Morphometrics of a neotropical sandfly subspecies, Lutzomyia carrerai thula

In spite of obvious and frequently observed morphological variation in geographic populations of sand flies, taxonomists are reluctant to create subspecies. In doing so they avoid confusion caused by the accumulation of new taxa, but they also obscure natural processes, some of them related to probable species emergence. We investigated here how far the partitioning of size, shape and form could be a relevant technique for exploring early evolutionary processes. We used a typical case of species, subspecies and cryptic species among three related taxa: Lutzomyia carrerai, its subspecies L. carrerai thula and L. yucumensis, a cryptic species of L. carrerai. Univariate and multivariate metric analyses showed global size differences, even between sympatric taxa (L. carrerai and L. yucumensis). When allometric effects were discounted, the subspecies L. c. thula still disclosed important differences from its putative type species, more pronounced than those existing between the two cryptic species, L. yucumensis and L. carrerai. A similar result was obtained after removing isometric size. These analyses question the validity of L. carrerai thula as a subspecies, and show that morphometrics may be a useful tool for separating simple geographic variation from evolutionary divergence.