Emergence patterns and latitudinal adaptations in development time of Odonata in North Sweden and Poland

Using exuviae, data are presented on emergence dates of dragonflies from northern Sweden and northwestern Poland. The 17 spp. sampled in Sweden showed considerable overlap in emergence periods. In Sweden, Leucorrhinia rubicunda was the first sp. to emerge (May 31) and Sympetrum danae the last (July 19). A comparison of first dates of emergence of spp. in Sweden and Poland showed a difference between 9 and 30 days, with all Polish spp. emerging first. Compared to spring species, summer species and obligate univoltine summer species showed less difference in first date of emergence between Swedish and Polish populations. In a laboratory experiment Leucorrhinia dubia was reared from both regions from the egg to final instar larva under northern Swedish and northwestern Polish photoperiods. Swedish larvae developed faster under a northern Swedish photoperiod compared to a northwestern Polish photoperiod. However, no such difference in development was found for northwestern Polish larvae. This suggests that there are genetic differences between both populations in response to photoperiod. The results are discussed in the context of compensation of larval development of northern populations in relation to photoperiod.