Open AccessSperm size evolution in African greenbuls (Passeriformes: Pycnonotidae)
Author(s) -
Omotoriogun Taiwo C.,
Albrecht Tomas,
Hořák David,
Laskemoen Terje,
Ottosson Ulf,
Rowe Melissah,
Sedláček Ondřej,
Lifjeld Jan T.
Publication year - 2016
Publication title -
biological journal of the linnean society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.906
H-Index - 112
eISSN - 1095-8312
pISSN - 0024-4066
DOI - 10.1111/bij.12663
Subject(s) - biology , sperm competition , sperm , evolutionary biology , phylogenetic tree , sexual selection , passerine , lineage (genetic) , zoology , phylogenetics , female sperm storage , clade , mating system , mating , genetics , gene
Sperm morphology is highly diversified across the animal kingdom and recent comparative evidence from passerine birds suggests that postcopulatory sexual selection is a significant driver of sperm evolution. In the present study, we describe sperm size variation among 20 species of African greenbuls and one bulbul (Passeriformes: Pycnonotidae) and analyze the evolutionary differentiation of sperm size within a phylogenetic framework. We found significant interspecific variation in sperm size; with some genera exhibiting relatively long sperm (e.g. Eurillas ) and others exhibiting short sperm head lengths (e.g. Phyllastrephus ). However, our results suggest that contemporary levels of sperm competition are unlikely to explain sperm diversification within this clade: the coefficients of inter‐male variation ( CV bm ) in sperm length were generally high, suggesting relatively low and homogeneous rates of extra‐pair paternity. Finally, in a comparison of six evolutionary or tree transformation models, we found support for both the Kappa (evolutionary change primarily at nodes) and Lambda (lineage‐specific evolutionary rates along branches) models in the evolutionary trajectories of sperm size among species. We therefore conclude that African greenbuls have more variable rates of sperm size evolution than expected from a neutral model of genetic drift. Understanding the evolutionary dynamics of sperm diversification remains a future challenge.