Data from: Moderate heritability and low evolvability of sperm morphology in a species with high risk of sperm competition, the collared flycatcher Ficedula albicollis

Spermatozoa represent the morphologically most diverse type of animal
cells and show remarkable variation in size across and also within
species. To understand the evolution of this diversity, it is important to
reveal to what degree this variation is genetic or environmental in origin
and whether this depends on species’ life‐histories. Here we applied
quantitative genetic methods to a pedigreed multigenerational data set of
the collared flycatcher Ficedula albicollis, a passerine bird with high
levels of extra‐pair paternity, to partition genetic and environmental
sources of phenotypic variation in sperm dimensions for the first time in
a natural population. Narrow‐sense heritability (h2) of total sperm length
amounted to 0.44±0.14 SE while the corresponding figure for evolvability
(estimated as coefficient of additive genetic variation, CVa) was
0.02±0.003 SE. We also found an increase in total sperm length within
individual males between the arrival and nestling period. This seasonal
variation may reflect constraints in the production of fully elongated
spermatozoa shortly after arrival at the breeding grounds. There was no
evidence of an effect of male age on sperm dimensions. In many previous
studies on laboratory populations of several insect, mammal and avian
species, heritabilities of sperm morphology were higher while
evolvabilities were similar. Explanations for the differences in
heritability may include variation in the environment (laboratory vs.
wild), intensity of sexual selection via sperm competition (high vs. low)
and genetic architecture that involves unusual linkage disequilibrium
coupled with overdominance in one of the studied species.