Morphometric Studies between Allopatric Populations of Pterophylla beltrani Bolivar and Bolivar and P. robertsi Hebard (Orthoptera: Tettigoniidae)

Abstract

The genus Pterophylla Kirby is characterized by great morphometric and acoustic variation among allopatric populations of the different species (Alexander 1967, Shaw 1968, Barrientos 1988). The plasticity of the group and much intraspecific variation have caused a history of taxonomic confusion (Hebard 1941, Shaw and Carlson 1969, North and Shaw 1980, Barrientos and Den Hollander 1994, Den Hollander and Barrientos 1994). Acoustic and morphometric characters have been useful in demonstrating geographic variation and separating species of Pterophylla (Shaw and Carlson 1969; Barrientos 1988). The present work examines morphometric variation between allopatric populations of Pterophylla spp. in northern Mexico. Males of seven allopatric populations of Pterophylla spp. were considered, with a sample size of 20 males per population, measuring 18 characters per male. The analysis separated populations into two groups: group 1 consisting of populations 1, 2, and 3, which corresponded to P. beltrani; and group 2 consisting of populations 4, 5, 6, and 7 which corresponded to P. robertsi. Mate choice and hybridization experiments between the populations confirmed the above results. The geographic range of P. beltrani was determined to extend from Nuevo Le6n, at the base of the eastern Sierra Madre, to Cuidad Victoria and Jaumave, Tamaulipas; the geographic range of P. robertsi was determined to extend from Llera, Tamaulipas to San Luis Potosi, including three additional populations of P. robertsi previously unknown in the State of Tamaulipas. Intermediate populations, i.e., populations 4, 5, and 6, were also intermediate in morphological characters with respect to the extreme populations of the geographic range of the species (north extreme population = population 1, P. beltrani; south extreme population = population 7, P. robertsi). The possible existence of a hybrid zone between the populations occurring where the geographic range of the species overlap is hypothesized.