Genetic variation for tolerance to high temperatures in a population of Drosophila melanogaster

CARMEN ROLANDI; LIGTHON, JOHN; DE LA VEGA GERARDO; SCHILMAN, PABLO E.; MENSCH, JULIAN

Ecology and Evolution

Wiley Online Library

Año: 2018

2045-7758

The range of thermal tolerance is one of the main factors influencinggeographic distribution of species. Climate change projections predictincreases in average and extreme temperatures over the coming decades,hence the ability of living beings to resist these changes will depend onphysiological and adaptive responses. On an evolutionary scale changeswill occur on the basis of individual inheritable differences of this type ofresponse. In this work, we studied the genetic basis of tolerance to hightemperatures in the fly Drosophila melanogaster, and whether this speciespresents sufficient genetic variability to allow expansion of its upperthermo-tolerance limit. To do so, we used adult flies derived from a naturalpopulation belonging to the Drosophila Genetic Reference Panel (DGRP),for which genomic sequencing data are available. We characterized thephenotypic variation of the upper thermal limit in 34 lines by measuringknock down temperature (i.e., critical thermal maximum (CTmax)) byexposing flies to a ramp of increasing temperature (0.25° C min-1).Fourteen percent of the variation in CTmax is explained by the geneticvariation across lines, without a significant sexual dimorphism. Through agenome-wide association study (GWAS) 12 single nucleotidepolymorphisms (SNPs) associated to the CTmax were identified. In most ofthese SNPs the minor alleles increased the upper thermal limit suggestingthat this natural population harbors raw genetic variation for expanding its heat tolerance. This potential upper thermal tolerance increase hasimplications under the global-warming scenario. Past climatic records showa very low incidence of days above CTmax (10 days over 25 years),however, future climate scenarios predict 243 days with extreme hightemperature above CTmax from 2045 to 2070. Thus, in the context of thefuture climate-warming, rising temperatures might drive the evolution ofheat tolerance in this population.