Unexpected male choosiness for mates in a spider

Abstract

Sexual selection theory traditionally considers choosiness for mates to be negatively related to intra-sexual competition. Males were classically considered to be the competing, but not the choosy, sex. However, evidence of male choosiness is now accumulating. Male choosiness is expected to increase with an individual's competitive ability, and to decrease as intra-sexual competition increases. However, such predictions have never been tested in field conditions. Here, we explore male mate choice in a spider by studying size-assortative pairing in two natural sites that strongly differ in the level of male-male competition. Unexpectedly, our results demonstrate that mate choice shifts from opportunism to high selectivity as competition between males increases. Males experiencing weak competition did not exhibit size-related mating preferences. By contrast, when competition was intense we found strong sizeassortative pairing due to male choice: while larger, more competitive males preferentially paired with larger, more fecund females, smaller males chose smaller females. Thus, we show that mating preferences of males vary with their competitive ability. The distinct preferences exhibited by males of different sizes seem to be an adaptive response to the lower reproductive opportunities arising from increased competition between males.

Reproductive Foragers: Male Spiders Choose Mates by Selecting among Competitive Environments

“…Because of this, male mate choice evolves considerably more easily when males can alter their mate preferences and reproductive behavior in response to the level of competition (Fawcett and Johnstone 2003;Härdling and Kokko 2005;Rowell and Servedio 2009;Venner et al 2010). Empirically, males are known to change their mate preferences in response to social factors such as competition from rival males (Bel-Venner et al 2008;Candolin and Salesto 2009), their recent history of mate encounters (Jordan and Brooks 2012), or the reactions of courted females (Patricelli et al 2002). By modifying their mate preferences, males that are not competitive in one context may increase their fitness by moving to social environments in which they are more likely to successfully compete (Härdling and Kokko 2005;Härdling et al 2008;Wada et al 2010), even if this means mating with females that may not be preferred in isolation.…”

Do unattractive friends make you look better? Context-dependent male mating preferences in the guppy

“…For example, in species where male-male competition is strong, the ability to physically outcompete rival males is crucial, and males are expected to prefer females associated with fewer or less aggressive, competitors, even if this means targeting low-quality females [7,8]. For example, in the spider Zygiella x-notata, males with weak competitive ability prefer less fecund females which reduces local competition with stronger rivals, and increases mating opportunities [9]. Similarly, in the three-spine stickleback (Gasterosteus aculeatus), male choosiness for larger females is reduced when the intensity of male competition increases [10].…”

The effect of male-male competition and ornament size on mean and variance of courtship intensity towards heterospecific and conspecific females

“…All males should not prefer the same female type because this will increase competition over preferred females and decrease the likelihood of obtaining the mating (Bel-Venner et al 2008). Thus, the competitive environment and male competitive ability can create variation in selectivity among males (Parker 1983, Mautz and Jennions 2011, but see Callander et al 2012.…”

“…However, this applies only if the number of mating partners exceeds the potential mating rate of the male (Härdling and Kokko 2005). On the contrary, poor competitors have less mating opportunities and should mate with every available female or even prefer low quality females to further reduce the level of male-male competition (Bel-Venner et al 2008, Venner et al 2010). This could also make low quality males more susceptible to hybridization.…”