Ithomia

Introduction

Butterflies in this genus are often very abundant and have a variety of wing colour patterns including transparent, yellow and 'tiger' (orange and black) patterns. They are commonly involved in mimicry with species in other genera of the Ithomiini such as Napeogenes, Hypothyris, Scada, Oleria and others. Many species show considerable geographic variation in colour pattern, with as many as nine sub-species described for some species.

The genus is distributed throughout tropical america, from Mexico through Central America to Brazil and Bolivia. Their centre of diversity is in the northern Andes and Central America. Several species are restricted to montane habitats

As is the case for most Ithomiini, host plants are primarily in the family Solanaceae. The most important genera known for central american species are Solanum, Acnistus, Lycianthes, Witheringia and Capsicum (DeVries, 1987). Host plant relationships in other parts of the range remain poorly studied.

Characteristics

Male butterflies in this genus and its sister genus Pagyris are easily recognised by a distinctive raised bump on the hindwing underside in a position that corresponds with the location of the androconial patch. This is an excellent character easily recognised in the field and females can generally be readily matched with males found in the same location, as there is little sexual dimorphism in the genus.

Discussion of Phylogenetic Relationships

The phylogenetic relationships presented here are based on an analysis of DNA sequence data from seven different gene regions (Mallarino et al., 2005). There was some conflict between the different gene regions sequenced, with different genes giving a different signal for some species such as I. hyala. However the combined evidence tree presented here is in agreement with the majority of gene regions in areas of conflict. There remain some areas in which relationships are poorly supported, notably among the species I. agnosia, I. pseudoagalla, I. lichyi and I. drymo, that are represented here as an unresolved polytomy.

Prior to this study there was no cladistic analysis of this genus, and little is known of variation in morphological characters such as genitalia that might be used to complement the molecular data.

Several revisions to previously proposed taxonomy were made on the basis of the DNA data. For example the western Ecuador population I. pseudoagalla was previously considered a race of I. agnosia, but is very distinct genetically and we consider it a good species.

References

Mallarino, R., E. Bermingham, K. R. Willmott, A. Whinnett, and C. D. Jiggins. 2004. Molecular systematics of the butterfly genus Ithomia (Lepidoptera: Ithomiinae): a composite phylogenetic hypothesis based on seven genes. Molecular Phylogenetics and Evolution 34:625-644.

DeVries, P. (1986) The Butterflies of Costa Rica Princeton Univ. Press, Princeton, NJ.