Phylogeography and climatic niche evolution in live oaks (Quercus series Virentes) from the tropics to the temperate zone

Abstract

Aim We investigated the phylogeography, geographical variation in leaf morphology, freezing tolerance and climatic niches of two widespread evergreen sister oak species (Quercus) in the series Virentes.Location South-eastern USA, Mexico and Central America.Methods Nuclear microsatellites and non-recombining nuclear and chloroplast DNA sequences were obtained from trees throughout the range of two sister lineages of live oaks, represented by Quercus virginiana in the temperate zone and Q. oleoides in the tropics. Divergence times were estimated for the two major geographical and genetic breaks. Differentiation in leaf morphology, analysed from field specimens, was compared with the molecular data. Freezing sensitivities of Q. virginiana and Q. oleoides populations were assessed in common garden experiments. ResultsThe geographical break between Q. virginiana and Q. oleoides was associated with strong genetic differentiation of possible early Pleistocene origin and with differentiation in freezing sensitivity, climatic envelopes and leaf morphology. A second important geographical and genetic break within Q. oleoides between Costa Rica and the rest of Central America showed a mid-Pleistocene divergence time and no differentiation in leaf morphology. Population genetic differentiation was greater but genetic diversity was lower within the temperate Q. virginiana than within the tropical Q. oleoides, and genetic breaks largely corresponded to breaks in leaf morphology.Main conclusions Two major breaks, one between Mexico and the USA at the boundary of the two species, and a more recent one within Q. oleoides between Honduras and Costa Rica, implicate climatic changes as potential causes. The latter break may be associated with the formation of the Cordillera de Guanacaste, which was followed by seasonal changes in precipitation. In the former case, an 'out of the tropics' scenario is hypothesized, in which the acquisition of freezing tolerance in Q. virginiana permitted colonization of and expansion in the temperate zone, while differences in climatic tolerances between the species limited secondary contact. More pronounced Pleistocene changes in climate and sea level in the south-eastern USA relative to coastal Mexico and Central America may explain the greater population differentiation within temperate Q. virginiana and greater genetic diversity in tropical Q. oleoides. These patterns are predicted to hold for other taxa that span temperate and tropical zones of North and Central America.

Global Patterns of Leaf Defenses in Oak Species

“…1A). While intraspecific variation in both climate and traits bears further investigation in oaks, we find that species identity explains an average of 44%-85% of total variance in climatic variables, which supports an earlier study in which leaf physiological traits show strong among-species variance relative to within-species variance, even across a strong latitudinal gradient (Cavender-Bares et al 2011).…”

“…1A). While intraspecific variation in both climate and traits bears further investigation in oaks, we find that species identity explains an average of 44%-85% of total variance in climatic variables, which supports an earlier study in which leaf physiological traits show strong among-species variance relative to within-species variance, even across a strong latitudinal gradient (Cavender-Bares et al 2011).We used eight of the 19 WorldClim climatic measures in our study, as follows: BIO1, mean annual temperature; BIO4, temperature seasonality, estimated as the standard deviation of temperature among months; BIO5, maximum temperature (mean temperature of the warmest month); BIO6, minimum temperature (mean temperature of the coldest month); BIO12, mean annual precipitation; BIO13, maximum precipitation, estimated as the mean precipitation of the wettest month; BIO14, minimum precipitation of the driest month; and BIO15, precipitation seasonality, estimated as the coefficient of variation in precipitation across months. We use the italicized abbreviations throughout this article for sake of readability.…”

Genetic diversity and structure of wild populations ofCarica papayain Northern Mesoamerica inferred by nuclear microsatellites and chloroplast markers

“…Although the vast majority of the world's tree diversity lies in the tropics, most of the evolutionary history and genetic knowledge comes from temperate and boreal forests, with a marked emphasis on pines, poplars and oaks (Dick, 2010). In Northern Mesoamerica, phylogeographical studies have focused mainly on montane temperate species or tropical species inhabiting cloud forest (Jaramillo Correa et al, 2008;Cavender-Bares et al, 2011;Gutiérrez-Rodr ıguez et al, 2011;Ornelas et al, 2013;Ru ız-S anchez and Ornelas, 2014). Moreover, Mesoamerica has been recognized as one of the centres of origin of many domesticated plant species (Vavilov, 1926), so natural populations of important crops species and their wild relative species inhabit this region.…”

Associations of Leaf Spectra with Genetic and Phylogenetic Variation in Oaks: Prospects for Remote Detection of Biodiversity

“…Populations experience contrasting climatic regimes and biotic factors in their sites of origin and may thus have adapted to their contrasting local conditions. Moreover, gene flow is limited among populations given that they are each several hundred kilometers apart, allowing for genetic drift and phenotypic divergence among them [35,36]. As a consequence, we expected that populations might be phenotypically differentiated.…”