GENETIC-EVIDENCE FOR A SIBLING SPECIES OF HELICONIUS-CHARITHONIA (LEPIDOPTERA, NYMPHALIDAE)

Heliconius charithonia is a widespread species which, unlike many Heli conius, is non-mimetic and shows little racial differentiation. Only o ne form, ''peruvianus', which occurs in the dry forest habitats of wes tern Ecuador and Peru: has a distinct and clearly mimetic colour patte rn. Here it was shown that H. peruvianus was distinct from H. charitho nia bassleri at allozyme loci (D = 0.25 over 22 loci). This differenti ation was ten limes greater than that between H. charithonia sampled f rom Ecuador and the Caribbean (D = 0.027) and was consistent with anal ysis of mitochondrial sequence data (3.4-4% sequence divergence betwee n H. peruvianus and H. charithonia). One individual with a H. peruvian us colour pattern and allozyme genotype was collected in an area where H. charithonia was known to be common, demonstrating that contact bet ween the taxa occurs in western Ecuador Furthermore, the allozyme geno type of another individual was heterozygous for four of fi;I e diagnos tic loci and was most likely an F1 hybrid between H. charithonia and H . peruvianus. These data imply that H. charithonia and H. pe,peruvianu s are distinct species which hybridize occasionally. This species pair show many similarities with W. erato and H. himera, which are similar ly differentiated genetically and also show ecological and colour patt ern differences. These species fulfil some of the predictions of both allopatric refugium and parapatric adaptationist models of speciation in the neotropics, suggesting that elements of both hypotheses may be true. (C) 1998 The Linnean Society of London.