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

ROLANDI CARMEN; SCHILMAN PABLO; DE LA VEGA GERARDO; LIGHTON JOHN; MENSCH JULIÁN

Ecology and Evolution

Wiley-Blackwell

Año: 2018

2045-7758

The range of thermal tolerance is one of the main factors influencing thegeographic 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 as the result of selective pressures on individual heritabledifferences. 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, for whichgenomic sequencing data are available. We characterized the phenotypicvariation of the upper thermal limit in 34 lines by measuring knock downtemperature (i.e., critical thermal maximum (CTmax)) by exposing flies toa ramp of increasing temperature (0.25° C min-1). Fourteen percent of thevariation in CTmax is explained by the genetic variation across lines,without a significant sexual dimorphism. Through a genome-wideassociation study 12 single nucleotide polymorphisms associated to theCTmax were identified. In most of these SNPs the less frequent alleleincreased the upper thermal limit suggesting that this population harborsraw genetic variation capable of expanding its heat tolerance. This potential upper thermal tolerance increase has implications under theglobal-warming scenario. Past climatic records show a very low incidenceof days above CTmax (10 days over 25 years), however, future climatescenarios predict 243 days with extreme high temperature above CTmaxfrom 2045 to 2070. Thus, in the context of the future climate-warming,rising temperatures might drive the evolution of heat tolerance in thispopulation by increasing the frequency of the alleles asociated with higher CTmax.