Ingi Agnarsson, Fi-Niaina Ramahefarisonc, Heiða Hlín Matthíasdóttir, Leyla Kudari, Magnús Máni Dagsson, Nína Guðrún Baldursdóttir, Ragnhildur Sara Bergsdóttir, Rakel Bærings Halldórsdóttir, Snorri Björn Magnússon, Snædís Huld Björnsdóttir, Matjaz Gregorič

Kleptoparasitism, the theft of resources from another organism, is a survival strategy found across the animal kingdom. Many argyrodinae cobweb spiders (Theridiidae) are obligatory kleptoparasites that have largely abandoned web building, relying instead on webs of larger hosts. Theory predicts, and limited prior research indicates, that kleptoparasites are not randomly distributed among host webs, and prior studies indicate that web architecture (size and tenure) and prey availability impact kleptoparasite abundance and host choice. We investigate the distribution of multiple argyrodine kleptoparasite species among three contrasting host types in Madagascar's Analamazaotra National Park: Nephilingis (Nephilidae, large nocturnal orb weavers), Caripetella (Pisauridae, large nocturnal sheet web builders), and Anelosimus (Theridiidae, small cathemeral social spiders constructing three-dimensional tangle webs). Although small in scope, this study is the first to take a real-time snapshot of multi-species endemic communities of spider kleptoparasites and their in-situ distribution across contrasting host webs. We found an unexpectedly high diversity of ten kleptoparasite species that, remarkably, are not conspecific with the five that were previously known from all of Madagascar. Kleptoparasite species composition and abundance varied across the three hosts: some appeared host-specific while others seemed versatile. In general, argyrodine kleptoparasites evidently discriminate among hosts but choose among them with varying degrees of astucity. At the community level, very limited data exist, and based on our study we can only speculate that species assembly into host webs involves a complex interplay between host preference and species competitive hierarchy. Future field research should investigate this system as a community of multiple interacting species to gain a more comprehensive understanding of the rules that may govern the assembly of diverse kleptoparasites into equally variable host webs. Synergistically, laboratory experiments are needed to elucidate key cues facilitating kleptoparasite web detection and choice; likely involving eavesdropping on pheromones intended for the hosts male.