Courtship signal evolution in Rabidosa Wolf Spiders
I am investigating the male courtship signals in two closely related species of wolf spider (Lycosidae), Rabidosa rabida and R. punctulata. These two species are syntopic, yet males exhibit very different secondary sexual characteristics, visual movements, and seismic components utilized during their courtship (click to see R. rabida and R. punctulata courtship). I hope to ascertain the various selection pressures involved in the divergence of courtship signal forms by determining their current signal function. To do this I investigate signal components in isolation as well as allowing them to interact and assess female responses.
I assess the information content of the various signal components (ornament, visual display, seismic) through diet manipulations used to diverge male condition. I also assess signal efficacy through mate choice trials where the various signal modalities are altered to eliminate transmission. Additionally, I am interested in how various signal components of complex signals interact resulting in different receiver responses. potential interactions between content-based and efficacy-based selection on signals by quantifying any impacts of condition dependent signaling (content) on signal efficacy via diet manipulation experiments.
Recently we have discovered an intriguing pattern of condition-dependent alternative mating tactics in the wolf spider Rabidosa punctulata. When encountering a female, males adopt one of two pure tactics: 1) Multimodal courtship - consisting of both a visual component (foreleg waves) and a seismic component (pedipalp stridulation), or 2) Direct mount - consisting of males grappling/holding females until female acquiescence and eventual copulation. Interestingly, large, good condition males forgo courtship and typically utilize the direct mount tactic, while small, poor condition males predominantly utilize courtship. Our initial studies suggest that large, good condition males may in fact be subjecting themselved to a more direct form (unbluffable) of assessment through direct mounting females. While small, poor condition males utilize a may indirect form of assessment, courtship, because their small size increases their vulnerability to sexual cannibalism.
My research focuses on identifying the tactic-related costs and benefits for males that has resulted in this somewhat counterintuitive pattern of mating tactic expression, where the best condition males are forgoing courtship. Several of the factors I have initially focused on include: 1) predator proximity, 2) habitat complexity, and 3) male-male competition.