Heterospecific courtships, Allee-effects and niche separation between Leptidea sinapis and Leptidea reali
(English)Manuscript (preprint) (Other (popular science, discussion, etc.))
Increasing attention is given to coevolutionary studies and to the role of ecology in local adaptation. The coevolutionary process can act in parallel throughout the distribution of species that interact in similar ecologies, whereas species interacting in varied ecological conditions might coevolve in different directions in different local populations. The butterflies Leptidea sinapis and L. reali have partitioned their niches differently in different parts of their sympatric distribution, with one species being a local habitat generalist in several different regions, and a local specialist in other areas where the sister species has adopted the habitat generalist role. Niche separation is likely independent of resource competition in this phytophagous system, and we study the potential for heterospecific sexual interference competition to redefine the suitability of a habitat and select for niche separation. We used the average female mating success in large outdoor cage experiments that varied both the absolute and relative density of the two species to estimate potential fitness costs of being in local minority. The mating success was unaffected by absolute density (conspecifics/m2) but strongly affected by the proportion of con- and heterospecifics in each cage. The proportion of mated females was ten times higher when a conspecific couple spent the day alone in the cage compared to when the single couple shared the cage with five heterospecific pairs. Being in the minority thus resulted in strong sexual interference from the locally more common competitor. We propose that these Allee effects select for habitat specialisation in the locally rare species as individuals leaving the core population likely suffer decreased fitness from spending time in heterospecific courtship. Hence, habitat suitability might depend less on local resource availability and more on the presence or absence of a local sexual competitor in this system.
Lepidoptera: Pieridae; sexual interference; male harassment; geographic mosaic; coevolution; mating success; source-sink; local adaptation; character displacement
IdentifiersURN: urn:nbn:se:su:diva-30792OAI: oai:DiVA.org:su-30792DiVA: diva2:274094