Genetic evidence for a sibling species of Heliconius charithonia (Lepidoptera; Nymphalidae)

Abstract

Heliconius charithonia is a widespread species which, unlike many Heliconius, is non-mimetic and shows little racial diVerentiation. Only one form, ‘peruvianus’, which occurs in the dry forest habitats of western Ecuador and Peru, has a distinct and clearly mimetic colour pattern. Here it was shown that H. peruvianus was distinct from H. charithonia bassleri at allozyme loci (D=0.25 over 22 loci). This diVerentiation was ten times greater than that between H. charithonia sampled from Ecuador and the Caribbean (D=0.027) and was consistent with analysis of mitochondrial sequence data (3.4‐4% sequence divergence between H. peruvianus and H. charithonia). One individual with a H. peruvianus colour pattern and allozyme genotype was collected in an area where H. charithonia was known to be common, demonstrating that contact between the taxa occurs in western Ecuador. Furthermore, the allozyme genotype of another individual was heterozygous for four of five diagnostic loci and was most likely an F1 hybrid between H. charithonia and H. peruvianus. These data imply that H. charithonia and H. peruvianus are distinct species which hybridize occasionally. This species pair show many similarities with H. erato and H. himera, which are similarly diVerentiated genetically and also show ecological and colour pattern diVerences. 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.