Distributional patterns of Pseudacteon associated with the Solenopsis saevissima complex 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.

Figure 1.

Bivariate plot of Pseudacteon species latitudinal maxima and latitudinal ranges. Latitudinal maxima are the maximum absolute latitudinal values for each species. These values were then reset to their original North-South polarity. Values between the lines extending from -23.5 and 23.5 are for species known only from the tropics, while those above the lines marked TZ (Temperate Zone) represent those species whose ranges extends into the tropics. Below the TZ lines, the species are exclusively temperate. Ranges for species in the northern and southern hemisphere extend south and north from their maxima, respectively.

Figure 2.

Relationship between latitude and sizes of locality assemblages of Pseudacteon. (a) locality assemblages of the Pseudacteon associated with the S. saevissima complex in South America, (b) locality assemblages in the Northern Hemisphere associated with all hosts.

Map 1.

Distributional records for all the Pseudacteon species hosted by ants in the Solenopsis saevissima complex. Localities with at least 5 species records are depicted with rectangles. These records are superimposed on a map approximating the native range of the host ant complex (after Pitts 2002 and Cuezzo 1999). Pseudacteon species names are given for records outside of this range.

Maps 2–5.

(2) Distribution of Pseudacteon affinis; (3) Distribution of Pseudacteon borgmeieri; (4) Distribution of Pseudacteon bulbosus and P. calderensis; (5) Distribution of Pseudacteon comatus

Maps 6–9.

(6) Distribution of Pseudacteon conicornis; (7) Distribution of Pseudacteon cultellatus; (8) Distribution of Pseudacteon curvatus; (9) Distribution of Pseudacteon dentiger

Maps 10–13.

(10) Distribution of Pseudacteon disneyi; (II) Distribution of Pseudacteon fowleri; (12) Distribution of Pseudacteon lenkoi; (13) Distribution of Pseudacteon litoralis

Maps 14–17.

(14) Distribution of Pseudacteon nocens: (15) Distribution of Pseudacteon nudicornis; (16) Distribution of Pseudacteon obtusus; (17) Distribution of Pseudacteon nr. Obtusus

Maps 18–21.

(18) Distribution of Pseudacteon pradei; (19) Distribution of Pseudacteon solenopsidis; (20) Distribution of Pseudacteon tricuspis; (21) Distribution of Pseudacteon wasmanni.