Open AccessDual function and associated costs of a highly exaggerated trait in a cichlid fish
Author(s) -
Rometsch Sina J.,
TorresDowdall Julián,
MachadoSchiaffino Gonzalo,
Karagic Nidal,
Meyer Axel
Publication year - 2021
Publication title -
ecology and evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.17
H-Index - 63
ISSN - 2045-7758
DOI - 10.1002/ece3.8383
Subject(s) - sexual selection , cichlid , trait , mate choice , natural selection , biology , fish <actinopterygii> , ornaments , secondary sex characteristic , scramble competition , selection (genetic algorithm) , competition (biology) , demography , zoology , ecology , fishery , geography , population , mating , computer science , programming language , biochemistry , archaeology , artificial intelligence , sociology , hormone , style (visual arts)
Exaggerated secondary sexual characteristics are apparently costly and seem to defy natural selection. This conundrum promoted the theory of sexual selection. Accordingly, exaggerated secondary sexual characteristics might be ornaments on which female choice is based and/or armaments used during male–male competition. Males of many cichlid fish species, including the adaptive radiation of Nicaraguan Midas cichlids, develop a highly exaggerated nuchal hump, which is thought to be a sexually selected trait. To test this hypothesis, we conducted a series of behavioral assays in F2 hybrids obtained from crossing a species with a relatively small hump and one with an exaggerated hump. Mate‐choice experiments showed a clear female preference for males with large humps. In an open‐choice experiment with limited territories, couples including large humped males were more successful in acquiring these territories. Therefore, nuchal humps appear to serve dual functions as an ornament for attracting mates and as an armament for direct contest with rivals. Although being beneficial in terms of sexual selection, this trait also imposes fitness costs on males possessing disproportionally large nuchal humps since they exhibit decreased endurance and increased energetic costs when swimming. We conclude that these costs illustrate trade‐offs associated with large hump size between sexual and natural selection, which causes the latter to limit further exaggeration of this spectacular male trait.