A feasible method to extract DNA from the cambium of high-canopy trees: from harvest to assessment

Muitas árvores tropicais possuem dossel alto e folhas não facilmente acessíveis. O uso de tecido de um órgão mais acessível (câmbio) para extração de DNA pode ser uma alternativa para estudos moleculares. Nós adaptamos uma metodologia viável para extrair DNA genômico de tecido cambial coletado no campo para avaliação com PCR. Testamos três condições de armazenamento (dois tampões e sílica gel) e quatro períodos após a coleta. Utilizamos protocolos descritos anteriormente e os testamos em três espécies encontradas em florestas amazônicas e outros biomas: Anadenanthera peregrina var. peregrina, Cedrela fissilis e Ceiba speciosa. Nosso protocolo foi eficaz na obtenção de DNA adequado para sequenciamento e genotipagem de microssatélites. Recomendamos o uso de sílica para armazenamento de longo prazo e o tampão com ácido ascórbico para curto prazo. (AU)

Diversity of mycorrhizal Tulasnella associated with epiphytic and rupicolous orchids from the Brazilian Atlantic Forest, including four new species.

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.

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

PREMISE OF THE STUDY: We investigated how genetic diversity is distributed across the range of Cedrela fissilis, a tree species associated with seasonal neotropical forests, to gain insights into competing biogeographic scenarios that explain how disjunct distributions of these forests were shaped. METHODS: A total of 250 samples were sampled from 18 sites across the species' range in Brazil and eastern Bolivia and genotyped with 10 microsatellite loci. An array of complementary methods-F statistics, analyses of molecular variance (AMOVA), and clustering analyses-assessed genetic diversity, population differentiation, and structure. KEY RESULTS: Most of the genetic diversity (82.5%) was partitioned within populations, but about 12% was due to differences among groups of populations on either side of the Cerrado or located within the Cerrado; mean expected heterozygosity and mean observed heterozygosity were 0.821 and 0.704, respectively. The 250 samples were sorted into two Bayesian groups: one group for each side of the Cerrado. The populations showed varying levels of admixture, with the greatest admixture evident in populations located toward central Brazil. CONCLUSIONS: 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.