Geographical analysis of diapause inducibility in European Drosophila melanogaster populations

Abstract

Seasonal overwintering in insects represents an adaptation to stressful environments and in European Drosophila melanogaster females, low temperatures and short photoperiods can induce an ovarian diapause. Diapause may represent a recent (<15Ky) adaptation to the colonisation of temperate Europe by D. melanogaster from tropical sub-Saharan Africa, because African D. melanogaster and the sibling species D. simulans, have been reported to fail to undergo diapause. Over the past few centuries, D. melanogaster have also invaded North America and Australia, and eastern populations on both continents show a predictable latitudinal cline in diapause induction. In Europe however, a new diapause-enhancing timeless allele, ls-tim, is observed at high levels in southern Italy (∼80%), where it appears to have arisen and has spread throughout the continent with a frequency of ∼20% in Scandinavia. Given the phenotype of ls-tim and its geographical distribution, we might predict that it would work against any latitudinal cline in diapause induction within Europe. Indeed we reveal that any latitudinal cline for diapause in Europe is very weak, as predicted by ls-tim frequencies. In contrast, we determine ls-tim frequencies in North America and observe that they would be expected to strengthen the latitudinal pattern of diapause. Our results reveal how a newly arisen mutation, can, via the stochastic nature of where it initially arose, blur an otherwise adaptive geographical pattern.

Genetic variation underlying local adaptation of diapause induction along a cline in a butterfly

“…The pattern found here is similar to findings in D. melanogaster , where different timeless variants in a latitudinal cline affected photoperiodically induced quiescence, which was modified by the genetic background (Tauber et al., ). The relationship between photoperiodically induced quiescence and diapause is intriguing given their similar clinal patterns (Pegoraro et al., ).…”

“…First, while the change in CPP among three northernmost populations is nearly two hours, all of these three populations have identical allele frequencies at period and timeless, and nearly identical frequencies at the neighbouring loci of timeless (kinesin, CROT) ( Figure 2 where different timeless variants in a latitudinal cline affected photoperiodically induced quiescence, which was modified by the genetic background (Tauber et al, 2007). The relationship between photoperiodically induced quiescence and diapause is intriguing given their similar clinal patterns (Pegoraro et al, 2017).…”

Induction of long-lived potential aestivation states in laboratoryAn. gambiaemosquitoes

“…As we do not know exact refugia conditions in the wild, but know that Anopheles mosquitoes prefer cooler, more humid refugia conditions [35] , this study uses realistic, but likely somewhat exaggerated, climate conditions to induce aestivation with a reduced temperature and photoperiod. Temperature was the major climatic variable found to extend lifespan in this study, accounting for roughly a doubling of longevity alone ( [44,45] . This suggests that diapause may be a generalized survival mechanism that is often preserved in tropical taxa and can be utilized to bridge the gap between seasonally favorable climatic conditions.…”

“…We found that by priming mosquitoes in conditions simulating the late wet season in Mali, and maintaining mosquitoes in reduced light/temperature, mean mosquito survival increased from 18.34 +/-0.65 to 48.02 +/-2.87 days, median survival increased from 19 (95% CI: 17-21) to 50 days (95% CI: [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58], and the maximum longevity increased from 38 to 109 days ( p-adj < 0.001). While this increase falls short of the 200+ day survival seen in field mosquitoes, this extension is substantially higher than previously found through environmental or dietary modulation and is hard to reconcile with states other than aestivation.…”

The reunion of two lineages of the Neotropical brown stinkbug in soybean lands in the heart of Brazil

“…A second hypothesis would be the occurrence of a latitudinal cline for one or more traits 52,53,54 . The species association with environmental gradients should also be considered, given possible differences in traits and adaptions such as reproductive diapause 27,55,56 .…”