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 finescale 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.Published online: 24 March 2015

Genetic Population Structure And Hybridization In Two Sibling Species, Tomoplagia Reticulata And Tomoplagia Pallens (diptera: Tephritidae).

Tomoplagia reticulata and T. pallens are sibling species that are specialists on Eremanthus glomerulatus. Besides adult terminalia, they show slight morphological differences and distinct geographic distributions. Once, however, they were found sympatrically. Using data from allozyme and mtDNA, we examined patterns of intra- and interspecific genetic structure, and investigated the possible occurrence of gene flow between them. Both species showed low diversity and high genetic structure, which can be linked to their high degree of specialization. Larval development occurs within flower heads, tissues that are available only during a short period of the year. Afterward, as they do not hibernate, they probably suffer a great reduction in population size, which leads to low genetic diversity. As monophagous insects, their population structure may correspond to the fragmented distribution of E. glomerulatus, which could isolate fly populations and increase inbreeding within them. One population exhibited a mixed genetic composition, compatible with one hybridization season when species were sympatric. This hybridization seems to be a rare event, due to T. pallens unusual range expansion.71298-31

Fine-scale genetic structure of the periwinkle echinolittorina lineolata (gastropoda: littorinidae) : the interplay between space and time

Some marine species show homogeneous populations across most of their distributional range, but also population genetic structure at a smaller geographic scale. This intriguing scenario can be caused by different spatial and temporal factors, such as local oceanographic features, larval aggregation during dispersal, variable reproductive success and even natural selection. In this study, we evaluated small-scale population genetic structure in Echinolittorina lineolata, a gastropod with homogeneous populations at a large geographic scale in Brazil. Three concatenated mitochondrial DNA markers were used to infer genetic diversity and assess population-genetic differentiation between two locations. Repeated sampling of juveniles over time allowed us to test for constancy of genetic differentiation across four generations. Our diversity analysis revealed 103 haplotypes with low nucleotide diversity. The majority of the haplotypes were unique, but four were in high frequency and commonly found in individuals from both locations. There was only one location-specific haplotype with high frequency. When considering all samples, we detected spatial population differentiation within the dispersal range of E. lineolata. However, spatial differentiation was present in the first two generations sampled, while the following two showed genetic homogeneity between locations. In addition, there was genetic differentiation among individuals sampled from distinct rocks inside each location. When comparing generations within locations, different results were observed: in one location the first two generations were genetically similar, but differed from the following two generations; in the other location there was no genetic differentiation among all four generations. We hypothesize that E. lineolata is influenced by variance in reproductive success and resulting kinship among recruits. However, other factors could also cause transient genetic structure. We suggest that these curious genetic patterns can be better understood by combining the genetic information with in-depth knowledge of the species' biology and local oceanographic feature851-2737

Fly-pollinated Pleurothallis (orchidaceae) Species Have High Genetic Variability: Evidence From Isozyme Markers.

We conducted an isozyme study in 22 populations of five Pleurothallis (Orchidaceae) species (12 loci in nine enzymatic systems). The genetic variability in all populations is surprisingly high (P = 58-83%, A = 2.1-3.8, H(e) = 0.25-0.43) in spite of the fact that the five species are pollinated by small flies whose behavior enables self-pollination. We suggest that self-incompatibility, inbreeding depression, and mechanical barriers that prevent self-pollination in these species are responsible for the maintainance of the high genetic variability. These traits are uncommon in Orchidaceae, but have been observed in these and some other species pollinated by flies or other pollinators with behavior that facilitates self-pollination. The genetic similarity among conspecific populations is also high for species with very short-range flying pollinators. Only one population of P. teres presented values of genetic similarity lower than usually observed in allopatric conspecific populations. Morphology, however, does not support its segregation as a new taxon. All species can be recognized by their enzymatic patterns, and the results agree with recently proposed taxonomic realignments. Conversely, the supposed affinities among these species based on floral morphology are not supported, and we hypothesize that it may be due to convergence in species with similar pollinators.88419-2

Expected Coalescence Times And Segregating Sites In A Model Of Glacial Cycles.

The climatic fluctuations of the Quaternary have influenced the distribution of numerous plant and animal species. Several species suffer population reduction and fragmentation, becoming restricted to refugia during glacial periods and expanding again during interglacials. The reduction in population size may reduce the effective population size, mean coalescence time and genetic variation, whereas an increased subdivision may have the opposite effect. To investigate these two opposing forces, we proposed a model in which a panmictic and a structured phase alternate, corresponding to interglacial and glacial periods. From this model, we derived an expression for the expected coalescence time and number of segregating sites for a pair of genes. We observed that increasing the number of demes or the duration of the structured phases causes an increase in coalescence time and expected levels of genetic variation. We compared numerical results with the ones expected for a panmictic population of constant size, and showed that the mean number of segregating sites can be greater in our model even when population size is much smaller in the structured phases. This points to the importance of population structure in the history of species subject to climatic fluctuations, and helps explain the long gene genealogies observed in several organisms.5466-7

Geophagy in the golden-faced saki monkey (Pithecia pithecia chrysocephala) in the Central Amazon

The golden-faced saki monkey Pithecia pithecia chrysocephala (Cebidae, Primates) was observed eating soil from termite nests during a long-term study of a family group in a Central Amazonian forest fragment. In this paper we describe the behaviour involved in the geophagy in these monkeys, and the results of geochemical and physical analyses of the termite nest material, as well as root mat and topsoil samples below the trees, in order to clarify the possible reasons for it. The sakis ate soil from nine arboreal termite nests on 26 soil feeding-bouts (in 853 observation hours); 25 soil feeding-bouts occurred in March 1987 (rainy season), during 19 days or 132 observation hours, and occupied 0.7% of the feeding time. Geophagy frequencies did not differ between sexes (17 feeding-bouts of four females and 8 for two males). Mineral composition was higher in arboreal termitaria than in the topsoil. Kaolinite was the major clay component. Tannin adsorptive capacity, tested through a modified radial diffusion method of Hagerman, was around 10-20%, similar to a control with kaolin (10-20%), but lower than bentonite or celite (30-45%). The observations reported here, although inconclusive as to the function of geophagy in this species, indicate that it is not a mineral supplement during times of scarcity or high consumption of leaves, as has been reported for other primates, nor that it is related to fruit consumption (redressing possible mineral imbalance), as has been suggested for some other frugivorous mammals. Our results do not rule out tannin adsorptive hypothesis for the ingestion of clays, but, being an irregular habit, we argue that it is most likely related to rare and occasional dietary components