Why are there so many species? What factors account for the diversity of life we see all around us? I apply a phylogenetic perspective to questions about the evolution of novel chemical, behavioral, and ecological traits to see if they confer greater survival and reproduction and whether these traits impact rates of species diversification, primarily using insects (fireflies and leaf beetles) as model systems. I am particularly interested to know if larval defensive traits have evolved into multi-trait suites, have afforded ‘escape’ from predation, and, whether they have fostered speciation in enemy-free space. Has sustained pressure, especially if imposed by continuously adapting enemies, been strong enough to select for defense divergence, enemy targeting, or directional trends in defense efficacy? Is a defensive trait effective against a broad spectrum of enemies, or instead, does it target a particular enemy or functional guild? These questions bear on how selection has shaped the assembly of a species’ defense arsenal. The enemy spectrum that a defense thwarts depends on whether different enemies exert conflicting selection, or if enemy guilds with similar modes of attack select for the same defense. Theory predicts that trait divergence can be a response to threats from several distinct enemy types, especially when a defense against one mode of attack entails a costly functional trade-off with a second defense against another type of threat. Such negative correlations between traits have seldom been quantified, but may be detected at higher levels of multi-trait functional integration. In the limit, I want to know whether defensive traits lack strong cross-resistance, such that trade-offs within an arsenal reflect conflicting selection by multiple enemies, and if defenses (or multi-trait arsenals) increase in potency as consistent with the idea of defense escalation.
Department of Ecology and Evolution
Stony Brook University
Stony Brook, NY 11794-5245 USA