Females of a gift-giving spider do not trade sex for food gifts: a consequence of male deception?

Abstract

BackgroundPolyandry is commonly maintained by direct benefits in gift-giving species, so females may remate as an adaptive foraging strategy. However, the assumption of a direct benefit fades in mating systems where male gift-giving behaviour has evolved from offering nutritive to worthless (non-nutritive) items. In the spider Paratrechalea ornata, 70% of gifts in nature are worthless. We therefore predicted female receptivity to be independent of hunger in this species. We exposed poorly-fed and well-fed females to multiple males offering nutritive gifts and well-fed females to males offering worthless gifts.ResultsThough the treatments strongly affected fecundity, females of all groups had similar number of matings. This confirms that female receptivity is independent of their nutritional state, i.e. polyandry does not prevail as a foraging strategy.ConclusionsIn the spider Pisaura mirabilis, in which the majority (62%) of gifts in nature are nutritive, female receptivity depends on hunger. We therefore propose that the dependence of female receptivity on hunger state may have evolved in species with predominantly nutritive gifts but is absent in species with predominantly worthless gifts.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-017-0953-8) contains supplementary material, which is available to authorized users.

Differential allocation in a gift-giving spider: males adjust their reproductive investment in response to female condition

“…Theoretical and empirical studies on differential allocation indicate that individuals can either increase or decrease their parental effort in response to the quality of their mating partners [9,13,66]. Previous studies with P. ornata show that the nuptial gift also functions as paternal effort because well-fed females that receive a nutritious gift lay more eggs than well-fed females that receive a worthless gift [38]. Thus, males could construct larger gifts when exposed to low-quality females to increase the fecundity of their partners and gain more fitness benefits.…”

“…Moreover, chemicals deposited by the male on the silk layer surrounding the gift entice the female to grab it [36], and the larger the gift, the longer copulation duration is [37]. Finally, the consumption of nutritive prey-gifts by females increases their fecundity, indicating that the offspring receives part of the nutrients contained in the gift [38]. Taken together, these findings indicate that preygifts in P. ornata entice females to copulate (i.e., mating effort) and provide food resources that enhance offspring production (i.e., paternal effort).…”

Males of a Neotropical spider adjust prey‐gift construction but not mate search in response to sperm competition

“…The duration of each copulation positively correlates with prey‐gift size (Klein et al, 2014), potentially allowing the male to transfer more sperm to the female. This higher investment in sperm transfer should increase male fitness in a context of sperm competition, as females can mate multiply (Pandulli‐Alonso et al, 2017). Therefore, while the prey‐gift is mainly a mating effort (Albo & Costa, 2010), it also influences how much a male will succeed in post‐mating competition.…”

“…Because P . ornata females are polyandrous (Pandulli‐Alonso et al, 2017), sperm competition is probably an important factor determining male reproductive success. Thus, we hypothesized that males should increase their reproductive effort as they perceive the risk of sperm competition (following the model by Parker et al, 2013).…”

Differential allocation in a gift-giving spider: males adjust their reproductive investment in response to female condition.

“…Finally, the consumption of nutritive prey-gifts by females increases their fecundity, indicating that the offspring receives part of the nutrients contained in the gift [38]. Taken together, these findings indicate that prey-gifts in P. ornata entice females to copulate (i.e., mating effort) and provide food resources that enhance offspring production (i.e., paternal effort).…”