10 resultados para Genetic and phenotypic correlation

em Publishing Network for Geoscientific


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Understanding the evolutionary history of threatened populations can improve their conservation management. Re-establishment of past but recent gene flow could re-invigorate threatened populations and replenish genetic diversity, necessary for population persistence. One of the four nominal subspecies of the common yellow-tufted honeyeater, Lichenostomus melanops cassidix, is critically endangered despite substantial conservation efforts over 55 years. Using a combination of morphometric, genetic and modelling approaches we tested for its evolutionary distinctiveness and conservation merit. We confirmed that cassidix has at least one morphometric distinction. It also differs genetically from the other subspecies in allele frequencies but not phylogenetically, implying that its evolution was recent. Modelling historical distribution supported the lack of vicariance and suggested a possibility of gene flow among subspecies at least since the late Pleistocene. Multi-locus coalescent analyses indicated that cassidix diverged from its common ancestor with neighbouring subspecies gippslandicus sometime from the mid-Pleistocene to the Holocene, and that it has the smallest historical effective population size of all subspecies. It appears that cassidix diverged from its ancestor with gippslandicus through a combination of drift and local selection. From patterns of genetic subdivision on two spatial scales and morphological variation we concluded that cassidix, gippslandicus and (melanops + meltoni) are diagnosable as subspecies. Low genetic diversity and effective population size of cassidix may translate to low genetic fitness and evolutionary potential, thus managed gene flow from gippslandicus is recommended for its recovery.

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DSDP Leg 73 sediment cores allow direct calibrations of magnetostratigraphy and biostratigraphy for much of the latest Cretaceous to Cenozoic in the mid-latitude South Atlantic Ocean. A complete record of the Cenozoic was not obtained, however, because strong dissolution, poor core recovery and intense core disturbance have masked the biostratigraphy or magnetostratigraphy over some intervals of all recovered sections. DSDP Leg 73 results show the following correlations: Early/middle Miocene in Chron 16 Oligocene/Miocene within Subchron C6CN Eocene/Oligocene within Subchron C13R Middle/late Eocene top of Chron C17 Early/late Paleocene top of Subchron C27N Cretaceous/Tertiary within Subchron C29R

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The zip folder comprises a text file and a gzipped tar archive. 1) The text file contains individual genotype data for 90 SNPs, 9 microsatellites and the mitochondrial ND4 gene that were determined in deep-sea hydrothermal vent mussels from the Mid-Atlantic Ridge (genus Bathymodiolus). Mussel specimens are grouped according to the population (pop)/location from which they have been sampled (first column). The remaining columns contain the respective allele/haplotype codes for the different genetic loci (names in the header line). The data file is in CONVERT format and can be directly transformed into different input files for population genetic statistics. 2) The tar archive contains NetCDF files with larval dispersal probabilities for simulated annual larval releases between 1998 and 2007. For each simulated vent location (Menez Gwen, Lucky Strike, Rainbow, Vent 1-10) two NetCDF files are given, one for an assumed pelagic larval duration of 1 year and the other one for an assumed pelagic larval duration of 6 months (6m).

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In colonial species, it is often assumed that locations in the center of the colony are of highest quality and provide highest breeding success. We tested this prediction, known as the "central-periphery model," in a King Penguin colony in the subantarctic Crozet Archipelago. Breeding activity and survival of 150 penguins, fitted with transponder tags, were monitored over an entire breeding season. Among these 150 birds, 50 bred on the slope at the upper periphery of the colony, where the rates of predation and parasitism by ticks were high. Fifty birds bred in the center of the colony, where rates of predation and tick parasitism were low, and 50 bred at the lower end of the colony, where the rate of tick parasitism was low but predation and flooding were important risks. We predicted that the center of the colony should provide the safest breeding place and consequently be characterized by the highest breeding success and be used by the highest-quality individuals. Yet we found that penguins breeding in the center of the colony had the same breeding success as those at both peripheral locations. In addition, penguins breeding on the upper slope had a higher survival rate than penguins breeding at the center or bottom of the slope and were likely of higher quality. Our study does not support the central-periphery model and emphasizes the complexity behind the relationships among breeding site, breeding success, and individual quality.

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The ecological theory of adaptive radiation predicts that the evolution of phenotypic diversity within species is generated by divergent natural selection arising from different environments and competition between species. Genetic connectivity among populations is likely also to have an important role in both the origin and maintenance of adaptive genetic diversity. Our goal was to evaluate the potential roles of genetic connectivity and natural selection in the maintenance of adaptive phenotypic differences among morphs of Arctic charr, Salvelinus alpinus, in Iceland. At a large spatial scale, we tested the predictive power of geographic structure and phenotypic variation for patterns of neutral genetic variation among populations throughout Iceland. At a smaller scale, we evaluated the genetic differentiation between two morphs in Lake Thingvallavatn relative to historically explicit, coalescent-based null models of the evolutionary history of these lineages. At the large spatial scale, populations are highly differentiated, but weakly structured, both geographically and with respect to patterns of phenotypic variation. At the intralacustrine scale, we observe modest genetic differentiation between two morphs, but this level of differentiation is nonetheless consistent with strong reproductive isolation throughout the Holocene. Rather than a result of the homogenizing effect of gene flow in a system at migration-drift equilibrium, the modest level of genetic differentiation could equally be a result of slow neutral divergence by drift in large populations. We conclude that contemporary and recent patterns of restricted gene flow have been highly conducive to the evolution and maintenance of adaptive genetic variation in Icelandic Arctic charr.

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Late Neogene planktonic foraminifera have been examined at Site 310 in the Central North Pacific and their stratigraphic ranges and frequencies are presented here. Blow's (1969) zonation developed for tropical regions has been applied where applicable. Where tropical index taxa are rare or absent in this temperate region, Globorotalia crassaformis, and the evolutionary bioseries G. conoidea - G. conomiozea and G. puncticulata - G. inflata have been found useful for zonal subdivisions. A correlation between stratigraphic ranges and frequency distributions of these species at Site 310 in the Central North Pacific, and Site 284 in the Southwest Pacific indicates that these species are relatively consistent biostratigraphic markers in temperate regions of both the North and South Pacific Oceans. An informal zonation for temperate latitudes of the Southwest Pacific has been established by Kennett (1973) and a similar zonal subdivision can be made at Site 310. Paleoclimatic/paleoceanographic interpretations based on coiling ratios, percent abundance, and phenotypic variations of Neogloboquadrina pachyderma indicate four major cold events during early, middle, and late Pliocene, and early Pleistocene. Faunal correlations of these events with similar events elsewhere in the Northeast and Southwest Pacific which have been paleomagnetically dated indicate the following approximate ages for these cold events: 4.7 Ma, 3.0 Ma, 2.6-1.8 Ma, and 1.2 Ma. Faunal assemblages have been divided into three groups representing cool, intermediate, and warmer water assemblages. Cool water assemblages are dominated by ~60% N. pachyderma; intermediate temperature faunas are dominated by species of Globigerina and Globigerinita and contain between 20% and 30% N. pachyderma. Warmer water assemblages are dominated by species of Globorotalia and contain <10% N. pachyderma. Frequency oscillations within these groups, in addition to paleotemperature parameters evident in N. pachyderma, afford refined paleoclimatic/paleoceanographic interpretations.