EFICACIA DE DOS TIPOS DE RECOLECTA PARA REGISTRAR LA DIVERSIDAD DE MELOLÓNTIDOS NOCTURNOS (COLEOPTERA: SCARABAEOIDEA)

Abstract

The traditional assumption is that nocturnal melolonthids are attracted to light and thus they have been collected using light sources. Recent research, however, has shown that not all species respond to light. This study was done to identify the optimum collection method for recording melolonthid diversity. Melolonthid specimens were collected from April to June in 2001 and 2002 from streetlamps and from host plants using handheld lights in three agricultural plots in San Cristóbal de Las Casas, Chiapas, Mexico. Data were analyzed by Kruskal-Wallis test, collection method within each site (agricultural plot per year) and overall between sites and collection method. Shannon-Winner and Bootstrap indices were generated and Wilcoxon and Mann-Whitney tests were run. The Hutcheson procedure was applied, and a logistical regression used to analyze the effect of collection method on the male:female ratio. A total of 11,091 specimens were collected from 20 species and seven morphospecies belonging to 11 genera. The most abundant species were Phyllophaga obsoleta (51.6%), P. tumulosa (25%) and Anomala sticticoptera (10.4%).Collection from host plants produced 19 species and from light sources 22 species. Both collection methods resulted in 14 species from the Phyllophaga, Diplotaxis, Hoplia, Anomala and Viridimicus genera. The Orizabus, Strategus and Macrodactylus genera were only collected from host plants and the Ancognatha, Cyclocephala and Xyloryctes genera only from light sources. Richness varied by collection method at only one site, both within the site (Z = 3.86, P < 0.05) and accounting for all observations (Z = 1.07, P = 0.285). The highest specimen abundance was collected from the host plants (75.11%). Diversity (H’) was 1.44 from hosts and 1.19 from light sources, and differed within site 1 (t294= 31.70, P = 0.001). The male:female ratio for P. tumulosa (P < 0.01) and P. obsoleta (P < 0.001) differed by collection method with the former increasing 75% when collected from light sources and the latter varying by site. The two collection methods are complementary for generating species abundance and richness data. Phyllophaga obsoleta, the species of greatest agricultural importance, had a higher abundance in collections from host plants.