We report a detailed analysis of the population genetic structure, mating system, and gene flow of heart of palm (Euterpe edulis Mart.-Arecaceae) in central Brazil. This palm is considered a keystone species because it supplies fruits for birds and rodents all year and is intensively harvested for culinary purposes. Two populations of this palm tree were examined, using 18 microsatellite loci. The species displays a predominantly outcrossed mating system (tm = 0.94), with a probability of full sibship greater than 70% within open-pollinated families. The following estimates of interpopulation genetic variation were calculated and found significant: FIT = 0.17, FIS = 0.12, FST = 0.06, and RST = 0.07. This low but significant level of interpopulation genetic variation indicates high levels of gene flow. Two adult trees were identified as likely seed parents (P > 99.9%) of juveniles located at a distance of 22 km. Gene flow over such distances has not been reported before for tropical tree species. The establishment and management of in situ genetic reserves or ex situ conservation and breeding populations for E. edulis should contemplate the collection of several hundreds open-pollinated maternal families from relatively few distant populations to maximize the genetic sampling of a larger number of pollen parents.

Eucalyptus breeding is typically conducted by selection in open-pollinated progenies. As mating is controlled only on the female side of the cross, knowledge of outcrossing versus selfing rates is essential for maintaining adequate levels of genetic variability for continuous gains. Outcrossing rate in an open-pollinated breeding population of Eucalyptus urophylla was estimated by two PCR-based dominant marker technologies, RAPD and AFLP, using 11 open-pollinated progeny arrays of 24 individuals. Estimated outcrossing rates indicate predominant outcrossing and suggest maintenance of adequate genetic variability within families. The multilcous outcrossing rate (t) estimated from RAPD markers (0.93$0.027), although in the same range, was higher ('0.01) than the estimate based on AFLP (0.89$0.033). Both estimates were of similar magnitude to those estimated for natural populations using isozymes. The estimated Wright's fixation index was lower than expected based on t possibly resulting from selection against selfed seedlings when sampling plants for the study. An empirical analysis suggests that 18 is the minimum number of dominant marker loci necessary to achieve robust estimates of t. This study demonstrates the usefulness of dominant markers, both RAPD and AFLP, for estimating the outcrossing rate in breeding and natural populations of forest trees. We anticipate an increasing use of such PCR-based technologies in mating-system studies, in view of their high throughput and universality of the reagents, particularly for species where isozyme systems have not yet been optimized.

Euterpe edulis is the species of palm found in the Atlantic Forest and Cerrado gallery forest that yields the best heart of palm. A battery of 18 highly polymorphic microsatellite markers was developed from an enriched genomic library. Using fluorescence automated detection an average of 10.6 alleles per locus were found on a sample of 66 individuals sampled from a natural population. These loci allow extremely precise paternity testing, estimation of gene flow and of parentage coefficients among trees in the wild.

Habitat loss threatens biodiversity in tropical forests, having harmful effects on population dynamics and, ultimately, determining the evolutionary destiny of species. Thus, understanding how habitat loss affects microevolutionary processes is an important step in the conservation of genetic resources. However, few studies have explored landscape genetics for plants in tropical environments. Our study evaluated the effects of a landscape-scale reduction in forest cover on genetic diversity and structure of Euterpe edulis (Arecaceae). The research was conducted in Atlantic Forest landscapes in Northeastern Brazil. We randomly chose 16 forest sites, each located in a 13 km 2 landscape with forest cover ranging from 6 to 83 %. After a survey of adults and seedlings in each sampling site, we found a minimum of five individuals of E. edulis at nine sites and sampled leafs from all adults within a 15 9 400 m plot and all seedlings within a 2 9 400 m subplot in each sampling site. We found that the gradient of remaining forest cover at the landscape scale did not affect the genetic diversity measured by any of the descriptors analyzed and each sampling site still harbored populations with high levels of genetic variability. However, we detected the presence of two distinct genetic groups with signs of admixture; the structural pattern of these groups differed between adults and seedlings, mainly in less forested landscapes areas. We believe that E. edulis is a good example of a tropical palm that is experiencing local extirpation before suffering loss of genetic alterations.

In soil, anoxia conditions generated by waterlogging induce changes in genetic, morphological and physiological processes, altering the growth and development of plants. Mass propagation of cacao (Theobroma cacao L.) plantlets (clones) is affected by waterlogging caused by heavy rains and irrigation methods used to induce rooting. An experiment was undertaken to assess the effects of a 45-day flooding (anoxia) on physiological and morphological traits of 35 elite cacao genotypes, aiming at potentially identifying those with greater tolerance to flooding of the growth substrate. Eighteen fluorochrome-labeled microsatellite (SSR) primer pairs were used to assess genetic variability among clones, with 248 alleles being amplified and used to calculate similarity coefficients. The resulting dendrogram indicated the presence of four major groups, in which two represented 60% and 31% of the genotypes tested. A general trend toward high levels of heterozygosity was also found for physiological and morphological traits. The survival index (IS) for flood tolerance observed varied from 30 to 96%. Clones TSA-654, TSA-656, TSA-792, CA-1.4, CEPEC-2009 and PH-17 showed an IS value above 94%, whereas CEPEC-2010, CEPEC-2002, CA-7.1 and VB-903 clones were those mostly affected by waterlogging, with IS value below 56%. All genotypes displayed lenticel and adventitious root formation in response to waterlogging, although with different intensities. To determine whether patterns of physiological response could be associated with tolerance to anoxia, a similarity-grouping analysis was performed using the ratio between waterlogged and control values obtained for a series of physiological variables assessed. No specific pattern of physiological and morphological responses to waterlogging was strictly associated with survival of plantlets. However, results revealed by the dendrogram suggest that absence of leaf chlorosis may be a proper trait to indicate cacao clones with higher survival rates under flooding conditions. Consequences of these findings are discussed in the context of developing improved strategies for mass production of clones from elite cacao genotypes.