The good fathers: efficiency of male care and the protective role of foster parents in a Neotropical arachnid

The evolution of exclusive paternal care in arthropods is influenced by both natural and sexual selection. Male care may simultaneously increase egg protection against natural enemies and male attractiveness to ovipositing females. When caring males desert or die, their clutches may be adopted either by females that provide flexible compensation of parental care or by males that may increase their own attractiveness caring for unrelated eggs. Whether foster parents are as efficient as the original owner males in protecting the clutch is a question that has rarely been addressed. Here we experimentally evaluated the efficiency of egg attendance provided by males of the mud-nest harvestman Quindina limbata. We also tested whether unattended nests are adopted by females and/or unrelated males, and compared the efficiency of the protection provided by foster parents with that provided by the original owner males. We found that when males were present inside the nest, nest visits by egg predators were much lower than in experimentally unattended nests. Ten conspecifics (8 males, 2 females) adopted experimentally unattended nests. Foster males were as efficient as the original owner males in decreasing nest visits by egg predators. The most important conclusions of our study are: (1) male protection is crucial for egg survival because unattended nests are promptly attacked by predators; (2) flexible compensation of parental care by females is rare; (3) males adopt unrelated nests and protect the eggs as efficiently as original owner males, probably because egg attendance is a sexually selected behaviour.