Development of microsatellite markers for Hancornia speciosa Gomes (Apocynaceae).

Herein, we describe 34 microsatellite loci developed using an enrichment genomic library for the tree species Hancornia speciosa Gomes (Apocynaceae). Thirty-five individuals were genotyped using 34 primers to analyze the polymorphisms at each locus. The number of alleles per locus ranged from 4 to 20. The average number of alleles was 8.11, and the expected heterozygosity ranged from 0.62 to 0.94. These microsatellite primers will be useful in population genetics studies for this species.

Demographic history and the low genetic diversity in Dipteryx alata (Fabaceae) from Brazilian Neotropical savannas.

Genetic effects of habitat fragmentation may be undetectable because they are generally a recent event in evolutionary time or because of confounding effects such as historical bottlenecks and historical changes in species' distribution. To assess the effects of demographic history on the genetic diversity and population structure in the Neotropical tree Dipteryx alata (Fabaceae), we used coalescence analyses coupled with ecological niche modeling to hindcast its distribution over the last 21 000 years. Twenty-five populations (644 individuals) were sampled and all individuals were genotyped using eight microsatellite loci. All populations presented low allelic richness and genetic diversity. The estimated effective population size was small in all populations and gene flow was negligible among most. We also found a significant signal of demographic reduction in most cases. Genetic differentiation among populations was significantly correlated with geographical distance. Allelic richness showed a spatial cline pattern in relation to the species' paleodistribution 21 kyr BP (thousand years before present), as expected under a range expansion model. Our results show strong evidences that genetic diversity in D. alata is the outcome of the historical changes in species distribution during the late Pleistocene. Because of this historically low effective population size and the low genetic diversity, recent fragmentation of the Cerrado biome may increase population differentiation, causing population decline and compromising long-term persistence.

Development and characterization of new microsatellites for Eugenia dysenterica DC (Myrtaceae).

Microsatellite markers were developed for population genetic analyses of the Neotropical tree Eugenia dysenterica DC (Myrtaceae), after construction of a shotgun genomic library for microsatellite discovery. Nine primers were designed, of which 5 yielded amplified product. These primers were polymorphic for 97 individuals collected in 3 distinct localities. The number of alleles per locus (primer) ranged from 3 to 11 and expected heterozygosities varied from 0.309 to 0.884. The probability of locus identity was ~1.88 x 10(-4) and the probability of paternity exclusion was ~0.9367. The 5 microsatellite primer pairs may be suitable for population genetic studies such as parentage and fine-scale genetic analyses of this species.

Genetic structure in fragmented populations of Solanum lycocarpum A. St.-Hil. with distinct anthropogenic histories in a Cerrado region of Brazil.

Solanum lycocarpum is a woody tree widely distributed in the Cerrado that reaches high population densities in disturbed environments. We examined the genetic diversity and population differentiation of six S. lycocarpum populations with different degrees of human disturbance in order to determine if they are negatively affected by anthropogenic activity. Three populations located in southern and three located in southeastern regions of Goiás State, Central Brazil, were genotyped with five microsatellite markers. The population located in a protected area had higher number of alleles (26) than the remaining populations (19 to 21 alleles). It indicates that extensive and continuous areas of preserved native vegetation contribute positively to the conservation of genetic diversity, even with S. lycocarpum that easily adapts to disturbed environments. The three southeastern populations, although fragmented, had preserved native vegetation and were not significantly different from each other (θp = 0.002). All other population pairs compared were significantly divergent (θp varied from 0.03 to 0.11 between pairs, P < 0.05). We found three distinct sets of allele frequencies. The three southeastern populations shared similar gene pools, as well as the two disturbed southern populations, which are secondary vegetation. The southern population located in protected area had the most dissimilar gene pool. In conclusion, populations showing a higher degree of human disturbance tends to show a larger population differentiation than expected from the isolation by distance model, which in the current scenario of the Cerrado destruction points out to a threat to the long-term conservation of the species.

Geographic shifts in climatically suitable areas and loss of genetic variability in Dipteryx alata ("Baru" Tree; Fabaceae).

Many species are expected to suffer strong shifts in their geographic ranges due to climate changes in the next 50 years, with severe consequences for biodiversity patterns and population structure. We used here an ensemble forecast approach for obtaining species' range in which multiple species distribution models and climatic models were combined to model loss of genetic variability in Baru, Dipteryx alata (Fabaceae), an economically important Neotropical tree native to the Cerrado of Brazil. We estimated a series of genetic parameters (number of alleles per locus, expected heterozygosity under Hardy-Weinberg equilibrium and mutation-drift equilibrium) for this species based on eight microsatellite loci. We then recalculated these parameters assuming that local populations in areas of low future environmental suitability will go extinct. All genetic parameters remained approximately constant up to a 50% threshold of climatic suitability in the future; after this critical threshold there is an abrupt reduction in all parameters, although the magnitude of shift is only about 10% of current values, on average. Thus, despite the shifts in geographic range and climatically suitable areas towards southeastern Brazil, our analyses do not predict a strong loss of genetic diversity in D. alata because of the broad tolerance of this species, which ensures large future ranges, contrasting with other Cerrado species that have been analyzed in a similar manner.

Genetic structure based on nuclear and chloroplast microsatellite loci of Solanum lycocarpum A. St. Hil. (Solanaceae) in Central Brazil.

Solanum lycocarpum (Solanaceae) is a woody species found in the Brazilian Cerrado. The flowers are pollinated by Xylocopa spp bees, and seeds are dispersed by mammals with distinct home range sizes. As a consequence, relative contributions of pollen and seeds to overall gene flow can vary according to different spatial scales. We studied the genetic structure of four natural populations of S. lycocarpum separated by 19 to 128 km, including individuals located along dirt roads that interlink three of the populations. A total of 294 individuals were genotyped with five nuclear and six chloroplast microsatellite markers. Significant spatial genetic structure was found in the total set of individuals; the Sp statistic was 0.0086. Population differentiation based on the six chloroplast microsatellite markers (θ(pC) = 0.042) was small and similar to that based on the five nuclear microsatellite markers (θ(p) = 0.054). For this set of populations, pollen and seed flow did not differ significantly from one another (pollen-to-seed flow ratio = 1.22). Capability for long distance seed dispersion and colonization of anthropogenic sites contributes to the ability of S. lycocarpum to maintain genetic diversity. Seed dispersion along dirt roads may be critical in preserving S. lycocarpum genetic diversity in fragmented landscapes.

Combining multiple models to predict the geographical distribution of the Baru tree (Dipteryx alata Vogel) in the Brazilian Cerrado.

The Brazilian Cerrado is a biome of great biodiversity, but detailed information about the diversity and distribution of species in this region is still insufficient for both testing ecological hypotheses and for conservation purposes. Among native plants in the Cerrado, Dipteryx alata Vogel (commonly known as the "Baru" tree), has a high potential for exploitation. The aims of this paper were to predict the potential spatial distribution of D. alata in the Brazilian Cerrado utilising five different niche modelling techniques. These techniques usually provide distinct results, so it may be difficult to choose amongst them. To adjust for this uncertainty, we employ an ensemble forecasting approach to predict the spatial distribution of the Baru tree. We accumulated a total of 448 occurrence points and modelled the subsequent predicted occurrences using seven climatic variables. Five different presence-only ecological niche modelling techniques (GARP, Maxent, BIOCLIM, Mahalanobis Distance and Euclidean Distance) were used and the performance of these models was compared using Receiver Operating Characteristics (ROC) and the Area Under the Curve (AUC). All models presented AUC values higher than 0.68, and GARP presented the highest AUC value, whereas Euclidean Distance presented the lowest. The ensemble forecasting approach suggested a high suitability for the occurrence of the Baru tree in the Central-Western region of the Brazilian Cerrado. Our study demonstrated that modelling species distribution using ensemble forecasting can be an important computational tool for better establishing sampling strategies and for improving our biodiversity knowledge to better identify priority areas for conservation. For the Baru tree, we recommend priority actions for conservation in the central region of the Cerrado Biome.

Plot size for progeny selection in maize (Zea mays L.).

Six progeny trials that included 147 half-sib progenies of maize (Zea mays L.) population ESALQ PB-5 were conducted for the purpose of studying plot size and its consequences in recurrent selection programs. The progenies were evaluated in three 7x7 duplicate simple lattice experiments using one-row plots of 5 m(2). At harvest each plot was partitioned into five sub-plots (sampling units), and data was collected from each sampling unit. At the same time and place the same progenies were evaluated in three 7x7 duplicate simple lattice experiments using 1-m(2) (linear row with 5 plants) plots. Data were collected for plant and ear height, ear diameter, total ear weight, and total grain yield. The data were combined by using adjacent sampling units, and the analyses were performed by considered five plot sizes in addition to those of the independent trials with 1-m(2) plots. The experiments with 1-m(2) plots were less efficient in discriminating for yield traits among progenies than those with 5-m(2) plots. The combination of plot size and number of progenies evaluated indicated that an optimum plot size for yield was between 3 and 4 m(2), or 15-20 plants per plot. With such sizes the expected gain was maximized for the four replications used in this study. If the total area covered by each progeny is constant, the maximum gain from selection, however, is attained by decreasing plot size and increasing the number of replications. The minimum size of plots is, however, limited by practical or theoretical criteria. Plot size affected the estimates of additive genetic variance, coefficient of heritability, and genetic coefficient of variation for all of the traits. No practical limitation was observed for conducting experiments with 1-m(2) plot.

Procedures for selecting composites based on prediction methods.

Procedures for selecting among parental varieties to be used in the synthesis of composites are discussed. In addition to the criterion based on the mean and variance of composites of the same size (k) proposed by Cordoso (1976), we suggest the index Ij=w1vj+w2 hj or I'j=(2/k) Ij for a preliminary selection among parental varieties. We show that by increasing k (size of the composite) I'j tends to gj, the general combining ability effect. Such a criterion is particularly important when n, the number of parental varieties, is large, so that the number of possible composites (Nc=2(n)-n-1) becomes too large to be handled when using the common prediction procedures. Yield data from a 9 × 9 variety diallel cross were used for illustration.