CAN BREEDING HABITAT BE SEXUALLY SELECTED?

Abstract

I propose that sexual dynamics, through mechanisms of sexual selection, can in part determine what constitutes specific breeding habitat. In this view, breeding-habitat features chosen by organisms, like certain morphological or other behavioral traits they exhibit, can be sexually selected, with the consequence that breeding habitats may not be uniquely aligned for ecological niche requirements. I distinguish sexual selection from natural selection because I mean to contrast sexual natural selection (sexual selection) from nonsexual natural selection (ecological selection). Thus, I suggest that ecological selection, acting on traits related to physical resources, and sexual selection, acting on traits related to mate choice, are potentially conflicting forces acting on breeding-habitat specificity. It is hardly novel to contend that sexual relations influence spatial patterns, but those influences have always been believed to operate within the confines of habitat sculpted by ecological selection. Here, sexual selection defines, in part, what constitutes breeding habitat. Certain predictions arise if sexual selection generates breeding-habitat specificity. Breeding habitat must be specific, though regional differences, including dramatic ones, are consistent with the idea. A shift in, or relaxation of, such specificity in nonbreeding situations is expected, given the flexibility in exploiting resources. Generalized traits, such as beaks equipped to exploit a variety of food sources, are predicted to prevail, because adaptive constraints from one period may compromise adaptive solutions for another. Finally, we would expect social factors to influence habitat occupancy