Patterns of Gene Flow in Encholirium horridum L.B.Sm., a Monocarpic Species of Bromeliaceae From Brazil

Abstract

Encholirium horridum is a bromeliad that occurs exclusively on inselbergs in the Atlantic Forest biome of Brazil. These rock outcrops form natural islands that isolate populations from each other. We investigated gene flow by pollen through paternity analyses of a bromeliad population in an area of approximately 2 ha in Espírito Santo State, Brazil. To that end, seed rosettes and seedlings were genotyped using nuclear microsatellite loci. A plot was also established from the same population and specimens were genotyped to evaluate their fine-scale spatial genetic structure (SGS) through analyses of spatial autocorrelation and clonal growth. Paternity analysis indicated that 80% of the attributed progenitors of the genotyped seedlings were from inside the study area. The pollen dispersal distances within the area were restricted (mean distance of 45.5 m, varying from 3 to 156 m) and fine-scale SGS was weak (F(ij) = 0.0122, P < 0.001; Sp = 0.009). Clonal growth was found to be a rare event, supporting the monocarpy of this species.

Do plant populations on distinct inselbergs talk to each other? A case study of genetic connectivity of a bromeliad species in an Ocbil landscape

“…The strong genetic structure found in both nuclear and plastidial genomes is in consonance with the first prediction, which enunciates the reduced dispersibility and strong differentiation of populations. Restricted pollen flow by paternity analysis was also detected in E. horridum (Hmeljevski et al., ). The second hypothesis, which predicts the elevated persistence of lineages and long‐lived individuals, is supported by the evidence of the long persistence of populations across time based on genetic data and potential dispersal routes.…”

“…The second hypothesis, which predicts the elevated persistence of lineages and long‐lived individuals, is supported by the evidence of the long persistence of populations across time based on genetic data and potential dispersal routes. Still, besides the absence of clonality in E. horridum , individuals are perennial and have slow growth (Hmeljevski et al., ). Other results, such as mean median genetic diversity of populations—probably purging of deleterious recessive genes (see Hmeljevski et al., )—pollination mediated by vertebrates (Hmeljevski, ), and higher importance of pollen dispersal for genetic exchange than dispersal by seeds, are indicative of the occurrence of the James Effect (i.e., the retention of heterozygosity by selection mechanisms; third hypothesis).…”

“…Still, besides the absence of clonality in E. horridum , individuals are perennial and have slow growth (Hmeljevski et al., ). Other results, such as mean median genetic diversity of populations—probably purging of deleterious recessive genes (see Hmeljevski et al., )—pollination mediated by vertebrates (Hmeljevski, ), and higher importance of pollen dispersal for genetic exchange than dispersal by seeds, are indicative of the occurrence of the James Effect (i.e., the retention of heterozygosity by selection mechanisms; third hypothesis). Lastly, the possible invasion of Atlantic Forest granitic inselbergs by routes from drier surrounding environments is in accordance with the fourth (Semiarid Cradle Hypothesis) prediction of the Ocbil theory.…”

“…Encholirium horridum occurs on inselbergs located from southern Bahia State to the northern Rio de Janeiro State, mainly in the states of Espírito Santo and Minas Gerais, in southeastern Brazil (Hmeljevski, Reis, & Forzza, ). The climate of the area of occurrence can be basically classified as Tropical wet‐dry (Aw; Köppen‐Geiger system), with an average temperature and annual precipitation of c. 24°C and 1,100 mm, respectively (http://pt.climate-data.org).…”

“…This bromeliad species has abundant populations with thousands of individuals. A study on fine‐scale spatial structure (SGS) and paternity analysis in one E. horridum population revealed weak SGS and restricted gene flow with pollination events that did not go beyond 45.5 m (Hmeljevski et al., ). Besides this, clonal growth was found to be a rare event, indicating that the species is monocarpic (Hmeljevski et al., ).…”