Dan van Blerk presents his research findings at the Conservation Symposium

You might remember last November that the MeaseyLab took part in the Conservation Symposium (see Blog post here). In 2022, the event was hybrid and Dan van Blerk decided that he'd travel up to KZN to present his research in person.

Because it was a hybrid event, Dan could be seen in person, but was also seen by everyone attending online.

The talk was also recorded and is available here for you to watch on the Conservation Symposium YouTube Channel.

Well done Dan!

van Blerk, D., Pegg, J. & Measey, J. (2022) Impacts of invasive fish on ghost frog tadpoles. Conservation Symposium. Scottburgh, KwaZulu-Natal. 30 October to 5 November 2022 

Andrea finishes his postdoc in the MeaseyLab

Dr Andrea Melotto has been working in the MeaseyLab for two years.  Andrea's project was to investigate the invasive population of Asian spiny toads, Duttaphrynus melanostictus, in Madagascar and compare these to the source population in the native range in Vietnam. Andrea performed a standard set of morphological, performance and behavioural traits.

He visited Madagascar in January and Vietnam in August 2022. Both of his trips were severely constrained by COVID restrictions, and each represented a triumph against the odds in his actually managing to get there. This work is in collaboration with Angelica Crottini from CIBIO, Portugal.

Andrea also worked on a project comparing Western Leopard Toads, Sclerophrys pantherina, to Raucous Toads, S. capensis, and Guttural Toads, S. gutturalis. We are eagerly awaiting the publication of this very exciting study.

It was great to have Andrea in the MeaseyLab and we wish him all the best in his future endevors. Watch this space to see the output of Andrea's work.

Tyrone Hayes visits MeaseyLab

The one and only Tyrone Hayes (University of California, Berkeley) is visiting the MeaseyLab this month in order to further  his research interests into African clawed frogs and the impacts that result from the herbicide Atrazine. The impacts of Atrazine on clawed frogs has been a theme in Tyrone’s career (e.g. Hayes 2004). Atrazine in the environment causes chemical castration and feminization of amphibians, and Tyrone’s work has led directly to the banned status of this herbicide in Europe. 

In response, the herbicide’s manufacturer, Syngenta harassed Tyrone and his family for years including  having him followed and hounding his family (see article in the New Yorker here). Ironically, Atrazine is still used in the United States and South Africa, as well as many other countries, so there is still work to be done in order to see the ban extended.

Having worked with laboratory supplied and invasive populations ofXenopus laevis, Tyrone is in South Africa to collect stocks of animals from the source populations (see van Sittert & Measey 2016). 

It’s great to be collaborating with such a giant in science, and we look forward to seeing more on this work on the blog in the future.

Further Reading:

Hayes, T.B. (2004) There Is No Denying This: Defusing the Confusion about Atrazine.  BioScience,54(12): 1138–1149,https://doi.org/10.1641/0006-3568(2004)054[1138:TINDTD]2.0.CO;2 

Van Sittert, L. & Measey, G.J. (2016) Historical perspectives on global exports and research of African clawed frogs (Xenopus laevis). Transactions of the Royal Society of South Africa  71: 157-166.https://doi.org/10.1080/0035919X.2016.1158747 

Moving from correlative to mechanistic approaches of modelling African Clawed Frog distribution

We have already produced a number of different correlative models to predict the distribution of African Clawed Frogs (Xenopus laevis) in Europe. In the latest paper by Philipp Ginal (PhD student of Dennis Roedder from Museum Koenig, Bonn), we take a new approach by using data from the physiology of several different populations of both adults and tadpoles of X. laevis.

What this new model tells us is that despite tadpoles being apparently frail and far less robust than adults, when you compare the physiological data generated by Natasha Kruger and Carla Wagener in their theses to that of adult frogs (data produced by Mohlamatsane Mokhatla and Laurie Araspin), the tadpoles actually have a broader thermal niche. This means that instead of adult distribution being limited by tadpoles, it's actually the other way around. 

This rather surprising result means that we are not going to see any reduction in the forecast range by including tadpoles in our model. Moreover, the adaptations seen in the adult French Xenopus have resulted in a far greater potential distribution for this group of animals in Europe, compared to the potential for frogs from either the Western Cape or Kwa-Zulu Natal.

Our results show the value of having more than one life-history trait in a species distribution model, even though this might not provide the expected result. In addition, we demonstrate the importance of rapid adaptation in invasive species that mean that they have far greater invasive potential than the populations from which they were founded.

To read more:

Ginal, P., N. Kruger, L. Araspin, M. Mokhatla, J. Secondi, A. Herrel, J. Measey and D. Rödder (in press) More time for aliens? Performance shifts lead to increased activity time budgets propelling invasion success. Biological Invasions https://doi.org/10.1007/s10530-022-02903-6 pdf

Performance of native and alien guttural toads

You may remember that some time back, there were many trips to exotic places by the toad team (see here and here). Although there have already been a number of papers that have come out from these trips (Baxter-Gilbert et al., 2020; Baxter-Gilbert et al., 2021; Baxter-Gilbert et al., 2022) - here is the final one of this series led by former MeaseyLab post-doc James Baxter-Gilbert (James is now employed at Mt Allison University - see here).  

In this manuscript, we based our question around the pathway that the toads had taken to invasion. Starting out in rural KZN, the toads have invaded the city of Durban before being moved (as urban toads) to Mauritius in 1922 (yes - 100 years ago!). There they were released in cane fields, quickly moving into urban areas and from there into the natural forests of the island. Toads were moved from urban Mauritius in 1925 to Reunion. Once again, they moved through the urban environment before entering the natural forests. Hence, we asked whether advantages gained in the urban environment could have helped these toads in their invasion pathway.

For most of the traits that we studied, we found no indication of help coming from the toads having passed through an urban filter before their invasion. However, the climbing performance trait did have results that suggested that urban areas, with their many barriers, could have preadapted toads so that when they invaded the islands they were able to do better at climbing - eventually moving up the trees!

Read more about this study here:

Baxter-Gilbert, J.H., Riley, J.L., Wagener, C., Baider, C., Florens, F.B.V., Kowalski, P., Campbell, M., & Measey, J.(2022) Island hopping through urban filters: anthropogenic habitats and colonized landscapes alter morphological and performance traits of an invasive amphibian. Animals 12(19), 2549; https://doi.org/10.3390/ani12192549 pdf