Rosser, NS; (2013) Speciation and biogeography of heliconiine butterflies. Doctoral thesis , UCL (University College London).

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Abstract

In this thesis I investigate the speciation and biogeography of neotropical heliconiine butterflies (Lepidoptera: Nymphalidae: Heliconiina). In Chapter 2, I present a large database of locality records for heliconiine species and subspecies, and use these data to test evolutionary and biogeographic hypotheses for their diversification. I find evidence that geographical gradients in species richness are driven at least in part by variation in speciation and/or extinction rates, rather than via evolutionary age or niche conservatism alone. The eastern Andes are characterised by high species richness and short phylogenetic branch lengths, suggesting that new species frequently arise there. Conversely, the Amazon basin is notable for high intra-specific phenotypic diversity. In Chapter 3, I use the geographic data to estimate the frequency of sympatric speciation in heliconiines. I find that the patterns of range overlap observed in heliconiines are consistent with sympatric speciation. However, parapatric speciation followed by a tendency for daughter species to expand rapidly into one another’s ranges presents a plausible alternative explanation. I also present evidence that shifts in mimetic wing colour patterns and host plants are associated with speciation in heliconiines, suggesting that ecological adaptation may be important in triggering speciation events. In Chapter 4, I test the prediction that hybrid zones between Andean and Amazonian races of Heliconius should be moving towards the Andes. I find the position of the hybrid zones to be unchanged from 1986 – 2011, and located on a band of peak rainfall at the edge of the Andes. This suggests that rainfall peaks act as "sinks" for dispersal in butterflies and stabilise the hybrid zones on this low fitness region. The results oppose the Pleistocene Refugium theory, which predicts that centres of ranges, rather than contact zones at the edges, should be centred on current rainfall peaks.

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