Low inbreeding depression in a sexual trait in the stalk-eyed fly Teleopsis dalmanni

Abstract

The genic capture hypothesis implies that the expression of sexual ornaments largely depends on genes affecting resource acquisition and use. The ornaments should thus show high degree of directional dominance typical of life-history traits, and conse- quently, they should be severely affected by inbreeding. Here we investigated the effect of inbreeding on a sexual ornament (male eyespan) in stalk-eyed fly, Teleopsis dalmanni. For comparison, we also measured inbreeding depression in non-sexual morphological traits: female eyespan as well as wing and thorax lengths in both sexes. Both eyespan, and other morphological traits we measured, showed significant inbreeding depression. In accord with predictions of genic capture hypothesis, male eyespan did decrease under inbreeding significantly more than female eyespan. However, the decline in male eyespan was fully explained by overall decline in body length. Moreover, the magnitude of inbreeding depression in male eyespan was considerably lower than that typically observed for life- histories; in fact, it fitted within the range typically characterizing morphological traits. We therefore conclude that our results provide weak support for genic capture hypothesis.