Different seasonal prevalences and life history in alien species Rhagadotarsus kraepelini and native species Aquarius paludum paludum (Hemiptera: Gerridae) in Japan

Abstract

We compared seasonal prevalences, proportion of long-winged morphs, and reproductive traits of females, in two water strider species, the alien species Rhagadotarsus kraepelini and the native species Aquarius paludum paludum, in Wakayama Prefecture, Japan. We sampled both species at four permanent and two vernal ponds from March to December 2009. In their natural habitats, R. kraepelini can show more than four generations per year, and A. paludum can do two ones, respectively. Eggs of R. kraepelini, which were deposited in floating plant litter, could survive dry and cold habitats for 4 months or more in winter. Whereas the proportion of long-winged A. paludum morphs decreased during the summer, that of long-winged R. kraepelini morphs was very low except during late summer. The number of reproductively viable A. paludum females decreased in September. Conversely, many females of R. kraepelini developed reproductive systems into November and only disappeared in early December. These results suggest that both traits of r strategist in R. kraepelini can be succeeded in Japan.