Data from: Enough for all: no mating effort adjustment to varying mate availability in a gift-giving spider

Reproduction is costly and since males possess a finite energetic budget,
resource allocation to one mating event may constrain investment in
subsequent matings. Consequently, males of many species evolved to adjust
their reproductive investment in response to mating opportunities. When
female availability is high, males are predicted to partition their
reproductive effort among multiple partners to avoid resource depletion
before mating opportunities have ceased. We tested this prediction in
males of the spider Pisaura mirabilis, which mate via costly nuptial gifts
consisting of silk-wrapped prey and are known to respond to social cues
(rivals’ presence) by adjusting their reproductive investment. We
manipulated the number of females exposed to males to induce perception of
high vs low mating opportunities, and scored male investment to pre-mating
traits (time allocated to gift construction and courtship) and traits at
mating (copulation duration) during interactions with a female. We
expected males facing higher mating opportunities to reduce their
investment in all measured traits, but instead found no differences in
male trait expression. These findings indicate lack of resource
partitioning in response to variation in female availability, as males may
be able to draw resources from non-reproductive traits (growth or immune
defense), or may increase their food intake at mating by partially
consuming the nuptial gift. Hence, despite their associated costs, by
providing a source of nutrition, nuptial prey gifts may weaken selection
for adaptive plasticity in male reproductive investment.