Analysis of geographic patterns of molecular, morphological, and bioclimatic variation to evaluate hypotheses of species boundaries in the South American montane genus Escallonia (Escalloniaceae)

Abstract

Escallonia is a morphologically and ecologically diverse clade of shrubs and small trees widely distributed in three hotspots of plant diversity. Previous studies suggested that extant species may have radiated rapidly and/or recently resulting in complex patterns of molecular variation across this genus. This result is apparently mirrored in morphology because species also display complex and overlapping patterns of morphological variation. Taken together, these patterns call into question the identity of all species within Escallonia. To evaluate the currently proposed hypotheses of species boundaries, I used molecular, morphological, and bioclimatic a data for 35 species and assessed three species criteria: genealogical exclusivity, morphological gaps, and climatic niche differences. Interpreting these data in the context of species as segments of evolutionary lineages, I provide evidence that most species (ca. 70%) within Escallonia represent distinct species on independent evolutionary trajectories. Instead of rejecting the current hypotheses of species limit, I argue for taxonomic stability as it provides a useful framework for studies aiming to understand the mechanisms driving the origin and evolution of species in hotspots of biodiversity.