Mating in the harvestman Leiobunum vittatum (Arachnida: Opiliones): from premating struggles to solicitous tactile engagement

Abstract

When mating interactions are influenced by multiple sources of selection, they may involve multiple stages of mate assessment. At each stage, a different set of morphological and behavioural traits may be important in determining the outcome of the interaction. Here, we test the potential for multiple sources of selection to shape mating interactions in Leiobunum vittatum harvestmen, commonly known as ‘daddy longlegs’. We provide a qualitative and quantitative study of mating interactions, and investigate the influence of multiple morphological traits on each of several distinct stages of their mating interactions. Mating interactions start with a struggle between males and females during which the male attempts to secure the females in a mating embrace. Success at this stage depends on the length of the male’s clasping pedipalps: those with shorter pedipalps (and thus greater mechanical advantage) were more successful. Male size relative to the female determines how quickly males achieve this embrace. Mating interactions then proceed to tactile exchanges between males and females, indicating the potential for mutual mate choice and/or peri- and post-copulatory selection. We found no morphological predictors of the timing of these later stages of the mating interactions, and suggest that the exchange of a nuptial gift is important for the dynamics of these stages. Overall, our results highlight L. vittatum as a potentially highly informative group for studying how traits involved in mating are shaped by the interaction of selection across multiple stages in mating interactions.

Male and Female Mate Choice in Harvestmen: General Patterns and Inferences on the Underlying Processes

“…However, pre-copulatory cannibalism has never been recorded in harvestmen (Acosta and Machado 2007), and in most species, males seem unable to detect females until direct physical contact is established (e.g., Willemart et al 2006;Fowler-Finn et al 2014). Once male and female detect each other, pre-copulatory interactions are generally brief and involve mostly tactile and close range chemical stimuli (Machado and Macías-Ordóñez 2007;Fig.…”

“…The subject "reproduction" is perhaps the most emblematic of such a fast advance. From 2007 to now, the existence of male dimorphism and alternative reproductive tactics has been discovered in many species , several new cases of both maternal and paternal care have been described (Requena et al 2013;Buzatto et al 2013), correlates of male mating success have been investigated (e.g., Buzatto and Machado 2008;Nazareth and Machado 2010;Fowler-Finn et al 2014), and the use of phylogenetic information to infer the evolution of sexually selected traits has increased (e.g., Burns et al 2013;.…”

Mating Is a Give-and-Take of Influence and Communication Between the Sexes

“…Consider mating behavior in Leiobunum vittatum harvestmen (Fowler-Finn et al 2014). Mating in this species begins when the male pounces on the female, wraps his legs around hers, and hooks his pedipalps on the base of her legs as she struggles and bobs.…”

“…In such cases, female tapping could be interpreted as solicitation of the nuptial gift and guiding the penis toward her as securing the nuptial gift. Also, because the females' mouthparts and genital opening are close by, it is difficult to distinguish oral from genital insertion (Fowler-Finn et al 2014). But even if a nuptial gift is involved, no intromission (whether oral or genital) ever occurred without the females' apparent help (Fowler-Finn et al 2014).…”

“…Also, because the females' mouthparts and genital opening are close by, it is difficult to distinguish oral from genital insertion (Fowler-Finn et al 2014). But even if a nuptial gift is involved, no intromission (whether oral or genital) ever occurred without the females' apparent help (Fowler-Finn et al 2014). Thus, even if females were soliciting a direct benefit from the males, they also helped them achieve intromission in every observed instance.…”