An extreme cold event leads to community-wide convergence in lower temperature tolerance in a lizard community

Abstract

Extreme climate events are predicted to increase in frequency and severity due to contemporary climate change. Recent studies have documented the evolutionary impacts of extreme events on single species, but no studies have yet investigated whether such events can drive community-wide patterns of trait shifts. On 22 January 2020, subtropical south Florida experienced an extreme cold episode during which air temperatures dropped below the lower thermal limit of resident lizard populations. In the week immediately after the cold event, we documented decreased lower thermal limits (CT min ) of six co-occurring lizard species that vary widely in ecology, body size and thermal physiology. Although cold tolerance of these species differed significantly before the cold snap, lizards sampled immediately after had converged on the same new, lower limit of thermal tolerance. Here, we demonstrate that extreme climate events can drive substantial and synchronous community-wide trait changes and provide evidence that tropical and subtropical ectotherms—often characterized as unable to withstand rapid changes in climatic conditions—can endure climatic conditions that exceed their physiological limits. Future studies investigating the mechanisms driving these trait shifts will prove valuable in understanding the ability of ectotherm communities to mitigate climate change.

Climate warming will increase chances of hybridization and introgression between two Takydromus lizards (Lacertidae)

“…This explains why T. septentrionalis and T. sexlineatus have a similar Tp level (~32°C for both species; Yang et al, 2008). Therefore, as has been reported for other squamate reptiles (Lin & Wiens, 2017;Lin, Zhu, et al, 2019;Lin, Chen, et al, 2019;Stroud et al, 2020), low winter temperature rather than high summer temperature plays a key role in limiting the distribution of the two species farther north. The lower limit of thermal tolerance (CTMin) generally decreases with the increase in latitude and/or altitude in lizards (Qu et al, 2011).…”

Structural basis of the super- and hyper-relaxed states of myosin II

“…The latter would presumably reflect the thick filament structure most accurately at actual torpor temperatures. We speculate that the phenomenon of iguanas (ectotherms) falling from trees and becoming immobile when environmental temperatures are abnormally low ( Stroud et al, 2020 ) may be caused in part by the refractory impact of temperature on the ability of their myosin heads to bind to actin; a similar effect may have contributed to extinction of the dinosaurs during the global cooling that followed the asteroid impact of 66 million years ago ( Vellekoop et al, 2014 ).…”

In situ adaptation and ecological release facilitate the occupied niche expansion of a non‐native Madagascan day gecko in Florida

“…grandis could potentially adapt physiologically to colder ambient temperatures, for instance if dispersing northward through Florida. Rapid in situ physiological adaptation of this nature has already been reported for several non‐native lizard species in Florida (Stroud et al., 2020). Furthermore, since its initial establishment in Florida in the 1990s, P .…”

“…The lack of evolutionary conservatism in the critical thermal minima (CT min ) (Brown, 1996) of lizards (Grigg & Buckley, 2013) suggests that P. grandis could potentially adapt physiologically to colder ambient temperatures, for instance if dispersing northward through Florida. Rapid in situ physiological adaptation of this nature has already been reported for several non-native lizard species in Florida (Stroud et al, 2020). Furthermore, since its initial establishment in Florida in the 1990s, P. grandis has been exposed to extreme coldweather events that have caused substantial cold-induced mortality in multiple non-native squamate species (Campbell, 2011;Fieldsend & Krysko, 2019a;Mazzotti et al, 2011Mazzotti et al, , 2016, illustrating how powerful selective forces might drive rapid population-level adaptation.…”

“…Non-native species often respond to novel environments via rapid in situ adaptation (Angetter et al, 2011;Kolbe et al, 2013;Stroud et al, 2020). Such in situ adaptation can be both behavioral (e.g., changing behavioral thermoregulation patterns; Brown, 1996;Lapwong et al, 2020) and physiological (e.g., increased cold tolerance; Kolbe et al, 2012;Leal & Gunderson, 2012;Stroud et al, 2020) and has been documented in a number of non-native reptiles (Kolbe et al, 2012(Kolbe et al, , 2013Lapwong et al, 2020;Leal & Gunderson, 2012;Stroud et al, 2020;While et al, 2015), including geckos (Lapwong et al, 2020;Stroud et al, 2020) and non-native lizards in Florida (Kolbe et al, 2012(Kolbe et al, , 2013Leal & Gunderson, 2012;Stroud et al, 2020).…”