Abstract
In nuptial gift-giving species females sometimes select their potential mates based on the presence and size of the gift. But in some species, such as the Neotropical polyandrous spider Paratrechalea ornate male gifts vary in quality, from nutritive to worthless, and this male strategy can be in conflict with female nutritional benefits. In this species, males without gifts experience a reduction in mating success and duration, while males that offer worthless or genuine nutritive gifts mate with similar frequencies and durations. The female apparently controls the duration of copulation. Thus, there is scope for females to favour males offering gifts and further if these are nutritious, via post-copulatory processes. We first tested whether females differentially store sperm from males that offer the highest nutritional benefits by experimentally presenting females with males that offer either nutritive or worthless gifts (uninterrupted matings). Second, we carried out another set of experiments to examine whether females can select sperm based only on gift presence. This time we interrupted matings after the first pedipalp insertion, thus matching number of insertions and mating duration for males that: offered and did not offer gift. Our results showed that the amount of sperm stored is positive related to mating duration in all groups, except in matings with worthless gifts. Gift presence itself did not affect the sperm stored by females, while they store similar number of sperm in matings with males offering either nutritive or worthless gifts. We discuss whether females prefer males with gifts regardless, if content, because it represents an attractive and/or reliable signal. Or alternatively, they prefer nutritive nuptial gifts, as they are an important source of food supply and/or signal of male donor ability.
Highlights
Processes of inter and intra-sexual selection have enormous potential to shape behavioural, morphological and physiological traits involved in securing copulations and fertilization
Nuptial Gift Content and Sperm Stored in Spiders sexual selection occurs internally in polyandrous females, and can comprise sperm competition [3] as well as cryptic female choice of sperm [2, 4,5,6,7,8,9] both responsible for biasing male paternity
We found a positive effect of mating duration on the number of sperm in the Fly gift-uninterrupted mating (F1,15 = 6.11, p = 0.03; Fig 3A), but not in the Worthless gift-uninterrupted mating (F1,14 = 2.87, p = 0.11; Fig 3A)
Summary
Processes of inter and intra-sexual selection have enormous potential to shape behavioural, morphological and physiological traits involved in securing copulations and fertilization. These selective pressures can act on male and female traits before (pre-copulatory), during (syn-copulatory) or after mating (post-copulatory) [1,2,3]. While sperm competition involves malesgamete competition inside the female, the idea of cryptic female choice refers to any mechanism performed by females to select malesgametes [2] These internal processes have been far complex to study because they can be shaped by either sex and by interactions between partners, as was recently discussed [10]. Female red flour beetles can differentially store sperm depending on the male physical condition, as matings with well fed males result in more sperm stored than those with starved males [5]
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