title: Non-random brood mixing suggests adoption in a colonial cichlid.
abstract: Parental care of unrelated offspring is widespread but not well understood. We used 11 polymorphic microsatellite loci to investigate the relatedness of fry and parentally caring adults in a 118-nest colony of the socially and genetically monogamous cichlid fishNeolamprologus caudopunctatusin Lake Tanganyika. There was a high proportion of brood mixing, with 59% of 32 broods containing fry unrelated to both parents, and 18% of all 291 sampled fry being unrelated to the breeding pair. There was no evidence of kin selection for adoption because the genetic and foster parents were not more related than expected by chance. Parentage was assigned to 12 adopted fry from 10 broods. Distances traversed by fry varied markedly, from less than one to over 40 meters. The larger distances suggest that at least some brood mixing was instigated by parents transporting portions of their broods in their mouths, as occurs in some cichlids. Further evidence of non-random brood mixing was that foreign fry did not differ in size from their foster siblings within broods, even though they were significantly larger than fry produced by the tending pairs within the colony. These findings suggest that at least some foreign fry had dispersed non-randomly and were adopted by their foster parents. Enlarged broods are known to provide reduced per capita predation, making it potentially adaptive for breeders to adopt unrelated offspring.
authors.affiliation: Konrad Lorenz Institute of Ethology, Austrian Academy of Sciences, and Department of Integrative Biology and Evolution, Veterinary University of Vienna and the Austrian Academy of Sciences, Savoyenstrasse 1a, 1160 Vienna, Austria.
authors.forename: Franziska C
authors.initials: FC
authors.lastname: Schaedelin
authors.forename: Wouter F D
authors.initials: WF
authors.lastname: van Dongen
authors.forename: Richard H
authors.initials: RH
authors.lastname: Wagner
keywords: adoption; brood farming out; brood mixing; cichlid; microsatellite analysis; parental care; parental investment