Ecophysiological models for global invaders: Is Europe a big playground for the African clawed frog?

Abstract

One principle threat prompting the worldwide decline of amphibians is the introduction of nonindigenous amphibians. The African Clawed Frog, Xenopus laevis, is now one of the widest distributed amphibians occurring on four continents with ongoing range expansion including large parts of Europe. Species distribution models (SDMs) are essential tools to predict the invasive risk of these species. Previous efforts have focused on correlative approaches but these can be vulnerable to extrapolation errors when projecting species' distributions in nonnative ranges. Recent developments emphasise more robust process‐based models, which use physiological data like critical thermal limits and performance, or hybrid models using both approaches. Previous correlative SDMs predict different patterns in the potential future distribution of X. laevis in Europe, but it is likely that these models do not assess its full invasive potential. Based on physiological performance trials, we calculate size and temperature‐dependent response surfaces, which are scaled to geographic performance layers matching the critical thermal limits. We then use these ecophysiological performance layers in a standard correlative SDM framework to predict the potential distribution in southern Africa and Europe. Physiological performance traits (standard metabolic rate and endurance time of adult frogs) are the main drivers for the predicted distribution, while the locomotor performance (maximum velocity and distance moved in 200 ms) of adults and tadpoles have low contributions.

More time for aliens? Performance shifts lead to increased activity time budgets propelling invasion success

“…However, correlative approaches all demonstrate the caveat that their predictions can reflect the realized niche of a species only, while the physiology of a species and its critical thermal thresholds as well as local adaptation or different life-history stages are neglected. A recent ecophysiological approach from Ginal et al (2021), which was also the precursor for this study, provided the first mechanistic SDMs for Europe. According to our knowledge, this was also the first time different life-history stages of an amphibian (tadpoles and adults) were included for modelling purposes.…”

“…Historically, X. laevis was exported to be used for human pregnancy testing, laboratory research (Gurdon and Hopwood 2003;van Sittert andMeasey 2016 2016) and the pet trade (Herrel and van der Meijden 2014;Measey 2017). In Europe, the species has established populations in Portugal (Rebelo et al 2010), Italy (Lillo et al 2005) and France (Fouquet 2001) with a predicted potential expansion of up to 2 million km 2 for Europe (Ginal et al 2021), such that it is now listed as an invasive species of Union concern (EU Regulation no. 2022/1203).…”

Mechanistic models project bird invasions with accuracy

“…1 ). For invasive species management, mechanistic approaches have so far been used to assess ectotherm invasion risks, showing much larger areas at risk of invasion, e.g., by African clawed frogs ( Xenopus laevis ) introduced to Europe 36 or cane toads ( Rhinella marina ) introduced to Australia 37 . Further applications include combining estimates of modeled energy expenditure with food availability to determine where introduced carp species 38 are most likely to invade the North American Great Lakes or to assess how climate change and human water storage practices shape invasive mosquito invasion risk across Australia 39 .…”

Population genomics ofXenopus laevisin southern Africa

“…By the mid-20 th century, this species had been adopted as a model organism for developmental biology (Cannatella and de Sá 1993; Gurdon 1996; Harland and Grainger 2011) owing in large part to its relative ease of maintenance in captivity and other useful attributes such as external fertilization and development. Xenopus laevis is also prevalent in the pet trade (Measey 2017) and invasive populations are now established in the United States, Mexico, Chile, France, Italy, Portugal, Japan, and China (Rebelo et al 2010; Measey et al 2012; Lillo et al 2013; Peralta-Garcia et al 2014; Ihlow et al 2016; Wang et al 2019; Ginal et al 2021; Vimercati et al 2021). Historical records demonstrate that exported individuals were sourced from multiple localities in southern Africa (van Sittert & Measey 2016), and some invasive populations are admixed (De Busschere et al 2016; Measey et al 2017).…”