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Ever felt like gettnig everyone together to strategize?

25 September 2019

Did making a strategy to work on amphibians have any real effect?

Back in 2009, we had a meeting to strategize about conservation research on amphibians in South Africa. The meeting was well attended, and consisted of a number of workshops where different groups tried to prioritise what should be done, and to which species. Together with other members of the workshop, we turned the results of this meeting into a book, which I edited, and was published by SANBI in early 2011. The book is available as a free pdf to download, and you can get your own copy here.

If you are stuck for names here, try downloading the book and going to the back page where they are all listed. There are many faces that have got older over the last 10 years!

While the book has attracted a steady number of citations over the years, its real value has been in demonstrating the agreed priorities of a community of South African herpetologists as to what needed to be done. In this way, it has leveraged funding for a great many projects and research programmes undertaken by various amphibian researchers in South Africa, both those who attended the 2009 meeting and some who didn’t.

This was the opinion of a similar group who met again in 2015 to decide whether or not the strategy had been worthwhile. For me, this was an uplifting experience as we often get so bogged down in the actual doing of something (in this case it was editing and writing much of the book, as well as conducting the IUCN red listing accounts that it also contained) that we miss or forget all about the big picture. Thus, there really is value in looking back and asking what the value was, and whether it’d be worth doing again.

Although it’s tempting to think that these meetings are all about the amphibians, they are actually all about the people. Building relationships and sharing visions for the future of research. To see who's in this photo and more about the day itself, take a look at the blog post from November 2015.

In the paper published today, together with a number of participants at the 2015 workshop, we tried to make a quantitative and qualitative assessment of research undertaken since the strategy was developed. We compared the 10 years prior to the strategy to the 10 years that followed, and we found:

  • A spike in the number of amphibian records for many species after the plan
  • A marked increase in the number of species descriptions for South African amphibians
  • The number of papers published had risen from 85 to 176,
    • with nearly a quarter of these on targeted taxa
  • An increase in the number of amphibian monitoring programs all over the country
  • The publication of a number of new amphibian books
    • Including books for children
    • And books in local languages
  • A surge in the number of MSc and PhDs awarded with amphibians as their primary subject.

In short, we found that compared to the 10 years before the strategy, the herpetological community in South Africa had resounding evidence of a profitable period, which many of those involved attribute, in part, to the existence of a common strategy document.

So strategizing does work; bringing people together and agreeing on common goals within a research community can aid both those already working in the field, but also give direction to emerging researchers. But this is not a static document, and any strategy needs refreshing with new people from within the community. Sadly, the same period has seen a number of retirements of leading figures in South African herpetology, but hasn’t seen the same number of replacements into permanent research positions. We have to hope that the large number of graduates produced will eventually find jobs where they can continue to come together to strategize for their future.

Read the Open Access paper here:

Measey, J., Tarrant, J., Rebelo, A.D., Turner, A.A., Du Preez, L.H., Mokhatla, M.M., Conradie, W. (2019) Has strategic planning made a difference to amphibianconservation research in South Africa? African Biodiversity & Conservation - Bothalia 49(1), a2428. https://doi.org/ 10.4102/abc.v49i1.2428

  Frogs  Lab  meetings

Natasha's Conversation piece

22 September 2019

Do you know whether it's friend or fo?

When alien species are moved to a new environment, they have a whole new set of predators and prey to become accustomed to. To determine whether the novel sensory inputs are predators or prey is very important, as this can translate to life or death. While adult frogs have sophisticated sensory organs, their tadpoles' senses are less developed but recognising predators is still very important.

In this popular piece for The Conversation, Natasha Kruger explains how African clawed frog, Xenopus laevis, tadpoles reacted when they were exposed to smells from different species in France. Natasha explains how familiarity with some of the smells, like predatory diving beetles, might be more famliiar than others, like crayfish which are not-native in sub-Saharan Africa.

What did the tadpoles do? 

You can read Natasha's explaination in this excellent popular write-up.

Natasha's PhD has been investigating the role of tadpoles in the invasion of the African clawed frog, Xenopus laevis. We're looking forward to lots of revelations of how tadpoles differ from their adult forms. 

Kruger, N (2019) Invasive tadpoles can recognise potential predators in new environments. The Conversationhttps://theconversation.com/invasive-tadpoles-can-recognise-potential-predators-in-new-environments-119673 

  Frogs  Lab  Xenopus

Predicting what amphibians will be tomorrow's pets

20 September 2019

Predicting the amphibian pet trade

The continued increase in numbers of live amphibians traded as pets has resulted in a number of problems for the individuals traded and the remnants of populations left behind. Not only are numbers of individuals increasing, but the pet trade is constantly looking for new species to trade that will keep shoppers coming back to their outlets: now not only physical shops but also online stores. Predicting what will be traded in the future is difficult, because predicting the future is confounded by ignorance of what will happen. But if we could determine what is likely to be traded, we might be able to set in place measures that stop the most vulnerable or most invasive species from becoming tomorrow’s problems.

This is the premise that Nitya Mohanty and I started with when we set out to determine what the most popular traits in the current pet trade are for amphibians. We searched the literature for lists of traded amphibians around the globe and used the assembled list to test for traits that set these species apart from other non-traded amphibians. To do this, we used a published dataset of amphibian traits called AmphiBIO, although this did limit us to traits that they had used and recorded in adequate numbers.

The result of our endeavours a long list (443) of traded species, which we were able to test for taxonomic biases, finding that there are indeed biases including 6 overtraded families. Next we found that the species traded tend to be larger, with bigger range sizes, and a ‘larval’ breeding type. Lastly, we used these traits to make a list of which species have these traits but are not in our list. This is a list of what might be likely to be traded in future.

Although we just conducted this work on amphibians, a similar approach could be taken for other popular groups that are often traded as pets, such as reptiles or birds. We also acknowledge that there are many more traits that are likely to make popular pets, such as colour and calls. Using this predictive framework would allow policy makers to decide whether or not to control the potential for future species to be traded, getting one step ahead of the unpredictable trade in pets.

Keen readers of the blog will remember that Nitya heard that this paper was accepted only minutes before he was due to present on it at the recent HAA meeting in Cape St Francis (see blog post here). And those of you with longer memories will realise that this is not the first time we have published on amphibians in the pet trade as there was a MeaseyLab publication on amphibians in YouTube videos (see here for the blog post & here to read that paper).

Mohanty, N.P. & Measey, J. (in press) The global pet trade in amphibians: species traits, taxonomic bias, and future directions. Biodiversity & Conservation. DOI: 10.1007/s10531-019-01857-x

  Frogs  Lab

What's the big idea?

17 September 2019

What’s the big idea?

In previous blog posts (see here), I’ve talked about the importance of having a hypothesis, and building that hypothesis in a logical framework within the introduction (see here). The introduction serves to inform the reader about why this particular hypothesis was chosen, introducing both the response and determinate variables, as well as the presumed mechanism by which the hypothesis can be falsified (or upheld).

In this post, I take the lead from my recent talk for the Herpetological Association of Africa (see blog post here), in which I talked about the need for herpetologists to respond to bigger theories in biological sciences.

This message was the result of work done in the MeaseyLab (but not yet completed!) on invasion hypotheses, where we (Nitya, James, Sarah, Natasha and I) checked 850+ papers on alien herps to see which of 33 common invasion hypotheses they had tested. The answer was disappointing, with <1% having used an invasion hypothesis.

In my talk, I suggested that this might not be true only of papers on herpetological invasions, but also of herpetology in general (although I concede that some areas, such as herp physiology are actually quite good). Further, I contend that using these wider hypotheses or theories would actually be good for the authors concerned, as it would likely garner them a wider audience. Moreover, a greater number of biologists might come to realise how valuable reptiles and amphibians are as models in biology.

So where would we find all of these big ideas?

There are quite a few papers that synthesise hypotheses in various areas of biology. Here I provide two, but I will endeavour to add more as I come across them… so watch this space (although not too keenly).

The first is by Mark Velland on theories in community ecology

The next is by Jane Catford on hypotheses in invasion biology, but I encourage you to look for more up to date versions (the newest is by Enders et al 2018, but this’ll change in time).

Each of these papers will give you a list of big ideas, together with the citations for seminal papers that have built them. You will note that many of these theories are very old with many dating back to Darwin.

Of course, there are many ways to approach and test these theories, but if you don’t know about them, then your work may actually make a considerable contribution to upholding or refuting them, but go totally unrecognised. When the significance of your work isn’t realised, it’s unlikely that it’ll be widely read and used.

Let’s face it, if all the effort of the work that we put into papers is just going to get buried, then is it really worth it? The work that we do is also really expensive, so making it as relevant as we can to a wide an audience possible is something that we should be concerned about.

So, I encourage you to stand on the shoulders of giants by using big ideas in your introduction. Make sure that the data that you collect can actually be used to respond to some of these big ideas. Then make sure that you cite them, giving them the importance that they deserve (yes, even as key words) so that others can find your work, and you might even find that one day, your work has shoulders that are broad enough for others to stand on!

The take home message:

1. As herpetologists we are not engaging with theories from ‘the literature’

2. Herps are great models [even snakes]

3.We have a lot to donate to many areas of biology, but we need to engage

Reading the literature can really expand your mind and horizons. When undertaking a literature review [or when reviewing a paper], take the time to think about not only what has been tested, but what could have been.

Further Reading

Catford, J.A., Jansson, R. and Nilsson, C., 2009. Reducing redundancy in invasion ecology by integrating hypotheses into a single theoretical framework. Diversity and Distributions15(1), 22-40.

Enders, M., Hütt, M.T. and Jeschke, J.M., 2018. Drawing a map of invasion biology based on a network of hypotheses. Ecosphere9(3), p.e02146.

Vellend, M., 2010. Conceptual synthesis in community ecology. The Quarterly review of biology85(2), 183-206.

  Lab  Writing

The HAA meeting 2019

13 September 2019

The HAA meeting at Cape St. Francis, Eastern Cape

Only 8 hours drive from Cape Town, and we arrived at Cape St. Francis in the Eastern Cape to attend the Herpetological Association of Africa's 14th conference.

Of course, once we were there, we all gave stunning talks from many members of the MeaseyLab, both those based at Stellenbosch University and elsewhere. Nitya got a special surprise when the paper on which his talk was based was accepted in the session before he talked! Very welcome news indeed!

It was good fun to get to the beach, meet up with plenty of herpers that we knew and meet new ones that we didn't know. A special mention to Alan Channing who received the HAA's highly prized life-time achievement award for his contribution to southern African frog taxonomy. More than 20 years ago (1998), I worked with Alan at UWC during my first Royal Society post-doc (see here). 

Here are some of the abstracts of the talks:

Kruger, N, Vimercati, G, Herrel, A, Secondi, J & Measey, J Spatial sorting on dispersal traits are stage dependent in the invasive amphibian Xenopus laevis in western France

Organisms are exposed to trade-offs constraining their anatomy, physiology, and behavior between dispersal and life-history traits. The spatial sorting theory predicts the enhancement of dispersal traits due to resource re-allocation at the periphery of expanding populations. A more nuanced view of spatial sorting emerges when one considers organisms with complex life cycles in which dispersal usually occurs at a particular ontogenic stage. It is currently not known if enhancement of dispersal traits in organisms with complex life cycle emerges only at the dispersal stage. In amphibians, larval development can influence life-history traits that directly influence dispersal in post-metamorphic juveniles. Spatial sorting for dispersal traits occurs in adults of the invasive African clawed frog, Xenopus laevis, in western France. Individuals have been expanding from a single introduction point since the 1980s colonizing an area of ~2000 km2. The mass of reproductive organs is reduced at the range periphery while the dispersal rate, probability and distance are increased. In X. laevis all stages are aquatic and dispersal is terrestrial. We predict that the enhancement or adaptation of dispersal traits due to spatial sorting occurs at the onset of their development regardless of dispersal ability of tadpoles. To test this, we conducted experiments in outdoor mesocosms and in microcosms in the lab. We surveyed tadpole development for 10 weeks from hatching to metamorphosis. We observed no effect of site position (core vs. periphery) on morphology, development, and survival of tadpoles. This study shows that spatial trait variation in pre-dispersal and dispersal stages are decoupled to a large extent in species with complex life cycles. In amphibians, tadpole development is constrained by factors such as initial density, food availability, and predation whereas in adults, resource allocation to dispersal can be enhanced at the dispersing stage and not at the pre-dispersal stage.

Measey, J, Baxter-Gilbert, J, Davies S, Kruger, N, Mohanty N How do herpetologists study invasions?

Invasion Biology is a young discipline, Charles Elton only coined the term in 1958. Although the subject was generally ignored by most people for 40 years, the last 20 years has seen a near exponential rise in papers by herpetologists on alien reptiles and amphibians (and not only by Rick Shine!). But how do herpetologists go about studying invasions? In this study, we reviewed 836 publications on alien herps and compared their objectives with 30 well known hypotheses from invasion biology. We found that although the field is rapidly expanding, very few researchers had specified any of the invasion hypotheses, but 26% had the data to test one or more. The most commonly tested hypothesis resembled the concept of the ‘ideal weed’, that invasion success of a non-native species depends on its specific traits (3.8%). Other popular hypotheses referred to habitat filtering (1.7%), preadaptation through human commensalism (1.8%), novel weapons (1.3%), novel associations (1.4%) and invasion meltdown (1.5%). Perhaps more excitingly, are the new hypotheses that herpetologists can donate to invasion biology, including spatial sorting, invasion hubs and hybridisation. We conclude that herpetologists need to pay more attention to existing hypotheses in invasion biology, many of which stem from classical questions in ecology. Better transdisciplinary communication will likely lead to increased impact of studies which could teach invasion biologists more about reptiles, amphibians and their amazing invasions.

Mohanty, N & Measey, J The global pet trade in amphibians: Species traits, taxonomic bias, and future directions

The burgeoning global pet trade in vertebrates has multi-pronged conservation implications, including overexploitation of native populations, spread of diseases, and invasions. The majority of amphibian invasions are due to the pet trade pathway and current lists of extra-limital amphibians (including those in trade) suggest that future invasions will encompass a broader taxonomic diversity than is known. Given that trade is dynamic, it is essential to move beyond currently traded species and understand which species are likely to be traded in the future and serve as candidates for invasions. In this study, we systematically assess amphibian species in the pet trade, i) characterising taxonomic bias, ii) evaluating species-traits as predictors of traded species and trade volume, and iii) forecasting likely future pets. We collated a global list of 443 traded amphibians and a regional dataset (USA) on trade volume. Species-traits (body size, native range size, clutch size, and breeding type) and conservation status, were considered as predictors of traded species and volume. Six Families contributed disproportionately to the amphibian pet trade; the likelihood for species to be traded was positively associated with body size, range size, and a ‘larval’ breeding type. However, species-traits performed poorly in predicting trade volume, suggesting an overriding effect of socio-economic aspects of the trade. The identified species-traits and taxonomic bias of the trade were then used to predict species likely to be traded as pets in the future. This study formalizes the knowledge on amphibian species that are traded as pets. We found a strong bias for certain Families, along with a preference for large-bodied and widely distributed species with a larval phase. Our results pave way for more trait-based approaches to forecast amphibians entering the trade. Such understanding of the pet trade can help pre-emptively tackle the pathway responsible for most invasions and disease spread in amphibians.

Peta, STP, Engelbrecht, GD & Measey, J Reptile and avian assemblage along a gradient of invasive alien plants in the critically endangered Woodbush Granite Grassland

Invasive alien plants species (IAPs) are a significant problem in South Africa and can pose complex and far-reaching challenges to biodiversity, with impacts on fauna poorly understood. The study aimed for multi-site comparison of reptile and bird assemblages between pristine grassland, alien plant invaded and plantation habitats. Reptiles and birds were surveyed using standard Y-shape trap array and fixed-point counts respectively. Vegetation structure and invasion intensity was determined using point-intercept method. Five IAPs were identified: Acacia mearnsii, Eucalyptus grandis, Pennisetum clandestinum, Pinus patula and Solanum mauritianum. Reptiles (23 individuals from 5 species) were recorded, with highest abundance and diversity in the grassland. Birds (2113 individuals from 67 species) showed the greatest abundance, diversity and richness in the invaded habitat. Trachylepis varia was a common reptile species, showing overlap between grassland and invaded habitat. Lygodactylus methuen was the only identified endemic reptile species. Grassland bird specialists (i.e. Anthus similisCisticola lais, and Sphenoeacus afer) were observed in more open and moderately invaded habitat but absent in denser and heavily invaded habitat. The study demonstrated that reptiles and birds respond differently to alien plants invasion. Reptiles were mostly supported by low vegetation cover, availability of microhabitats e.g. rocks and bare ground for thermoregulation while birds responded to rich vegetation stratification. Clearing of invasive alien plants can be considered as management strategy if it is to promote biodiversity. Clearing can create more thermal opportunities for reptiles and accommodate open habitat bird species.

Telford, N, Channing, A & Measey, J Origin of invasive populations of the Guttural Toad, Sclerophrys gutturalis

The Guttural toad, Sclerophrys gutturalis, has three established invasive populations on Mauritius, Reunion and in Constantia, a peri-urban area of Cape Town, South Africa. The native range of this toad covers much of central and southern Africa. Here we use mitochondrial DNA (mtDNA) to sample across the range of the natural distribution (from Kenya to South Africa) and compare ND2 and 16S sequences to those from animals sampled from each of the three invasive populations. We show that all invasive populations refer to the same mtDNA clade, which is naturally distributed in north-eastern South Africa, but not from adjoining Mozambique or southernmost Eastern Cape areas. Our findings corroborate previous reports of deliberate introductions from South Africa to Mauritius, and from Mauritius to Reunion. Similarly, our results suggest a single accidental translocation within South Africa from the northeast to Constantia. Our findings highlight the combination of anthropophilic behavior, and extreme long-distance dispersal occurring with accidental translocation for this species. We caution that accidental pathways are likely to continue into the future, with increasing numbers of invasive populations of this species.

Wagener, C, Kruger, N & Measey, J Xenopus laevis progeny display local adaptation of physiological performance to environmental extremes

Altitudinal variation of environmental temperatures is expected to shape the evolution of physiological functions of widespread populations. Adaptation to thermal extremes can create altitudinal differentiation in ectotherm physiological performance. In this study, a common garden experimental approach was employed to determine whether thermal adaptations to contrasting environmental regimes are heritable and how these thermal adaptations affect performance. To address this, we compared the critical thermal limits and swimming performance of African clawed frog (Xenopus laevis) tadpoles bred from two adult populations captured from high (~ 2000 m above sea level) and low (~ 5 m above sea level) altitudinal extremes. Parental-origin significantly affected tadpoles’ critical thermal minima (CTmin), maximum velocity, maximum acceleration, total distance and distance travelled in the first 200 m.s-1. Tadpoles with low-altitude parental-origins had a higher optimal temperature (Topt) for swimming performance and CTmin than tadpoles with high-altitude parental-origins. Performance of tadpoles bred from high-altitude adults was significantly higher at cooler temperatures and lower at the highest test temperature, in comparison with tadpoles bred from low-altitude adults. These results suggest that thermal performance curves of X. laevis tadpoles have adapted in response to contrasting local environmental conditions experienced by adults. Future studies should focus on whether similar thermal performance trait variations are present in other populations of the widely distributed African clawed frogs (X. laevis).

Jordaan, PR, Measey, J, Hanekom, CC, Greend, AN, Woolcocke, AB, Combrink, X Grassland and savanna fossorial herpetofaunal densities

Ecological data on soil living amphibians and reptiles are largely lacking. Specialised methods relying on substrate excavation are required to adequately quantify fossorial herpetofaunal densities as surveying techniques which rely on surface movement (e.g. pitfall or funnel trap surveys) are biased against soil-living species which infrequently move over the soil surface. As part of a larger study, we quantified baseline densities for fossorial herpetofauna in grassland at Sileza Nature Reserve and in savanna at Tembe Elephant Park. All sites were underlain by aeolian sand. Grassland surveys were conducted at two adjoining sites, one during summer, and one in winter while both savanna sites were only surveyed during winter. Quadrats of 4 m2 (2 m x 2 m) were excavated to a mean depth of 0.25 m (volume of 1 m3) as most species of fossorial herpetofauna are considered to live at shallow soil depths. The excavated substrate was momentarily stored in 20 litre buckets before being sifted through a 2 mm x 2 mm (4 mm2) metal mesh, exposing soil living reptiles and amphibians. Grassland fossorial herpetofaunal densities were marginally lower during winter (0.56 individuals.m-2) compared to the summer (0.67 individuals.m-2) survey. Grassland species richness consisted of a single amphibian, Breviceps mossambicus, as well as five reptile species. Although amphibian species richness was considerably lower in grassland compared to reptiles, densities were higher especially during summer. Inter-seasonal demographic variability was observed in the grassland amphibian population with higher numbers of juveniles present during the summer. Herpetofaunal fossorial densities at savanna sites were on average more than four times lower (0.11 and 0.14 individuals.m-2 respectively) compared to grassland. Once again, the only amphibian present was B. mossambicus, but in much lower densities (0.01 and 0.02 individuals.m-2). It is hoped that the outcomes of this study will contribute to a better ecological understanding of soil megafauna in grassland and savanna ecosystems.

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