Montane speciation patterns in Ithomiola butterflies (Lepidoptera: Riodinidae): are they consistently moving up in the world?

Abstract

Tropical lowland areas have often been seen as the centres of terrestrial species proliferation, but recent evidence suggests that young species may be more frequent in montane areas. Several montane speciation modes have been proposed, but their relative frequencies and predominant evolutionary sequence remain unclear because so few biogeographic and phylogenetic studies have tested such questions. I use morphological data to generate a phylogenetic hypothesis for all 11 species of the riodinid butterfly genus Ithomiola (Riodininae: Mesosemiini: Napaeina). These species are shown here to be all strictly geographically and elevationally allo-or parapatrically distributed with respect to their closest relatives in lowland and montane regions throughout the Neotropics. The overwhelming pattern in Ithomiola is of repeated upward parapatric speciation across an elevational gradient, and the genus appears to provide the clearest example to date of vertical montane speciation. All of the young derived species are montane and all of the old basal species are confined to the lowlands, supporting the hypothesis of montane regions largely as 'species pumps' and lowland regions as 'museums'. Possible reasons for the post-speciation maintenance of parapatric ranges in Ithomiola are discussed.

Diversification of clearwing butterflies with the rise of the Andes

“…The rise of the Andes could also have driven adaptive radiation across the available elevational gradient, as suggested in the riodinid butterfly genus Ithomiola (Hall, 2005). However, in the case of Oleriina, although shifts in altitudinal ranges are associated with speciation (Table 1), they tend to be rare (Fig.…”

“…Butterflies are likely to be limited by physiological and ecological constraints, particularly among ithomiines where mimetic species often share the same altitudinal niche (Chazot et al ., 2014). However, exceptions are found in some groups such as the riodinid butterfly genus Ithomiola that radiated across an elevational gradient in the Andes (Hall, 2005). …”

Diversification of the cold-adapted butterfly genus Oeneis related to Holarctic biogeography and climatic niche shifts

“…A clade is rarely the pure product of allopatry (Muller and Beharegaray, 2010;Imada et al, 2011). Geographical speciation can be coupled with ecological speciation (Hall, 2005;Willmott et al, 2001;Matos-Maravi et al, 2013) involving the differentiation of species lineages by changes in habitat use or behaviour (Jiggins, 2008;Chamberlain et al, 2009). Diversification along climatic gradients, such as moisture (Rieseberg et al, 1999;Gee, 2004) or temperature (Keller and Seehausen, 2012) has been documented in several clades.…”

Glaciations, gradients, and geography: multiple drivers of diversification of bush frogs in the Western Ghats Escarpment

“…The survival of older lineages and occurrence of recent lineages could result from different processes operating in the lowland and highland regions of tropical mountains [10]. However, the processes generating these patterns of diversification remain poorly studied [6,11]. The contrasting processes acting within mountains can therefore provide critical insights towards understanding the drivers of diversification.…”

“…Hence, understanding the process of diversification within clades is critical for explaining patterns of diversity in space [5]. Mountain regions in the tropics provide unique opportunities to explore the causes and consequences of diversification [6]. These regions are considered as active centres of speciation and are regarded as species pumps [7,8].…”