Nuclear phylogeography of the temperate tree species Chiranthodendron pentadactylon (Malvaceae): Quaternary relicts in Mesoamerican cloud forests.

BACKGROUND: The Mexican hand tree or Canac (Chiranthodendron pentadactylon) is a temperate tree species of cloud and pine-oak forests of southern Mexico and Guatemala. Its characteristic hand-shaped flower is used in folk medicine and has constituted the iconic symbol of the Sociedad Botánica de México since 1940. Here, the evolutionary history of this species was estimated through phylogeographic analyses of nuclear DNA sequences obtained through restriction site associated DNA sequencing and ecological niche modeling. Total genomic DNA was extracted from leaf samples obtained from a representative number (5 to 10 per sampling site) of individuals distributed along the species geographic range. In Mexico, population is comprised by spatially isolated individuals which may follow the trends of cloud forest fragmentation. By contrast, in Guatemala Chiranthodendron may constitute a canopy dominant species near the Acatenango volcano. The distributional range of this species encompasses geographic provinces separated by the Isthmus of Tehuantepec. The objectives of the study were to: (i) estimate its genetic structure to define whether the observed range disjunction exerted by the Isthmus of Tehuantepec translates into separate populations, (ii) link population divergence timing and demographic trends to historical climate change, and (iii) test hypotheses related to Pleistocene refugia. RESULTS: Patterns of genetic diversity indicated high levels of genetic differentiation between populations separated by the Isthmus. The western and eastern population diverged approximately 0.873 Million years ago (Ma). Demographic analyses supported a simultaneous split from an ancestral population and rapid expansion from a small stock approximately 0.2 Ma corresponding to a glacial period. The populations have remained stable since the LIG (130 Kilo years ago (Ka)). Species distribution modelling (SDM) predicted a decrease in potential distribution in the Last Interglacial (LIG) and an increase during the Last Glacial Maximum (LGM) (22 Ka), Mid-Holocene (6 Ka) and present times. CONCLUSIONS: Divergence time estimations support the hypothesis that populations represent Quaternary relict elements of a species with broader and northernmost distribution. Pleistocene climatic shifts exerted major influence on the distribution of populations allowing dispersion during episodes of suitable climatic conditions and structuring during the first interglacial with a time period length of 100 Kilo years (Kyr) and the vicariant influence of the Isthmus. Limited demographic expansion and population connectivity during the LGM supports the moist forest hypothesis model.

Correction to: Nuclear phylogeography of the temperate tree species Chiranthodendron pentadactylon (Malvaceae): Quaternary relicts in Mesoamerican cloud forests.

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Genetic structure, phylogeography, and migration routes of Bouteloua gracilis (Kunth) Lag. ex Griffiths (Poaceae:Chloridoideae).

Blue grama grass (Bouteloua gracilis) populations are found in widely variable environments, tolerating drought, alkaline soils and different levels of grazing. Many ploidy levels have been reported for this species that is also considered to be phenotypically plastic and morphologically variable. Recently a decline in its cover and frequency in the North American shortgrass steppe and central Mexico has been reported although much about the biology of the species is unknown, including genetic diversity throughout its distribution. Genetic and phylogeographic structure and phylogenetic relationships among B. gracilis were estimated employing next generation sequencing of a high number of SNPs and loci. Population genetics and Structure analyses were performed. We compared the marginal likelihoods of different migration models using MIGRATE and obtained the best population model of migration for our data. Demographic expansion of B. gracilis was observed graphically with a mismatch distribution obtained in DNAsp. Bayesian and Maximum Likelihood methods were used to resolve phylogenetic relationships among B. gracilis and its closely related species as well as within B. gracilis populations. B. gracilis is sister to the B. chasei and B. herrera arrietae clade. Among the populations of the species two highly supported clades were resolved, grouping samples from Mexico and USA respectively. Allele frequencies determined three population clusters: CUSA from the Great Plains, MEX from central and southern Mexico, and WUSA-NMEX from northern Mexico and the western mountainous region of USA, the latter of which contains an allele admixture of the other two clusters. The haplotype network revealed an ancestral haplotype originating in Mexico, from which the rest of the haplotypes diversified to the north. Both evidence of gene flow and isolation among populations was observed. Genetic clusters are not genetically structured and variation is higher among populations. The genetic and morphological data do not support recognition of ecotypes or infraespecific taxa. However, the Great Plains populations are least diverse, making them most vulnerable to environmental change.

Hidden in plain sight: Morphological and phylogenetic evidence for Bouteloua arizonica, a species distinct from Bouteloua aristidoides (Poaceae, Chloridoideae).

Two varieties of Bouteloua aristidoides have been recognized, the widespread var. aristidoides and the more narrowly distributed var. arizonica. The two varieties differ in inflorescence form even more than that seen between many other closely related species of Bouteloua. We therefore asked whether these taxa might be better regarded as distinct species. A total of 93 vouchers were studied by using morphometry (principal components analysis and statistical tests), leaf micromorphology, ancestral state reconstruction, and/or molecular (ITS, trnC-rpoB and trnT-L-F) phylogenetic analyses. Except from the ITS tree, all results supported elevation of B. aristidoides var. arizonica to the rank of species, thus the new combination Bouteloua arizonica (M.E. Jones) L.F. Cuellar & Columbus comb. nov. et stat. nov., is proposed. Chloroplast and combined chloroplast-nuclear molecular trees depicted var. arizonica as monophyletic (even in sympatric populations with var. aristidoides) and reveals phylogenetic structure within var. aristidoides for which the presence of new undescribed varieties of B. aristidoides (different from B. arizonica) is addressed. B. arizonica differs from B. aristidoides in having fewer branches per inflorescence, a bigger branch with more spikelets, and a shorter branch extension. Scanning electron microscopy revealed the presence of papillae on leaves of B. arizonica as a clear synapomorphy. Growing mature plants of B. arizonica from seeds in a greenhouse revealed a strong cleistogamous nature for this species for which gene flow in sympatric populations with B. aristidoides seems unlikely. A taxonomic treatment and distribution map for identification of B. arizonica is provided.