Size matters: Antagonistic effects of body size on courtship and digging in a wolf spider with non-traditional sex roles

Body size, nuptial gift characteristics and courtship behaviour, among other traits, can reflect the quality of a potential mate and, thus, might be under sexual selection. To maximize their mating success, individuals can show behavioural plasticity in sexual context. Allocosa senex is a burrow-digging wolf spider that exhibits reversal in courtship roles and in sexual size-dimorphism expected for spiders. Males construct the mating refuge and females prefer males that build longer burrows, which are considered as nuptial gifts because they are delivered to them after mating. This study aims to determine whether male body size and female reproductive status influence burrow dimensions, courtship displays, female preferences and cannibalism rate in A. senex. For that purpose, we allowed males to construct burrows and performed sexual trials under laboratory conditions. Larger males were more courted by females, and in turn, they expressed more vibratory behaviours during courtship. However, and contrary to our expectations, smaller males constructed longer burrows. We suggest that males of A. senex exhibit size-dependent behavioural plasticity, and when they are smaller, they invest more in burrow construction to compensate their lower opportunities of courting intensively as larger males. In addition, females courted differentially according to their reproductive status, overriding male preferences for virgin females. This study opens several doors to future research regarding mutual choice in A. senex and the traits assessed by males and females during courtship, as well as about the influence of intrinsic and extrinsic factors shaping reproductive decision-making in this and other wandering spider species.

Female mating status affects male mating tactic expression in the wolf spider Rabidosa punctulata

Males and females have conflicting interests on the frequency and outcomes of mating interactions. Males maximize their fitness by mating with as many females as possible, whereas choosy females often reduce receptivity following copulation. Alternative male mating tactics can be adaptive in their expression to a variety of mating contexts, including interactions with a relatively unreceptive mated female. Male Rabidosa punctulata wolf spiders can adopt distinctive mating tactics when interacting with a female, a complex courtship display, and/or a more coercive direct mount tactic that often involves grappling with females for copulation. In this study, we set up female mating treatments with initial trials and then paired mated and unmated females with males to observe both female remating frequencies and the male mating tactics used during the interactions. Males adopted different mating tactics depending on the mating status of the female they were paired with. Males were more likely to adopt a direct mount tactic with already-mated females and courtship with unmated females. Already-mated females were considerably less receptive to males during experimental trials, although they did remate 34% of the time, the majority of which were with males using a direct mount tactic. Whereas males adjusting to these contextual cues were able to gain more copulations, the observation of multiple mating in female R. punctulata introduces the potential for sperm competition. We discuss this sexual conflict in terms of the fitness consequences of these mating outcomes for both males and females.

A Probable Case of Incipient Speciation in Schizocosa Wolf Spiders Driven by Allochrony, Habitat Use, and Female Mate Choice

There is growing evidence that speciation can occur between populations that are not geographically isolated. The emergence of assortative mating is believed to be critical to this process, but how assortative mating arises in diverging populations is poorly understood. The wolf spider genus Schizocosa has become a model system for studying mechanisms of assortative mating. We conducted a series of experiments to identify the factors that control mate pair formation in a Schizocosa population that includes both ornamented and nonornamented males. We show that the population also includes two previously unrecognized female phenotypes. One female phenotype mates mostly or exclusively with ornamented males, and the other mates mostly or exclusively with unornamented males. Assortative mating within these groups is maintained by differences in maturation time, microhabitat use, and female mate preference. We conclude that the population is not a single species, as previously believed, but rather an incipient species pair with multiple overlapping mechanisms of reproductive isolation. The identification of a new incipient species pair in the well-studied and rapidly speciating Schizocosa clade presents new opportunities for the study of speciation without geographic isolation.

Male Armaments and Reproductive Behavior in "Nutcracker" Camel Crickets (Rhaphidophoridae, Pristoceuthophilus)

Males of many species possess striking weaponry used in intrasexual competition for access to females. Until recently, there were no known cases of male weaponry being used against females in sexual coercion. However, in the camel cricket, Pristoceuthophilus marmoratus, males use modified hind legs to fight with each other and also to trap females and force them to copulate. To determine whether hind leg armaments serve similar fighting and mating functions in morphologically similar congeners, we performed a comparative survey of armament use in intra- and inter-sexual interactions in four additional species of Pristoceuthophilus (P. arizonae and three undescribed species: P. 'Huachuca summer,' P. 'Madera' and P. 'Mt. Pinos'). Intrasexual leg fighting occurred in all species for which trials were performed, and hints of sexual coercion occurred in two species (P. 'Huachuca summer' and P. 'Mt. Pinos'), suggesting additional cases of a uniquely dual-purpose armament. These findings suggest an evolutionary exaptation of hind leg armaments in this genus, wherein an intrasexual fighting weapon took on a secondary function of sexual coercion.