title: Latitude, elevational climatic zonation and speciation in New World vertebrates.
abstract: Many biodiversity hotspots are located in montane regions, especially in the tropics. A possible explanation for this pattern is that the narrow thermal tolerances of tropical species and greater climatic stratification of tropical mountains create more opportunities for climate-associated parapatric or allopatric speciation in the tropics relative to the temperate zone. However, it is unclear whether a general relationship exists among latitude, climatic zonation and the ecology of speciation. Recent taxon-specific studies obtained different results regarding the role of climate in speciation in tropical versus temperate areas. Here, we quantify overlap in the climatic distributions of 93 pairs of sister species of mammals, birds, amphibians and reptiles restricted to either the New World tropics or to the Northern temperate zone. We show that elevational ranges of tropical- and temperate-zone species do not differ from one another, yet the temperature range experienced by species in the temperate zone is greater than for those in the tropics. Moreover, tropical sister species tend to exhibit greater similarity in their climatic distributions than temperate sister species. This pattern suggests that evolutionary conservatism in the thermal niches of tropical taxa, coupled with the greater thermal zonation of tropical mountains, may result in increased opportunities for allopatric isolation, speciation and the accumulation of species in tropical montane regions. Our study exemplifies the power of combining phylogenetic and spatial datasets of global climatic variation to explore evolutionary (rather than purely ecological) explanations for the high biodiversity of tropical montane regions.
authors.affiliation: Departamento de Ciencias Biológicas, Laboratorio de Biología Evolutiva de Vertebrados, Universidad de los Andes, Apartado 4976 Bogotá, Colombia. ccadena@uniandes.edu.co
authors.forename: Carlos Daniel
authors.initials: CD
authors.lastname: Cadena
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Kozak
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Gómez
authors.forename: Juan Luis
authors.initials: JL
authors.lastname: Parra
authors.forename: Christy M
authors.initials: CM
authors.lastname: McCain
authors.forename: Rauri C K
authors.initials: RC
authors.lastname: Bowie
authors.forename: Ana C
authors.initials: AC
authors.lastname: Carnaval
authors.forename: Craig
authors.initials: C
authors.lastname: Moritz
authors.forename: Carsten
authors.initials: C
authors.lastname: Rahbek
authors.forename: Trina E
authors.initials: TE
authors.lastname: Roberts
authors.forename: Nathan J
authors.initials: NJ
authors.lastname: Sanders
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Schneider
authors.forename: Jeremy
authors.initials: J
authors.lastname: VanDerWal
authors.forename: Kelly R
authors.initials: KR
authors.lastname: Zamudio
authors.forename: Catherine H
authors.initials: CH
authors.lastname: Graham
mesh_terms: D000531:Altitude; D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D002980:Climate; D049810:Genetic Speciation; D005843:Geography; D007843:Latin America; D009656:North America; D010802:Phylogeny; D014714:Vertebrates / Q000145:classification* / Q000235:genetics