title: Heterospecific aggression bias towards a rarer colour morph.
abstract: Colour polymorphisms are a striking example of phenotypic diversity, yet the sources of selection that allow different morphs to persist within populations remain poorly understood. In particular, despite the importance of aggression in mediating social dominance, few studies have considered how heterospecific aggression might contribute to the maintenance or divergence of different colour morphs. To redress this gap, we carried out a field-based study in a Nicaraguan crater lake to investigate patterns of heterospecific aggression directed by the cichlid fish, Hypsophrys nicaraguensis, towards colour polymorphic cichlids in the genus Amphilophus. We found that H. nicaraguensis was the most frequent territorial neighbour of the colour polymorphic A. sagittae. Furthermore, when manipulating territorial intrusions using models, H. nicaraguensis were more aggressive towards the gold than dark colour morph of the sympatric Amphilophus species, including A. sagittae. Such a pattern of heterospecific aggression should be costly to the gold colour morph, potentially accounting for its lower than expected frequency and, more generally, highlighting the importance of considering heterospecific aggression in the context of morph frequencies and coexistence in the wild.
authors.affiliation: Section of Ecology, Department of Biology, University of Turku, Turku 20014, Finland Department of Biosciences, Åbo Akademi University, Turku 20520, Finland topilehtonen@gmail.com.
authors.forename: Topi K
authors.identifier: http://orcid.org/0000-0002-1372-9509
authors.initials: TK
authors.lastname: Lehtonen
authors.affiliation: School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Will
authors.initials: W
authors.lastname: Sowersby
authors.affiliation: School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Bob B M
authors.initials: BB
authors.lastname: Wong
mesh_terms: D000374:Aggression; D000818:Animals; D023681:Cichlids / Q000235:genetics* / Q000502:physiology*; D003116:Color; D003163:Competitive Behavior; D009527:Nicaragua; D010858:Pigmentation / Q000235:genetics; D011110:Polymorphism, Genetic; D013731:Territoriality
keywords: coexistence; colour polymorphism; fitness cost; heterospecific aggression; morph frequency; species interaction