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1.
Genetic variation in populations, both natural and restored, is usually considered crucial for response to short‐term environmental stresses and for long‐term evolutionary change. To have the best chance of successful long‐term survival, restored populations should reflect the extant variation found in remnants, but restored sites may suffer from genetic bottlenecks as a result of founder effects. Kankakee Sands is a large‐scale restoration being conducted by The Nature Conservancy (TNC) in northwestern Indiana. Our goal was to test for loss of genetic variation in restored plant populations by comparing them with TNC’s seed source nursery and with local remnant populations that were the source of nursery seed and of the first few restored sites. Allozyme analysis of Baptisia leucantha, Asclepias incarnata, Coreopsis tripteris, and Zizia aurea showed low levels of allozyme diversity within all species and reductions in polymorphism, alleles per locus, and expected heterozygosity between remnants and restorations for all species except A. incarnata. Almost all lost alleles were rare; restored populations contained almost 90% of alleles at polymorphic loci that occurred in remnants at frequencies greater than 1%. Allele frequencies for most loci did not differ between remnants and restored sites. Most species showed significant allele frequency differentiation among remnant populations and among restored sites. Our results indicate that seed collection techniques used at Kankakee Sands captured the great majority of allozyme variation present in seed source remnant populations.  相似文献   

2.
The field of ecological restoration is growing rapidly, and the sourcing of suitable seed is a major issue. Information on the population genetic structure of a species can provide valuable information to aid in defining seed collection zones. For a practical contribution from genetics, a rapid approach to delineating seed collection zones using genetic markers (amplified fragment length polymorphisms [AFLPs]) has been developed. Here, we test the effects of sampling regime on the efficacy of this method. Genetic data were collected for an outcrossing seeder, Daviesia divaricata ssp. divaricata, an important species in urban bushland restoration in Perth, Western Australia. The effect of sample size and number of AFLP markers on estimates of genetic variation and population structure was examined in relation to implications for sourcing material for restoration. Three different sample sizes were used (n= 8, 15, and 30) from six urban bushland remnants. High levels of genetic diversity were observed in D. divaricata (87.4% polymorphic markers), with significant population differentiation detected among sampled populations (ΘB= 0.1386, p < 0.001). Although sample size does not appear to affect the spatial pattern in principle co‐ordinates analysis (PCA) plots, the number of polymorphic loci increased with sample size and estimates of population subdivision (FST and ΘB) and associated confidence intervals decreased with increasing sample size. We recommend using a minimum of 30 plants for sourcing seed for restoration projects.  相似文献   

3.
The ecological restoration of native plant communities requires the collection of large amounts of seed. Use of non-local provenance seed can have detrimental consequences for the success of restoration if there is a home-site advantage, and for nature conservation through the erosion of natural patterns of population genetic structuring and/or genetic swamping (and extirpation) of locally significant genotypes. As part of an ongoing project to genetically delineate local provenance seed collection zones for species within a large urban bushland remnant of high conservation value, we assessed population genetic differentiation in two widespread coastal leguminous species, Acacia rostellifera and A. cochlearis (Fabaceae), commonly used in restoration programmes in SW Australia. Using amplified fragment length polymorphism (AFLP), we found very high levels of genetic differentiation among populations, with an analysis of molecular variance (AMOVA) showing more than 50% of the total genetic variance to be partitioned among populations (ΦST=0.58 and 0.51 for A. rostellifera and A. cochlearis, respectively), and marked non-overlap of almost all potential seed source populations from the local population in ordinations. Our results suggest extremely restricted natural dispersal among populations, possibly due to a combination of low seed set, seed dispersal by ants, clonality, a linear distribution of naturally fragmented populations and possibly low outcrossing rates. We suggest a narrow seed collection zone should be applied to these species for the conservation of genetic diversity and natural patterns of population genetic structure, and we highlight the value and importance of provenance evaluation to ecological restoration.  相似文献   

4.
An increasingly important practical application of the analysis of spatial genetic structure within plant species is to help define the extent of local provenance seed collection zones that minimize negative impacts in ecological restoration programs. Here, we derive seed sourcing guidelines from a novel range‐wide assessment of spatial genetic structure of 24 populations of Banksia menziesii (Proteaceae), a widely distributed Western Australian tree of significance in local ecological restoration programs. An analysis of molecular variance (AMOVA) of 100 amplified fragment length polymorphism (AFLP) markers revealed significant genetic differentiation among populations (ΦPT = 0.18). Pairwise population genetic dissimilarity was correlated with geographic distance, but not environmental distance derived from 15 climate variables, suggesting overall neutrality of these markers with regard to these climate variables. Nevertheless, Bayesian outlier analysis identified four markers potentially under selection, although these were not correlated with the climate variables. We calculated a global R‐statistic using analysis of similarities (ANOSIM) to test the statistical significance of population differentiation and to infer a threshold seed collection zone distance of ~60 km (all markers) and 100 km (outlier markers) when genetic distance was regressed against geographic distance. Population pairs separated by >60 km were, on average, twice as likely to be significantly genetically differentiated than population pairs separated by <60 km, suggesting that habitat‐matched sites within a 30‐km radius around a restoration site genetically defines a local provenance seed collection zone for B. menziesii. Our approach is a novel probability‐based practical solution for the delineation of a local seed collection zone to minimize negative genetic impacts in ecological restoration.  相似文献   

5.
A common ecological restoration approach is the reestablishment of vegetation using seed mixtures. To preserve the natural genetic pattern of plant species local seed material should be used. Consequently, seed transfer zones (seed production areas and seed provenance regions) have been delineated for ecological restoration in Germany. Although it is assumed that these transfer zones represent genetic variation, there remains a lack of empirical data. In this study, we analyzed whether seed transfer zones reflect the genetic variation of the common grassland species Lathyrus pratensis. We sampled 706 individuals from 37 populations in Bavaria, Germany and analyzed genetic variation using amplified fragment length polymorphisms. In our study, we observed higher levels of genetic variation and fragment rarity in the southern Bavarian populations compared to northern populations. Our analyses revealed a strong genetic differentiation between southern and northern Bavarian populations delineated along the Danube River. However, seed production areas and seed provenance regions reflected genetic variation of L. pratensis only to a limited degree. Our study illustrates that the level of genetic variation within populations strongly depends on population history. Furthermore, the geomorphological and climatic attributes, which have been used to delineate seed provenance regions, do not reduce gene flow among populations. Seed collections for gene banks and seed production should comprise seeds from populations in southern and northern Bavaria representing the strong genetic variation between both regions, but prioritize southern populations due to higher levels of variation.  相似文献   

6.
Restoration of diverse native plant communities typically requires the collection of large amounts of seed. Thus, practitioners often struggle to find adequate supplies near project sites and need to know from how far they can collect without compromising restoration success—how far does local provenance extend? We addressed this issue by assessing genetic variation within, and differentiation among, 12 potential seed source populations of Persoonia longifolia, a key component of the jarrah forest of Western Australia. An analysis of molecular variance of 66 polymorphic amplified fragment length polymorphism markers partitioned 92% of the total genetic variation within populations and 8% among populations, indicating relatively weak but statistically significant population genetic differentiation. Ordination of these genetic data showed marked west/east and north/south gradients. Pairwise population genetic dissimilarity was correlated with both geographic distance and environmental distance derived from five climate variables. However, partial Mantel tests showed that the relationship between genetic and geographic distance was not independent of environmental distance, suggesting a non‐neutral signature in these markers. Bayesian outlier analysis identified two markers, and spatial analysis method tests identified highly significant associations between these two markers and three environmental variables. Frequency differences at these markers across populations suggested the possibility of climatically adapted provenances. The global significance value from analyses of similarities for these two markers correlated to a general provenance distance of 47 km, in contrast to a threshold of 60 km for the complete dataset. Guidelines for seed sourcing that consider these population genetic data should lead to more effective ecological restoration with this species.  相似文献   

7.
Rarely assessed in the success of ecological restoration projects is the maintenance of genetic variation in restored populations and, critically, their offspring. A founding population sourced from a limited genetic pool of nonlocal provenance seed can result in genetic bottlenecking and inbreeding, potentially reducing future population resilience and restoration success. We used microsatellite markers to assess the genetic variation of natural and restored populations, and their offspring, in Banksia attenuata R.Br. (Proteaceae), a keystone species of Banksia woodlands in south‐west Australia. Both natural and restored populations, and their offspring, displayed similarly high levels of heterozygosity (He range = 0.57–0.62) and allelic diversity (Ne range = 6.67–8.86) across 7 microsatellite loci. There was very weak population divergence (FST = 0.006) between the restored population and the adjacent natural population, indicating local provenance sourcing of seed. Genetic structuring within the natural population was weak, but detectable at 10 m and more strongly genetically structured than the restored population (Sp = 0.006 and 0.002, respectively). Complete outcrossing, low‐correlated paternity, and very low bi‐parental inbreeding were observed in both populations. Extensive pollen dispersal was observed within and among populations, with >50% of paternity assigned to sires beyond the local population. In a greenhouse experiment, differences in the overall performance of seedlings from natural and restored populations were negligible. Results indicate the successful genetic management of B. attenuata in this restoration project, from which general principles emphasizing the use of diverse local provenance seeds, genetic integration, and delivery of pollinator services are supported.  相似文献   

8.
A combination of founder effects and local adaptation – the Monopolization hypothesis – has been proposed to reconcile the strong population differentiation of zooplankton dwelling in ponds and lakes and their high dispersal abilities. The role genetic drift plays in genetic differentiation of zooplankton is well documented, but the impact of natural selection has received less attention. Here, we compare differentiation in neutral genetic markers (FST) and in quantitative traits (QST) in six natural populations of the rotifer Brachionus plicatilis to assess the importance of natural selection in explaining genetic differentiation of life‐history traits. Five life‐history traits were measured in four temperature × salinity combinations in common‐garden experiments. Population differentiation for neutral genetic markers – 11 microsatellite loci – was very high (FST = 0.482). Differentiation in life‐history traits was higher in traits related to sexual reproduction than in those related to asexual reproduction. QST values for diapausing egg production (a trait related to sexual reproduction) were higher than their corresponding FST in some pairs of populations. Our results indicate the importance of divergent natural selection in these populations and suggest local adaptation to the unpredictability of B. plicatilis habitats.  相似文献   

9.
10.
Gene flow is usually thought to reduce genetic divergence and impede local adaptation by homogenising gene pools between populations. However, evidence for local adaptation and phenotypic differentiation in highly mobile species, experiencing high levels of gene flow, is emerging. Assessing population genetic structure at different spatial scales is thus a crucial step towards understanding mechanisms underlying intraspecific differentiation and diversification. Here, we studied the population genetic structure of a highly mobile species – the great tit Parus major – at different spatial scales. We analysed 884 individuals from 30 sites across Europe including 10 close‐by sites (< 50 km), using 22 microsatellite markers. Overall we found a low but significant genetic differentiation among sites (FST = 0.008). Genetic differentiation was higher, and genetic diversity lower, in south‐western Europe. These regional differences were statistically best explained by winter temperature. Overall, our results suggest that great tits form a single patchy metapopulation across Europe, in which genetic differentiation is independent of geographical distance and gene flow may be regulated by environmental factors via movements related to winter severity. This might have important implications for the evolutionary trajectories of sub‐populations, especially in the context of climate change, and calls for future investigations of local differences in costs and benefits of philopatry at large scales.  相似文献   

11.
In Ohio and elsewhere, recent grassland plantings in the federal Conservation Reserve Program (CRP) have become much more extensive than native prairie remnants. The seed source for CRP grasslands in Ohio often comes from as far away as Missouri or Texas, which may be undesirable from the standpoint of conservation genetics. The goal of this study was to examine the potential for gene flow from large, recently introduced populations of Big bluestem (Andropogon gerardii, Poaceae) to small local populations of this outcrossing perennial species. We examined the potential for cross‐pollination between three local populations and three introduced CRP populations by comparing flowering phenologies. Flowering times overlapped extensively, indicating that cross‐pollination is possible where local and introduced genotypes co‐occur. To compare genetic variation in local and CRP populations, we analyzed variation at 68 RAPD loci in six populations of each type. Somewhat surprisingly, we found no significant differences in the genetic diversity or composition between the two groups (local vs. CRP). In summary, we found that local and introduced populations of Big bluestem have the potential to interbreed, based on their flowering periods, but further research is needed to determine whether local genotypes harbor unique genetic variation that could be jeopardized by hybridization with introduced genotypes.  相似文献   

12.
Comparative analyses of spatial genetic structure of populations of plants and the insects they interact with provide an indication of how gene flow, natural selection and genetic drift may jointly influence the distribution of genetic variation and potential for local co‐adaptation for interacting species. Here, we analysed the spatial scale of genetic structure within and among nine populations of an interacting species pair, the white campion Silene latifolia and the moth Hadena bicruris, along a latitudinal gradient across Northern/Central Europe. This dioecious, short‐lived perennial plant inhabits patchy, often disturbed environments. The moth H. bicruris acts both as its pollinator and specialist seed predator that reproduces by laying eggs in S. latifolia flowers. We used nine microsatellite markers for S. latifolia and eight newly developed markers for H. bicruris. We found high levels of inbreeding in most populations of both plant and pollinator/seed predator. Among populations, significant genetic structure was observed for S. latifolia but not for its pollinator/seed predator, suggesting that despite migration among populations of H. bicruris, pollen is not, or only rarely, carried over between populations, thus maintaining genetic structure among plant populations. There was a weak positive correlation between genetic distances of S. latifolia and H. bicruris. These results indicate that while significant structure of S. latifolia populations creates the potential for differentiation at traits relevant for the interaction with the pollinator/seed predator, substantial gene flow in H. bicruris may counteract this process in at least some populations.  相似文献   

13.
We investigated the influence of differing life history traits on the genetic structure of the related species Mimetes fimbriifolius and Mimetes hirtus (Proteaceae), which occur in the South African fynbos. Both species are bird‐pollinated and ant‐dispersed, but differ in rarity, longevity, ecological strategy and the fragmentation of their distribution area. We used AFLPs to study genetic variation within and between 21 populations of these two species across their distribution range. AFLP analysis revealed significantly higher genetic variation within populations of M. fimbriifolius than within M. hirtus. While M. fimbriifolius clearly lacked any significant genetic differentiation between populations, a distinct geographic pattern was observed for M. hirtus. Differentiation was, however, stronger at the regional (ΦPT = 0.57) than at the local scale (ΦPT = 0.08). Our results clearly indicate that even closely related species that share the same mode of pollination and seed dispersal can differ in their genetic structure, depending on the magnitude of fragmentation, longevity of individuals and ecological strategy.  相似文献   

14.
Question: How do studies of the distribution of genetic diversity of species with different life forms contribute to the development of conservation strategies? Location: Old‐growth forests of the southeastern United States. Methods: Reviews of the plant allozyme literature are used to identify differences in genetic diversity and structure among species with different life forms, distributions and breeding systems. The general results are illustrated by case studies of four plant species characteristic of two widespread old‐growth forest communities of the southeastern United States: the Pinus palustris – Aristida stricta (Longleaf pine – wiregrass) savanna of the Coastal Plain and the Quercus – Carya – Pinus (Oak‐hickory‐pine) forest of the Piedmont. Genetic variation patterns of single‐gene and quantitative traits are also reviewed. Results: Dominant forest trees, represented by Pinus palustris(longleaf pine) and Quercus rubra (Northern red oak), maintain most of their genetic diversity within their populations whereas a higher proportion of the genetic diversity of herbaceous understorey species such as Sarracenia leucophylla and Trillium reliquum is distributed among their populations. The herbaceous species also tend to have more population‐to‐population variation in genetic diversity. Higher genetic differentiation among populations is seen for quantitative traits than for allozyme traits, indicating that interpopulation variation in quantitative traits is influenced by natural selection. Conclusion: Developing effective conservation strategies for one or a few species may not prove adequate for species with other combinations of traits. Given suitable empirical studies, it should be possible to design efficient conservation programs that maintain natural levels of genetic diversity within species of conservation interest.  相似文献   

15.
The impact of demographic parameters on the genetic population structure and viability of organisms is a long‐standing issue in the study of fragmented populations. Demographic and genetic tools are now readily available to estimate census and effective population sizes and migration and gene flow rates with increasing precision. Here we analysed the demography and genetic population structure over a recent 15‐year time span in five remnant populations of Cabanis's greenbul (Phyllastrephus cabanisi), a cooperative breeding bird in a severely fragmented cloud forest habitat. Contrary to our expectation, genetic admixture and effective population sizes slightly increased, rather than decreased between our two sampling periods. In spite of small effective population sizes in tiny forest remnants, none of the populations showed evidence of a recent population bottleneck. Approximate Bayesian modelling, however, suggested that differentiation of the populations coincided at least partially with an episode of habitat fragmentation. The ratio of meta‐Ne to meta‐Nc was relatively low for birds, which is expected for cooperative breeding species, while Ne/Nc ratios strongly varied among local populations. While the overall trend of increasing population sizes and genetic admixture may suggest that Cabanis's greenbuls increasingly cope with fragmentation, the time period over which these trends were documented is rather short relative to the average longevity of tropical species. Furthermore, the critically low Nc in the small forest remnants keep the species prone to demographic and environmental stochasticity, and it remains open if, and to what extent, its cooperative breeding behaviour helps to buffer such effects.  相似文献   

16.
Seabirds are considered highly mobile, able to fly great distances with few apparent barriers to dispersal. However, it is often the case that seabird populations exhibit strong population genetic structure despite their potential vagility. Here we show that Galapagos Nazca booby (Sula granti) populations are substantially differentiated, even within the small geographic scale of this archipelago. On the other hand, Galapagos great frigatebird (Fregata minor) populations do not show any genetic structure. We characterized the genetic differentiation by sampling five colonies of both species in the Galapagos archipelago and analyzing eight microsatellite loci and three mitochondrial genes. Using an F‐statistic approach on the multilocus data, we found significant differentiation between nearly all island pairs of Nazca booby populations and a Bayesian clustering analysis provided support for three distinct genetic clusters. Mitochondrial DNA showed less differentiation of Nazca booby colonies; only Nazca boobies from the island of Darwin were significantly differentiated from individuals throughout the rest of the archipelago. Great frigatebird populations showed little to no evidence for genetic differentiation at the same scale. Only two island pairs (Darwin – Wolf, N. Seymour – Wolf) were significantly differentiated using the multilocus data, and only two island pairs had statistically significant φST values (N. Seymour – Darwin, N. Seymour – Wolf) according to the mitochondrial data. There was no significant pattern of isolation by distance for either species calculated using both markers. Seven of the ten Nazca booby migration rates calculated between island pairs were in the south or southeast to north or northwest direction. The population differentiation found among Galapagos Nazca booby colonies, but not great frigatebird colonies, is most likely due to differences in natal and breeding philopatry.  相似文献   

17.
Genetic Diversity and the Reintroduction of Meadow Species   总被引:2,自引:0,他引:2  
Abstract: Restoration of formerly nutrient‐poor and species‐rich grasslands generally leads to an increase in species diversity. However, species without a persistent seed bank and with poor dispersal ability often do not re‐establish spontaneously. Here, reintroduction is an option. If existing populations are comparable in their genetic composition, any population will do. This is not the case if populations have local adaptations. Unfortunately, whether populations are adapted locally is not easily determined, in contrast to assessing differentiation using neutral genetic markers. We used AFLP to study genetic diversity of Cirsium dissectum and Succisa pratensis within and among several Junco‐Molinion plant communities in the Netherlands (up to 200 km apart) that were potential source populations, and followed the reintroduction using seeds from these populations. Also, vegetative growth phase characteristics of three populations of C. dissectum were analyzed under controlled conditions. Most of the genetic variation in these cross‐fertilizing species was found within populations. Small but significant genetic differences in band frequencies were found among populations (Fst 0.100 ‐ 0.135). The first generation of reintroduced plants contained less polymorphic bands than the source populations. The genetic differences caused by reintroduction using a limited number of seeds (founder effects) were significant in all except one case (Fst 0.012 ‐ 0.101 between source and corresponding reintroduced population), but the magnitude was smaller than the source population differentiation. In assignment tests, reintroduced populations resembled their source population more than any other population, but all populations contained sizeable proportions of plants that were assigned to most similar plants from other populations, indicating that the populations are only marginally distinct. Calculations show that reintroduction from more than one source population introduces significantly more polymorphic bands into the new population, capitalizing on the existence of band frequency differences among populations.  相似文献   

18.
For restoration purposes, nature conservation generally enforces the use of local seed material based on the “local‐is‐best” (LIB) approach. However, in some cases recommendations to refrain from this approach have been made. Here we test if a common widespread species with no obvious signs of local adaptation may be a candidate species for abandoning LIB during restoration. Using 10 microsatellite markers we compared population genetic patterns of the generalist species Daucus carota in indigenous and formerly restored sites (nonlocal seed provenances). Gene diversity overall ranged between He = 0.67 and 0.86 and showed no significant differences between the two groups. Hierarchical AMOVA and principal component analysis revealed very high genetic population admixture and negligible differentiation between indigenous and restored sites (FCT = 0.002). Moreover, differentiation between groups was caused by only one outlier population, where inbreeding effects are presumed. We therefore conclude that the introduction of nonlocal seed provenances in the course of landscape restoration did not jeopardize regional species persistence by contributing to inbreeding or outbreeding depressions, or any measurable adverse population genetic effect. On the basis of these results, we see no obvious objections to the current practice to use the 10‐fold cheaper, nonlocal seed material of D. carota for restoration projects.  相似文献   

19.
We tested the effects of life‐history traits on genetic variation and conducted a comparative analysis of two plant species with differing life‐history traits co‐occurring in the highly endangered renosterveld of South Africa. We selected eighteen renosterveld remnants with varying degrees of size and isolation where populations of the herbaceous, annual and insect‐pollinated Hemimeris racemosa and the shrubby perennial and both wind‐ and insect‐pollinated Eriocephalus africanus occurred. We postulated a lower genetic variation within populations and increased genetic variation between populations in the annual than in the perennial species. Genetic variation was lower within populations of H. racemosa than within E. africanus, as is typical for annual compared to perennial species. Variation within populations was, however, not correlated with fragment size or distance in either of the two species and genetic variation between populations of the two species was comparable (ΦST = 0.10, 0.09).  相似文献   

20.
One of the most intriguing questions in plant ecology is which evolutionary strategy allows widely distributed species to increase their ecological range and grow in changing environmental conditions. Phenotypic plasticity and local adaptations are major processes governing species range margins, but little is known about their relative contribution for tree species distribution in tropical forest regions. We investigated the relative role of phenotypic plasticity and local adaptation in the ecological distribution of the widespread palm Euterpe edulis in the Brazilian Atlantic Forest. Genetic sampling and experiments were performed in old‐growth remnants of two forest types with higher (Seasonal Semideciduous Forests vs. Submontane Rainforest) and lower biogeographic association and environmental similarities (Submontane Rainforest vs. Restinga Forest). We first assessed the molecular genetic differentiation among populations, focusing on the group of loci potentially under selection in each forest, using single‐nucleotide polymorphism (SNPs) outliers. Further, we looked for potential adaptive divergence among populations in a common garden experiment and in reciprocal transplants for two plant development phases: seedling establishment and sapling growth. Analysis with outlier loci indicated that all individuals from the Semideciduous Forest formed a single group, while another group was formed by overlapping individuals from Submontane Rainforest and Restinga Forest. Molecular differentiation was corroborated by reciprocal transplants, which yielded strong evidence of local adaptations for seedling establishment in the biogeographically divergent Rainforest and Semideciduous Forest, but not for Restinga Forest and Submontane Rainforest. Phenotypic plasticity for palm seedling establishment favors range expansion to biogeographically related or recently colonized forest types, while persistence in the newly colonized ecosystem may be favored by local adaptations if climatic conditions diverge over time, reducing gene flow between populations. SNPs obtained by next‐generation sequencing can help exploring adaptive genetic variation in tropical trees, which impose several challenges to the use of reciprocal transplants.  相似文献   

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