Volcanism and paleoclimate change drive diversification of world's largest whip spider (Amblypygi).

The tropics contain many of the most biodiverse regions on Earth but the processes responsible for generating this diversity remain poorly understood. This study investigated the drivers of diversification in arthropods with stenotopic ecological requirements and limited dispersal capability using as model the monotypic whip spider (Amblypygi) genus Acanthophrynus, widespread in the tropical deciduous forests of Mexico. We hypothesized that for these organisms, the tropical deciduous forests serve as a conduit for dispersal, with their disappearance imposing barriers. Given that these forests are located in a region of complex geological history and fluctuated in extent during the Pliocene-Pleistocene glacial/interglacial cycles we couple molecular clock dating, paleoclimatic niche modeling and ancestral area reconstruction to test if and how habitat fragmentation promoted diversification in Acanthophrynus. Concomitant with the expected role of landscape change, we demonstrate that orogeny of the Trans-Mexican Volcanic Belt, in the Late Miocene/Early Pliocene (6.95-5.21 mya), drove the earliest divergence of Acanthophrynus through vicariance. Similarly, as expected, the later onset of glaciations strongly impacted diversification. Whereas a more stable climate in the southern part of the distribution enabled further diversification, a marked loss of suitable habitat during the glaciations only allowed dispersal and diversification in the north to occur later, resulting in a lower overall diversity in this region. Importantly, barriers and diversification patterns identified in Acanthophrynus are reflected in the phylogeography of codistributed vertebrates and arthropods, emphasizing the profound impact of Trans-Mexican Volcanic Belt orogeny and glacial/interglacial cycles as drivers of diversification in the Mexican Neotropics. This article is protected by copyright. All rights reserved.