Karina Martins

Genetic structure of Bertholletia excelsa populations from the Amazon at different spatial scales

Population genetic structure and genetic diversity levels are important issues to understand population dynamics and to guide forest management plans. The Brazil nut tree (Bertholletia excelsa Bonpl.) is an endemic species, widely distributed through Amazonian upland forests and also an important species for the local extractive economy. Our aim was to analyze the genetic structure of Brazil nut trees at both fine and large scales throughout the Amazon Basin, contributing to the knowledge base on this species and to generate information to support plans for its conservation. We genotyped individuals from nine sites distributed in five regions of the Brazilian Amazon using 11 microsatellite loci. We found an excess of heterozygotes in most populations, with significant negative inbreeding coefficients (f) for five of them and the fine-scale structure, when present, was very small. These results, as a consequence of self-incompatibility, indicate that conservation plans for B. excelsa must include the maintenance of genetic diversity within populations to ensure viable amounts of seeds for both economic purposes and for the local persistence of the species.

Pollen and seed flow patterns of Carapa guianensis Aublet. (Meliaceae) in two types of Amazonian forest

Various factors affect spatial genetic structure in plant populations, including adult density and primary and secondary seed dispersal mechanisms. We evaluated pollen and seed dispersal distances and spatial genetic structure of Carapa guianensis Aublet. (Meliaceae) in occasionally inundated and terra firme forest environments that differed in tree densities and secondary seed dispersal agents. We used parentage analysis to obtain contemporary gene flow estimates and assessed the spatial genetic structure of adults and juveniles. Despite the higher density of adults (diameter at breast height ≥ 25 cm) and spatial aggregation in occasionally inundated forest, the average pollen dispersal distance was similar in both types of forest (195 ± 106 m in terra firme and 175 ± 87 m in occasionally inundated plots). Higher seed flow rates (36.7% of juveniles were from outside the plot) and distances (155 ± 84 m) were found in terra firme compared to the occasionally inundated plot (25.4% and 114 ± 69 m). There was a weak spatial genetic structure in juveniles and in terra firme adults. These results indicate that inundation may not have had a significant role in seed dispersal in the occasionally inundated plot, probably because of the higher levels of seedling mortality.

The role of very small fragments in conserving genetic diversity of a common tree in a hyper fragmented Brazilian Atlantic forest landscape

In hyper fragmented biomes, conservation of extant biota relies on preservation and proper management of remnants. The maintenance of genetic diversity and functional connectivity in a landscape context is probably key to long-term conservation of remnant populations. We measured the genetic diversity in seedlings and adults of tree Copaifera langsdorffii and evaluated whether edge and density-dependent effects drive natural regeneration in a set of very small and degraded Brazilian Atlantic forest fragments. We evaluated the role of small remnants in the conservation of genetic diversity in a hyper fragmented landscape and discuss the challenge of long-term population sustainability of such altered habitats. High genetic diversity in adults indicated these fragments are valuable targets for C. langsdorffii in situ conservation, but both genetic diversity and divergence among patches decreased in seedlings. In our landscape, regeneration increased as it neared edges and adults; suggesting this population is resilient to fragmentation. However, at a broader scale, current levels of gene flow have not been sufficient to prevent the loss of genetic diversity across generations. Restoration plans, even at a small scale, are necessary to promote fragment connectivity and spatially expand opportunities for the fairly restricted gene flow observed in this severely fragmented Brazilian Atlantic forest region.

Allelic diversity in populations of Solanum lycocarpum A. St.-Hil (Solanaceae) in a protected area and a disturbed environment

This study aimed to compare the genetic diversity of populations of Solanum lycocarpum A.St.-Hil between natural and human disturbed environments, with the assumption that protected areas have greater genetic diversity than disturbed areas. For this study, two populations were sampled in Goias State, Brazil. One was located in a conservation unit, Serra de Caldas Novas State Park, in the Caldas Novas municipality. The other was located in a pasture area in the municipality of Morrinhos. The two populations are 41 km apart. We sampled 60 individuals from each population, which were genotyped with five microsatellite loci (SSR). The highest number of alleles was recorded in the population of the conservation unit, where we found 11 exclusive and five rare alleles. In the disturbed area, we recorded only three exclusive alleles and one rare allele. Although we did not observe significant inbreeding in these populations, genetic divergence between them was high (GST (Hedrick)=0.147 =0.147) for a species with long distance seed dispersal. The results corroborate the hypothesis that the population in the less disturbed area harbors greater allelic diversity. They also confirm the effectiveness of using protected areas to preserve the genetic diversity of the species.

Mating system variation among populations, individuals and within and among fruits in Bertholletia excelsa

Abstract The aim of this study was to investigate variation in mating system among three Brazilian Amazon populations of the tree Bertholletia excelsa with different levels of anthropogenic interventions. We collected open-pollinated seeds from one natural population, remnant trees dispersed in a pasture, and trees from a plantation. Outcrossing rate not varied among the populations and indicates that all seeds were originated from outcrossing (tm=1.0). Mating among relatives was significant higher in the plantation than forest and pasture populations, probably due the fact that many trees are related in the plantation. Correlated mating was significantly higher in pasture (rp=0.47) and plantation (rp=0.51) than in the natural population (rp=0.22), suggesting that trees in natural population are pollinated by a higher number of pollen donors. The paternity correlation was significantly higher within (rp(w)=0.41) than among fruits (rp(a)=0.18), showing a higher probability to find full-sibs within than among fruits. The fixation index was generally lower in seed trees than in their seedlings, suggesting selection for heterozygous individuals from seedling to adult stages. Progeny arrays collected from the natural population had a lower proportion of pairwise full-sibs than in pasture and plantation and higher variance effective size (2.75) than trees in pasture (2.15) and plantations (2.22). Results highlight that seed collections for conservation, breeding and reforestation programs preferentially should be carried out in natural populations due low proportion highest variance effective size within progeny.

PARÂMETROS GENÉTICOS PARA A CONSERVAÇÃO DE Hymenaea courbaril L. NA AMAZÔNIA SUL-OCIDENTAL

A perda de diversidade em regioes tropicais tem sido pauta em diversas discussoes governamentais e nao governamentais, com foco principalmente na fragmentacao e destruicao de ecossistemas naturais. No entanto, tomadas de decisoes sobre a conservacao de recursos geneticos precisam ser pautadas em parâmetros geneticos populacionais, especialmente para as especies com interesse economico que sao alvo de maior interferencia humana. Este trabalho teve como objetivo definir e avaliar parâmetros geneticos para a conservacao de populacoes de jatoba (Hymenaea courbaril) na regiao sul-ocidental da Amazonia brasileira. A especie e uma das que possuem madeira mais valiosa e e uma das mais intensamente exploradas na Amazonia brasileira. O estudo foi realizado em tres areas de florestas preparadas para a exploracao madeireira, segundo plano de manejo sustentavel. Calculou-se, com uso de oito locos de marcadores microssatelites, a diversidade genetica, os estimadores para a conservacao da especie e a divergencia entre as populacoes. As populacoes com menor densidade populacional (< 0,08 ind.ha-1) apresentaram maior diversidade genetica e indice de fixacao elevado. A populacao com maior densidade populacional (0,25 ind.ha-1) foi a que apresentou menor diversidade genetica e ausencia de endogamia. A Area Minima Viavel para conservacao da especie foi compativel com a realidade do local de estudo, com uma ressalva de uma das populacoes onde ha necessidade de uma area muito maior em relacao as demais. A divergencia genetica foi elevada (Gst = 0,344) e as populacoes foram classificadas como Unidades Independentes para o Manejo.

Genetic variation and effective population size of a Myracrodruon urundeuva (Engler) Fr. Allem. provenance and progeny test

ABSTRACT Ex situ conservation of tree species in provenance and progeny tests allow the estimation of genetic parameters for quantitative traits and are also useful for tree breeding programs. This study aimed at estimating the genetic variability of provenance and progeny test of Myracrodruon urundeuva and providing subsidies for ex situ conservation and the use of germplasm in breeding programs. We also estimated the variance effective population size () of seeds sampled from this test, simulating six different scenarios for test management and seed collection strategies. We estimated genetic parameters for diameter at breast height (DBH), total height, volume and fork in 31-year-old provenance and progeny test established with 91 open-pollinated progenies from five provenances, allocated in a compact family block design at Pederneiras Experimental Station, Sao Paulo, Brazil. The genetic-statistical analysis was based on REML/BLUP procedure. Significant genetic differences were detected only among progenies within provenances. Individual heritability was high for DBH, height, and volume. We hypothesize that inter-tree competition inflated these estimations and have, consequently, overrated the estimates for genetic gain. Thus, this test should be mainly used for conservation purposes. The estimates for varied considering different scenarios, showing that female gametic control is the best strategy to achieve higher gains on , being an important suggestion for the management and seed collection strategies in dioecious species as M. urundeuva.

Pollen and seed dispersal of Brazil nut trees in the southwestern Brazilian Amazon

Pollen and seed dispersal patterns greatly influence the spatial distribution of plant genetic diversity. Microsatellite-based parentage analysis provides accurate estimates of contemporary gene dispersal. Although most tropical trees have been shown to exhibit widespread pollen dispersal, few studies have estimated contemporary gene dispersal after seedling establishment. Bertholletia excelsa (Lecythidaceae) is pollinated by large-bodied bees, while previous seed-tracking experiments suggest their seeds are mainly dispersed across very short distances by scatter-hoarding rodents, who primarily act as seed predators. Here we used parentage analysis to provide contemporary estimates of pollen and seed dispersal in B. excelsa recruits. We examined six 25-ha plots located in two natural stands in the Acre River valley, in the southwestern Brazilian Amazon. We used 11 microsatellite markers to estimate genetic diversity and fixation index parameters in adults, seedlings and saplings. Genetic diversity was moderate and did not differ across size classes or sampling locations. We assigned pollen and seed parents for < 20% of the recruits, indicating that most events of realized gene flow occurred beyond our 25-ha plots. Only 10 parentage assignments were confirmed with 80% confidence. Pollen distance ranged from 33 to 372 m and seed dispersal from 58 to 655 m. Actual seed-dispersal distances were far greater than the estimates obtained in previous seed-tracking experiments. Thus, studies encompassing larger sampling areas are necessary to determine a more representative spatial scale of B. excelsa’s pollen and seed dispersal capacity in natural stands.

Genetic diversity of Bertholletia excelsa, an Amazonian species of wide distribution

Background Amazonian upland forests are expansive and can comprise large continuous tracts. There have been several studies on the population genetic structure of species in this kind of forest, but there are few studies that aim to understand genetic structure throughout the Amazon [1]. The Brazil-nut tree, Bertholletia excelsa, is a monotypic genus, endemic to upland forests and distributed along almost the entire expanse of the Amazon [2-5]. Genetic diversity distribution through Amazon forest is an understudied issue, specially in plants. Quantifying and understanding population genetic structure, associated to gene flow and mating system studies are recognized as important tools for the development of strategies for conservation and management. Such information can also be helpful in identifying effects of habitat fragmentation [6,7]. This study aimed to evaluate genetic structure of B. excelsa populations in the Amazon and to verify if the structuring is influenced by distance between them.