title: Divergence at the edges: peripatric isolation in the montane spiny throated reed frog complex.
abstract: BACKGROUND
  Peripatric speciation and peripheral isolation have uncertain importance in species accumulation, and are largely overshadowed by assumed dominance of allopatric modes of speciation. Understanding the role of different speciation mechanisms within biodiversity hotspots is central to understanding the generation of biological diversity. Here, we use a phylogeographic analysis of the spiny-throated reed frogs and examine sister pairings with unbalanced current distributional ranges for characteristics of peripatric speciation. We further investigate whether forest/grassland mosaic adapted species are more likely created through peripatric speciation due to instability of this habitat type.
  
  
  RESULTS
  We reconstructed a multi-locus molecular phylogeny of spiny-throated reed frogs which we then combined with comparative morphologic data to delimit species and analyze historical demographic change; identifying three new species. Three potential peripatric speciation events were identified along with one case of allopatric speciation. Peripatric speciation is supported through uneven potential and realized distributions and uneven population size estimates based on field collections. An associated climate shift was observed in most potentially peripatric splits. Morphological variation was highest in sexually dimorphic traits such as body size and gular shape, but this variation was not limited to peripatric species pairs as hypothesized. The potentially allopatric species pair showed no niche shifts and equivalent effective population sizes, ruling out peripatry in that speciation event. Two major ecological niche shifts were recovered within this radiation, possibly as adaptations to occupy areas of grassland that became more prevalent in the last 5 million years. Restricted and fluctuating grassland mosaics within forests might promote peripatric speciation in the Eastern Arc Biodiversity Hotspot (EABH).
  
  
  CONCLUSIONS
  In our case study, peripatric speciation appears to be an important driver of diversity within the EABH biodiversity hotspot, implying it could be a significant speciation mechanism in highly fragmented ecosystems. Extensive peripatric speciation in this montane archipelago may explain the abundance of discrete lineages within the limited area of the EABH, as inferred in remote island archipelagos. Future phylogenetic studies incorporating demographic and spatial analyses will clarify the role of peripatric speciation in creating biodiversity hotspots.
authors.affiliation: Committee on Evolutionary Biology, University of Chicago, 1025 E. 57th St. Culver Hall 402, Chicago, IL, 60637, USA. lucinda.lawson@uc.edu.|Life Sciences, Field Museum of Natural History, 1400 S. Lake Shore Dr., Chicago, IL, 60605, USA. lucinda.lawson@uc.edu.|Department of Biological Sciences, University of Cincinnati, 614 Rieveschl Hall, Cincinnati, OH, 45220, USA. lucinda.lawson@uc.edu.
authors.forename: Lucinda P
authors.initials: LP
authors.lastname: Lawson
authors.affiliation: Committee on Evolutionary Biology, University of Chicago, 1025 E. 57th St. Culver Hall 402, Chicago, IL, 60637, USA. jbates@fieldmuseum.org.|Life Sciences, Field Museum of Natural History, 1400 S. Lake Shore Dr., Chicago, IL, 60605, USA. jbates@fieldmuseum.org.
authors.forename: John M
authors.initials: JM
authors.lastname: Bates
authors.affiliation: Tropical Biodiversity Section, Science Museo of Trento, Via della Scienza e del lavoro, 38122, Trento, Italy. mmenegon@gmail.com.
authors.forename: Michele
authors.initials: M
authors.lastname: Menegon
authors.affiliation: Biogeography Research Group, Department of Environmental Sciences, University of Basel, Basel, 4056, Switzerland. simon.loader@unibas.ch.
authors.forename: Simon P
authors.initials: SP
authors.lastname: Loader
mesh_terms: D000351:Africa, Eastern; D000818:Animals; D001001:Anura / Q000145:classification* / Q000235:genetics*; D044822:Biodiversity; D002980:Climate; D017753:Ecosystem; D005260:Female; D008297:Male; D010802:Phylogeny; D058974:Phylogeography