INTERSPECIFIC COMPETITION FOR TREE HOLES - CONSEQUENCES FOR MATING SYSTEMS AND COEXISTENCE IN NEOTROPICAL DAMSELFLIES

Male mating strategies of pseudostigmatid damselflies that breed in tree holes vary from resource defense to nonlocalized mate searching. Because females were most predictably found in forest light gaps and oviposited randomly with respect to tree-hole volume, morphology, and tree condition, the spatial distribution of neither females nor oviposition sites sufficiently accounted for differences in male mating strategies. Tree holes over 1 L in volume were the best larval habitats because they supported multiple cohorts per season. The two largest species emerged from larger tree holes than did the two smaller guild members. A laboratory experiment demonstrated that in large holes, small individuals of Megaloprepus eventually killed larger individuals of the two smaller Mecistogaster species, whereas Mecistogaster survived to emergence in small holes if they were the first to hatch there. A field experiment demonstrated that Mecistogaster colonized tree holes earlier in the wet season than did the two larger guild members, thereby gaining the head start in growth critical to its survival. The inferior competitive ability of its larvae countered any advantage that Mecistogaster adult males might otherwise derive from defending tree holes and resulted in seasonal clumping of emerging adults. In contrast, by defending large tree holes, male Megaloprepus coerulatus increased their chances of producing multiple offspring and sons of high quality.