The Phylogenetic Pattern of Speciation and Wing Pattern Change in Neotropical Ithomia Butterflies (Lepidoptera: Nymphalidae)

Abstract

Abstract. Species level phylogenetic hypotheses can be used to explore patterns of divergence and speciation. In the tropics, speciation is commonly attributed to either vicariance, perhaps within climate-induced forest refugia, or ecological speciation caused by niche adaptation. Mimetic butterflies have been used to identify forest refugia as well as in studies of ecological speciation, so they are ideal for discriminating between these two models. The genus Ithomia contains 24 species of warningly colored mimetic butterflies found in South and Central America, and here we use a phylogenetic hypothesis based on seven genes for 23 species to investigate speciation in this group. The history of wing color pattern evolution in the genus was reconstructed using both parsimony and likelihood. The ancestral pattern for the group was almost certainly a transparent butterfly, and there is strong evidence for convergent evolution due to mimicry. A punctuationist model of pattern evolution was a significantly better fit to the data than a gradualist model, demonstrating that pattern changes above the species level were associated with cladogenesis and supporting a model of ecological speciation driven by mimicry adaptation. However, there was only one case of sister species unambiguously differing in pattern, suggesting that some recent speciation events have occurred without pattern shifts. The pattern of geographic overlap between clades over time shows that closely related species are mostly sympatric or, in one case, parapatric. This is consistent with modes of speciation with ongoing gene flow, although rapid range changes following allopatric speciation could give a similar pattern. Patterns of lineage accumulation through time differed significantly from that expected at random, and show that most of the extant species were present by the beginning of the Pleistocene at the latest. Hence Pleistocene refugia are unlikely to have played a major role in Ithomia diversification.

A test of the sympatric host race formation hypothesis in Neodiprion (Hymenoptera: Diprionidae)

“…Fitzpatrick & Turelli 2006;Jiggins et al 2006), our results were largely inconclusive. Thus, regardless of taxon and divergence mode, it appears that ARC assumptions (i.e.…”

Diversification of clearwing butterflies with the rise of the Andes

“…Most ithomiine genera are diverse in wing pattern and mimicry is suggested as a driver of diversification in some clades (Jiggins et al ., 2006; Elias et al ., 2008). In Heliconius butterflies, sister species almost always differ in mimetic pattern and mimetic pattern has been shown to contribute to reproductive isolation (e.g.…”

Patterns of Species, Phylogenetic and Mimicry Diversity of Clearwing Butterflies in the Neotropics

“…S pecies were classifi ed among 23 mimicry groups, following previous classifi cation (e.g., Willmott and Mallet 2004 ;Jiggins et al 2006 ;Elias et al 2008 , Table 1 and Fig. 1 ).…”

“…In the case of ithomiine butterfl ies, previous studies found that Napeogenes , Ithomia and Oleria likely originated in the northern Andes and subsequently diversifi ed throughout both the Andes and the rest of the Neotropics (Elias et al 2009 ;de-Silva et al 2015 ;de-Silva et al 2010 ). Shifts of altitudinal range and colour pattern are also correlated (Chazot et al 2014 ) and are involved in speciation events (Jiggins et al 2006 ;Elias et al 2009 ), and may likely have increased speciation rate in montane regions. In addition, hostplant diversity has been proposed to drive diversifi cation in phytophagous insects (Janz et al 2006 ) and particularly in ithomiines (Willmott and Freitas 2006 ), whose Solanaceae hostplants are most diverse in the Andes and the upper Amazon, and to a lesser extent in the Atlantic Forest (Knapp 2002 ; PBI Solanum Project; http://www.nhm.ac.uk/ research-curation/research/projects/solanaceaesource/ ).…”