Habitat segregation of sympatric Mnais damselflies (Odonata: Calopterygidae): microhabitat insolation preferences and competition for territorial space

Abstract

Distribution and abundance of sympatric Mnais costalis and M. pruinosa damselflies were studied in a low mountain stream in Shiga, Japan, from 2008 through 2012. The reproductive seasons of the two species overlapped almost entirely: both species emerged in early May and disappeared in late June each year. Males of both species hold territories within the same stretch of the river; however, M. costalis was more abundant on the lower stream, while M. pruinosa was more abundant on the upper stream. Canopy openness varied at territorial sites. Results of these observations suggest that habitat segregation of the two species is due to different preference for light/shade conditions. Morisita’s R
_δ index suggests that interspecific exclusion (or avoidance) contributes to the habitat segregation of the two species.

Keywords: Odonata, damselfly, habitat preference, light condition, exclusiveness, Mnais costalis, Mnais pruinosa

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