MORPHOMETRIC PATTERNS AMONG DIVING BEETLES (COLEOPTERA, NOTERIDAE, HYGROBIIDAE, AND DYTISCIDAE)

A study of shape and size in relation to swimming strategies among Hyd radephaga, with an emphasis on Dytiscidae, was performed with nearly 1 600 adult specimens belonging to the families Noteridae (2 species), H ygrobiidae (1 species), and Dytiscidae (74 species). The data were stu died by means of bivariate correlations, scatter plots, and two multiv ariate statistical methods (factor and cluster analysis). The main mor phometric groups found included (i) large to medium-sized, streamlined , wide species with the maximum width in the rear part of the body and the maximum height in the front part, with short tibiae and long tars i; they are considered to be adapted to high-speed swimming in open wa ters; (ii) small to medium-sized species with a spherical body and lon g femora; they are considered to be adapted to manoeuvring in stagnant waters; (iii) small species with a discontinuous outline, a narrow bo dy, and long, slender legs; they are considered to be poor swimmers in running waters; and (iv) small to medium-sized species having, in gen eral, a streamlined, relatively high body with short, wide legs; they are considered to be adapted to crawling among dense vegetation or det ritus. Despite the clear relationships between systematics and morphom etry, most characters were found to be homoplastic a number of times w ithin the families studied. This supports the adaptive interpretation of the morphometry of the species.