The reintroduction of the Chequered Skipper butterfly to England is one of the outstanding conservation success stories of the last ten years. I’ve been proud to play a part – see these old posts here, here and here – and in particular supervising Jamie Wildman’s PhD work. The second paper from his thesis has just been published and in it Jamie documents how you can identify individual butterflies by their markings and use this information to estimate the population size, life-span, and movements of Chequered Skippers. The technique could also be applied to other distinctively marked butterflies.
Here’s the reference with a link to a read-only version of the study:
If you need a PDF, get in touch via my Contact page.
Here’s the abstract:
The chequered skipper butterfly Carterocephalus palaemon was reintroduced to Fineshade Wood, England in 2018 as part of a Butterfly Conservation-led project following several years of planning. From 2019–2022, the population was sampled each May–June by the lead author, timed count volunteers, Butterfly Conservation staff, and casual observers.
A novel photographic mark-recapture (PMR) technique was trialled as an alternative to mark-release-recapture (MRR). In conjunction with timed counts, PMR was used to photoidentify individual C. palaemon through each butterfly’s upperside (ups) wing markings, estimate daily and gross population size, detect movements, and determine lifespan. As capture and recapture can be achieved non-invasively using PMR, habitat disturbance, the potential to influence butterfly behaviour, accelerate wing wear, affect mate selection and predation, and heighten mortality risk through handling are eliminated. We found PMR to be a viable alternative to MRR for a sensitive reintroduction of a low-density species with unique ups markings such as C. palaemon. Using capture histories generated through PMR, from a known founder population size of 42 butterflies in 2018, we estimated the population at Fineshade Wood had increased to 618 butterflies (+ 1371.43%) by 2022.
Movements of up to 2.22 km over a time period of 17 days were also detected. Lastly, we discuss the implications of PMR for population sampling of other Lepidopterans, and the potential to improve cost-efficiency of the technique using machine-based learning tools.
It must be the best part of a decade since the last time I visited Cannock Chase Area of Outstanding Natural Beauty. When I was still teaching at the University of Northampton we took students there every year to show them the diverse lowland heath landscapes, the ancient oak forest, the birch woods and the alder carr that runs through one of the small valleys.
Now that Karin and I have moved back to Britain, I can revisit some of these old haunts to see how much they have changed. Yesterday I returned to Cannock Chase with a group of friends, all former or current academics, a mix of geographers and ecologists. As we walked we discussed the local ecology and geomorphology, speculating or enlightening, as our knowledge allowed.
Highlights for me included a stunning, newly emerged male Orange Tip butterfly (Anthocharis cardamines) basking in the warm sunshine. I was also intrigued by these hour-glass shaped Hawthorn trees (Crataegus monogyna), presumably the product of grazing of older trees by deer that can cannot reach the highest stems (I said there was a bit of speculation going on!)
The swampy Sherbrook Valley always fascinates me, with its primeval atmosphere and dominating tussock grasses:
Look closer, however, and you see some real flowering gems such as Wood Sorrel (Oxalis acetosella) clinging to mossy stumps and broken branches:
All in all it was a great day: good company, wonderful landscape and wildlife, perfect weather, and lunch in a nearby pub.
You might be wondering about the title to this post. Well, next week I head to the Kunming Institute of Botany for three months of fieldwork and paper writing, and to deliver some talks. Then I’m briefly back in the UK before heading to the International Botanical Congress in Madrid for a week. During that time I’ll try to post about my adventures on the blog.
During the 2020 lockdown caused by the COVID-19 pandemic, I coordinated an international network of pollination ecologists who used standardised methods to collect data in their gardens. I blogged about it at the time – see here and here for instance – and also put up a post when the data paper from that work was published.
Several research groups are now working with that huge data set and interrogating it for answers to a wide range of questions. The first group to actually publish a paper from the data is a largely Chinese set of researchers from the Key Laboratory of Plant Resources, Conservation and Sustainable Utilization, at the South China Botanical Garden in Guangzhou, assisted by Kit Prendergast and myself.
In this paper we’ve considered how robust these plant-pollinator networks are to simulated extinctions of species, and how this is affected by the elevation, latitude, and plant species diversity of the network.
Here’s the full reference with a link to the study:
If you can’t access it and need a PDF, please send me a request via my Contact page.
Here’s the abstract:
Plant-pollinator interactions play a vital role in the maintenance of biodiversity and ecosystem function. Geographical variation in environmental factors can influence the diversity of pollinators and thus, affect the structure of pollination networks. Given the current global climate change, understanding the variation of pollination network structure along environmental gradients is vital to predict how global change will affect the ecological interaction processes. Here, we used a global plant-pollinator interaction data collection by the same sampling method at the same period to explore the effects of elevation, latitude, and plant richness on the structure and robustness of pollination networks. We analyzed a total of 87 networks of plant-pollinator interactions on 47 sites from 14 countries. We conducted a piecewise structural equation model to examine the direct and indirect effects of elevation, latitude, and plant richness on the network robustness and analyzed the function of network structure in elucidating the relationship between robustness and these gradients. We found that plant richness had both positive effects on robustness under random and specialist-first scenarios. Elevation, latitude, and plant richness affected network connectance and modularity, and ultimately affected network robustness which were mediated by nestedness under specialist-first and random scenarios, and by connectance under the generalist-first scenario. This study reveals the indirect effects of elevation, latitude, and plant richness on pollination network robustness were mediated by nestedness or connectance depended on the order of species extinctions, implying that communities with different pollination network structures can resist different extinction scenarios.
Yesterday I received an email containing the following press release. I thought it might interest readers of the blog so I am copying it in full with no edits. I had a quick look over the report and it’s amazingly detailed and comprehensive. It’s a shame that the report only covers insects, but that probably reflects my current bias given that my next book, due out in February, is about pollinating birds! Press release follows:
Governor Polis and the Department of Natural Resources Release Pollinator Report
BROOMFIELD – Today, Governor Polis in partnership with The Colorado Department of Natural Resources (DNR), Colorado State University Extension, Xerces Society for Invertebrate Conservation, and University of Colorado Museum of Natural History released the Colorado Native Pollinating Insects Health Study which is the most robust and detailed account of pollinator health ever undertaken in Colorado history. As directed by SB22-199, Native Pollinating Insects Protection Study, sponsored by Senators Sonya Jaquez Lewis and Kevin Priola, and Representatives Cathy Kipp and Meg Froelich, signed by Governor Polis on May 27, 2022, the study assesses the health of Colorado’s native pollinators, evaluates state policies for safeguarding pollinators, and makes recommendations on how to preserve and protect pollinators in Colorado.
“Pollinators play a critical role in Colorado life. From Crested Butte’s beautiful spring meadows to Palisade Peaches and Rocky Ford melons, Colorado’s pollinators sustain our flora and enable many foundational industries in every corner of the state. As our climate changes, we must safeguard the pollinators that generate and regenerate the Colorful Colorado we love,” said Governor Polis
Colorado is home to various native insects and bats whose pollinating services are at the heart of healthy environments and economies. Pollinators are critical to Colorado’s economy and our agricultural production and food systems, and they are essential for flowering plants that support the state’s wildlife ecosystem and add color to Colorado’s beautiful landscapes.
“Colorado is fortunate to have a tremendous diversity of plants and animals, but pollinating insects are perhaps the least studied but most beneficial for our ecosystems, economy and quality of life,” said Dan Gibbs, Executive Director, Colorado Department of Natural Resources. “I greatly appreciate the time and effort of the study authors who truly did a deep dive into the current state of pollinating insects and state policies and structures. I look forward to working with Colorado legislators and stakeholders in pursuing the best policies to ensure pollinating insect protection and long-term health.”
Colorado is home to over 1,000 species of bees—nearly 30% of North America’s and approximately 5% of the world’s bee species—and nearly 300 species of butterflies, representing over 40% of the diversity of butterflies in North America north of Mexico, some of which are already listed under the federal Endangered Species Act. This report underscores the importance of the Polis administration’s goals to tackle Colorado’s greenhouse gas emissions, prepare industries for the impending effects of climate change, and create more sustainable living in Colorado for pollinator populations.
“Our ecosystems rely on pollinators, which is why I’ve championed measures that limit toxic chemicals from harming pollinators and put forth a statewide assessment to better understand the problems our pollinators face and identify practices to better sustain them,” said Senator Sonya Jaquez Lewis, D-Longmont. “Today’s report shows that there’s plenty to do moving forward, and I am looking forward to continuing our work to protect pollinators and the ecosystems that are dependent on them.”
“I’m excited that we have this report to help us understand the extent of pollinator decline in Colorado. While Colorado ranks fifth nationally for the rate of honey-bee die-offs, we haven’t known as much about native pollinating insects. This threatens our food production, biodiversity and health of our ecosystems,” said Rep. Cathy Kipp, D-Fort Collins. “We created the Native Pollinating Insects Protection Study in 2022 to identify ways to better protect and support the native Colorado pollinators, like different bee species, butterflies, and moths, that are also essential to maintaining a healthy environment. These findings will help direct future legislation to create a safer environment for our pollinators, protect our food supply and support biodiversity.”
Promoting policies that benefit native pollinating insects represents an opportunity to foster healthy and sustainable pollinator populations, especially in agricultural and urban habitats. This includes enhancing pollinator-friendly native plantings along I-76 following its designation as a Colorado Pollinator Highway by the Colorado Department of Transportation and other existing state plans such as the state’s Natural Areas Program, and Wildlife Action Plan among others.
“Working on the Pollinator Health Study has been an amazing opportunity to collaborate with so many locally, nationally, and internationally recognized experts in the field of pollinator conservation. In addition to the immense amount of information within the report, this study highlights the importance of collaboration between scientists and land management agencies to bring together the many facets needed for conserving native pollinating insects,” said Deryn Davidson, Sustainable Landscape State Specialist, Colorado State University Extension. “Having the existing research on Colorado pollinators paired with recommended land management practices in one, comprehensive document is an incredible tool for policy makers, land managers, and really anyone interested in actionable steps for pollinator conservation.”
Areas of immediate action and priorities highlighted by the Pollinator Report include:
Priority 2: Protect, restore, and connect pollinator habitats.
Priority 3: Mitigate environmental changes that negatively impact pollinators and their habitats.
Priority 4: Reduce the risks from pesticides to pollinating insects.
Priority 5: Monitor and support native and managed pollinator health.
Governor Polis announced his annual budget proposal on November 1, focusing on ensuring Colorado is more affordable, sustainable, and liveable. The Governor included $100,000 to support education and incentives to encourage the use of pesticide alternatives in agricultural production and residential or commercial landscaping. On May 17, 2023, Governor Polis signed Neonic Pesticides as Limited-Use Pesticides, sponsored by Senators Kevin Priola and Sonya Jaquez Lewis and Representatives Kyle Brown and Cathy Kipp, which protects pollinators from harmful toxins.
Obviously the title of this post is click-bait, as there’s LOTS of things that I wish more people knew about pollination! But here’s one that really gets my (Yule) goat.
I’ve lost track of the number of times that I’ve read statements in books and research papers such as “bees collect lots of pollen from flowers therefore they are good pollinators”. Even worse, I sometimes see studies where pollen has been removed from “pollen baskets” or other scopae, then used as a measure of the importance of those bees as pollinators.
In both cases it seems to have been forgotten that bees are collecting pollen to feed their larvae and pollen that ends up in scopae is generally not available for pollination.
That’s the purpose of the Venn diagram at the top of this short post, to remind us that there can be a disconnect between what bees are doing and what plants require: foraging for pollen only partly correlates with flower pollination. Indeed, the same argument applies to any animal that feeds itself or its young on pollen, including pollen wasps (Maserinae), Heliconia butterflies, and some flower-visiting hoverflies, birds and bats.
It’s not only loss of pollen from reproduction that’s important here: depending on the size and behaviour of the bees relative to the shape and size of the flower, they may go nowhere near the stigma, so even if they are carrying viable pollen, it can be lost as far as the plant is concerned.
Note also that many bee species will collect pollen from wind-pollinated plants such as grasses, oaks, etc. Indeed in some species the availability of such pollen is extremely important – see Manu Saunders’ review on this topic and more recent papers that cite it. Again, it emphasises the partial disconnect between pollen collecting by bees and pollination of flowers by bees.
Assessing which flower visitors are actually pollinators is not technically demanding but it can be time consuming. The minimum that you need is single visit deposition (SVD) experiments in which you expose unvisited flowers to one visit by the potential pollinator. Then you assess how much pollen has landed on the stigma or (better) whether the visit results in seed set.
If you want to know more about the evidence that’s required to determine if a flower visitor is or is not a pollinator, they are codified in the “Cox-Knox Postulates” that I discuss in my book Pollinators & Pollination: Nature and Society.
Biodiversity Net Gain (or BNG) promises to transform the way that we approach nature conservation in the UK. I’ve been giving a lot of thought to what this might mean for insect pollinators and have produced a new report that summarises the opportunities that BNG presents and how we can make the most of them. You can download a copy of that report by following this link.
This is meant to be a working document and as BNG progresses, and our understanding of its impacts on pollinators increases, I will update it. In the meantime, please do feel free to comment.
There’s an estimated 350,000 described species of pollinators, and many, many more undescribed. Only about 20,000 of these (i.e. less than 6%) are bee species, although you wouldn’t know it from the media obsession with bees. It’s important and and timely, therefore, that a team of South American scientists have come together to propose a special issue of the Journal of Applied Entomology that focuses on these “other” insects.
The special issue will be called “The Neglected Pollinators: Understanding the Importance of Lesser-Known Insect Taxa in Pollination”. Consider submitting a manuscript if you work on anything except bees! Here’s the link to the details of how to submit your work:
As part of our roles as ambassadors of the new conservation organisation Restore (more of which later this year), several of us including Dave Goulson, George McGavin, and myself, are promoting this online petition to get the government to take the issue of neonicotinoid pesticides seriously. Here’s some text from Dave explaining the situation with a link to a petition that you can sign:
“For three years in a row our government has granted farmers special permission to use banned neonicotinoid pesticides on sugar beet. This is contrary to the expert advice of their own Expert Committee on Pesticides, who specifically recommended that permission should not be granted. It also flies in the face of a huge body of scientific evidence showing that these chemicals are phenomenally toxic to all insect life, and that their use on any crop contaminates soils, hedgerow plants, and nearby streams and ponds for years to come. We are in a crisis, with insect populations in freefall. It is about time our government woke up to this, and acted accordingly. This petition https://petition.parliament.uk/petitions/631948 is a necessary means of holding the government to account. Please sign and share, as signing will ensure the issue is debated in Parliament.”
This petition now has more than 15,000 signatures which ensures that it gets a response from the Government. If it reaches 100,000 mark, it will trigger a debate in Parliament. Please sign and promote this important initiative!
It’s been a couple of years since I last did a talk or workshop for the Wildlife Trust for Bedfordshire, Cambridgeshire & Northamptonshire. But I’m pleased to say that they’ve invited me back and you can join me tomorrow evening for an online introductory talk about pollinators and pollination in the UK.
The talk starts at 7pm UK time and full details of how to sign up are in the link below:
It’s been quite a while since I posted about the Chequered Skipper Reintroduction Project – see my earlier posts here and here. But my involvement has continued, albeit geographically removed from Northamptonshire, and I thought I’d give a brief update with two good news stories.
The headline story is, of course, the success of the project. Since its reintroduction in summer 2018, the Chequered Skipper population has thrived and grown and is now the first self-sustaining population in England since it went extinct there in 1976. Not only that, but the management within Rockingham Forest that was designed to improve the habitat for this butterfly has also benefitted a range of other species, including plants, insects and birds.
How do we know this? Well, the situation on the ground is being intensively monitored by the project team and the passionate volunteers who are helping to count butterflies and other species every year. The data collected from these activities has fed into Jamie Wildman’s PhD thesis where he’s collated and analysed the results. And that’s the second item of good news: yesterday Jamie successfully defended his PhD thesis and was awarded a pass with very minor corrections!
I’m actually not surprised because it’s a great thesis with some fascinating results that not only document this reintroduction but also rewrite the history of the decline and extinction of the English populations of Chequered Skipper. The first paper from that is out – see this post – and there’s more to follow shortly.
Once again, huge congratulations to Jamie and thanks to the project team and the other supervisors for their hard work. Here’s my favourite photo of Jamie, second from the left and just starting out on his PhD journey back in 2018.
Prof. Jeff Ollerton - ecological scientist and author 