Local adaptation with high gene flow: temperature parameters drive adaptation to altitude in the common frog (Rana temporaria)

Abstract

Both environmental and genetic influences can result in phenotypic variation. Quantifying the relative contributions of local adaptation and phenotypic plasticity to phenotypes is key to understanding the effect of environmental variation on populations. Identifying the selective pressures that drive divergence is an important, but often lacking, next step. High gene flow between high- and low-altitude common frog (Rana temporaria) breeding sites has previously been demonstrated in Scotland. The aim of this study was to assess whether local adaptation occurs in the face of high gene flow and to identify potential environmental selection pressures that drive adaptation. Phenotypic variation in larval traits was quantified in R. temporaria from paired high- and low-altitude sites using three common temperature treatments. Local adaptation was assessed using QST–FST analyses, and quantitative phenotypic divergence was related to environmental parameters using Mantel tests. Although evidence of local adaptation was found for all traits measured, only variation in larval period and growth rate was consistent with adaptation to altitude. Moreover, this was only evident in the three mountains with the highest high-altitude sites. This variation was correlated with mean summer and winter temperatures, suggesting that temperature parameters are potentially strong selective pressures maintaining local adaptation, despite high gene flow.

Phenotypic divergence of the common toad (Bufo bufo) along an altitudinal gradient: evidence for local adaptation

“…The autocorrelogram shows that a significant differentiation in larval period should indeed occur in our system when the difference in altitude is at least 1000 m. Such a countergradient variation pattern has been already demonstrated in various organisms, including amphibians, especially along latitudinal gradient (review in Conover et al, 2009). However, some amphibian studies have provided evidence also for a countergradient variation in growth rate (for example, Berven and Gill, 1983;Laurila, 2005, 2009;Laurila et al, 2008;Orizaola et al, 2010;Muir et al, 2014), which is not the case in our study. The growth rate was slower only in high altitude and metamorphic mass was gradually reduced with increasing altitude.…”

“…900 m). This result could mean that the strength of divergent selection may not be different enough between medium and high altitudes to drive differentiation in development rate or that there are constraints for the maximum development rate (Porcher et al, 2004;Hangartner et al, 2012;Muir et al, 2014). The autocorrelogram shows that a significant differentiation in larval period should indeed occur in our system when the difference in altitude is at least 1000 m. Such a countergradient variation pattern has been already demonstrated in various organisms, including amphibians, especially along latitudinal gradient (review in Conover et al, 2009).…”

“…The intraspecific variation of body size along altitudinal gradients seems to differ among species (Morrison and Hero, 2003;Cvetković et al, 2009). Growth and development rates seem to follow a countergradient pattern (that is, individuals from colder environments grow or develop more slowly in situ, but are able to grow or develop more rapidly than conspecifics from warmer parts of the range when compared in a common garden setting; Conover and Schultz, 1995, Ficetola and De Bernardi, 2005, 2006Marquis and Miaud, 2008) but exceptions exist (for example, Sommer and Pearman, 2003) and explicit tests of local adaptation are lacking ( (Berven, 1982a,b) but see Muir et al, 2014).…”

“…When conducted as common garden or transplant experiments, these studies provide evidence for a genetic basis for quantitative trait differentiation among populations (Connover and Schultz, 1995). However, few studies have attempted to determine the relative contributions of different processes that contribute to genetic and phenotypic divergence along environmental gradients (but see Antoniazza et al, 2010;Hangartner et al, 2012;Muir et al, 2014).…”

Life-History Responses to the Altitudinal Gradient

“…More frequently, selection for stress tolerance induces ecotypic differentiation in the form of local adaptations, exemplified by significant non-additive gene-environment interactions and populations that show genetic differences, and performances, corresponding to the conditions met along the gradient (Törang et al 2015;Muir et al 2014). Since environmental variation occurs at small spatial scales across elevations, strong local selection and limited gene flow are required to promote local adaptation sensu strictu (i.e.…”