Zanella et al. 2015 (Conference Paper) Bromeliaceae

Natural hybridization between two sympatric species of bromeliads from the Atlantic Forest: evolutionary implications

Author(s):—C. Zanella, C. Palma-Silva, M. Goetze & F. Bered 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:—Hybridization and introgression are important for understanding the process of speciation, the movement of genes across species boundaries and the maintenance of species cohesion. The degree of reproductive isolation among related species is an important factor influencing the genetic integrity of species and hybrid formation. Multiple pre- and postzygotic components are responsible for reproductive isolation among plant species pairs. Vriesea carinata and V. incurvata are two bromeliad species of the Tillandsioideae subfamily (Bromeliaceae) with high ornamental appeal, suffering impacts from illegal extraction. Both species are endemic and distributed along the Brazilian Atlantic Rainforest (BAF), with populations occurring in sympatry. These bromeliads showed sequential flowering along the year, with a short period of flowering overlap, and share the same floral visitor; both were pollinated by hummingbirds. Here, we investigated the potential of natural hybridization in four sympatric populations of Vriesea carinata and Vriesea incurvata. A total of 279 individuals of four sympatric populations were sampled, one allopatric population of V. carinata and one allopatric population of V. incurvata were also sampled, to be analyzed as reference populations. All samples were genotyped with 14 nuclear microsatellites and two cpDNA regions (matK gene and trnL-trnF intergenic spacer) were sequenced. Bayesian Structure results of all four sympatric populations analyzed presented hybrids (a total of 19; 9.1% of the total individuals sampled; 0.10 < q < 0.90) between V. carinata and V. incurvata. Nevertheless, considering NewHybrids results, more hybrids were identified. Bayesian assignmentanalysis detected the presence of F2 and backcrosses towards V. incurvata. cpDNA network identified low haplotypic sharing, resulting probably from ancestral polymorphism or bidirectional introgression between these two species. Interestingly, populations at lower latitudes showed more hybrids than populations further south, this pattern could be influenced by ecological factors, since these species show sequential flowering with a short period of overlap and pollinator sharing. A latitudinal gradient can be influenced by the seasons,
temperature, rainfall and consequently affect the species? flowering period. The temporal difference in the
flowering period of the two species may act as a strong prezygotic reproductive barrier, being the main force
responsible for species cohesion. The presence of reproductive barriers has allowed these species to persist
in sympatry for extended periods of time, ensuring the maintenance of species cohesion.

Keywords:—Vriesea; Hybridization; Introgression.