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Population Structuring (population + structuring)
Selected AbstractsAge-related movement patterns and population structuring in southern garfish, Hyporhamphus melanochir, inferred from otolith chemistryFISHERIES MANAGEMENT & ECOLOGY, Issue 4 2009M. A. STEER Abstract, The southern garfish, Hyporhamphus melanochir (Val.), is an important inshore fishery species in South Australia. Over the past few years there have been concerns with this fishery, which is now considered to be over-exploited. Currently, the fishery is assumed to consist of two separate stocks, but there is no understanding of movement patterns both within and between these two stocks to justify this assumption. Otolith chemistry was used to infer age-related patterns of movement, delineate potential sub-populations and determine the extent of mixing within South Australian coastal waters. Results indicated that the population structuring of garfish is more complex than previously assumed and it seems that stocks can be discriminated at a much finer spatial scale. Garfish collected from sites separated by <60 km displayed significantly different chemical signatures (relative concentrations of 7Li, 24Mg, 55Mn, 88Sr and 138Ba) in their otoliths, especially during their second year of growth, indicating that they had inhabited different water bodies. From a broader perspective, South Australian garfish can be partitioned into six regional components with various levels of inter-mixing. From these results, it was suggested that assessment and management of the fishery may have to be restructured to align with the smaller spatial units. [source] Genetic interactions between marine finfish species in European aquaculture and wild conspecificsJOURNAL OF APPLIED ICHTHYOLOGY, Issue 4 2001Youngson The principal species of marine aquaculture in Europe are Atlantic salmon (Salmo salar), sea bass (Dicentrarchus labrax) and sea bream (Sparus auratus). For Atlantic salmon and sea bass, a substantial part of total genetic variation is partitioned at the geographical population level. In the case of sea bream, gene flow across the Azores/Mediterranean scale appears to be extensive and population structuring is not detected. For Atlantic salmon and sea bass, natural population structure is at risk from genetic interaction with escaped aquaculture conspecifics. The locally adaptive features of populations are at risk from interbreeding with non-local aquaculture fish. Wild populations, generally, are at risk from interactions with aquaculture fish that have been subject to artificial selection or domestication. Atlantic salmon is the main European aquaculture species and its population genetics and ecology have been well-studied. A general case regarding genetic interactions can be based on the information available for salmon and extended to cover other species, in the appropriate context. A generalized flow chart for interactions is presented. Salmon escape from aquaculture at all life stages, and some survive to breed among wild salmon. Reproductive fitness in the escaped fish is lower than in native, wild fish because of behavioural deficiencies at spawning. However, as the number of salmon in aquaculture greatly exceeds the number of wild fish, even small fractional rates of escape may result in the local presence of large numbers, and high frequencies, of escaped fish. At present, policy and legislation in relation to minimizing genetic interactions between wild and aquaculture fish is best developed for Atlantic salmon, through the recommendations of the Oslo Agreement developed by the North Atlantic Salmon Conservation Organization and subsequent agreements on their implementation. In future, the potential use of genetically modified fish in aquaculture will make additional policy development necessary. Improved containment is recommended as the key to minimizing the numbers and therefore the effects of escaped fish. Emergency recovery procedures are recommended as a back-up measure in the case of containment failure. Reproductive sterility is recommended as a future key to eliminating the genetic potential of escaped fish. The maintenance of robust populations of wild fish is recommended as a key to minimizing the effects of escaped fish on wild populations. [source] A long-standing Pleistocene refugium in southern Africa and a mosaic of refugia in East Africa: insights from mtDNA and the common eland antelopeJOURNAL OF BIOGEOGRAPHY, Issue 3 2010Eline D. Lorenzen Abstract Aim, Previous genetic studies of African savanna ungulates have indicated Pleistocene refugial areas in East and southern Africa, and recent palynological, palaeovegetation and fossil studies have suggested the presence of a long-standing refugium in the south and a mosaic of refugia in the east. Phylogeographic analysis of the common eland antelope, Taurotragus oryx (Bovidae), was used to assess these hypotheses and the existence of genetic signatures of Pleistocene climate change. Location, The sub-Saharan savanna biome of East and southern Africa. Methods, Mitochondrial DNA control-region fragments (414 bp) from 122 individuals of common eland were analysed to elucidate the phylogeography, genetic diversity, spatial population structuring, historical migration and demographic history of the species. The phylogeographic split among major genetic lineages was dated using Bayesian coalescent-based methods and a calibrated fossil root of 1.6 Ma for the split between the common eland and the giant eland, Taurotragus derbianus. Results, Two major phylogeographic lineages comprising East and southern African localities, respectively, were separated by a net nucleotide distance of 4.7%. A third intermediate lineage comprised only three haplotypes, from Zimbabwe in southern Africa. The estimated mutation rate of 0.097 Myr,1 revealed a more recent common ancestor for the eastern lineage (0.21 Ma; 0.07,0.37) than for the southern lineage (0.35 Ma; 0.10,0.62). Compared with the latter, the eastern lineage showed pronounced geographic structuring, lower overall nucleotide diversity, higher population differentiation, and isolation-by-distance among populations. Main conclusions, The data support the hypothesis of Pleistocene refugia occurring in East and southern Africa. In agreement with palynological, palaeovegetation and fossil studies, our data strongly support the presence of a longer-standing population in the south and a mosaic of Pleistocene refugia in the east, verifying the efficacy of genetic tools in addressing such questions. The more recent origin of the common eland inhabiting East Africa could result from colonization following extinction from the region. Only two other dated African ungulate phylogenies have been published, applying different methods, and the similarity of dates obtained from the three distinct approaches indicates a significant event c. 200 ka, which left a strong genetic signature across a range of ungulate taxa. [source] Morphometric convergence and molecular divergence: the taxonomic status and evolutionary history of Gymnura crebripunctata and Gymnura marmorata in the eastern Pacific OceanJOURNAL OF FISH BIOLOGY, Issue 4 2009W.D. Smith To clarify the taxonomic status of Gymnura crebripunctata and Gymnura marmorata, the extent of morphological and nucleotide variation between these nominal species was examined using multivariate morphological and mitochondrial DNA comparisons of the same characters with congeneric species. Discriminant analysis of 21 morphometric variables from four species (G. crebripunctata, G. marmorata, Gymnura micrura and Gymnura poecilura) successfully distinguished species groupings. Classification success of eastern Pacific species improved further when specimens were grouped by species and sex. Discriminant analysis of size-corrected data generated species assignments that were consistently accurate in separating the two species (100% jackknifed assignment success). Nasal curtain length was identified as the character which contributed the most to discrimination of the two species. Sexual dimorphism was evident in several characters that have previously been relied upon to distinguish G. crebripunctata from G. marmorata. A previously unreported feature, the absence of a tail spine in G. crebripunctata, provides an improved method of field identification between these species. Phylogenetic and genetic distance analyses based on 698 base pairs of the mitochondrial cytochrome b gene indicate that G. crebripunctata and G. marmorata form highly divergent lineages, supporting their validity as distinct species. The closely related batoid Aetoplatea zonura clustered within the Gymnura clade, indicating that it may not represent a valid genus. Strong population structuring (overall ,ST = 0·81,P < 0·01) was evident between G. marmorata from the Pacific coast of the Baja California peninsula and the Gulf of California, supporting the designation of distinct management units in these regions. [source] Extensive intraspecific polymorphism detected by SSCP at the nuclear C- mos gene in the endemic Iberian lizard Lacerta schreiberiMOLECULAR ECOLOGY, Issue 3 2006RAQUEL GODINHO Abstract C- mos is a highly conserved intronless gene that has proved useful in the analysis of ancient phylogenetic relationships within vertebrates. We selected the Iberian endemic Schreiber's green lizard (Lacerta schreiberi) that persisted in allopatric refugia since the late Pliocene to investigate the utility of the C- mos nuclear gene for intraspecific phylogeographic studies. Our combination of DNA sequencing with the high resolving power of single-strand conformational polymorphism (SSCP) effectively discriminated four common alleles showing strong population structuring (FST = 0.46). In addition, reconstruction of allele phylogenetic relationships further improved our understanding of C- mos spatial patterns of variation and allowed a comparison with previously described mitochondrial DNA data. Finally, limited sequencing of an extended C- mos fragment in six additional Lacerta species showed extensive polymorphism, to our knowledge representing a rare example of variation in a highly conserved nuclear gene. [source] Postglacial colonization of the Tibetan plateau inferred from the matrilineal genetic structure of the endemic red-necked snow finch, Pyrgilauda ruficollisMOLECULAR ECOLOGY, Issue 6 2005YAN HUA QU Abstract Most phylogeographical studies of postglacial colonization focus on high latitude locations in the Northern Hemisphere. Here, we studied the phylogeographical structure of the red-necked snow finch Pyrgilauda ruficollis, an endemic species of the Tibetan plateau. We analysed 879 base pairs (bp) of the mitochondrial cytochrome b gene and 529 bp of the control region in 41 birds from four regional groups separated by mountain ranges. We detected 34 haplotypes, 31 of which occurred in a single individual and only three of which were shared among sampling sites within regional groups or among regional groups. Haplotype diversity was high (h = 0.94); nucleotide diversity was low (ð = 0.00415) and genetic differentiation was virtually non-existent. Analyses of mismatch distributions and geographically nested clades yielded results consistent with contiguous range expansion, and the expansion times were estimated as 0.07,0.19 million years ago (Ma). Our results suggest that P. ruficollis colonized the Tibetan plateau after the extensive glacial period (0.5,0.175 Ma), expanding from the eastern margin towards the inner plateau. Thus, in contrast to many of the postglacial phylogeographical structures known at high latitudes, this colonization occurred without matrilineal population structuring. This might be due to the short glacial cycles typical of the Tibetan plateau, adaptation of P. ruficollis to cold conditions, or refugia and colonized habitat being semicontinuous and thus promoting population mixing. [source] Expressed sequence tag-derived microsatellites for the cool-water marine copepod Calanus finmarchicusMOLECULAR ECOLOGY RESOURCES, Issue 6 2007JIM PROVAN Abstract The copepod Calanus finmarchicus is the major contributor to zooplankton biomass in the North Atlantic and Norwegian Sea, but recent studies have shown a 70% decrease in abundance as well as a northward shift in the species' range. Insights into dispersal capabilities gained from population genetic studies will be crucial in predicting the response of C. finmarchicus communities to climate change and, consequently, we have developed a set of expressed sequence tag-derived microsatellite markers to allow fine-scale elucidation of population structuring and dispersal. Ten polymorphic markers displayed between two and 19 alleles, with levels of expected heterozygosity ranging from 0.044 to 0.924. [source] Isolation and characterization of DNA microsatellite primers for Cynoscion acoupa, the most exploited sciaenid fish along the coast of BrazilMOLECULAR ECOLOGY RESOURCES, Issue 3 2006IZENI P. FARIAS Abstract The northern mangrove coast of Brazil comprises the Brazilian states of Amapá, Pará and Maranhão. Fishes from the coastal mangrove region form a principal component of the local fishery, and account for 58% of all fish landed. The most commonly landed fishes are those of the family Sciaenidae. Cynoscion acoupa is one of the most exploited sciaenid species, with over 600 tons landed each year. Therefore, we developed 17 microsatellite markers to investigate genetic variability and population structuring of this species along the coast of Brazil. [source] Population genetic structure of rock ptarmigan in the ,sky islands' of French Pyrenees: implications for conservationANIMAL CONSERVATION, Issue 2 2009N. Bech Abstract Expected consequences of global warming include habitat reduction in many cool climate species. Rock ptarmigan is a Holarctic grouse that inhabits arctic and alpine tundra. In Europe, the Pyrenean ptarmigan inhabits the southern edge of the species' range and since the last glacial maximum its habitat has been severely fragmented and is restricted to high-alpine zones or ,sky islands'. A recent study of rock ptarmigan population genetic in Europe found that the Pyrenean ptarmigan had very low genetic diversity compared with that found in the Alps and Scandinavia. Habitat fragmentation and reduced genetic diversity raises concerns about the viability of ptarmigan populations in the Pyrenees. However, information on population structuring and gene flow across the Pyrenees, which is essential for designing a sound management plan, is absent. In this study, we use seven microsatellites and mitochondrial control region sequences to investigate genetic variation and differentiation among five localities across the Pyrenees. Our analyses reveal the presence of genetic differentiation among all five localities and a significant isolation-by-distance effect that is likely the result of short dispersal distances and high natal and breeding philopatry of Pyrenean ptarmigan coupled with severe habitat fragmentation. Furthermore, analysis of molecular variance, principal component analysis and Bayesian analysis of genetic structuring identified the greatest amount of differentiation between the eastern and main parts of the Pyrenean chain separated by the Sègre Valley. Our data also show that the Canigou massif may host an isolated population and requires special conservation attention. We propose a management plan which includes the translocation of birds. If a sky island structure affects genetic divergence in rock ptarmigan, it may also affect the genetic structure of other sky island species having low dispersal abilities. [source] Social Network Analysis of the Genetic Structure of Pacific IslandersANNALS OF HUMAN GENETICS, Issue 3 2010John Edward Terrell Summary Social network analysis (SNA) is a body of theory and a set of relatively new computer-aided techniques used in the analysis and study of relational data. Recent studies of autosomal markers from over 40 human populations in the south-western Pacific have further documented the remarkable degree of genetic diversity in this part of the world. I report additional analysis using SNA methods contributing new controlled observations on the structuring of genetic diversity among these islanders. These SNA mappings are then compared with model-based network expectations derived from the geographic distances among the same populations. Previous studies found that genetic divergence among island Melanesian populations is organised by island, island size/topography, and position (coastal vs. inland), and that similarities observed correlate only weakly with an isolation-by-distance model. Using SNA methods, however, improves the resolution of among population comparison, and suggests that isolation by distance constrained by social networks together with position (coastal/inland) accounts for much of the population structuring observed. The multilocus data now available is also in accord with current thinking on the impact of major biogeographical transformations on prehistoric colonisation and post-settlement human interaction in Oceania. [source] Spatial expansion and population structure of the neotropical malaria vector, Anopheles darlingi (Diptera: Culicidae)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009PEDRO M. PEDRO Extensive population structuring is known to occur in Anopheles darlingi, the primary malaria vector of the Neotropics. We analysed the phylogeographic structure of the species using the mitochondrial cytochrome oxidase I marker. Diversity is divided into six main population groups in South America: Colombia, central Amazonia, southern Brazil, south-eastern Brazil, and two groups in north-east Brazil. The ancestral distribution of the taxon is hypothesized to be central Amazonia, and there is evidence of expansion from this region during the late Pleistocene. The expansion was not a homogeneous front, however, with at least four subgroups being formed due to geographic barriers. As the species spread, populations became isolated from each other by the Amazon River and the coastal mountain ranges of south-eastern Brazil and the Andes. Analyses incorporating distances around these barriers suggest that the entire South American range of An. darlingi is at mutation,dispersal,drift equilibrium. Because the species is distributed throughout such a broad area, the limited dispersal across some landscape types promotes differentiation between otherwise proximate populations. Moreover, samples from the An. darlingi holotype location in Rio de Janeiro State are substantially derived from all other populations, implying that there may be additional genetic differences of epidemiological relevance. The results obtained contribute to our understanding of gene flow in this species and allow the formulation of human mosquito health protocols in light of the potential population differences in vector capacity or tolerance to control strategies. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 854,866. [source] | |||||||||||||