Landscape genetic structure of bur oak (Quercus macrocarpa) savannas in Illinois

Craft, Kathleen J.; Ashley, Mary V.

doi:10.1016/j.foreco.2006.11.005

Cited by 59 publications

(53 citation statements)

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“…Collectively these results suggests that gene flow is relatively low among the fragmented populations of Ontario, particularly between Niagara and Norfolk, and this will likely impact the future genetic diversity of northerly populations of M. acuminata. High genetic diversity can be maintained in fragmented tree populations if there is high outcrossing and if pollinators are highly mobile (Noreen and Webb 2013); in other words, forest fragmentation should have deleterious effects on genetic diversity only if pollen or seed dispersal curves conform to the boundaries of forest fragments (Craft and Ashley 2007). In this way, trees that experience regular long-distance seed or pollen dispersal may not be greatly impacted by habitat fragmentation.…”

Section: Sustainability Of Genetic Diversitymentioning

confidence: 99%

“…Restricted gene flow among tree populations living in fragmented habitat can lead to increased genetic differentiation and an accompanying reduction in genetic diversity following genetic drift; thus, habitat fragmentation may ultimately lead to reproductive isolation, poor recruitment, and reduced fitness as a result of inbreeding or pollen limitation (Young et al 1996;Lowe et al 2005;Ghazoul 2005). However, these outcomes are not inevitable in trees that can maintain high levels of pollen-mediated gene flow across fragmented habitat (Craft and Ashley 2007). In addition, long-lived tree species may have a delayed response to the effects of habitat fragmentation, and if mature trees either pre-date fragmentation, or span only one or two generations postfragmentation, they may exhibit little evidence of reduced genetic diversity (Craft and Ashley 2007;Ortega et al 2010).…”

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confidence: 99%

“…However, these outcomes are not inevitable in trees that can maintain high levels of pollen-mediated gene flow across fragmented habitat (Craft and Ashley 2007). In addition, long-lived tree species may have a delayed response to the effects of habitat fragmentation, and if mature trees either pre-date fragmentation, or span only one or two generations postfragmentation, they may exhibit little evidence of reduced genetic diversity (Craft and Ashley 2007;Ortega et al 2010). Therefore, the balance between relatively high genetic diversity associated with pollen or seed dispersal (Piotti 2009), and decreased genetic diversity resulting from genetic drift, can vary between regions and species, making it difficult to predict the effects of fragmentation on the genetic diversity and differentiation of tree species (reviewed in Young et al 1996;Ghazoul 2005;Lowe et al 2005).…”

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Conservation genetics of Magnolia acuminata, an endangered species in Canada: Can genetic diversity be maintained in fragmented, peripheral populations?

2015

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The genetic diversity of peripheral populations is potentially important to the future adaptive capacity of species, although may be difficult to predict. A large number of species-at-risk in Canada are at the northern edge of their distribution, and many of these live in fragmented habitat. We used nuclear and chloroplast markers to assess patterns of genetic diversity and differentiation within and among populations of Canadian Magnolia acuminata (Cucumber tree), an endangered species in Canada that extends as far north as the fragmented Carolinian forest in southern Ontario. We also compared the genetic composition of Canadian M. acuminata to populations sampled throughout its central distribution in the USA. We found a high proportion of shared microsatellite alleles, plus a single cpDNA haplotype, distributed throughout the entire M. acuminata range. We also found that despite occupying fragmented habitat at their range periphery, Canadian populations showed little reduction in genetic diversity relative to the USA populations, and we attribute this to effective historical dispersal in a longlived, polyploid species. However, a combination of private alleles, genetic substructuring, and lower levels of genetic diversity in seedlings compared to mature trees, suggests that current levels of gene flow are relatively low among Canadian populations. Therefore, despite high levels of genetic diversity in Canadian M. acuminata, managers should be aware that without intervention, populations will likely become increasingly isolated and experience a reduction in genetic diversity which in turn may threaten their long-term survival in Canada.

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Section: Sustainability Of Genetic Diversitymentioning

confidence: 99%

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confidence: 99%

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Conservation genetics of Magnolia acuminata, an endangered species in Canada: Can genetic diversity be maintained in fragmented, peripheral populations?

2015

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“…, 2002). For example, in an open, fragmented landscape, Craft & Ashley (2007) could not detect population structure for Quercus macrocarpa over 200‐km geographical distances. In addition, Muir et al.…”

Section: Introductionmentioning

confidence: 97%

“…, 2002; Bacles et al. , 2005; Craft & Ashley, 2006, 2007). High within‐site nuclear diversity is a common finding for oaks, and it is usually attributed to long‐distance pollen flow (Dow & Ashley, 1996; Streiff et al.…”

Section: Introductionmentioning

confidence: 99%

Patterns of seed dispersal and pollen flow inQuercus garryana(Fagaceae) following post‐glacial climatic changes

Marsico

Hellmann²,

Romero‐Severson

2009

Journal of Biogeography

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Aim We examined the genetic structure of Quercus garryana to infer post-glacial patterns of seed dispersal and pollen flow to test the hypotheses that (1) peripheral populations are genetically distinct from core populations and from one another; (2) genetic diversity declines towards the poleward edge of the species' range; and (3) genetic diversity in the chloroplast genome, a direct measure of seed dispersal patterns, declines more sharply with increasing latitude than diversity in the nuclear genome. We address our findings in the context of known historical oak distribution from pollen core data derived from previously published research.Location Oak-savanna ecosystems from southern Oregon, USA (core populations/non-glaciated range) northward to Vancouver Island, British Columbia, Canada (peripheral populations/glaciated range).Methods We genotyped 378 trees from 22 sites with five chloroplast and seven nuclear microsatellite loci. For both sets of markers, we estimated genetic diversity and differentiation using an analysis of molecular variance and generated Mantel correlograms to detect genetic and geographical distance correlations. For the nuclear markers, we also used a Bayesian approach to infer population substructure.Results There was a large degree of population differentiation revealed by six chloroplast haplotypes, with little (£ 3) or no haplotype diversity within sites. Peripheral island locations shared the same, maternally inherited chloroplast haplotype, whereas locations in mainland Washington had greater haplotype diversity. In contrast, genetic diversity of the nuclear markers was high at all locations sampled. Populations clustered into two groups and were significantly positively correlated over large spatial scales (£ 200 km), although allele richness decreased significantly with latitude. Population substructure was observed between core and peripheral populations because rare alleles were absent in peripheral localities and common allele frequencies differed. Main conclusionsThe observed pattern of chloroplast haplotype loss at the northern periphery suggests restricted seed dispersal events from mainland sites to peripheral islands. This pattern was unexpected, however, as refugial oak populations remained near the current post-glacial range even during the Last Glacial Maximum. Using nuclear markers, we found high within-population diversity and population differentiation only over large spatial scales, suggesting that pollen flow is relatively high among populations.

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Nuclear and chloroplast DNA phylogeography reveals high genetic diversity and postglacial range expansion in Quercus mexicana

Sánchez‐Acevedo,

González‐Rodríguez,

Torres‐Miranda

et al. 2023

American J of Botany

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PremisePhylogeographical studies are fundamental for understanding factors that influence the spatial distribution of genetic lineages within species. Population expansions and contractions, distribution shifts, and climate changes are among the most important factors shaping the genetic compositions of populations.MethodsWe investigated the phylogeography of an endemic oak, Quercus mexicana (Fagaceae), which has a restricted distribution in northeastern Mexico along the Sierra Madre Oriental and adjacent areas. Nuclear and chloroplast DNA microsatellite markers were used to describe the genetic diversity and structure of 39 populations of Q. mexicana along its entire distribution area. We tested whether population expansion or contraction events influenced the genetic diversity and structure of the species. We also modeled the historical distributional range of Q. mexicana (for the Mid Holocene, the Last Glacial Maximum, and the Last Interglacial) to estimate the extent to which climate fluctuations have impacted the distribution of this oak species.ResultsOur results revealed high genetic diversity and a low genetic structure in Q. mexicana populations. Ecological niche models suggested historical fluctuations in the distributional range of Q. mexicana. Historical range changes, gene flow, and physical barriers seem to have played an important role in shaping the phylogeographic structure of Q. mexicana.ConclusionsOur study indicates that the genetic structure of Q. mexicana may have been the result of responses of oak trees not only to heterogeneous environments present in the Sierra Madre Oriental and adjacent areas, but also to elevational and latitudinal shifts in response to climate changes in the past.This article is protected by copyright. All rights reserved.

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Landscape genetic structure of bur oak (Quercus macrocarpa) savannas in Illinois

Cited by 59 publications

References 45 publications

Conservation genetics of Magnolia acuminata, an endangered species in Canada: Can genetic diversity be maintained in fragmented, peripheral populations?

Conservation genetics of Magnolia acuminata, an endangered species in Canada: Can genetic diversity be maintained in fragmented, peripheral populations?

Patterns of seed dispersal and pollen flow inQuercus garryana(Fagaceae) following post‐glacial climatic changes

Nuclear and chloroplast DNA phylogeography reveals high genetic diversity and postglacial range expansion in Quercus mexicana

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