Distributional Patterns ofPseudacteonAssociated with theSolenopsis saevissimaComplex in South America

Abstract

Classical biological control efforts against imported fire ants have largely involved the use of Pseudacteon parasitoids. To facilitate further exploration for species and population biotypes a database of collection records for Pseudacteon species was organized, including those from the literature and other sources. These data were then used to map the geographical ranges of species associated with the imported fire ants in their native range in South America. In addition, we found geographical range metrics for all species in the genus and related these metrics to latitude and host use. Approximately equal numbers of Pseudacteon species were found in temperate and tropical regions, though the majority of taxa found only in temperate areas were found in the Northern Hemisphere. No significant differences in sizes of geographical ranges were found between Pseudacteon associated with the different host complexes of fire ants despite the much larger and systemic collection effort associated with the S. saevissima host group. The geographical range of the flies was loosely associated with both the number of hosts and the geographical range of their hosts. Pseudacteon with the most extensive ranges had either multiple hosts or hosts with broad distributions. Mean species richnesses of Pseudacteon in locality species assemblages associated with S. saevissima complex ants was 2.8 species, but intensively sampled locations were usually much higher. Possible factors are discussed related to variation in the size of geographical range, and areas in southern South America are outlined that are likely to have been under-explored for Pseudacteon associated with imported fire ants.

Geographical transition zone of Solenopsis fire ants (Hymenoptera: Formicidae) and Pseudacteon fly parasitoids (Diptera: Phoridae) in the state of São Paulo, Brazil

“…However, P. affinis, P. dentiger, P. disneyi, P. pradei, P. tricuspis and P. wasmanni were attracted by the two fire ants species (Table 2). Of these parasitoids, P. tricuspis and P. disneyi have regional biotypes and attack different Solenopsis species (Pesquero 1997, Calcaterra et al 2005; P. pradei and P. wasmanni occur in areas having an association with more than one fire ant host species (Patrock et al 2009), but P. affinis and P. dentiger seem to be limited to the distribution area of S. saevissima (Pesquero 1997, Patrock et al 2009.…”

“…This subject is little explored in communities of Pseudacteon, but the predominance (84%) of local assemblies with a lower richness (up to four species) as compared with the richness observed for regional assemblies in South America (Patrock et al 2009), and the convergence of structure between two regional communities in Brazil (Pesquero 1997) suggest the role of competition in the community structure of these insects.…”

“…Previous research has resulted in considerable knowledge about the taxonomy and geographic distribution of Pseudacteon decapitating flies in South America (Patrock et al 2009, Plowes et al 2009. Due to the high species richness of fire ants and the natural occurrence of parasitoids in South America, the host specificity is an important aspect to be considered when selecting natural enemies for fire ant biological control in the US (Vazquez et al 2004, Folgarait et al 2005b.…”

“…Of the 36 described Pseudacteon species that parasitize fire ants in the Neotropical region, 19 are associated with S. saevissima and S. invicta in South America, and 16 are listed as common to both species of fire ants (Patrock et al 2009). However, 11 of these species have ranges that are mostly limited to one species or another.…”

“…However, 11 of these species have ranges that are mostly limited to one species or another. Only five species of parasitoids (P. borgmeieri Schmitz, P. cultellatus Borgmeier, P. nudicornis Borgmeier, P. solenopsidis Schmitz and P. tricuspis Borgmeier) have ranges that broadly overlap with both fire ant species (Patrock et al 2009). Furthermore, the oviscape of P. nudicornis, P. cultellatus, and P. tricuspis shows intraspecific variation (Porter & Pesquero 2001), suggesting the occurrence of populations in process of reproductive isolation.…”