Oliveira et al. 2015 (Conference Paper) Encholirium, Rocky Outcrops

Microsatellite data reveal unexpected patterns on Encholirium spectabile population genetic structure

Author(s):—R.C.G. Oliveira, T. Wöhrmann, F. Krapp, M. Alves, K. Weising & A.M. Benko-Iseppon in Benko-Iseppon, A.M.; Alves, M. & Louzada, R. (2015) An overview and abstracts of the First World Congress on Bromeliaceae Evolution. Rodriguésia 66(2): A1-A66.

Publication:— (2015).

Abstract:—Brazilian dry forest Caatinga occupies most of the Brazilian Northeast region, which is known for its extreme environmental conditions, supporting a distinct flora composition as a result of influences from soil, altitude and climatic factors. In this region Encholirium spectabile (Bromeliaceae, Pitcairnioideae) presents striking morphological variation, mainly concerning populations from the northern portion of the ?Espinhaço? Range that include individuals with short pedicels, differing from the long pedicel observed in specimens found mostly on the Caatinga depression, Borborema plateau and Raso da Catarina. The species is almost exclusivelyfound on rocky outcrops and less frequently on shallow and rocky soils, conferring an island-like geographic distribution. In order to assess the population genetic structure of E. spectabile, eight nuclear and four chloroplast microsatellite markers were applied to 240 individuals collected from 21 Caatinga populations. The results were analyzed using the statistics programs STRUCTURE, ARLEQUIN, HAPLOTYPE, GENEPOP and FSTAT. In general terms, populations presented patterns in accordance to other bromeliads from rocky outcrops (Fst nuclear = 0.3604; Fst chloroplast = 0.9055). No correlation between genetic and geographic distances was recognized. For the genetic nuclear data, Bayesian clustering by STRUCTURE revealed two groups (K=2), clustering populations from western Caatinga and Borborema plateau together and isolating them from the central-eastern limit of Raso da Catarina, contrasting to the expectations considering morphological features. Similar patterns were also observed for chloroplast data, where shared haplotypes occurred between northern and southern populations whereas central-eastern populations presented distinct haplotypes.Limited gene flow between these regions was also predicted (Nem ~ 0.1182). The differentiation between these two areas was clear when population pairwise Fst values were compared, since values between these two groups were higher. It was also possible to compare chloroplast and nuclear genetic structure, revealed by AMOVA, uncovering a more efficient nuclear gene flow (5.1 times) than chloroplast, suggesting that pollination plays the main role in gene flow. The dissimilarities between clusters were not expected for this species, as the most important morphological differentiation is between north and south. Since this species presents other variable morphological features, the circumscription of subgroups within this species remains difficult. In this case, environmental factors seem to be responsible for speciation in progress, whereas the observed genetic structure suggests that these two groups represent cryptic species.

Keywords:—Encholirium; Ssr; Cpssr.