Sexual selection research on spiders: progress and biases

Abstract

The renaissance of interest in sexual selection during the last decades has fuelled an extraordinary increase of scientific papers on the subject in spiders. Research has focused both on the process of sexual selection itself, for example on the signals and various modalities involved, and on the patterns, that is the outcome of mate choice and competition depending on certain parameters. Sexual selection has most clearly been demonstrated in cases involving visual and acoustical signals but most spiders are myopic and mute, relying rather on vibrations, chemical and tactile stimuli. This review argues that research has been biased towards modalities that are relatively easily accessible to the human observer. Circumstantial and comparative evidence indicates that sexual selection working via substrate-borne vibrations and tactile as well as chemical stimuli may be common and widespread in spiders. Pattern-oriented research has focused on several phenomena for which spiders offer excellent model objects, like sexual size dimorphism, nuptial feeding, sexual cannibalism, and sperm competition. The accumulating evidence argues for a highly complex set of explanations for seemingly uniform patterns like size dimorphism and sexual cannibalism. Sexual selection appears involved as well as natural selection and mechanisms that are adaptive in other contexts only. Sperm competition has resulted in a plethora of morphological and behavioural adaptations, and simplistic models like those linking reproductive morphology with behaviour and sperm priority patterns in a straightforward way are being replaced by complex models involving an array of parameters. Male mating costs are increasingly being documented in spiders, and sexual selection by male mate choice is discussed as a potential result. Research on sexual selection in spiders has come a long way since Darwin, whose spider examples are reanalysed in the context of contemporary knowledge, but the same biases and methodological constraints have persisted almost unchanged through the current boom of research.

Spermathecal morphology and sperm dynamics in the female Schizocosa malitiosa (Araneae: Lycosidae)

“…Twentyfour hours after remating, encapsulated and decapsulated sperm cells were mixed, indicating sperm mixing rather than stratification. The absence of stratification found here agrees with many findings of sperm mixing in spiders (see Elgar, 1998;Uhl, 1998Uhl, , 2002Eberhard, 2004;Huber, 2005) and deviates from the assumption that the female genital morphology is the best predictor of sperm priority patterns (Austad, 1984). However, mixing was not complete in the head and stalk regions, and the two types of sperm cells were distributed in a heterogeneous pattern (Fig.…”

Proximate Causes of Rensch’s Rule: Does Sexual Size Dimorphism in Arthropods Result from Sex Differences in Development Time?

“…In butterflies and spiders there is a slight but nonsignificant trend toward Rensch's rule, in agreement with inconsistent previous results on spiders (cf. Head 1995;Prenter et al 1999;Hormiga et al 2000;Huber 2005). In Hymenoptera and beetles the relationship does not differ from isometry, with possibly even a hint of a pattern opposite to Rensch's rule (cf.…”

Potential for CFC in Black Widows (Genus Latrodectus): Mechanisms and Social Context

“…The possibility that these contractions could be triggered by male stimulation of the epigynal hairs during courtship and mating is particularly intriguing. Since males typically move the embolus across the epigynum multiple times before insertion is achieved, repeated contact between the pedipalps and these hairs is common ( 5,6,7 Kaston 1970) and may serve a stimulatory function ('copulatory courtship,' e.g., Huber 2005;Eberhard and Huber 2010). Whether the fertilization valve is activated during copulation, is linked to stimulation of the epigynal hairs, and whether paternity is affected could be studied with a combination of mating trials, sensory-hair ablation (e.g., Aisenberg et al 2015), muscle physiology, and freeze-fixation (Huber 1993).…”