Mitochondrial DNA provides an insight into the mechanisms driving diversification in the ithomiine butterfly Hyposcada anchiala (Lepidoptera: Nymphalidae: Ithomiinae)

Alaine Whinnett,Gerardo Lamas,Marie Zimmermann,Keith R Willmott,Fraser Simpson,Andrew V.Z Brower,James Mallet

doi:10.14411/eje.2005.089

Abstract

Geographic subspecies of several ithomiine butterflies on the lower east Andean slopes display a black and orange "melanic tiger" aposematic wing pattern that occurs from Colombia to Bolivia, while geographically adjacent lowland subspecies typically bear a coloured, "tiger" pattern. However, it is not clear whether subspecies with similar wing patterns in different regions have arisen through independent events of convergent adaptation, possibly through parapatric differentiation, or result from allopatric differentiation, as proposed by the refuge hypothesis. Here, we examine geographic patterns of divergence in the widespread and common ithomiine butterfly Hyposcada anchiala. We present phylogenetic hypotheses for 5 subspecies of H. anchiala, based on 1567 bp mitochondrial DNA. All topologies indicated that a single switch in mimetic pattern best explained the wing patterning of the H. anchiala studied here. This finding suggests that the subspecies of H. anchiala studied here result from at least two stages of differentiation, and is consistent with a single colonisation into a novel altitudinal zone coincident with a wing pattern switch, followed by subsequent divergence within, rather than across altitudinal zones. The subspecies divergences indicated diversifications were consistent with the Pleistocene. Furthermore, the lowland subspecies were more recently derived than the montane taxa, in contrast to predictions of the "Andean species pump" hypothesis.

Highlights

Species richness reaches a global peak at the western edge of the Amazon basin and adjacent east Andean foothills (Robbins & Opler, 1996)
To avoid problems associated with missing characters, sequences were edited to a final alignment covering the 1567 bp region amplified in all specimens
Despite the rapid substitution rate of mitochondrial DNA (mtDNA) compared to most nuclear regions, sequence results yielded only low levels of divergence among H. anchiala subspecies

Summary

Introduction

Species richness reaches a global peak at the western edge of the Amazon basin and adjacent east Andean foothills (Robbins & Opler, 1996). There is little agreement on the main causes for this high diversity, and a number of competing hypotheses have been proposed. The Pleistocene forest refuge hypothesis (Haffer, 1969) has perhaps received the most attention (Brown, 1979, 1982, 1987; Hall & Harvey, 2002; Sheppard et al, 1985), and a number of east Andean lower elevation putative forest refugia have been identified (Brown, 1979, 1982). The rapid changes in both biotic and abiotic environments at the base of the eastern Andes could have helped generate the high species diversity in this region. Fjeldså (1994) went on to propose that Andean slopes act as a “species pump” for birds, where new species originate before subsequent dispersal into the Amazon lowlands

Methods

Results

Conclusion