Nest‐site selection in a neotropical arachnid with exclusive male care: Proximate cues and adaptive meaning

Nest‐site selection is a crucial decision made by parents because inadequate sites may expose the offspring and the parent to harsh abiotic and biotic conditions. Although nest‐site selection has been reported for some species of arthropods, the proximate cues used by parents to select the nest site and the adaptive meaning of nest‐site selection are still poorly understood. We investigated nest‐site selection in the harvestman Quindina limbata, in which males build mud nests on the surface of fallen logs and perform parental care. This species inhabits tropical forests where rainfall destroys nearly 50% of the nests, representing an important selective force shaping nest‐site selection. We followed 139 nests and recorded the position (angle) where these nests were located on the fallen log surface. Males showed a complex pattern of nest‐site selection that responded to three proximate cues: the direct impact of raindrops on the upper half of the fallen log, the drag force caused by flowing water on the laterals of the fallen log, and water saturation on the lowest part of the fallen log. These selective pressures created a bimodal pattern of nest distribution on the lower half of the fallen logs. The peaks of this distribution occurred in places where nests are protected from the direct impact of raindrops, the drag force caused by flowing water is not high, and the risk of nest flooding is low. The possible adaptive meaning of nest‐site selection is to minimize the risk of nest destruction, which imposes energetic costs to males that need to build another nest. Nest‐site selection may also minimize reproductive costs because males with damaged nests show decreased attractiveness to females. Finally, nest‐site selection may increase offspring fitness minimizing the risk of egg mortality associated with nest destruction and anoxia when nests are flooded. Males of a neotropical arachnid build mud nests on fallen logs and care for the eggs laid inside them. The peaks of nest distribution around the fallen logs occur in places where nests are protected from the direct impact of raindrops, the drag force caused by flowing water is low, and the risk of nest flooding is low. Nest‐site selection minimizes the risk of nest destruction, increases male attractiveness because females avoid damaged nests, and probably decreases egg mortality.