Testing historical explanations for gradients in species richness in heliconiine butterflies of tropical America

Abstract

We compiled a large database of 58 059 point locality records for 70 species and 434 subspecies of heliconiine butterflies and used these data to test evolutionary hypotheses for their diversification. To study geographical patterns of diversity and contact zones, we mapped: (1) species richness; (2) mean molecular phylogenetic terminal branch length; (3) subspecies richness and the proportion of specimens that were subspecific hybrids, and (4) museum sampling effort. Heliconiine species richness is high throughout the Amazon region and peaks near the equator in the foothills and middle elevations of the eastern Andes. Mean phylogenetic terminal branch length is lowest in the eastern Andes and tends to be low in species-rich areas. By contrast, areas of high subspecies richness, where subspecies overlap in range and/or hybridize, are concentrated along the course of the Amazon River, with the eastern Andes slopes and foothills relatively depauperate in terms of local intraspecific phenotypic diversity. Spatial gradients in heliconiine species richness in the Neotropics are consistent with the hypothesis that species richness gradients are driven at least in part by variation in speciation and/or extinction rates, resulting in observed gradients in mean phylogenetic branch length, rather than via evolutionary age or niche conservatism alone. The data obtained in the present study, coupled with individual case studies of recently evolved Heliconius species, suggest that the radiation of heliconiine butterflies occurred predominantly on the eastern slopes of the Andes in Colombia, Ecuador, and Peru, as well as in the upper/middle Amazon basin.

Biodiversity Conservation and Phylogenetic Systematics

“…Our results are mostly consistent with that suggestion, since peaks in richness in the eastern Andes and upper Amazon, as identifi ed here, have also been reported in Heliconius butterfl ies (Rosser et al 2012 ) and the genus Adelpha (Willmott 2003 ).…”

Genome-wide evidence for speciation with gene flow inHeliconiusbutterflies

“…The entire distribution of H. melpomene is shown in gray. The entire distribution of the H. cydno/timareta clade is shown with dots (Rosser et al 2012). Colors depict distributions of races used in this study, with dots indicating the sampling locations, and correspond to the colored dots on the tree.…”

Multilocus Species Trees Show the Recent Adaptive Radiation of the Mimetic Heliconius Butterflies

“…The importance of Müllerian mimicry as a driver of individual speciation events has been wellestablished (Mallet et al 1998;Jiggins 2008) whereas the macroevolutionary processes governing the evolution of the group have been largely neglected in empirical studies (but see Rosser et al 2012). Precise understanding of the evolution of the mimicry rings, as well as associated processes such as hybridization, requires knowledge of the relative timing of the divergence events and motivated the most widely cited study of the molecular clock in Arthropoda (Brower 1994a).…”

“…Importantly, the first dated phylogeny of Heliconiini is not calibrated to an absolute standard, making it impossible to make inferences about the relation of the diversification process and the contemporaneous geological and climatic events. A recent comparative study suggests that the majority of Heliconius lineages originated in the northeastern Andes and spread to other parts of the continent (Rosser et al 2012). The cumulative results of over 200 systematic studies demonstrate that most South American tropical clades have experienced periods of significantly elevated net diversification rate in response to Andean orogenesis, alterations in the hydrology and sediment dynamics of the present-day Amazon Basin, as well as local and global climatic changes Turchetto-Zolet et al 2013).…”