Raw Data Pavón-Peláez et al Beh Eco Soc 2021
Description
In the spider Paratrechalea ornata, males offer either a nutritive (prey) or a worthless (prey leftovers) wrapped gift to females. Both gift types confer similar mating success and duration, and afford males a higher success rate than when they offer no gift. The nature of the gift is potentially dependent on prey availability, but it may also arise through intrinsic individual differences (male’s hunting ability). We allocated males (n = 36) to one of two groups. In the “Worthless” group, no prey items were available, while in the “Nutritive-Worthless” group, males had access to a live housefly and could produce a nutritive prey gift. In both groups, males could also produce either no gift or a worthless gift from a mealworm exuviae. We let males’ court individual females over five consecutive trials and examined the differences by using an analysis of repeatability. We found that males were plastic in their decision making, presenting the female either a nutritive or a worthless gift in the Nutritive-Worthless group. But, they were more likely to present a worthless gift in the Worthless group and when they were large. However, rather than worthless gift-giving being a cheap tactic, males highly invest in silk when producing such gifts. Our data suggest males can adjust their behaviour differentially investing in the gift content or in the silk wrapping according to prey availability and their own size. This content quality – silk-wrapping trade-off is probably determining the final fitness success of these mating tactics in P. ornata.
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To examine whether male mating tactics (nutritive/worthless/no gift) are shaped by intrinsic individual male differences, we repeatedly allowed males (N = 36) to court different females over five consecutive trials. We used 42 females that were randomly exposed several times (range 2-8) to different males. Each male was allocated to either the Worthless or the Nutritive-Worthless treatment group and then introduced to a novel female once every four days. Males in both treatment groups had comparable courting opportunities but differed in the type of gift they could produce. In the Worthless group (N = 18 males), nutrient rich prey were absent thus males could either offer no gift or a silk-wrapped worthless gift consisting of exuviae of a mealworm (Tenebrio molitor larva). In the Nutritive-Worthless group (N = 18 males), males were provided with a live housefly (Musca domestica) and exuviae of a mealworm, which allowed them to offer a silk-wrapped nutrient rich gift, a worthless gift or no gift. Data analysis We used Generalized Linear Mixed Models – GLMM in R free software (Core Team 2019). Among the running models we assessed each simplification with the Akaike Information Criterion (AIC) using the ΔAIC > 2 criterion until arriving to the most parsimonious model that could be fitted (Burnham and Anderson 2002). All selected models were subject to the customary residual analyses (Pinheiro and Bates 2006) and were found to have a satisfactory fit. Repeatability in mating tactics: individual differences We first characterized individual consistency in nuptial gift production (silk wrapping occurrence of an item) and whether individual males invest differentially in gift production (item used, latency and duration of silk wrapping and number of silk-wrapping bouts) in the Nutritive-Worthless group in which males can produce the two gift types. We estimated the individual repeatability for all reported response variables using LME with REML implemented with the rptR package (Nakagawa and Schielzeth 2010). We included gift type as a fixed effect when analysing variables related to silk investment (latency and duration of silk wrapping and number of silk-wrapping bouts). Resource dependent mating tactics: prey availability Second, we examined the effect of prey availability using a GLMM with binomial distributions and logit link function to analyse the probability of males to produce a nuptial gift (wrapped any item in silk) against not producing one, producing a worthless gift (wrapped an exuviae in silk) against the data of nutritive and no gift pooled together. We analysed the occurrence of worthless gifts within each treatment group by performing a Chi-square test of expected against observed data. Silk investment in nutritive and worthless gifts Third, we used GLMM with Gamma and Poisson distribution (log link function), to examine latency and duration of silk wrapping (min), and number of silk wrapping bouts.