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 analysis provides a robust method for understanding the ways in which human interventions in ecosystems may affect genetic diversity and species survival, providing an empirical basis for evidence-based conservation and management planning. This review aims to (1) describe the most informative and widely-used molecular markers for genotype analysis, and describe the methods for using that genotype data to understand (2) genetic diversity and structure; and (3) mating system, pollen and seed dispersal. For each area of investigation we discuss the types of analyses that can be performed, the software available for the analyses, what the analyses indicate, and provide examples from the literature of studies using these approaches. The review focuses on Neotropical tree species because Neotropical forests are highly diverse, are under particular threat from anthropogenic landuse change, and trees are useful model organisms to investigate patterns over evolutionary time and across geographical space.
the genus Tulasnella often forms mycorrhizas with orchids and has worldwide distribution. Species of this genus are associated with a wide range of orchids, including endangered hosts. initially, species identification relied mostly on morphological features and few cultures were preserved for later phylogenetic comparisons. In this study, a total of 50 Tulasnella isolates were collected from their natural sites in Minas Gerais, Brazil, cultured, and subjected to a phylogenetic analysis based on alignments of sequences of the internal transcribed spacer (itS) of the nuclear ribosomal DnA. our results, based on phylogeny, integrated with nucleotide divergence and morphology, revealed the diversity of isolated Tulasnella species, which included four new species, namely, Tulasnella brigadeiroensis, Tulasnella hadrolaeliae, Tulasnella orchidis and Tulasnella zygopetali. the conservation of these species is important due to their association with endangered orchid hosts and endemic features in the Brazilian Atlantic forest.
Quaternary climatic fluctuations have shaped the geographic distribution of lineages, potentially affecting the demography, genetic structure, and patterns of genetic diversity of extant species. Different phylogeographic scenarios have been proposed for plants in neotropical cloud forests during the Last Glacial Maximum based on paleoecological data: the dry refugia hypothesis (DRH) and the moist forest hypothesis. We specifically focus on the Brazilian Atlantic Forest (BAF) range of Cedrela fissilis (Meliaceae), sampling 410 specimens from 50 localities. Our study combines analyses of the genetic diversity, phylogeographic patterns, and past geographic distributions with a particular focus on highland populations. We identified 283 alleles across the 11 microsatellite loci, ranging from 18 to 33 alleles per locus, distributed across five genetic groups. Most populations of C. fissilis from the BAF exhibited a diffuse genetic structure, reflected in low pairwise FST values, which could be the consequence of high gene flow. In addition, the plastid data showed a connection between the western, southern, and eastern populations in the North‐East of Brazil, but no association between genetic data and elevation was observed. Habitat suitability projections over the past 140 000 years showed less fragmentation relative to the present, indicating a higher connectivity and gene flow. Our results provide support for both the moist forest as well as the DRH, suggesting that most likely, a mixture of these processes has acted through space and time.
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