α and β Diversity of a Tachinid Parasitoid Community Over Space and Time

Abstract

Many species of Tachinidae are important parasitoids of herbivorous insects in natural and managed systems; yet, little is known about tachinid diversity and how this diversity is distributed across space and time. Here, pan trap sampling was used to analyze the richness, microhabitat speciÞcity, and seasonal diversity of a tachinid parasitoid community in an oakÐ mesquite savanna of Southeastern Arizona. Twenty-four traps were set out monthly during the growing season in three different microhabitats (open grassland, woodland understory, and woodland canopy). In total, 79 tachinid species were sampled with an estimated total diversity of 122 species. Most individual traps sampled few species; yet, variation in species composition ( diversity) among sampling dates and microhabitats was high, accounting for 40 Ð70% of the total diversity. SigniÞcant intraspeciÞc aggregation was not observed across traps or microhabitats, but it was observed across dates, suggesting that the activity of tachinid species may be associated with host phenology and seasonal periods of precipitation. The diversity associated with microhabitat and sampling date was signiÞcantly greater than expected. Tachinid species diversity was highest in the canopy traps, whereas the open-exposed traps exhibited high abundances of relatively few species, and understory traps sampled few individuals of few species. Most species tended to be sampled where their hosts would be expected to be found, although males were also frequently sampled in microhabitats associated with mate Þnding. These patterns of diversity and abundance may aid in understanding parasitoidÐ host associations and variation in rates of parasitism by tachinid sies.