Gait changes in a line of mice artificially selected for longer limbs.

In legged terrestrial locomotion, the duration of stance phase, i.e., when limbs are in contact with the substrate, is positively correlated with limb length, and negatively correlated with the metabolic cost of transport.

Genic capture and the genetic basis of sexually selected traits in the zebra finch.

The lek paradox, in which female choice erodes genetic variation in male sexually selected traits, is a fundamental issue in sexual selection. If females gain only genetic benefits from preferentially having their ova fertilized by males with particular traits, what maintains variation in these traits? Under strong directional selection mediated through mate choice, the alleles for beneficial male traits are expected to go to fixation and exhibit little variation. A theoretical solution to the lek paradox is the genic capture hypothesis which states that: costly male traits subject to female choice are condition dependent, that male condition is dependent on genes at many loci and exhibits additive genetic variance, and that positive genetic correlations exist between sexually selected traits and condition.

Genetic effects on sperm design in the zebra finch.

Sperm design and function are important determinants of male reproductive success and are expected to be under strong selection. The way that spermatozoa phenotypes evolve is poorly understood, because there have been few studies of the quantitative genetics of sperm. Here we show, in the zebra finch Taeniopygia guttata, an extraordinary degree of inter-male variation in sperm design that is independent of sperm swimming velocity.

Selection and utilization of spermatozoa in the reproductive tract of the female zebra finch Taeniopygia guttata.

The numbers and proportion of spermatozoa reaching different parts of the female reproductive tract after a single natural insemination were investigated in zebra finches Taeniopygia guttata. The number of spermatozoa transferred during a single, natural copulation was estimated by comparing the number of spermatozoa in the seminal glomera of males that had performed a single copulation with control males. The mean number of spermatozoa per ejaculate was 5.