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 (<15 Ky) 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.
Bibliographical noteFunding Information:
CPK and ET gratefully acknowledge grant support from the BBSRC and NERC, CPK thanks the European Commission (6th Framework, EUCLOCK grant no 018741), which supported VZ. VZ (partly) and ERT were supported by BBSRC studentships and GF was supported by an Erasmus studentship. We thank Trudy Mackay and Paul Schmidt for generously contributing the American populations and Nishal Patel for technical support. Stefano Vanin helped VZ collect the Spanish population.
© 2017 The Authors
ASJC Scopus subject areas
- Insect Science