Dataset Information

Genetic divergence and signatures of natural selection in marginal populations of a keystone, long-lived conifer, Eastern White Pine (Pinus strobus) from Northern Ontario.

ABSTRACT: Marginal populations are expected to provide the frontiers for adaptation, evolution and range shifts of plant species under the anticipated climate change conditions. Marginal populations are predicted to show genetic divergence from central populations due to their isolation, and divergent natural selection and genetic drift operating therein. Marginal populations are also expected to have lower genetic diversity and effective population size (Ne) and higher genetic differentiation than central populations. We tested these hypotheses using eastern white pine (Pinus strobus) as a model for keystone, long-lived widely-distributed plants. All 614 eastern white pine trees, in a complete census of two populations each of marginal old-growth, central old-growth, and central second-growth, were genotyped at 11 microsatellite loci. The central populations had significantly higher allelic and genotypic diversity, latent genetic potential (LGP) and Ne than the marginal populations. However, heterozygosity and fixation index were similar between them. The marginal populations were genetically diverged from the central populations. Model testing suggested predominant north to south gene flow in the study area with curtailed gene flow to northern marginal populations. Signatures of natural selection were detected at three loci in the marginal populations; two showing divergent selection with directional change in allele frequencies, and one balancing selection. Contrary to the general belief, no significant differences were observed in genetic diversity, differentiation, LGP, and Ne between old-growth and second-growth populations. Our study provides information on the dynamics of migration, genetic drift and selection in central versus marginal populations of a keystone long-lived plant species and has broad evolutionary, conservation and adaptation significance.

SUBMITTER: Chhatre VE

PROVIDER: S-EPMC4032246 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Genetic divergence and signatures of natural selection in marginal populations of a keystone, long-lived conifer, Eastern White Pine (Pinus strobus) from Northern Ontario.

Chhatre Vikram E VE Rajora Om P OP

PloS one 20140523 5

Marginal populations are expected to provide the frontiers for adaptation, evolution and range shifts of plant species under the anticipated climate change conditions. Marginal populations are predicted to show genetic divergence from central populations due to their isolation, and divergent natural selection and genetic drift operating therein. Marginal populations are also expected to have lower genetic diversity and effective population size (Ne) and higher genetic differentiation than centra ...[more]

PMID: 24859159

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Project description:Whether old-growth (OG) forests have higher genetic diversity and effective population size, consequently higher conservation value and climate adaptive potential than second-growth (SG) forests, remain an unresolved issue. We have tested the hypothesis that old-growth forest tree populations have higher genetic diversity, effective population size (NE ), climate adaptive potential and conservation value and lower genetic differentiation than second-growth forest tree populations, employing a keystone and long-lived conifer, eastern white pine (EWP; Pinus strobus). Genetic diversity and population structure of old-growth and second-growth populations of eastern white pine (EWP) were examined using microsatellites of the nuclear and chloroplast genomes and single nucleotide polymorphisms (SNPs) in candidate nuclear genes putatively involved in adaptive responses to climate and underlying multilocus genetic architecture of local adaptation to climate in EWP. Old-growth and second-growth EWP populations had statistically similar genetic diversity, inbreeding coefficient and inter-population genetic differentiation based on nuclear microsatellites (nSSRs) and SNPs. However, old-growth populations had significantly higher chloroplast microsatellites (cpSSRs) haploid diversity than second-growth populations. Old-growth EWP populations had significantly higher coalescence-based historical long-term NE than second-growth EWP populations, but the linkage disequilibrium (LD)-based contemporary NE estimates were statistically similar between the old-growth and second-growth EWP populations. Analyses of population genetic structure and inter-population genetic relationships revealed some genetic constitution differences between the old-growth and second-growth EWP populations. Overall, our results suggest that old-growth and second-growth EWP populations have similar genetic resource conservation value. Because old-growth and second-growth EWP populations have similar levels of genetic diversity in genes putatively involved in adaptive responses to climate, old-growth, and second-growth populations may have similar adaptive potential under climate change. Our results could potentially be generalized across most of the boreal and temperate conifer forest trees. Our study contributes to address a long-standing issue, advances research field and knowledge about conservation and ecological and climate adaptation of forest trees.

Project description:Juvenile, female and male nematodes were discovered in wood chips of white pine Pinus strobus from Ashley Falls, MA. Initial observations suggested these nematodes might be PWN, but closer morphological and molecular characterization proved otherwise. Comparison of measured features with those in the literature indicated this nematode population had some unique characteristics. The specimens were identified as Bursaphelenchus antoniae Penas et al., 2006 based on 18S rDNA molecular sequence vs only 95% similarity with PWN B. xylophilus. Compared to the previously described Portuguese population of B. antoniae, the sequences generated for the MA population were 98.3% similar in the ITS1, 2 rDNA and 99.9% similar for 28S rDNA. There was 99.2% similarity between the COI sequences of the US and Portuguese isolates of B. antoniae. This population has morphology consistent with that of Penas et al., 2006; however, the female tail on this MA pine population is mucronate and more attenuated than in B. antoniae from Portuguese P. pinaster found in association with Hylobius sp. Ecological associations of both populations of B. antoniae are discussed.Juvenile, female and male nematodes were discovered in wood chips of white pine Pinus strobus from Ashley Falls, MA. Initial observations suggested these nematodes might be PWN, but closer morphological and molecular characterization proved otherwise. Comparison of measured features with those in the literature indicated this nematode population had some unique characteristics. The specimens were identified as Bursaphelenchus antoniae Penas et al., 2006 based on 18S rDNA molecular sequence vs only 95% similarity with PWN B. xylophilus. Compared to the previously described Portuguese population of B. antoniae, the sequences generated for the MA population were 98.3% similar in the ITS1, 2 rDNA and 99.9% similar for 28S rDNA. There was 99.2% similarity between the COI sequences of the US and Portuguese isolates of B. antoniae. This population has morphology consistent with that of Penas et al., 2006; however, the female tail on this MA pine population is mucronate and more attenuated than in B. antoniae from Portuguese P. pinaster found in association with Hylobius sp. Ecological associations of both populations of B. antoniae are discussed.

Project description:Climate change will increase autumn air temperature, while photoperiod decrease will remain unaffected. We assessed the effect of increased autumn air temperature on timing and development of cold acclimation and freezing resistance in Eastern white pine (EWP, Pinus strobus) under field conditions. For this purpose we simulated projected warmer temperatures for southern Ontario in a Temperature Free-Air-Controlled Enhancement (T-FACE) experiment and exposed EWP seedlings to ambient (Control) or elevated temperature (ET, +1.5°C/+3°C during day/night). Photosynthetic gas exchange, chlorophyll fluorescence, photoprotective pigments, leaf non-structural carbohydrates (NSC), and cold hardiness were assessed over two consecutive autumns. Nighttime temperature below 10°C and photoperiod below 12 h initiated downregulation of assimilation in both treatments. When temperature further decreased to 0°C and photoperiod became shorter than 10 h, downregulation of the light reactions and upregulation of photoprotective mechanisms occurred in both treatments. While ET seedlings did not delay the timing of the downregulation of assimilation, stomatal conductance in ET seedlings was decreased by 20-30% between August and early October. In both treatments leaf NSC composition changed considerably during autumn but differences between Control and ET seedlings were not significant. Similarly, development of freezing resistance was induced by exposure to low temperature during autumn, but the timing was not delayed in ET seedlings compared to Control seedlings. Our results indicate that EWP is most sensitive to temperature changes during October and November when downregulation of photosynthesis, enhancement of photoprotection, synthesis of cold-associated NSCs and development of freezing resistance occur. However, we also conclude that the timing of the development of freezing resistance in EWP seedlings is not affected by moderate temperature increases used in our field experiments.

Dataset Information

Genetic divergence and signatures of natural selection in marginal populations of a keystone, long-lived conifer, Eastern White Pine (Pinus strobus) from Northern Ontario.

Publications

Genetic divergence and signatures of natural selection in marginal populations of a keystone, long-lived conifer, Eastern White Pine (Pinus strobus) from Northern Ontario.

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