title: Observations on sex ratio and behavior of males in Xyleborinus saxesenii Ratzeburg (Scolytinae, Coleoptera).
abstract: Strongly female-biased sex ratios are typical for the fungalfeeding 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 Xyleborini's 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.
authors: Department of Behavioural Ecology, Institute of Ecology and Evolution, University of Bern, Baltzerstrasse 6, 3012 Bern, Switzerlan.
authors: Peter
authors: P
authors: H W Biedermann
references: J Evol Biol. 2004 Mar;17(2):257-64
references: 15009259
references: Bull Entomol Res. 2001 Aug;91(4):255-64
references: 11587621
references: Proc Natl Acad Sci U S A. 1995 Oct 10;92(21):9861-5
references: 7568233
references: Bull Entomol Res. 2010 Apr;100(2):231-9
references: 19698196
references: Science. 1967 May 26;156(3778):1120-2
references: 6024191
references: Nat New Biol. 1972 Mar 29;236(65):111-2
references: 4502806
references: Evolution. 2004 Apr;58(4):790-8
references: 15154555
references: Proc Natl Acad Sci U S A. 2004 Apr 27;101(17):6520-3
references: 15087494
references: Am Nat. 2002 Oct;160 Suppl 4:S67-98
references: 18707454
references: Microb Ecol. 1985 Sep;11(3):267-76
references: 24221366
references: Environ Entomol. 2009 Aug;38(4):1096-105
references: 19689888
references: Science. 1967 Apr 28;156(3774):477-88
references: 6021675