Gone with the rain: negative effects of rainfall on male reproductive success in a nest-building arachnid

In nest-building species, offspring survival and reproductive success of parental individuals are strongly influenced by nest quality. Thus, quantifying the influence of abiotic conditions on nest integrity is important to predict the effects of weather variability on the fitness of parental individuals. Here, we investigated how rainfall affects nest integrity and how nest integrity influences males’ attractiveness and nest tenure. Our study species was the harvestman Quindina limbata, in which males build mud nests on fallen logs and protect the eggs against predators and fungi. Our data set comprises 12 months of regular inspections of 149 nests in a Costa Rican rainforest. We found that almost 50% of the nests were destroyed by rainfall. The drag force caused by rainfall running on the fallen log surface negatively affected nest integrity. Fungi cover on nests was influenced by an interaction between rainfall and nest position on the fallen log. Irrespective of their body size, males in nests with high integrity received more eggs than males in nests with low integrity. Fungi cover did not influence the number of eggs received by the males. Finally, nest integrity and fungi cover did not affect nest tenure, but males that did not receive eggs for a long time tended to abandon their nests. Considering that intense rainfall occurs all year long in tropical forests, males should build their nests in protected sites that preserve nest structure. Protected sites may keep nest structure better preserved, improve offspring survival, attract more females, and increase males’ reproductive success. The reproductive success of nest-building individuals is strongly influenced by nest quality. We investigated how rainfall affects nest integrity and consequently male mating success in an arachnid with exclusive paternal care. Rainfall destroyed 50% of the nests, and damage extension depended on precipitation volume and nest location. Males in high-integrity nests received more eggs than males in low-integrity nests. Thus, males should build nests in protected sites to preserve nest integrity and attract more females.