要旨
Strongly female-biased sex ratios are typical for the fungal feeding haplodiploid Xyleborini (Scolytinae, Coleoptera), and are a result of inbreeding and local mate competition (LMC) These ambrosia beetles are hardly ever found outside of trees and thus male frequency and behavior have not been addressed in any empirical studies to date In fact, for most species the males remain undescribed Data on sex ratios and male behavior could, however, provide important insights into the Xyleborinis mating system and the evolution of inbreeding and LMC in general
In this study I used in vitro rearing methods to obtain the first observational data on sex ratio male production, male and female dispersal, and mating behavior in a xyleborine ambrosia beetle Females of Xyleborinus saxesenii Ratzeburg produced between 0 and 3 sons per brood, and the absence of males was relatively independent of the number of daughters to be fertilized and the maternal brood sex ratio Both conformed to a strict LMC strategy with a relatively precise and constant number of males If males were present they eclosed Just before the first females dispersed, and stayed in the gallery until all female offspring had matured They constantly wandered through the gallery system presumably in search of unfertilized females, and attempted to mate with larvae, other males, and females of all ages Copulations however only occurred with immature females From galleries with males nearly all females dispersed fertilized Only a few left the natal gallery without being fertilized and subsequently went on to produce large and solely male broods If broods were male less dispersing females always failed to found new galleries
