidae).
Q&A with Dr Daniel Marchán
How can we distinguish morphologically identical species where we don’t have access/funds for genetic analysis of specimens? When species are separated genetically, it is good practice to go back and re-examine the morphology to see if a difference can be found. For example, with Lumbricus terrestris and Lumbricus herculeus it was found that L. herculeus was smaller on average than L. terrestris. With Lumbricus rubellus, it has been found that the different lineages have different positions of the genital papilla. There are still instances where we can’t find differences in the morphology, and in these cases, we will need to rely on genetic barcoding (it is getting cheaper) and emerging technologies that may enable identification in the field.
Why do the specimens of some endogeic species (particularly Allolobophora chlorotica and Aporrectodea caliginosa) appear greener when found in soils prone to waterlogging?As far as I am aware, the colouration in Allobobophora chlorotica is related to the lineage of an individual earthworm. The green lineages prefer wetter soils and the pink lineages prefer drier soils. I’ve not seen green forms of Aporrectodea caliginosa but differences in colour in this species could also be due to cryptic lineages, but it could also be due to phenotypic plasticity. We do see more green pigmentation in earthworms that prefer wetter soils, such as Allolobophora molleri which is found in western Spain and is only found close to rivers, to help improve them take up more oxygen from water.
Is there a genetic relationship between earthworm species that are able to display autotomy behaviour where they can drop their tail as a predator defence mechanism? We don’t really know which species can and cannot use autonomy as a defence mechanism, so it is not possible to answer this question with confidence at this point in time. We know so little about earthworms so there are still lots of studies on the behaviour of different species that are needed to build up this kind of information. My guess would be that it is not related to phylogeny as I have observed a single species in the genus Scherotheca displaying autotomy readily, whereas other species within this genus do not appear to undertake this behaviour.
Literature references
Marchán et al (2023) Understanding the diversification and functional radiation of Aporrectodea (Crassiclitellata, Lumbricidae) through molecular phylogenetics of its endemic species: https://doi.org/10.1016/j.ejsobi.2023.103559
Marchán, D. F., Novo, M., Fernández, R., De Sosa, I., Trigo, D., & Cosín, D. J. D. (2016). Evaluating evolutionary pressures and phylogenetic signal in earthworms: a case study-the number of typhlosole lamellae in Hormogastridae (Annelida, Oligochaeta). Zoological Journal of the Linnean Society, 178(1), 4-14. DOI: 10.1111/zoj.12410
Marchán, D. F., Fernández, R., de Sosa, I., Cosín, D. J. D., & Novo, M. (2017). Pinpointing cryptic borders: Fine-scale phylogeography and genetic landscape analysis of the Hormogaster elisae complex (Oligochaeta, Hormogastridae). Molecular Phylogenetics and Evolution, 112, 185-193. DOI: 10.1016/j.ympev.2017.05.005
Marchán, D. F., Fernández, R., de Sosa, I., Sánchez, N., Cosín, D. J. D., & Novo, M. (2018). Integrative systematic revision of a Mediterranean earthworm family: Hormogastridae (Annelida, Oligochaeta). Invertebrate Systematics, 32(3), 652-671. DOI: 10.1071/IS17048
Marchán, D. F., Novo, M., Sánchez, N., Domínguez, J., Cosín, D. J. D., & Fernández, R. (2020). Local adaptation fuels cryptic speciation in terrestrial annelids. Molecular phylogenetics and evolution, 146, 106767. DOI: 10.1016/j.ympev.2020.106767
Marchán, D. F., Fernández, R., Domínguez, J., Díaz Cosín, D. J., & Novo, M. (2020). Genome-informed integrative taxonomic description of three cryptic species in the earthworm genus Carpetania (Oligochaeta, Hormogastridae). Systematics and biodiversity, 18(3), 203-215. DOI: 10.1080/14772000.2020.1730474
Marchán, D. F., Jiménez, S., Decaëns, T., & Domínguez, J. (2021). Systematic revision of Gatesona (Crassiclitellata, Lumbricidae), an endemic earthworm genus from the Massif Central (France). PLoS One, 16(9), e0255978. DOI: 10.1371/journal.pone.0255978
Marchán, D. F., Csuzdi, C., Decaëns, T., Szederjesi, T., Pizl, V., & Domínguez, J. (2021). The disjunct distribution of relict earthworm genera clarifies the early historical biogeography of the Lumbricidae (Crassiclitellata, Annelida). Journal of Zoological Systematics and Evolutionary Research, 59(8), 1703-1717. DOI: 10.1111/jzs.12514
Marchán, D. F., Decaëns, T., Domínguez, J., & Novo, M. (2022). Perspectives in Earthworm Molecular Phylogeny: Recent Advances in Lumbricoidea and Standing Questions. Diversity, 14(1), 30. DOI: 10.3390/d14010030
Marchán, D. F., James, S. W., Lemmon, A. R., Lemmon, E. M., Novo, M., Domínguez, J., Díaz Cosín, D. J. & Trigo, D. (2022). A strong backbone for an invertebrate group: anchored phylogenomics improves the resolution of genus-level relationships within the Lumbricidae (Annelida, Crassiclitellata). Organisms Diversity & Evolution, 22(4), 915-924. DOI: 10.1007/s13127-022-00570-y
Navarro, A. M., Pinadero, S. J., Decaëns, T., Hedde, M., Novo, M., Trigo, D., & Marchán, D. F. (2023). Catch-All No More: Integrative Systematic Revision of the Genus Allolobophora Eisen, 1874 (Crassiclitellata, Lumbricidae) with the Description of Two New Relict Earthworm Genera. Journal of Zoological Systematics and Evolutionary Research, 2023, 5479917. DOI: 10.1155/2023/5479917
Novo, M., Fernández, R., Andrade, S. C., Marchán, D. F., Cunha, L., & Cosín, D. J. D. (2016). Phylogenomic analyses of a Mediterranean earthworm family (Annelida: Hormogastridae). Molecular phylogenetics and evolution, 94, 473-478. DOI: 10.1016/j.ympev.2015.10.026
Popović, F. J., Stojanović, M. M., Domínguez, J., Sekulić, J. M., Trakić, T. B., & Marchán, D. F. (2022). Molecular analysis of five controversial Balkanic species of Allolobophora (sensu lato) Eisen, 1873 (Lumbricidae, Clitellata) with emendation of the genus Cernosvitovia Omodeo, 1956. Zootaxa, 5116(3), 351-372. DOI: 10.11646/zootaxa.5116.3.3
Take a journey around the world, detailing some of the weird and wonderful earthworms discovered by Dr Sam James, and the stories behind his research expeditions at home and in the far-flung corners of the world.
Dr Sam James is one of the world’s leading experts in earthworm ecology and diversity. Dr James has a PhD in Biology and was an organic farmer in Iowa for 10 years, where he taught a wide range of life science courses at several universities. He also has many international research collaborations in Europe, Asia, and South America.
Q&A with Dr Sam James
What percentage of earthworm species would you estimate have been described to science to date? I can still find new species in the USA – I recently received a new species from Oklahoma that I will need to describe! There are still large areas that have never been searched for earthworms. Overall I don’t think we’ve even found half of the earthworm species that exist in the world. I wouldn’t be surprised if we could double the number of species globally just from French Guiana, Guyana, Suriname, Venezuela and Brazil.
Which country do you think is potentially sitting on the highest number of undescribed species? Tropical countries have the highest diversity. French Guiana currently holds the record for diversity within a hectare. Guyana and Suriname are also very diverse with an enormous number of earthworms. We could probably say the same thing about Brazil, Thailand, Laos and Vietnam. there are large areas in India and China where the earthworm species haven’t been studied. Any place that has topographical complexity (such as mountains and valleys) with intact original vegetation has a large number of earthworms. I had specimens sent to me from New Zealand and I couldn’t identify more than half of them!
What is the most peculiar characteristics across all the earthworms you have seen? The Fried Eggs Worm (Archipheretima middletoni) has to be at the top for the weird and wonderful! And not only for the colouration! Your first thought is how can something that is essentially a piece of meat crawling around the floor be coloured so brightly, but it was surprisingly difficult to see. The yellow and white spots look like reflections of light from wet leaves on the forest floor, so it probably provides the worm with great camouflage from predators that don’t see colour so well – it took me a while to get my eye in for them. The young earthworms of this species were also only found 2-3 metres off the ground in the leaf axis of these Pandanus plants and I’d only ever find one per plant. The adults were free-living on the ground – not even underneath the leaf litter!
Have there been any studies into how the littoral species manage to tolerate the saline/osmotic stress of seawater? I found a small pink worm in the Virgin Islands in soil well above sea level. This was soil watered by the rain. It turned out to be Pontodrilus litoralis. A short distance away on the beach I found another P. litoralis living in full strength seawater sub-irrigated sand. That is quite a remarkable osmotic feat for a soft-bodied animal that breathes through its skin – to be able to survive in these two extremes!
Is it easy to find the giant earthworm species in the places where they occur? Giant earthworms are really hard to catch. Finding the signs isn’t so difficult – their large casts and large burrows give them away. Digging them out is no mean feat. The best way to catch them is to find where they live and stake them out until you get rain and then collect them up when they have come to the surface.
Literature references
Anderson, F. E., Williams, B. W., Horn, K. M., Erséus, C., Halanych, K. M., Santos, S. R., & James, S. W. (2017). Phylogenomic analyses of Crassiclitellata support major Northern and Southern Hemisphere clades and a Pangaean origin for earthworms. BMC Evolutionary Biology, 17(1), 123. DOI: 10.1186/s12862-017-0973-4
James, S. W. (2009). Revision of the earthworm genus Archipheretima Michaelsen (Clitellata: Megascolecidae), with descriptions of new species from Luzon and Catanduanes Islands, Philippines. Organisms Diversity & Evolution, 9(3), 244.e1-244.e16. DOI: 10.1016/j.ode.2009.03.004
To celebrate the wonderful diversity of earthworms from around the world, we brought earthworm scientists from around the globe together to teach anyone interested in earthworms about the world of earthworms beyond the UK.
Worms of the World Virtual Symposium
The Worms of the World virtual symposium took place on 25 Mar 2023 and featured the following presentations and speakers:
Take a journey around the world, detailing some of the weird and wonderful earthworms discovered by Dr Sam James, and the stories behind his research expeditions at home and in the far-flung corners of the world.
Phylogenetic Tools to Dig Out the Evolutionary History of Earthworms
Dr Daniel Fernandez Marchán
The morphology of earthworms is as obscure as their habitat, and this complicates our understanding of their evolutionary relationships and historical biogeography. Dr Daniel Marchán reviews different applications of genetic tools to shed light on these big questions, with an emphasis on the rare, endemic and threatened species.
The Orinoco Llanos of Columbia and Venezuela were home to a mystery. These tropical wetlands are home to a landscape dominated by densely packed, regularly spaced mounds of soil. These Surales can be up to 5 m in diameter and 2 m tall and cover an area almost the size of Scotland! Rumsaïs Blatrix takes us on a journey to South America to discover how the mystery of the Surales was solved by her research team.
Earthworms are well-known ecosystem engineers, profoundly affecting soil processes. They are generally considered beneficial organisms that improve soil quality. But what happens when earthworms are introduced to ecosystems that have evolved with no or very different kinds of earthworms? Prof Katalin Szlávecz discusses the impacts of non-native earthworms in the Atlantic region of North America.
The Pine Hoverfly (Blera fallax) is critically endangered in Britain, reduced to just one population in a small forest patch in the Cairngorms National Park in Scotland. Since 2018, the Royal Zoological Society of Scotland (RZSS) has been running a conservation breeding programme for this important pollinator at its Highland Wildlife Park Zoo. Following a record-breaking breeding season in 2021, the RZSS team started reintroducing pine hoverflies back into the Caledonian forests they once inhabited. Hear about the progress of this project and how the partnership between RZSS, the Rare Invertebrates in the Cairngorms project, and Forestry and Land Scotland is working to rescue one of Britain’s most endangered invertebrates.
Q&A with Helen Taylor
Dr Helen Taylor is the conservation programme manager at the Royal Zoological Society of Scotland and has been leading the pine hoverfly conservation breeding and release project since 2019. Helen is a conservation reintroduction specialist who has worked with multiple bird species, managed the Knapdale beaver reinforcement project, and has recently become an invertebrate convert, managing RZSS’ Pine Hoverfly, Pond Mud Snail, and Dark Bordered Beauty moth conservation breeding for release programmes.
Do other invertebrates use these rot holes?
Other invertebrates do use the rot holes, including other hoverflies and many other things like slugs. We even once found a newt. We’re not aware of any predators – but we do not have the data about what is happening within these rot holes to comment on this definitively. The food webs occurring within these rot holes is not well understood and it would be great to have more data on this.
Do they like gorse as well?
Not that we are aware of. We think that they need open-cup flowers, like on rowan, so we don’t think the flower shape is quite right on gorse. Flies are not as great at navigating into a closed cup flower (like a foxglove) and prefer to hover around a flat-shaped flower. However, an adult has been seen on a bell-shaped flower, so we’re always open to new information! There is not much gorse on the current sites, and we’ve never observed it – but we don’t know for sure.
Are the depths of the lagoons/troughs important in the larval survival rate?
That’s an interesting question! We do have different depths but we try not to disturb the larvae once we have released them into the rot holes. This makes it really difficult to measure the survival rate. Recording the number of pupal cases does not necessarily relate to the number of larvae as we can’t guarantee we are finding them all. There is some evidence that they may sometimes leave the rot hole to pupate and a number of other reasons why the pupal case may not be there, such as disintegration or predation. There is currently a student looking at rot hole characteristics and it will be exciting to see what they find as it may help us answer some of these questions.
Did you choose to rear 8,000 larvae due to rearing capacity or population viability across the release sites?
The 8,000 is what we’re able to produce with our rearing capacity. We can house around 150 adults at any one time and the maximum number of larvae we’ve gotten from those adults is 8,000. That doesn’t mean that we are not getting more eggs than that, but it’s difficult to know how many we’re losing between the egg stage and the 2nd or 3rd instar when we can safely handle the larvae without damaging them. If we could produce more larvae with 150 adults, we’d be happy to do so and release more. We can put 60-80 larvae in a rot hole if it is deep enough and holding water. It’s also a lot of work to create habitat and monitor them so realistically there would be a limit to how many we could cope with considering the capacity of the current team.
Were the original batch of larvae all collected from a native population?
Yes – the 25 original larvae that we used to start our conservation breeding programme were collected from the remnant population in the Cairngorms. The year that they were collected was selected by the Pine Hoverfly Steering Group as it was a really good year for that population, so the risk to that population was lower than usual. We continue to take 1 or 2 individuals from the original population each year and add them into the conservation programme each year to try and boost genetic diversity.
How big is the inbreeding threat to this population of Pine Hoverflies?
We are concerned about inbreeding because all of the larvae we managed to breed in the first season came from a maximum of 2 females, possibly just 1! We continue to take 1 or 2 individuals from the original population each year and add them into the conservation programme each year to try and boost genetic diversity. We also really carefully manage our breeding lines with a very complicated spreadsheet to make sure we are always outbreeding as much as possible. Despite all this, the likely lack of genetic diversity is still a concern but it is difficult to mitigate against it when there is potentially so little genetic diversity in the wild.
How genetically similar is the remaining UK population to the continental population?
The Pine Hoverfly is found in other places in Europe and the possibility of bringing across individuals from Scandinavia (specifically Sweden and Finland) has been considered). Dr Ellen Rotheray did some genetic work using a handful of micro-satellite markers back in 2012 to look at the genetic difference between the Scottish population and the Scandinavian population, and she did find some differences. Since then, The Pine Hoverfly has now had its genome sequenced by the Darwin Tree of Life project and our RZSS WildGenes team here at Edinburgh Zoo is now using this much higher resolution data to create a genomic database for our conservation breeding population. We can compare this to data for the Scandinavian population to see how different they really are genetically and whether a reintroduction from Scandinavia would be appropriate if the British population were to go extinct. However, there are other considerations aside from genetics if we were to reintroduce individuals from another country – they could bring along a parasite or pathogen with them that we don’t have here, or they could have key behavioural differences (such as using spruce trees, which is seen in Swedish pine hoverfly, but has not been observed in our native population).
Are there plans for releases in other UK sites in the future?
Hopefully, we need to identify good sites first and we need to see the Pine Hoverfly successfully established at the current release site in the longer term to gain proof of concept. It’s important that we follow an evidence-based approach when it comes to choosing sites and planning releases.
Is there anything the public or volunteers can do to help?
entoLIVE webinars feature guest invertebrate researchers delving into their own invertebrate research. All events are free to attend and are suitable for adults of all abilities – a passion for invertebrates is all that’s required!
While the Large Marsh Grasshopper (Stethophyma grossum) is the biggest and most handsome of all British grasshoppers, it’s also one of the rarest. The degradation and loss of their preferred habitat, fens and peat bogs, have constricted their range considerably. Today, it survives almost exclusively in the valley mires and wet heaths of the New Forest and Dorset. This talk will introduce how a partnership project led by Citizen Zoo and involving Norfolk Wildlife Trust, the Wildlife Trust for Beds, Cambs & Northants and Natural England has returned the large marsh grasshopper to a number of wetlands across Norfolk. This project is pioneering community engagement in which local people are trained in grasshopper husbandry to become Citizen Keepers.
Stuart Green is the Lead Entomologist for Citizen Zoo and manages the Hop of Hope grasshopper reintroduction project. Citizen Zoo wants to live in a world filled with wildlife. Through their projects and services, they rebuild nature to a more functional state and bring people out into the great outdoors through their engagement programmes. They’re a social enterprise committed to rewilding & conservation, and growing rapidly through their expanding portfolio of projects and network of clients & partners to Rewild Our Future.
Q&A with Stuart Green
What is the lifespan of a Large Marsh Grasshopper? The oldest individual recorded alive on the bog is 7 weeks after release. He was an adult for around a week before release, so that means he’d been mature for 8 weeks. The development time within the locust cage is about one month, but this would be longer in the wild. So this means that he was probably about 12 weeks old in total. We can be pretty confident most adults will not make it to that ripe old age, as they are likely to be eaten by predators or die due to other causes.
What predators and parasites will prey on Large Marsh Grasshoppers? Spiders are probably the main predator, with evidence of grasshopper mortality in the form of mummified grasshoppers in Labyrinth Spider webs (Agelena labyrinthica). Interestingly, these silk-wrapped corpses were almost exclusively males – possibly more vulnerable due to their smaller size, but also more mobile and so more likely to fall into a spider’s web. Other predators would include all sorts of birds (including birds of prey), reptiles and small mammals. Water traps on site have picked up a Tachinid fly that lays its eggs on to the adult grasshopper and parasitises it. There has also been an upsurge in Locust Blow Fly (Stomorhina lunata) in the UK, though we’ve yet to see them in our patch of East Anglia yet. These flies lay their eggs into the freshly laid grasshopper eggs, with the fly larvae feeding on the grasshopper egg. These could potentially have a big impact if they move into our sites. As with most insects, it is likely that the most mortality occurs within the egg and early nymph stages. The adults tend to be able to look after themselves a bit better and escape predators.
How do they survive through the winter? Adults die off soon after the first winter frosts. … overwintering in egg hibernation, known as diapause.
Which grasses or other plants do you feed them on?? We tend to feed them on Cocksfoot Grass (Dactylis glomerata) in captivity due to the fact it is stiff and doesn’t wilt so easily in the locust cages under the light bulb, allowing the grasshoppers to climb up and bask under the light. They’ll eat most grasses, and will also eat sedges – including the heads of sedges, rushes and grasses as well. We observed that they showed no difficulty adapting from the food provided in captivity to available plants in the bogs they were released into.
When monitoring grasshoppers, is it easier to see them where the grass is mown and would this impact survey comparison? If they are in dense vegetation the females are much harder to see. On the other hand, the males give themselves away by stridulating and climbing higher up the vegetation. Surveys really do need to be undertaken on hot, sunny days (ideally above 27 degrees Celcius), when the grasshoppers are active to ensure that surveys are comparable.
As natural dispersion is limited due to habitat fragmentation, is there value in exchanging DNA with the Dutch populations? Permission to do this is much more complex than releasing from UK populations as additional permits and safeguards would be needed. Biosecurity would be one concern as we would need to ensure that we’re not also importing parasites and pathogens that occur in mainland Europe but don’t naturally occur in the UK. To date, we’ve observed low mortality from individuals bred in captivity and have had no observations of parasitoids. We’ve observed horsehair worm parasites in a few individuals we collected from the New Forest to add to our breeding stock, but these died on emergence because they live in water. The New Forest populations seem to be strong and healthy, so I think the gene pool should be OK to support our Norfolk reintroductions.
Can new people get involved with the Hope of Hope project this year? Yes, but numbers are limited by the number of locust cages that we have – which is just 20 (including the two that I use). We’re hoping to have 18 Citizen Keepers this year and some of our volunteers will be returning. We prefer to recruit our Citizen Keepers locally from Norfolk or Cambridgeshire, within an hour’s drive of our release sites, and will be recruiting soon (see the Citizen Zoo website). For those further afield, you can help improve our understanding of grasshoppers nationally by recording grasshoppers in your garden or local green spaces. submit your grasshopper recordings to the Grasshoppers and Related Insects Recording Scheme of Britain and Ireland via iRecord or the iRecord Grasshopper app.
entoLIVE webinars feature guest invertebrate researchers delving into their own invertebrate research. All events are free to attend and are suitable for adults of all abilities – a passion for invertebrates is all that’s required!
Flying squids are fascinating organisms. They exist in their own kingdom in the mesopelagic realm, where they attain huge biomasses and are crucial for energy and matter cycles in the water column. Besides their ecological importance, they are also important economically, as they sustain almost 50 % of current cephalopod landings in the world. Fernando will give a short snapshot of their mysterious and amazing life, as well as how each species is related to the other.
Fernando Ángel Fernández-Álvarez is a marine zoologist specialising in cephalopods with a focus on the oceanic squids that occupy offshore pelagic environments. As the object of his doctoral dissertation, flying squids occupy a special spot in his heart. Among other topics, he has studied their evolutionary relations, their reproductive biology and how sperm is transferred among males and females, who will store them for long periods of time.
Q&A withFernando Ángel Fernández-Álvarez
Do you approve of the new farming ideas for squid? I don’t see the methods being used for octopus farming being feasible for squid. There are debates regarding the intelligence of octopus and squid, and if this means that it is unethical to eat them but this is not an area that my research is involved in and I’d prefer not to enter into that debate in this talk. I’m aware that there is an entoLIVE webinar coming up on invertebrate sentience so this is a great question for that talk!
Can even the large Humboldt squid fly? Yes, they do. In 2015, I was fishing for flying squid a few years ago in the Gulf of California and a colleague was actually hit in the chest by a Humboldt squid subadult propelling itself from the water! It’s only the smaller individuals that can do this and once they get to a certain weight you won’t find them propelling themself out of the water.
Can the female store the sperm until she is strong enough to create eggs? Yes they can store sperm from very young ages. I have seen immature females storing sperm. In the Humboldt Squid (Dosidicus gigas) large morphotype, females may cannibalise smaller males so mature males may be reluctant to mate with the larger mature females!
Are flying squid at risk from over-fishing? Flying squid have huge biomasses. Although they are caught in large numbers, there is a huge number of flying squid in the sea. To my knowledge, there is no indication of overfishing threatening flying squid populations – but this is still something that we should watch. Many species that are overfished are from the higher trophic levels, so it is likely to be better to eat species that exist in the lower trophic levels.
With 3 years of La Nina, should there be much larger squid in a few years? I can’t really comment on the situation right now, but a few years back one researcher was still finding the small morphotype. In theory, if the conditions were extended you could end up with larger squid but we don’t know how many generations would be needed for this to happen.
Are episodes of squids being washed up to shore mainly caused of their massive mortalities after spawning? This is usually for other reasons. When breeding they will more often sink where they are and it is unlikely that they will reach the coast. Toxic algae can poison the squid and cause these mass mortality events. Another reason could be that they get disoriented during migration and end up washed up on the shore.
What is the function of the buccal papillae? That is a very good question. We’re not entirely sure but it is found in other squids and is likely to be related to the diet of the squids. I believe that it may be related to the manipulation of the particulate organic material they eat. Interestingly, these buccal papillae disappear the moment they start to hunt actively.
Do flying squids school all or part of the time? Cephalopod paralarvae do not form schools. In fact, the beginning of the schooling behaviour marks the end of their lives as paralarvae in many squids. There is not much information on many flying squids, but most oceanic squids school during at least some portion of their subadult lives. They also can aggregate for spawning, but I wouldn´t call that schooling behaviour.
Why is it that the vast majority of cephalopods are predators? That´s a very good question. I am no paleontologist, so please take my answer on this with a grain of salt. I believe that evolutionary constraints are actually at hand: most likely ancient coleoids were predators with quick metabolisms and short lives fueled by a voracious diet based on other animals. Thus, all neocoleoid cephalopods we find today are still living in the same way. The three exceptions to this predatory lifestyle we find inside the neocoleoids, the vampire, the ram’s horn squid and flying squid paralarvae, are likely evolutionary innovations for thriving in environments with low density of prey for the Vampire Squid (Vampyroteuthis infernalis) and the Ram’s Horn Squid (Spirula spirula), and to take advantage of an explored trophic resource by other cephalopod paralarvae in the case of flying squids. The only extant non-coleoid cephalopods, Nautilus and Allonautilus species, most likely did not depart in their evolutionary path from a slower pace of life and opportunistic diet.
Are there any concerns for squid in the early stages of life that arise from human behaviour, climate change, pollution, and commercial fishing behaviour? This is a very unexplored topic. It is very likely that our impacts over the sea through chemical, light, sound and any other kind of pollution we create can alter the behaviour of early life stages of cephalopods, and even lead to increased mortalities. Climate change would definitely affect embryo development and survival and can speed up paralarval development, which might not be a good thing for them. Some commercial fishing methods such as trawling are nonspecific and can also affect small squids and octopuses.
Fernández-Álvarez et al (2020) Global biodiversity of the genus Ommastrephes (Ommastrephidae: Cephalopoda): an allopatric cryptic species complex: https://doi.org/10.1093/zoolinnean/zlaa014
Hoving et al (2013) Extreme plasticity in life-history strategy allows a migratory predator (jumbo squid) to cope with a changing climate: https://doi.org/10.1111/gcb.12198
Jeena et al (2023) Insights into the divergent evolution of the oceanic squid Sthenoteuthis oualaniensis (Cephalopoda: Ommastrephidae) from the Indian Ocean: https://doi.org/10.1111/1749-4877.12705
entoLIVE
entoLIVE webinars feature guest invertebrate researchers delving into their own invertebrate research. All events are free to attend and are suitable for adults of all abilities – a passion for invertebrates is all that’s required!
1-4 billion hoverflies migrate into and out of southern Britain each year. Despite the fact that these migratory insects help control pest species (such as aphids) and provide important pollination ecosystem services, migratory flies do not receive anywhere close to the same attention within research as migratory vertebrates such as birds, whales and turtles. An Exeter University study on insect migration is addressing this knowledge gap.
Dr Will Leo Hawkes is an insect migration scientist from North Wales, based at the University of Exeter. He travels to insect migration hotspots around the world to study this most remarkable of natural phenomena.
Q&A with Dr Will Leo Hawkes
Are you able to estimate the biomass of migratory flies? Yes, it is possible – the two species of hoverflies which my supervisor recorded going over southern England recorded about 4 million which is 80 tonnes per year. We recorded all insects going through the Pyrenees and about 90% of those were flies. We estimated well over 100 tonnes of insects per year for the whole of the Pyrenees per year, based on the single pass that we monitored and scaled up. However, I think that our estimation is probably a big underestimate and I think the numbers and biomass are probably much greater.
Is there any evidence that some migratory flies “fatten up” before migration? Yes – they get really fat with round bodies that look like they are about to burst! The autumn migrants are always so much bigger than the summer migrants. Migratory generation adults tend to be stronger flyers with better immune systems and improved visions – like little “super flies”! The development of a fly into a migratory fly is determined when they are third instar larvae and depends on the length of light in the day while in the third instar of development. If these specific conditions are present in the third instar, their genetics will shift and cause the development of a migratory adult.
What is known about current migratory fly numbers when compared to historical populations? One really exciting study was undertaken in southwest Germany by Wolf Gatter. Hoverflies migrating through the mountains here were studied in exactly the same way for more than 40 years between 1978 and 2019. Terrifyingly they found that migratory aphid-eating hoverflies (like marmalades) have declined by 97%. This finding is likely mirrored across other sites like the Alps and the Pyrenees. Having been to these sites and seen how many insects fly through now, it’s actually hard to imagine that this is a fraction of what there used to be. The only bit of hope is that migratory flies have so many generations and may be able to recover quickly if the issues that are causing the declines are dealt with. The truth is that we have so little data on migratory flies that it’s hard to make overarching statements as what is happening in Germany may not be typical of other sites. This is why it is important to have systematic studies that are repeatable
Have you used the big dataset created by the UK Hoverfly Recording Scheme in your research? In our Pyrenees study, we used the Hoverfly Recording Scheme data to find out when these migratory peaks occurred and compared this to data on lots of environmental variables to look for any correlations. We found that the best predictor of large-scale migration was increased autumnal temperatures (i.e. there were higher numbers coming through during warmer autumns). This dataset is an amazing resource and so useful, with fellow researchers using the data extensively to better understand hoverflies. This is why it is important that biological recorders and the general public submit their hoverfly records to iRecord (preferably with a photo). There are some great ID resources out there too, such as Steven Falks’s hoverfly Flickr albums and Britain’s Hoverflies WILDGuide.
What do locust blowfly larvae eat when in the UK? The Locust Blowfly (Stomorhina lunata) mostly lay its eggs in locusts, but may be laying its eggs in native Orthoptera found in the UK. Most migratory species tend to be generalists rather than specialists and are often flexible with their behaviours.
Did you use tech such as image processing or AI to count the flies from the video frames? I’d love to be able to tell you it was all automated – that would have made my job so much easier. We tried so hard to make it automatic but because of the strong winds there was too much movement and it had to be done by manually. It took forever and I had many long days in a dark room counting the flies in each frame of the footage! For each sampling trip, I’d have a couple months in the Pyrenees in the sun, followed by just over a month of counting flies from the footage and another month of identifying the flies that we caught in the lab.
Is it understood why the return journey is in one generation? It’s not understood entirely but I think it’s because in autumn everything starts dying off so it makes more sense in terms of energy to make the long trip to an area where there is a lot more food available. Flies are quite flexible and if we experience an Indian summer and there are plenty of flowers still blooming they will stay around a bit longer.
Does the large investment that goes into migration make migratory insects more prone to population decline and extinction in the event of man-made or natural catastrophic events? Most migratory species are generalists in nature and so can survive on a wider range of foods than specialists. This actually tends to make them quite flexible when faced with difficult conditions. This doesn’t mean they are immune to risk and pesticides are known to be a problem. Specialist species, such as the Pine Hoverfly (Blera fallax) that will be featured in an entoLIVE later this month, are much more at risk as they are less mobile. A single Drone Fly (Eristalis tenax) lays about 200-400 eggs, with the survival rate for individual flies relatively low. Many of these flies will die because they fly off in the wrong direction and it is only the ones that make the big journeys to the correct place that will survive.
Were the flies on Marion Island known to be there previously or was this an accidental finding? I think it was purely accidental. Some researchers went to the island and identified some good spots to sample flies and set up Malaise traps (flight interception traps that look like a tent). The migratory blowflies just happened to be passing at that time and were found in the traps!
How do you know how many generations complete the various legs of the journey? There is still a lot we don’t know. What we do know, we know from general observations and citizen science projects, such as when there is an influx of a particular species. Butterfly migrations are better understood than other insect groups and have been used as a proxy for a lot of fly migration work. It would be great if we could put little trackers on the backs of these insects and work out where they go (and how far they go) in the spring. The spring and autumn migrations are completely different from each other, with the big autumn migrations being mostly females and the spring migrations being an approximately 50/50 split. I’ve also only ever seen the pathogens (the fungi coming out of the bodies) on the spring migrants and I think this is probably due to them spending longer in certain places or having more generations (or just the males are more prone to infection). It really is a wonderful field of study to be part of as it is only just beginning and i can probably count on my hands the number of people looking at insect migrations. There is still huge voids in our geographic knowledge of insect migration, such as in South America and Western Asia. We need more fly migration researchers.
Can flies be said to be gregarious in migrating, like locusts? This is a question I really want to answer with a study. We don’t really know but when I was in Cyprus we had hundreds of thousands of dragonflies just appear one day. They were swarming around and eating the flies and other insects and then they just left. Then a few days later we saw a group of similar numbers heading back the opposite way. This has also been reported anecdotally from Borneo with distinct groups of migrating dragonflies. I suspect that if any insect is going to display this social behaviour it is most likely to be dragonflies. Flies don’t arrive in swarms, but they do arrive at peak times together and it kind of makes sense for them to arrive together for mating. I’d like to see more work into the possibility of social behaviour in flies.
While using the flight simulator to quantify the hoverfly’s flying direction, what criteria did you set up to identify the fly as a migrant? We caught the flies as they were flying through a mountain pass nearly 2300m up in the Pyrenees. They were all heading south and there is simply not enough habitat up in this location for the hoverflies to exist if they were doing anything but passing through.
Could it be that where there are concentrations of insect-eating birds there will be more insects then? No one has direct evidence for this yet, but I’m sure that the birds will use concentrations as fuel. Birds are clever too and so I’m sure they can target the insects year after year. In fact, the amur falcons which migrate across the Indian ocean are thought to do so because they are following globe skimmer dragonflies which do the same migration!
How does a hoverfly fly? A great question, they’re amazing fliers, they flap their wings so fast which allows them to hover. They are also incredibly efficient fliers, using barely any energy as they fly as they can burn fat directly to turn into fuel. Rather than having to break the fat down first like us humans have to do.
Where does your interest in flies come from? I’ve always adored insects, ever since I was very little crawling around the garden insects were the subject of my curiosity. They were much easier to catch than birds, and didn’t bite as hard as a badger! I think flies are just so fascinating and they have so many stories to tell. I feel very lucky to be able to tell a few of them to human ears.
entoLIVE webinars feature guest invertebrate researchers delving into their own invertebrate research. All events are free to attend and are suitable for adults of all abilities – a passion for invertebrates is all that’s required!
Biological Recording 