Sperm morphology is highly variable across animals and is a great model for studying the evolution of sexually selected traits.
Ariel Kahrl, a Ph.D. student in Bob Cox’s lab at the University of Virginia, gave a talk on a study which she and coauthor Cox did just that. They sampled sperm from native and introduced populations of Anolis sagrei, A. distichus, and A. cristatellus to look at variation in morphology.
Interestingly, they found that introduced and native populations often varied in sperm morphology (i.e., head, midpiece, and tail lengths). Moreover, these effects were consistent between the three species tested!
Kahrl also pointed out that the variation observed in sperm morphology between males of a single species was often as large as that observed between different species. This study suggests that sperm morphology is highly plastic and/or is capable of rapid evolution in response to environmental change. Further work is needed to elucidate what selective pressures are driving the variation observed between introduced and native populations of these three species.