Geographic variation of metric properties within the neotropical sandflies.

Traditional morphometrics remains a useful tool for differentiating sandflies species, particularly closely related taxa. Within a single species, however, size variation among geographic populations might interfere with species distinction. In the past decades, a search for a metric property less prone to individual variations led to the use of ratios, and more recently to the use of size-free variables (after tentative size extraction). While morphometrics is continuously enriched with new, more efficient techniques describing shape, the question remains for the morphologist whether an efficient removing of within-species size variation is sufficient to produce stable, specific characters. Is a single species metrically recognizable in spite of its geographical variation? To address this question the intraspecific variation in 10 neotropical sandflies was examined within and between large South American ecogeographic regions: the Amazonian region, the Sub-Andean and the Chaco regions of Bolivia, and the Atlantic Coast of Brazil. Thus, the geographic stability of metric properties, as derived from measurements between landmarks, was investigated 10 times allowing a total of 29 inter-regional and 13 intra-regional conspecific comparisons. Metric proportions remained stable among conspecific populations of a single ecogeographic region. From one region to another, however, size-independent changes were significant and their amount was correlated with altitude. This could reflect an important role of some environmental changes in shaping the insects, and should be taken into account when using morphometrics to identify sandflies.