Some years ago, browsing in a second hand bookshop, I happened across a copy of an old magazine from 1950 called Nigeria. Published by the then colonial government, it was a miscellaneous collection of articles about the culture, geography and natural history of that fascinating West African country. Although aspects of the contents are problematical by modern standards, I bought it because of a short article about a wild plant with enormous flowers and a remarkable pollination strategy. In particular, the spectacular photograph of a man holding a flower that’s the length of his forearm grabbed my attention: who couldn’t love a flower like that?!
These types of flowers are pollinated by flies, a common strategy in the Birthwort family (Aristolochiaceae) to which the plant belongs. This strategy of fly pollination in which flies are deceived into visiting the flowers by their stink and colour, and temporarily trapped in the enclosed chamber, is something that I explore in detail in my book Pollinators & Pollination: Nature and Society, particularly in the genus Ceropegia. Those plants show convergent evolution with the pollination systems of Aristolochiaceae, though they are unrelated.
Pararistolochia goldieana has a wide distribution across West Africa, including Cameroon, Equatorial Guinea, Nigeria, and Sierra Leone. The IUCN Red List categorises it as ‘Vulnerable’ due to habitat loss. The population where these photographs were taken is described on the final page of the article:
During field work in Gabon in the 1990s I was fortunate enough to encounter a species of Pararistolochia in the rainforest of Lopé National Park. It was a different species to P. goldieana, with rather smaller but no less spectacular flowers, and it stank to high heaven! We knew it was there long before we saw it. I collected some flies from the flowers and had them identified, though I’ve never published the data: it’s available if anyone is working on a review of pollination in the family.
This 1950 article is anonymous, so I don’t know who to acknowledge for the amazing images. However the botanist R.W.J. Keay was working on a revision of the family for the Flora of West Tropical Africa project at the time, so it may have been written by him.
As I mentioned in my previous post, it’s currently Invasive Species Week in the UK. Non-native species which have negative environmental impacts and disrupt infrastructure are a global phenomenon, of course, and almost all regions of the world have been impacted by species that originated elsewhere. One alien species that is of growing concern in Australia is the western honey bee Apis mellifera. We often think of bees as being relatively benign organisms, but a number of species have been introduced around the world and may compete with native species for nectar and pollen, and nesting sites.
In the second paper from my collaboration with Dr Kit Prendergast, we’ve assessed how introduced honey bees change the structure of bee-flower visitation networks in Australian urban habitats. The main finding is that when honey bees are common, they dominate these networks in ways that indicate significant competition with native bee species. You can get a sense of that from the figure above: the honey bees are in red, native bees in yellow, native plants in light green, and non-native plants in dark green. The length of the bars is proportional to the abundance of these plants and bees.
To say that honey bees ‘dominate’ these networks is an understatement: not only are they vastly more abundant than the other bees, but they visit almost all of the different types of flowers in the network, regardless of whether they are native or introduced.
Although the honey bee bullshit machine often claims that western honey bees are dying out, the exact opposite is true: across the world, managed Apis mellifera numbers are higher than ever, as you can see from the following chart based on figures from the United Nations Food and Agriculture Organization (UN-FAO):
Whilst the growth in honey bee numbers is a good thing for honey producers, bee farmers, and small-scale subsistence farmers, there are environmental consequences to the increase in hives, as we have shown.
If anyone wants a PDF of the paper, please use the Contactform. The full reference for the study and the abstract is:
The European honeybee Apis mellifera is a highly successful, abundant species and has been introduced into habitats across the globe. As a supergeneralist species, the European honeybee has the potential to disrupt pollination networks, especially in Australia, whose flora and fauna have co-evolved for millions of years. The role of honeybees in pollination networks in Australia has been little explored and has never been characterised in urban areas, which may favour this exotic species due to the proliferation of similarly exotic plant species which this hyper-generalist can utilise, unlike many native bee taxa. Here, we use a bipartite network approach to compare the roles, in terms of species-level properties, of honeybees with native bee taxa in bee-flower (‘pollination’) networks in an urbanised biodiversity hotspot. We also assessed whether the abundance of honeybees influences overall network structure. Pollination networks were created from surveys across seven residential gardens and seven urban native vegetation remnants conducted monthly during the spring-summer period over two years. There were consistent differences in species-level properties between bee taxa, with honeybees often differing from all other native bees. Honeybees had significant impacts on network properties, being associated with higher nestedness, extinction slopes of plants, functional complementarity and niche overlap (year two), as well as lower weighted connectance and generalisation. These associations all are indicative that competition is occurring between the introduced honeybee and the native bee taxa in bee-flower networks. In conclusion, the introduced honeybee occupies a dominant, distinct position in bee-flower networks in urban habitats in the southwest Western Australian biodiversity hotspot
This is a guest post by Helen Tedds who is currently researching for a PhD at the University of Northampton. Although Helen’s work is far removed from my usual research and consultancy interests of plant-pollinator interactions, I’m proud to be part of her supervisory team! Amphibians were one of my early natural history obsessions, and invasive plants and pollinators are a long standing interest of mine. In this post Helen discusses her research on the UK reptile and amphibian pet trade.
This week (24th-30th May 2021) is Invasive Species Week, an annual event led by the GB NNSS (Non-Native Species Secretariat) to raise awareness of invasive species and how we can help prevent their spread. Generally, the term ‘invasive species’ is defined as an introduced organism that has an adverse impact on its environment by causing ecological and economic damage. They are one of the top five causes of worldwide biodiversity loss through habitat damage, preying on or out-competing other species. They can also spread disease to other species, including humans. The estimated cost of invasive species to the UK’s economy is more than £1.7 billion  which is caused by things like damage to buildings [e.g. from the dreaded Japanese Knotweed (Fallopia japonica – fig. 1)], interference with food production, delays on work projects, and the expense of dealing with them. The number of new species being introduced to the UK is rapidly on the increase and can be exacerbated by climate change. This is an urgent problem that without intervention will continue to escalate!
Fig. 1: Japanese knotweed (Fallopia japonica) damaging a brick wall
In 2015 I embarked on a PhD that aimed to quantify the pet herpetofauna (reptile and amphibian) trade across England, mainly to understand the associated socio-economic factors and animal welfare consequences of this. Investigating invasive species was low on my already-full agenda, however, it has been a rabbit hole I ended up going down (pun intended: rabbits were named Britain’s most costly invasive species in 2010 according to The Guardian)!
The exotic pet trade has long been known to be a means of new species entering an environment (either through escape or deliberate release), but according to a recent study in Frontiers of Ecology it now ranks as a primary cause of invasive species. It has long been illegal to release any non-native species into the wild under the Wildlife and Countryside Act 1981, however more recent legislation has been enacted to prohibit the trade of invasive species. Whilst the term ‘invasive’ can be subjective, in the UK a species officially considered to be invasive is listed in retained EU law: Invasive non-native (alien) animal species: rules in England and Wales. That’s not to say that other ‘feral’ pets are not ‘invasive’. There are concerns that Indian ring-necked parakeets (Psittacula krameria – fig. 2) that have spread across the UK are potentially out-competing some of our native birds for nesting sites in tree hollows. However there needs to be a body of evidence built to support these claims before a species is added to the legislation.
Fig. 2: Indian ring-necked parakeet (Psittacula krameria)
In terms of herpetofauna, there is only one invasive species of amphibian listed in the legislation, the North American bullfrog (Lithobates catesbeianus- fig. 3), and one species of reptile, the common slider turtle (Trachemys scripta) along with all sub-species, including T. s. elegans, T. s. scripta, and T. s. troostii -fig. 4-6). North American bullfrogs pose a threat to our already vulnerable native amphibians as they will eat frogs, newts, and other similar sized animals, and slider turtles threaten our waterfowl as they will eat bird eggs, as well as insect larvae.
The law has prohibited anyone from keeping, breeding, and selling these species since August 2016. If you owned one before the law came into force (turtles can be very long-lived) then you have what are called ‘grandfather rights’ where the animal can remain in your possession until the end of its days. If an owner can no longer take care of the turtle they cannot re-sell it- it is best to relinquish them to a rehoming centre that has the relevant license where they can live out the rest of their lives, such as The National Turtle Sanctuary at Lincolnshire Wildlife Park.
Part of my research into quantifying the herpetofauna trade has involved sampling from pet shops and online classified adverts as to what species are for sale. So far, I have officially documented 431 different reptile species, and 122 different amphibian species, and this number is set to grow as I continue to analyse four years’ worth of data. All these species are non-native, and whilst most of them would not survive in our British climate, there are some causes for concern.
In October 2020 a fellow PhD student, Ali North, got in touch with me as she is currently investigating the drivers of establishment and spread of a non-native amphibian in the UK, the alpine newt (Ichthyosaura alpestris- fig. 7). Her project uses distribution data of alpine newts in their native range across mid-Europe with an aim to predict the invasion risk of this species in the UK. I was interested to learn from her that these newts have established various populations in the UK but most concerningly are known to be a vector of chytridiomycosis which can be transmitted to our native amphibians. As part of her research at the University of Plymouth, ZSL Institute of Zoology, and the ARC Trust, Ali wanted to know how often alpine newts had occurred in my data sampling seeing as the pet trade is a potential route for non-native species entering the wild. It turns out that my data set had only 16 records of alpine newts (out of tens of thousands of records) which is not very many, however, do not be fooled by small numbers! It does not take many individual pets being released into the wild for a potentially invasive species to wreak havoc on an ecosystem. Whilst the understanding of alpine newts as an invader is in its infancy, I was delighted to be able to assist Ali with this part of her research and I look forward to reading her final thesis. If you have spotted an alpine newt in the UK you can also help towards her project by reporting it here: https://www.arc-trust.org/news/have-you-seen-an-alpine-newt-in-the-uk
Another interesting thing that my data collection has highlighted is that despite slider turtles being banned from sale for over four years now, they are still appearing on online classified websites such as Preloved, Pets4Homes, and Gumtree. Not only is this illegal, but it is also against the minimum standards set out by the Pet Advertising Advisory Group (PAAG) which these websites agree to adhere to as voluntary members. Since I started collecting data in July 2017 to the time of publishing this blog there have been at least 102 adverts selling slider turtles, and these were the more obvious ones. On deeper investigation some adverts selling yellow-bellied sliders listed them as just the letters ‘YBS’ meaning that they would not be flagged when searching using key words. These adverts have consistently appeared in my data set at a rate of about two per month, with a noticeable spike in Oct-Dec 2020 at a rate of five per month, so there does not appear to be a downward trend since the legislation came into force. Also, some other adverts just listed animals using the word ‘turtle’ or ‘terrapin’; not only does this allow the potential for slider adverts to slip through the net but it also further violates PAAG minimum standards by not advising potential buyers what the species is. How can someone research the correct care information if they don’t know what species they are buying?
Another invasive species that I came into close contact with recently, coincidentally whilst in the process of writing this blog, was in my local park- Elmdon Park in Solihull. An invasive water weed, Azolla filiculoides, or red water fern (fig. 8), had suddenly appeared in one of the park’s ponds. This weed is believed to have entered UK water systems from the ornamental pond and aquarium trade either by spreading via birds’ legs between ponds or from people emptying fish tanks into wild water bodies. It spreads on the surface of water bodies, blocking out sunlight and decreasing oxygen, thereby killing native wildlife.
Fig. 8: Red water fern (Azolla filiculoides) in Elmdon Park, Solihull
I sit as Secretary on Elmdon Park Support Group’s committee and run their social media pages, so I found myself reading more about this weed and treatments used to control it, in order to inform the local community on what would happen. The Warwickshire Wildlife Trust lease the land and therefore must foot the treatment bill, which turns out to be the use of a weevil (Stenopelmus rufinasus- fig. 9), affectionately known as ‘Weevil Knievel’ The weevil eats the weed but doesn’t come cheap at a cost of a few hundred pounds for just one container of them. So here we have another casualty to our native wildlife because of the pet trade.
Fig 9: ‘Weevil Knievel’ (Stenopelmus rufinasus)
So, what can we do? Further research into identifying potentially invasive species will help in raising public awareness, whilst initiatives such as Invasive Species Week will spread the message on the consequences of releasing non-native species into our UK ecosystems. But there persists a deeper problem whereby some people fail to properly research the needs of the pets they buy, or fully understand how big they will grow, and feel that it’s easier to release them into the wild rather than to relinquish them via more responsible methods. This is perhaps the area of human-animal interactions that needs more attention and research.
Tedds, H.L., Sneddon, S., Ollerton, J., Clubb, R., and McCormick, W.D., Herps across England: investigating the scale of the reptile and amphibian trade: UFAW Recent Advances in Animal Welfare Science VII Conference Poster, 30th June- 1st July 2020, online.
Bottom line is that the global coffee production in 2019/20 was the result of 24 TRILLION flower visits by bees! That’s down a little from the previous year, but it’s still a LOT of visits by a HELL of a lot bees!
Humans affect the land on which they live in many different ways, and this in turn influences local biodiversity. Sometimes this has positive effects on local wildlife: consider the diversity of birds to be found in well-managed suburban gardens, for example. But often the effect is negative, especially when the land is intensively managed or habitats are destroyed, for example via deforestation or urban development.
This is not a new phenomenon – according to a recent study, most of the habitable parts of the planet have been shaped by humans for at least 12,000 years (see Ellis et al. 2021). What is new, however, is the scale and the speed with which land-use is changing, which are far greater than they have been historically. An important question is the extent to which this change in land-use intensity is affecting pollinator diversity in different parts of the world. Over the past 18 months I’ve been collaborating on a project led by Joe Millard (as part of his PhD) and Tim Newbold which uses the Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (PREDICTS) database to address that very question.
The study was global in scale and used data from 12,170 sites to assess the affect of land-use intensity on 4502 pollinating species. The findings are really fascinating; highlights include:
In comparison to natural vegetation, low levels of land-use intensity can have a positive effect on the diversity of pollinators.
For most land categories, greater intensity of land-use results in significant reductions in diversity and abundance of pollinators, however. For example, for urban sites there’s a 43% drop in number of species and a drop in 62% pollinator abundance from the least to the most intensive urban sites.
On cropland, strong negative responses of pollinators to increasing intensity are only found in tropical areas, although different taxonomic groups vary in their responses.
The latter finding is especially concerning given that: (i) most pollinator diversity is found in the tropics; (ii) the majority of tropical crops are insect pollinated; and (3) tropical agriculture is becoming increasingly intensive and land use is likely to rapidly change in the coming decades.
The full reference for the study, with all authors, is:
Millard, J., Outhwaite, C.L., Kinnersley, R., Freeman, R., Gregory, R.D., Adedoja, O., Gavini, S., Kioko, E., Kuhlmann, M., Ollerton, J., Ren, Z.-X. & Newbold, T. (2021) Global effects of land-use intensity on local pollinator biodiversity. Nature Communications 12, 2902. https://doi.org/10.1038/s41467-021-23228-3
The terms ‘Natural Capital’, ‘Ecosystem Services’, and ‘Nature-Based Solutions’ seem to generate one of two emotions in some people: confusion and irritation. Confusion stems from not appreciating that these are different, though closely related, concepts, as I will show below. Irritation often is the result of seeing ecosystem ‘valuation’ as a neo-liberal plot to somehow ‘sell-off nature’. I’ve discussed this irritation in the past – see this old post for instance about ‘How do we value nature?‘ – so I’m not going to dwell on it: some people see the advantage of using these concepts, others don’t. And that’s fine. But I will touch briefly on the confusion aspect because it pertains to a discussion on Twitter this morning that was stimulated by this tweet from Prof. James Bullock, in which he saw the three concepts as re-packaging on the same ideas under different (and confusing) names.
James and I have been friends for a long time, and there’s things we agree on and things we disagree on. And that’s also fine. But as I pointed out in my response to the tweet, I think that these concepts are different, and that they logically flow together. To me, Ecosystem Services are the benefits to society provided by Natural Capital. Nature-Based Solutions are strategies or schemes for targeting Natural Capital creation or enhancement (e.g. flood meadows or woodland) to provide Ecosystem Services (e.g. flood management or carbon storage).
The analogy that I used (which a few people seemed to appreciate) is that this is the difference between books, what we learn from books, and decisions on how to produce more books.
Finding organisms that have not previously been described by scientists is not unusual; every year, hundreds of ‘new’ species enter the taxonomic literature, a testament to how little we still understand about the Earth’s biodiversity. The majority of these species are insects, because that’s the most diverse group of organisms on the planet. But new species of plants and fungi also turn up regularly: for example in 2020, botanists and mycologists at Kew named 156, including some from Britain.
So although discovering undescribed species is not uncommon, any field biologist will tell you that it’s an exciting moment to spot something that you’re never seen before and which could turn out to be new. That was certainly the case when my colleague Dr Annemarie Heiduk’s attention was drawn to a South African plant that was clearly something special. As Anne said to me this week:
‘I will never ever forget the very moment when I spotted it and immediately knew it was something no-one has ever seen before. And I was so lucky to find it in flower. I cannot describe how beautiful it looked sticking out of the surrounding grass vegetation. It is certainly one of a kind and I really know how lucky I was to have found it. Not once did it ever cross my mind that I will discover a novel Ceropegia species, let alone one that is so distinct!’
Anne has been honoured in this way not just because she discovered the plant, but also because, to quote the paper, she:
‘is a pollination ecologist who with her research on the floral chemistry and deceptive pollination strategies of Ceropegia trap flowers has acquired recognition as an expert in this field’
Anne tells me that she has already collected pollinator and floral scent data for this new species, so we can look forward to seeing that published in the near future. I described the fascinating pollination ecology of Ceropegia, including some of Anne’s earlier work, in my recent book. This is a genus of plants that has intrigued me since I first saw photographs of them and started growing them as a teenager, 40 years ago. Since then I’ve published several papers about their pollination strategies, and how they compare with the family Apocynaceae as a whole: see the following links for some examples:
One of my earliest exposures to botany was growing houseplants as a teenager, encouraged by my dad who, as I discussed in Pollinators & Pollination: Nature and Society, was a very keen gardener. It was my dad who taught me about rooting cuttings in water, how to germinate seeds, and so forth. These are gifts of knowledge that I will always treasure and which I have passed on to my own offspring.
So I was delighted to accept an invitation to run a workshop at the LEAF Houseplant Festival in Market Harborough that takes place from 30th to 31st May this year. Tickets can be booked by following that link, though be aware that they are limited due to social-distancing regulations, and it’s first come, first served.
The workshop that I am running is called ‘Potting Up’ and will focus on the different kinds of potting media to use, how to tailor your compost to specific types of plants, and so forth. As you might expect, I’ll be using my knowledge of plant ecology to explain why different plants have different requirements, and what those requirements are.
As well as running the workshop, Karinand I will be selling off some of our own collection of houseplants on a ‘Pre-loved Plants’ stall. We are in the process of selling our house in Northampton and we need to downsize!
Finally, I will also have a limited number of copies of Pollinators & Pollination: Nature and Society for sale. If you would like to reserve a signed copy to pick up on the day, please use the Contact form.
I look forward to seeing some of you there: it will be great to actually mix with people, have face-to-face discussions, and interact with an audience that’s in the same room as me!
The article focuses on some of the myths and misunderstandings that I dealt with in my book Pollinators & Pollination: Nature and Society. It also points out that, even in a place like Britain with a long tradition of natural history study, there’s still much for the patient observer to discover. If you’re interested in a PDF, drop me a line via the Contact page.
I meant to post about this earlier but it’s been a really busy few weeks, so apologies if this is late in the day for any of you. Tomorrow morning there’s a webinar being run by the Public Policy Exchange entitled: “Protecting British Pollinators”. There’s an interesting set of speakers and I’ve been asked to provide the opening introduction and to chair the event.
Here’s the link for more details and booking information: