Morphometrics of a neotropical sandfly subspecies, Lutzomyia carrerai thula

In spite of obvious and frequently observed morphological variation in geog raphic populations of sand flies, taxonomists are reluctant to create subsp ecies. In doing so they avoid confusion caused by the accumulation of new t axa, but they also obscure natural processes, some of them related to proba ble species emergence. We investigated here how far the partitioning of siz e, shape and form could be a relevant technique for exploring early evoluti onary processes. We used a typical case of species, subspecies and cryptic species among three related taxa: Lutzomyia carrerai, its subspecies L. car rerai thula and L. yucumensis, a cryptic species of L. carrerai. Univariate and multivariate metric analyses showed global size differences, even betw een sympatric taxa (L. carrerai and L. yucumensis). When allometric effects were discounted, the subspecies L. c. thula still disclosed important diff erences 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 morphometr ics may be a useful tool for separating simple geographic variation from ev olutionary divergence. (C) 2000 Academie des sciences/Editions scientifique s et medicales Elsevier SAS.