Getting high to work out how low they can go
Invasive species often have large native ranges that encompass a number of different environments. The African clawed frog Xenopus laevis is most commonly referred to as coming from a Mediterranean climate. However, in its native range this species is almost ubiquitous in all of southern Africa from the Highlands of Malawi through the tropical lowlands of Mozambique and KwaZulu-Natal, and in the deserts of the Karoo and Namibia. Included in this natural range is a remarkable elevational gradient from sea level all the way up to over 3,300 m in elevation.
We were interested in sampling animals along this elevation gradient to determine how they changed in the thermal performance curves. Back in 2020 Laurie sampled animals every 1,000 m in elevation (see blog post here). We also left temperature loggers at all of these sites to see how the natural environments varied over the course of a year (see blog post here and here).
The results of Laurie's study are published today and show that the thermal profile of animals has a left shift to lower temperatures as they move up the elevational gradient. This means that animals that we captured in Lesotho have a lower optimal temperature for their endurance performance. However, the upper temperature limit for all of these animals was the same irrespective of where they were collected.
The results of this study put a rather different context on the potential of this species to invade different areas outside their native range. We now know that the species can tolerate very cold temperatures throughout the year at higher elevations.
Although this work sounds relatively simple, don't forget that Laurie had to chase these frogs at lots of different temperatures all day every day for weeks and weeks. This represents an incredible amount of work. Well done Laurie!
Read more about this work at:
Araspin, L., Wagener, C., Padilla, P., Herrel, A., Measey, J. (2023) Shifts in the thermal dependence of locomotor performance across an altitudinal gradient in native populations of Xenopus laevis. Physiological and Biochemical Zoology Journal https://doi.org/10.1086/725237
