title: A mistletoe tale: postglacial invasion of Psittacanthus schiedeanus (Loranthaceae) to Mesoamerican cloud forests revealed by molecular data and species distribution modeling.
abstract: BACKGROUND
  Ecological adaptation to host taxa is thought to result in mistletoe speciation via race formation. However, historical and ecological factors could also contribute to explain genetic structuring particularly when mistletoe host races are distributed allopatrically. Using sequence data from nuclear (ITS) and chloroplast (trnL-F) DNA, we investigate the genetic differentiation of 31 Psittacanthus schiedeanus (Loranthaceae) populations across the Mesoamerican species range. We conducted phylogenetic, population and spatial genetic analyses on 274 individuals of P. schiedeanus to gain insight of the evolutionary history of these populations. Species distribution modeling, isolation with migration and Bayesian inference methods were used to infer the evolutionary transition of mistletoe invasion, in which evolutionary scenarios were compared through posterior probabilities.
  
  
  RESULTS
  Our analyses revealed shallow levels of population structure with three genetic groups present across the sample area. Nine haplotypes were identified after sequencing the trnL-F intergenic spacer. These haplotypes showed phylogeographic structure, with three groups with restricted gene flow corresponding to the distribution of individuals/populations separated by habitat (cloud forest localities from San Luis Potosí to northwestern Oaxaca and Chiapas, localities with xeric vegetation in central Oaxaca, and localities with tropical deciduous forests in Chiapas), with post-glacial population expansions and potentially corresponding to post-glacial invasion types. Similarly, 44 ITS ribotypes suggest phylogeographic structure, despite the fact that most frequent ribotypes are widespread indicating effective nuclear gene flow via pollen. Gene flow estimates, a significant genetic signal of demographic expansion, and range shifts under past climatic conditions predicted by species distribution modeling suggest post-glacial invasion of P. schiedeanus mistletoes to cloud forests. However, Approximate Bayesian Computation (ABC) analyses strongly supported a scenario of simultaneous divergence among the three groups isolated recently.
  
  
  CONCLUSIONS
  Our results provide support for the predominant role of isolation and environmental factors in driving genetic differentiation of Mesoamerican parrot-flower mistletoes. The ABC results are consistent with a scenario of post-glacial mistletoe invasion, independent of host identity, and that habitat types recently isolated P. schiedeanus populations, accumulating slight phenotypic differences among genetic groups due to recent migration across habitats. Under this scenario, climatic fluctuations throughout the Pleistocene would have altered the distribution of suitable habitat for mistletoes throughout Mesoamerica leading to variation in population continuity and isolation. Our findings add to an understanding of the role of recent isolation and colonization in shaping cloud forest communities in the region.
authors.affiliation: Departamento de Biología Evolutiva, Instituto de Ecología, A.C., Carretera antigua a Coatepec No. 351, El Haya, Xalapa, Veracruz, 91070, Mexico. francisco.ornelas@inecol.mx.
authors.forename: Juan Francisco
authors.initials: JF
authors.lastname: Ornelas
authors.affiliation: Departamento de Biología Evolutiva, Instituto de Ecología, A.C., Carretera antigua a Coatepec No. 351, El Haya, Xalapa, Veracruz, 91070, Mexico.|Department of Plant and Microbial Biology & The University and Jepson Herbaria, University of California, Berkeley, 431 Koshland Hall, Berkeley, CA, 94270, USA.
authors.forename: Etelvina
authors.initials: E
authors.lastname: Gándara
authors.affiliation: Departamento de Biología Evolutiva, Instituto de Ecología, A.C., Carretera antigua a Coatepec No. 351, El Haya, Xalapa, Veracruz, 91070, Mexico.
authors.forename: Antonio Acini
authors.initials: AA
authors.lastname: Vásquez-Aguilar
authors.affiliation: Departamento de Biología Evolutiva, Instituto de Ecología, A.C., Carretera antigua a Coatepec No. 351, El Haya, Xalapa, Veracruz, 91070, Mexico.
authors.forename: Santiago
authors.initials: S
authors.lastname: Ramírez-Barahona
authors.affiliation: Departamento de Biología Evolutiva, Instituto de Ecología, A.C., Carretera antigua a Coatepec No. 351, El Haya, Xalapa, Veracruz, 91070, Mexico.
authors.forename: Andrés Ernesto
authors.initials: AE
authors.lastname: Ortiz-Rodriguez
authors.affiliation: Departamento de Biología Evolutiva, Instituto de Ecología, A.C., Carretera antigua a Coatepec No. 351, El Haya, Xalapa, Veracruz, 91070, Mexico.|Cátedras CONACYT-Instituto de Investigaciones sobre los Recursos Naturales, Universidad Michoacana de San Nicolás de Hidalgo, Av. San Juanito Itzícuaro s/n, Col. Nueva Esperanza, Morelia, Michoacán, CP 58330, Mexico.
authors.forename: Clementina
authors.initials: C
authors.lastname: González
authors.affiliation: Departamento de Biología Evolutiva, Instituto de Ecología, A.C., Carretera antigua a Coatepec No. 351, El Haya, Xalapa, Veracruz, 91070, Mexico.
authors.forename: María Teresa
authors.initials: MT
authors.lastname: Mejía Saules
authors.affiliation: Centro Regional del Bajío, Instituto de Ecología, A.C., Avenida Lázaro Cárdenas 253, Pátzcuaro, Michoacán, 61600, Mexico.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Ruiz-Sanchez
mesh_terms: D001499:Bayes Theorem; D005075:Biological Evolution; D057231:Climate Change; D017753:Ecosystem; D065928:Forests; D051456:Gene Flow; D014644:Genetic Variation; D006239:Haplotypes; D006801:Humans; D028183:Loranthaceae / Q000145:classification / Q000235:genetics*; D008954:Models, Biological; D010802:Phylogeny; D058974:Phylogeography
keywords: Loranthaceae; Mesoamerica; Mistletoes; Phylogeography; Pleistocene; Psittacanthus