Evidence for a cryptic species complex in the ant parasitoid Apocephalus paraponerae (Diptera: Phoridae)

Cryptic species complexes occur in many taxa, in particular in the insect order Diptera. Here we describe a possible new cryptic species complex in the family Phoridae. Three lines of evidence suggest that Apocephalus paraponerae, an ant parasitoid, is actually a complex of at least four genetically distinct but morphologically almost indistinguishable populations attacking at least three different ant hosts. First, the host-location cues used by A. paraponerae to locate two of the host species differ. Second, A. paraponerae attracted to these two ant host species differ consistently in average hind femur length and costal vein length, two measures of body size. Finally, mtDNA sequence comparisons of individuals from a variety of locations and host ant species indicate high sequence divergence between populations and low sequence divergence within populations. We discuss aspects of host location behaviour that may be important in cryptic species formation, and we speculate that many such cryptic complexes may exist in this family and others with similar mechanisms of host location and exploitation.