Contemporary patterns of genetic diversity of cedrela fissilis offer insight into the shaping of seasonal forests in eastern South America

Abstract

In C. fissilis, genetic diversity is structured according to geography: the Atlantic range and the Chiquitano range each harbor a genealogical lineage. Interfertility and varying levels of admixture between lineages provide strong evidence that the lineages evolved under geographic, but not genetic, isolation. Admixture is of recent origin, owing to population expansion. Cedrela fissilis shares this dual pattern of distribution of genetic diversity with other phylogenetically unrelated taxa that are typically associated with seasonal forests.

Genetic diversity of Cedrela fissilis (Meliaceae) in the Brazilian Atlantic Forest reveals a complex phylogeographic history driven by Quaternary climatic fluctuations

“…S3). This result corroborates findings of Mangaravite et al (), who tested for heterozygosity excess in microsatellite data of C. fisslis and found no significant heterozygosity excess (which would be indicative of a genetic bottleneck) in any of the populations.…”

“…This does not reject the drier and cooler climate reported for the Southeast based on palynological data (Behling, ), as C. fissilis shifted its distribution toward central Brazil, and returning southward after the LGM. This is further corroborated by three additional findings: (i) high levels of admixture between the two genealogical lineages (Mangaravite et al, ), (ii) the presence of a new lineage in another ecotone, also between the Cerrado and the BAF (Diaz‐Soto et al, ), and (iii) the discovery of a new species of Cedrela from the center of Brazil (Huamán‐Mera et al, unpublished data). Additional sampling in the center of Brazil is required to increase the genetic structure resolution and to obtain a thorough history of the Paraná basin and its importance for the diversity in the BAF.…”

“…They found that the species consists of two distinct genealogical lineages: one centered in the Chiquitano range and the other one in the Atlantic range, separated by the Cerrado (Brazillian savanna). These patterns were confirmed using 10 microsatellite markers by Mangaravite et al (2016). In the Atlantic range, populations occur from 20 m to more than 1600 m above sea level (Mangaravite et al, 2016).…”

“…Dispersal ability is a key factor that influences gene flow (Freeland, ), and the level of admixture among populations of C. fissilis reflects gene flow likely by dispersal across the entire Atlantic range. Indeed, long‐distance dispersal has been an important process that shaped not only the current distribution of C. fissilis (Garcia et al, ; Mangaravite et al, ), but the entire genus from deep time to the present (Muellner et al, ; Koecke et al, ). The low habitat suitability in the north‐east of the Brazilian Atlantic coast during the LIG together with the strong genetic structure (genetic group 5 and haplotypes H5, H7, and H14) and high genetic divergence (see F ST values of SER population) of the north‐eastern populations suggest that long‐distance dispersal to this region might have occurred following the late‐Quaternary climatic fluctuations.…”

“…The phylogeographic connection between the FR2 population and the northeastern populations could constitute a relic of such a “Peri‐Amazonian” dispersal. Indeed, FR2 and populations in the center of Brazil exhibit a high admixture pattern from either the Atlantic or Chiquitano range (Mangaravite et al, ; Diaz‐Soto et al, ; Huamán‐Mera, unpublished data). The “Parana Atlantic” route may have a high impact on the genetic diversity found in the northern C. fissilis populations, because the network analysis indicated two independent connections between the north‐eastern and the Atlantic coast, suggesting independent dispersals.…”