Helpende en misleidende signalen in vrouwelijke lichaamskleur bij het Lantaarntje (Ischnura elegans)

Hammers, M. & H. Van Gossum, 2012. Helping and misleading signals in female body coloration in Ischnura elegans. Brachytron 15(1): 16-24. Various animal species show coexistence of differently colored and genetically inherited phenotypes. Sometimes these polymorphisms only occur in one sex, either only in males or only in females. When only occurring in females, this is considered to result from sexual conflict. Sexual conflict occurs when males and females differ in their optimal number of matings. In promiscuous species, male reproductive success typically increases with increasing numbers of matings, while for females just a few matings are optimal. Further matings are costly and reduce female reproductive success. In the damselfly Ischnura elegans, mature females occur as one of three differently coloured morphs. In addition, each of these morphs undergoes irreversible colour changes from immature to mature age. Intriguingly, one of the mature female morphs shows resemblance in phenotype to the conspecific male, specifically in body colouration (andromorph), The other two female morphs show different body colouration (gynomorphs). We explored three main questions concerning the occurrence and coexistence of these different female morphs in the damselfly I. elegans. Firstly, we asked whether variation in the relative frequencies of different female morphs occurs among populations and whether social or environmental factors can explain patterns in such variation. Among populations, large variation in female morph frequencies was observed, with andromorphs sometimes being the least, and sometimes being the most abundant female morph. Andromorph frequencies declined across populations with increasing ambient temperature. Secondly, we explored if males are aided by female body colouration to find and recognize suitable mating partners. Males appeared to avoid mating immature individuals, which may be explained by differences in colour characteristics between immature and mature females. Thirdly, we asked whether andromorphs can be considered male-mimics that, as a result of their colour, succeed in reducing male harassment. Our work showed that andromorphs and males could not be distinguished based on colouration of their pale body parts. In line with this observation, males showed low mating interest for andromorphs, suggesting that andromorphs may indeed succeed in escaping from excessive male mating interest. Together our results show that colour signals by female damselflies may both help and hinder males in their mating decisions. Further, it appears that male harassment alone does not adequately explain female colour polymorphism in damselflies, and that other factors may play a significant role.