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Rapid adaptation of French Xenopus

15 September 2020

Laurie's new paper shows rapid adaptive shifts for invasive Xenopus to cooler France

In the first paper of her PhD, MeaseyLab student Laurie Araspin (jointly supervised by Anthony Herrel of the NMHN Paris) shows how adult Xenopus laevis introduced to France in the 1980s have already shifted their temperature dependence of locomotor performance.

The work has particular interest as it shows how rapid adaptations in invasive species allows them to function in different environments to that of their native range. In this study, Laurie used adults collected from the South African Cape and subtropical KwaZulu-Natal (watch a video of that collection here). Despite these massive differences in collection localities, once they were acclimated in the lab there was no difference in their performance. The French animals, however, maintained a massive difference left shift (to cooler temperatures) in their thermal performance. 

This is just the start of Laurie's exploration into the rapid adaptive physiological shifts shown by invasive populations of X. laevis when compared to their native South African populations. Despite COVID restrictions, Laurie's work continues in Paris and in 2021 we hope to have her in South Africa sampling some of the more extreme environments for African Clawed Frogs.

To read the paper in full:

Araspin, L., A. Serra Martinez, C. Wagener, J. Courant, V. Louppe, P. Padilla, J. Measey and A. Herrel (2020) Rapid shifts in the temperature dependence of locomotor performance in an invasive frog, Xenopus laevis, implications for conservation. Integrative and Comparative Biology   60(2):456–466 https://doi.org/10.1093/icb/icaa010 pdf  

  Frogs  Lab  Xenopus

James & Natasha present in Canada

12 September 2020

MeaseyLab at the 7th Annual Meeting of the Canadian Herpetological Society

Drs Natasha Kruger and James Baxter-Gilbert both presented their work at the 7th Annual Meeting of the Canadian Herpetological Society online today. 

Perhaps the most remarkable event was that Natasha's talk coincided with local loadshedding (a South African term for a scheduled electricity blackout). Natasha then delivered the entireity of her presentation using her phone as a modem and with a flashlight on her desk. Super impressive!

 

There was a great shuffling of seats and reaching for (Canadian) beer when Natasha settled down to give her presentation on perceptions of predators for invasive African Clawed frogs in France

INVASIVE CLAWED FROG, XENOPUS LAEVIS, CAN IDENTIFY LOCAL PREDATORS REGARDLESS OF COEXISTENCE TIME

Natasha Kruger, Anthony Herrel, Jean Secondi, and John Measey

Invasive species are exposed to novel predators after their establishment in a novel environment. Defences against novel predators may not be efficient at least at an initial stage. The presence of an anti-predator defence is an important parameter that may determine the ability of local communities to control the expansion of invasive populations. The African clawed frog, Xenopus laevis, is a globally invasive amphibian. In western France it faces predators functionally similar to predators found in its native range (South Africa), however, its invasive range has expanded to overlap the range of an invasive crayfish predator. We tested whether naïve X. laevis tadpoles from the invasive French population exhibit anti-predator response to local predators, and whether the response depends on the degree of relatedness with predators encountered in the native range of the frog. Alternatively, if naïve tadpoles may express generic neophobia to any cue they are not familiar with. We exposed naïve lab-reared tadpoles to a non-predator water snail, Planorbarius corneus, a native beetle, Dytiscus dimidiatus, and an invasive crayfish, Procambarus clarkii. Species of the Dytiscus genera are present across southern Africa while no related species to crayfish occur in X. laevis’ native range. We found that X. laevis tadpoles innately reduce their activity when exposed to D. dimidiatus and P. clarkii stimulus cues. The innate response to P. clarkii indicates that X. laevis tadpoles are not naïve to the invasive crayfish. Thus, limiting the effects of these predators on the control of X. laevis, however, previous studies have found that P. clarkii mitigate the effects of other invaders. The complex interactions between co-invaders are essential to explore.

Then James provided his overview on the rapid exolution of size in invasive island populations of Guttural Toads:

SHRINKING BEFORE OUR ISLES: THE RAPID EXPRESSION OF INSULAR DWARISM IN THE INVASIVE POPULATIONS OF GUTTURAL TOAD (Sclerophrys gutturalis) IN MAURITIUS AND RÉUNION

James Baxter-Gilbert, Julia L. Riley, Carla Wagener, Nitya. P. Mohanty, and John Measey

Island ecosystems have traditionally been hailed as natural laboratories for examining phenotypic change, including dramatic shifts in body size (e.g., island gigantism or insular dwarfism). Similarly, biological invasions can drive rapid localised adaptations within modern timeframes. Here we compare the morphology of two invasive guttural toad (Sclerophrys gutturalis) populations in Mauritius (est. 1922) and Réunion (est. 1927) to their genetic source population from Durban, South Africa. We found that female toads on both islands were significantly smaller than mainland counterparts (reduction in body size by 33.9% and 25.9%, respectively), as were males in Mauritius (22.4%). We also discovered a significant reduction in the relative hindlimb length of both sexes, on both islands, compared to mainland toads (ranging from 3.4 - 9.0%). Our findings suggest that the dramatic reshaping of an invasive amphibians’ morphology, leading to insular dwarfism, can result in less than 100 years.

James and Natasha during the meeting with their fellow delegates

...and who could forget how James dressed up for his travelogue. All in the name of the show folks...


Everything you ever wanted to know about Indian Bullfrog invasions

10 September 2020

All about Indian Bullfrog invasions

Sometimes is great to have all the information in one place, and here we can see a great example of this with a synthesis of research on the Indian Bullfrog by Nitya Mohanty. In this study, Nitya partnered up with Angellica Crottini who had extensive data about the bullfrog invasion on Madgascar, and Raquel Garcia who introduced the SDM modelling know how. 

In this paper, Nitya suggests that these bullfrogs are potential problems in more parts of the world, should they be introduced there. This is an important lesson in a time when we are still seeing the intentional introduction of American Bullfrogs for farming in different parts of the world.

Hopefully, this publication will highlight the potential problems of the Indian Bullfrog, and it won't end up being introduced to lots more places.

Read the entire article here:

Mohanty, N.P., Crottini, A., Garcia, R.A. & Measey, J. (in press) Non-native populations and global invasion potential of the Indian bullfrog Hoplobatrachus tigerinus: A synthesis for risk-analysis. Biological Invasions https://doi.org/10.1007/s10530-020-02356-9 pdf

  Frogs  Lab

A talk on Cane Toads by Georgia Ward-Fear

30 August 2020

A talk on Cane Toads - by Georgia Ward-Fear

At the end of 2019, Georgia and I began writing a chapter together on ethics in amphibian invasions. This turned out to be quite an undertaking, and it was a great privaledge to work with Georgia on this now accepted manuscript (see here for link to come...). I mentioned to Georgia that I was giving a class on Invasion Biology to our 3rd year undergraduates at Stellenbosch University, and she immediately volunteered to give them a talk all about Cane Toads. She recorded this ahead of time, and so I share it with you below:

Cane Toads have become a specially important group to the MeaseyLab since we started studying Guttural Toads some five years ago. The two species both belong to the family Bufonidae, but are not otherwise closely related. However, both being large bufonids we became interested in whether the same adaptations that have been extensively researched in Cane Toads could also be found in Guttural Toads. Indeed, so much work has now been done on Cane Toads, that we can use this as inspiration for questions for a long time to come.

Thanks so much to Georgia for stepping forward and volunteering to present for the BDE345 students - I'm sure that they really appreciated it. You're a star!


Table Mountain Ghost Frogs need cold water

11 August 2020

New study looks at requirements for Table Mountain Ghost Frog tadpoles

In a new study, published today by MeaseyLab alumnus Zishan Ebrahim and colleagues, they determined the requirements of the tadpoles of Table Mountain Ghost Frogs, Heleophryne rosei. The iconic Table Mountain Ghost Frog only lives in the streams and kloofs around Table Mountain and nowhere else on the Cape peninsula (or anywhere else in the world). Previously, researchers had determined that the tadpoles require perennial flow (streams that don't dry) in order for the tadpoles to inhabit them. This then is the reason why Table Mountain is the only massif on the peninsula with the frogs. However, in a paper published today, Zishan Ebrahim shows that the frogs also have a sweet spot of temperatures above (and presumably below) which they can't tolerate. 

Zishan monitored physical parameters of Table Mountain's stream water for many years finding that tadpoles don't inhabit all of the streams with perennial flow on the mountain. The warm water that flows down some of the streams could be influenced by the complex hydrological installations on top of the mountain that were originally installed to supply fresh water for the city. Now much of the water on top of the mountain sits in dams where it heats in the sun and may influence the temperature in the streams. There are other problems on Table Mountain, most notably invasive trees, that are also likely to change the hydrological properties of the water and impact on the Ghost frogs and their tadpoles. 

Read more about the conservation relevance of this work in this recently published paper:

Ebrahim, Z, de Villiers, A. and Measey, J (2020) Assessing water conditions conducive to tadpoles of the Table Mountain Ghost Frog (Heleophryne rosei) and the relevance to their conservation Koedoe Vol 62 (1): a1581 DOI: https://doi.org/10.4102/koedoe.v62i1.1581 

  Frogs  Lab
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