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Title: BIOGEOGRAPHY AND MACROECOLOGY OF PHORID FLIES THAT ATTACK FIRE ANTS IN SOUTHEASTERN BRAZIL AND ARGENTINA

Author
item FOLGARAIT, PATRICIA - UNIV NACIONAL DE QUILMES
item BRUZZONE, O - UNIV NACIONAL DE QUILMES
item Porter, Sanford
item PESQUERO, MARCOS - UNIV FEDERAL DE SAO CARLO
item GILBERT, LARRY - UNIVERSITY OF TEXAS

Submitted to: Journal of Biogeography
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/20/2004
Publication Date: 3/29/2005
Citation: Folgarait, P.J., Bruzzone, O., Porter, S.D., Pesquero, M.A., Gilbert, L. 2005. Biogeography and macroecology of phorid flies that attack fire ants in southeastern Brazil and Argentina. Journal of Biogeography. 32: 353-367.

Interpretive Summary: Two imported fire ants (Solenopsis richteri and Solenopsis invicta) have become serious pests in the United States. In their native ranges, these and related south American fire ants are distributed across a great variety of habitats and climatic zones, and are accompanied by six to eight species of Pseudacteon decapitating flies. In North America, S. invicta now ranges from Florida to western Texas and California and northward into Tennessee and North Carolina. Success in introducing particular Pseudacteon phorids as part of biological control measures against S. invicta has varied across climatic zones. There is a lack of knowledge about the physiological capacities of these phorids as well as their correlated climatic tolerances across latitudinal gradients which can be very useful for a successful introduction of biological control agents. In this paper scientists from the Universidad Nacional de Quilmes, Buenos Aires Argentina; USDA-ARS, CMAVE, Gainesville, FL; Universidade Federal de Sao Carlo, Brazil, and the University of Texas at Austin analyzed the geographical information from field collections of phorids in relation to climatic, hosts, and habitat patterns. The goals were to put together for first time all the scattered geographic information about South America fire ant decapitating flies, to estimate their richness by phytogeographical regions, to calculate their geographic ranges, to perform a climatic analysis for these distributions, to determine groups and communities based on several types of variables. Richness estimations depended on the phytogeographical region considered. Cluster multivariate analyses based on climatic, phytogeographic, and host data distinguished a 'cerrado' fly group and a 'widespread' fly group. Temperature and precipitation explained most of the fly distribution patterns. Geographic ranges and areas estimated for the Pseudacteon species correlated well between each other. Pseudacteon species with higher mid-latitudinal ranges occupied broader geographical areas and confronted more stressful environmental conditions. Information from this study will be useful in selecting fly species and biotypes for possible field release as fire ant biocontrol agents in the United States.

Technical Abstract: Two members of the Saevissima group of the fire ant genus Solenopsis, S. richteri and S. invicta, have become serious pests when introduced from Argentina/Brazil to other continents. In their native ranges, these and related south American Solenopsis are distributed across a great variety of habitats and climatic zones, and are accompanied by six to eight species of Pseudacteon parasitoids in each locality. In North America, S. invicta, introduced free of its phorid fauna, now ranges from Florida to western Texas and California and northward into Tennessee and North Carolina. Success in introducing particular Pseudacteon phorids as part of biological control measures against S. invicta has varied across climatic zones. There is a lack of knowledge about the physiological capacities of these phorids as well as their correlated climatic tolerances across latitudinal gradients which can be very useful for a succesful introduction of biological control agents. Here we analyzed using several approaches the geographical information from field collections of phorids in relation to climatic, hosts, and habitat patterns. Our goals were to put together for first time all the scattered information about South America fire ants phorids, to estimate their richness by phytogeographical regions, to calculate their geographic ranges, to perform a climatic analysis for these distributions, to determine groups and communities based on several types of variables, and to test Rappoport´s biogeographical rule and find a mechanism for it. Richness estimations using ICE and Mmean estimators were similar or higher than the observed values depending on the phytogeographical region considered. Cluster multivariate analyses based on climatic, phytogeographic, and host data distinguished distinct groupings of Pseudacton species. One group was defined as the 'cerrado' because it was confined mainly to tropical savannah areas. The other was called 'widespread', because of its broad geographical distribution. 'Widespread' included a subgroup 'Chaco' and a 'maritime' subgroup due to their particularities in extreme temperatures and precipitation. Ordination multivariate analyses showed 1) two climatic gradients throughout the study area: one of temperature and the other of precipitation, and 2) that climatic variables significantly explained the observed assemblages of phorids despite the great variation across sites and phorids. Maps derived from the ordination analyses allowed us to define eight communities whose geographical distribution resembled that of phytogeographical regions. Geographic ranges and areas estimated for the Pseudacteon species correlated well between each other. We found a significant and positive correlation between geographic areas and mid latitudinal points corroborating Rapoport´s rule. Mantel Tests based on climatic variables confirmed our application of Rappoport´s rule for Pseudacteon showing that species with higher mid-latitudinal ranges occupy broader geographical areas and confront more stressful environmental conditions. Our approach and findings can be applied to the choosing of specific phorids, or perhaps other organisms, for biocontrol efforts within climatically defined regions.