Abstract
Alloparental care – care for unrelated young – is rare in animals, and its ecological or evolutionary advantages or, alternative maladaptive nature, remain unclear. We investigate alloparental care in the socially monogamous cichlid fish Perissodus microlepis from Lake Tanganyika that exhibits bi‐parental care. In a genetic parentage analysis, we discovered a surprisingly high percentage of alloparental care represented by brood mixing, extra‐pair paternity and extra‐pair maternity in all broods that we investigated. The percentage of nondescendant juveniles of other parents, i.e., brood mixing, ranged from 5% to 57% (mean = 28%). The distribution of genetic parentage also suggests that this socially monogamous species has, in fact, polygamous mating system. The prevalence of genetically mixed broods can be best explained by two, not mutually exclusive hypotheses on farming‐out and fostering behaviors. In the majority of broods, the sizes of the parents’ own (descendant) offspring were significantly larger than those of the adopted (nondescendant) juveniles, supporting the ‘selfish shepherd effect’ hypothesis, i.e., that foster parents preferentially accept unrelated “smaller or not larger” young since this would tend to lower the predation risks for their own larger offspring. There was also a tendency for larger parents particularly mothers, more so than smaller parents, to care predominantly for their own offspring. Larger parents might be better at defending against cuckoldry and having foreign young dumped into their broods through farming‐out behavior. This result might argue for maladaptive effects of allopatric care for the foster parents that only larger and possibly more experienced pairs can guard against. It needs to be determined why, apparently, the ability to recognize one's own young has not evolved in this species.
Highlights
Parental care behavior evolves in response to the interplay of mating system, sexual selection, reproductive biology and ecology (e.g., Baylis 1981; Keenleyside 1991)
Ecology and Evolution published by John Wiley & Sons Ltd
Evidence is accumulating that alloparental care can increase the fitness of alloparents through (1) protection of their young against predation (Wisenden 1999) or (2) mating benefits [e.g., female mating a 2016 The Authors
Summary
Parental care behavior evolves in response to the interplay of mating system, sexual selection, reproductive biology and ecology (e.g., Baylis 1981; Keenleyside 1991). Alloparental care – care for nondescendant young through brood mixing and/or extra-pair matings (Wisenden 1999) – is a rare, but taxonomically widespread, phenomenon that is found in several groups of animals including mammals and birds (Riedman 1982), social insects (Hogendoorn et al 2001) and fishes The ecological circumstances that favor alloparental care and its evolutionary origins and benefits remain controversial since, obviously, investment in nondescendant young is expected to incur fitness costs on the caregiver while the potential fitness benefits often remain unclear (CluttonBrock 1991; Roldan and Soler 2011).
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