Genetic admixture and lineage separation in a southern A

SANTIAGO MORELLO; SILVANA M. SEDE

AoB PLANTS

Oxford University Press

Lugar: Oxford; Año: 2016 vol. 8

Mountain uplifts have generated new ecologic opportunities for plants, and triggered evolutionary processes,favouring an increase on the speciation rate in all continents. Moreover, mountain ranges may act as corridorsor barriers for plant lineages and populations. In South America a high rate of diversification has been linked toAndean orogeny during Pliocene/Miocene. More recently, Pleistocene glacial cycles have also shaped species distributionand demography. The endemic genus Escallonia is known to have diversified in the Andes. Species with similarmorphology obscure species delimitation and plants with intermediate characters occur naturally. The aim ofthis study is to characterize genetic variation and structure of two widespread species of Escallonia: E. alpina andE. rubra. We analyzed the genetic variation of populations of the entire distribution range of the species and we alsoincluded those with intermediate morphological characters; a total of 94 accessions from 14 populations were usedfor the Amplified Fragment Length Polymorphism (AFLP) analysis. Plastid DNA sequences (trnS-trnG, 30trnV-ndhCintergenic spacers and the ndhF gene) from sixteen accessions of Escallonia species were used to construct aStatistical Parsimony network. Additionally, we performed a geometric morphometrics analysis on 88 leaves from35 individuals of the two E. alpina varieties to further study their differences. Wright?s Fst and analysis of molecularvariance tests performed on AFLP data showed a significant level of genetic structure at the species and populationlevels. Intermediate morphology populations showed a mixed genetic contribution from E. alpina var. alpina and E.rubra both in the Principal Coordinates Analysis (PCoA) and STRUCTURE. On the other hand, E. rubra and the two varietiesof E. alpina are well differentiated and assigned to different genetic clusters. Moreover, the StatisticalParsimony network showed a high degree of divergence between the varieties of E. alpina: var. alpina is more closelyrelated to E. rubra and other species than to its own counterpart E. alpina var. carmelitana. Geometric morphometricsanalysis (Elliptic Fourier descriptors) revealed significant differences in leaf shape between varieties. We found thatdiversity in Escallonia species analyzed here is geographically structured and deep divergence between varieties ofE. alpina could be associated to ancient evolutionary events like orogeny. Admixture in southern populations couldbe the result of hybridization at the margins of the parental species? distribution range.