Data from: Rapid experimental evolution of reproductive isolation from a single natural population

Ecological speciation occurs when local adaptation generates reproductive
isolation as a by-product of natural selection. Although ecological
speciation is a fundamental source of diversification, the mechanistic
link between natural selection and reproductive isolation remains poorly
understood, especially in natural populations. Here, we show that
experimental evolution of parasite body size over 4 y (approximately 60
generations) leads to reproductive isolation in natural populations of
feather lice on birds. When lice are transferred to pigeons of different
sizes, they rapidly evolve differences in body size that are correlated
with host size. These differences in size trigger mechanical mating
isolation between lice that are locally adapted to the different sized
hosts. Size differences among lice also influence the outcome of
competition between males for access to females. Thus, body size directly
mediates reproductive isolation through its influence on both intersexual
compatibility and intrasexual competition. Our results confirm that
divergent natural selection acting on a single phenotypic trait can cause
reproductive isolation to emerge from a single natural population in real
time.