EVIDENCE FOR HYBRIDIZATION BETWEEN PARAMACROPOSTRONGYLUS-IUGALIS AND PARAMACROPOSTRONGYLUS-TYPICUS (NEMATODA, STRONGGLOIDEA) IN GREY KANGAROOS, MACROPUS-FULIGINOSUS AND MACROPUS-GIGANTEUS, IN A ZONE OF SYMPATRY IN EASTERN AUSTRALIA

Specimens of Paramacropostrogylus iugalis and P. typicus, collected fr om eastern (Macropus giganteus) and western (M. fuliginosus) grey kang aroos in New South Wales and Queensland, were examined morphologically and electrophoretically at 4 enzyme loci previously demonstrated to b e diagnostic between the 2 species, Collections of P. iugalis from M. giganteus from outside the zone of sympatry of the 2 kangaroo species conformed electrophoretically and morphologically with previous studie s. Within the zone of sympatry, the 2 nematode species were distinguis hable electrophoretically, with most P. iugalis occurring in M. gigant eus and all P. typicus occurring in M. fuliginosus. Some specimens of P. iugalis were identified in M. fuliginosus and, in both host species , nematodes were encountered with electrophoretic profiles intermediat e between P. iugalis and P. typicus. The frequent occurrence in these specimens of heterozygotes suggested that the genetic barriers between the 2 nematode species were not complete and that genetic interchange (i.e. hybridisation) was occurring. (C) 1997 Australian Society for P arasitology.