Congolian Tropical Forest Frog Using Demographic Model Selection

Received: 25 January 2017 | Accepted: 17 July 2017 DOI: 10.1111/mec.14266

ORIGINAL ARTICLE

Evaluating mechanisms of diversification in a Guineo- Congolian tropical forest frog using demographic model selection

1Department of Biology, The University of Texas at Arlington, Arlington, TX, USA Abstract 2Department of Biology, University of The accumulation of biodiversity in tropical forests can occur through multiple Washington, Seattle, WA, USA allopatric and parapatric models of diversification, including forest refugia, riverine 3Burke Museum of Natural History and Culture, University of Washington, Seattle, barriers and ecological gradients. Considerable debate surrounds the major diversifi- WA, USA cation process, particularly in the West African Lower Guinea forests, which contain 4 Museum fur€ Naturkunde – Leibniz a complex geographic arrangement of topographic features and historical refugia. Institute for Evolution and Biodiversity Science, Berlin, Germany We used genomic data to investigate alternative mechanisms of diversification in 5African Amphibian Conservation Research the Gaboon forest frog, Scotobleps gabonicus, by first identifying population struc- Group, Unit for Environmental Sciences and Management, North-West University, ture and then performing demographic model selection and spatially explicit analy- Potchefstroom, South Africa ses. We found that a majority of population divergences are best explained by 6 Flora Fauna & Man, Ecological Services allopatric models consistent with the forest refugia hypothesis and involve diver- Ltd., Tortola, British Virgin Island gence in isolation with subsequent expansion and gene flow. These population 7Florida Museum of Natural History, University of Florida, Gainesville, FL, USA divergences occurred simultaneously and conform to predictions based on climati- 8Amphibian and Reptile Diversity Research cally stable regions inferred through ecological niche modelling. Although forest Center, The University of Texas at Arlington, Arlington, TX, USA refugia played a prominent role in the intraspecific diversification of S. gabonicus, we also find evidence for potential interactions between landscape features and his- Correspondence Daniel M. Portik and Matthew K. Fujita, torical refugia, including major rivers and elevational barriers such as the Cameroo- Department of Biology, The University of nian Volcanic Line. We outline the advantages of using genomewide variation in a Texas at Arlington, Arlington, TX, USA. Emails: [email protected]; mkfujita@uta. model-testing framework to distinguish between alternative allopatric hypotheses, edu and the pitfalls of limited geographic and molecular sampling. Although phylogeo-

Funding information graphic patterns are often species-specific and related to life-history traits, addi- National Science Foundation, Grant/Award tional comparative studies incorporating genomic data are necessary for separating Number: DEB # 1457232, DEB #1202609; National Science Foundation GRFP; Vincent shared historical processes from idiosyncratic responses to environmental, climatic J. Coates Genomics Sequencing Laboratory and geological influences on diversification. at UC Berkeley, supported by NIH, Grant/ Award Number: S10 OD018174; Museum KEYWORDS of Comparative Zoology (Harvard University) Africa, amphibians, ecological niche model, forest refugia, historical demography, Lower Guinea, phylogeography, riverine barrier

1 | INTRODUCTION 1.1 | Alternative models of diversification for tropical Africa The Guineo-Congolian tropical rainforests of Africa contain excep- tional spe