SPATIAL GENETIC STRUCTURE IN TWO TAMARACK [<i>LARIX LARICINA</i>(DU ROI) K. KOCH] POPULATIONS WITH DIFFERING ESTABLISHMENT HISTORIES

Knowles, Peggy; Perry, Daniel J.; Foster, Heather A.

doi:10.1111/j.1558-5646.1992.tb02062.x

Cited by 66 publications

(46 citation statements)

References 21 publications

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“…These contrasting patterns of autocorrelation in relation to the distance of the seedlings to the seed sources are commonly observed (see review in Troupin et al 2006). Similarly, seedlings underneath maternal trees exhibited large SGS, while dispersed seedlings showed less SGS in Quercus robur (Hampe et al 2010) or no relation at all in an expanding L. laricina sub-population (Knowles et al 1992). SGS might also be influenced by the genetic clustering within the data set (Born et al 2008a).…”

Section: Sgs Forms and Persists Over Timementioning

confidence: 88%

Pursuing glacier retreat: genetic structure of a rapidly expanding Larix decidua population

Pluess

2010

Molecular Ecology

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One of the greatest threats to the long-term viability of migrating plant species is the loss of genetic diversity due to founder effects. Populations can expand as a response to climate change, but it is uncertain if long-lived plant species can maintain sufficient genetic diversity at the leading edge of migrating populations. This study uses an expanding Larix decidua population investigated along a chronosequence at landscape (350 ha) and local (0.8 ha) scales to test whether accelerated migration as a result of climate warming has the potential to intensify genetic erosion. Nine SSR markers revealed similar genetic diversity among eight sub-populations along the chronosequence (overall H(e) = 0.73; SE=0.04). Sub-populations were not genetically differentiated and all sampled individuals (N=730) formed one major genetic cluster indicating homogenizing gene flow despite spatial genetic structure (SGS) up to 80 m. At the local scale, individuals at the leading edge [early successional sub-population (ESSP), N =140] and a sub-population at equilibrium [late successional sub-population (LSSP), N = 290] revealed high genetic diversity in largest-sized cohorts. SGS among juveniles occurred up to 30 m in LSSP but there was no structure in ESSP. Accordingly, a maximum likelihood paternity assignment revealed local gene dispersal in LSSP (2-48 m) and intermediate-to-long distance dispersal into ESSP (115-3132 m). The findings indicate intensive mixing of the genes in this expanding population instead of founder effects and support the view that genetic diversity can be maintained in a long-lived species during rapid population expansion driven by climate warming.

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Section: Sgs Forms and Persists Over Timementioning

confidence: 88%

Pursuing glacier retreat: genetic structure of a rapidly expanding Larix decidua population

Pluess

2010

Molecular Ecology

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“…Although a number of experimental studies have demonstrated that selection pressures can vary over very short distances in spatially contiguous plant populations (e.g., Kalisz 1986;Stewart and Schoen 1987;Stratton 1992Stratton , 1994, significant spatial substructure is not always found (e.g., Dewey and Heywood 1988;Knowles et al 1992;reviewed in Waser 1993). In such cases, absence of differentiation is usually attributed to high levels of pollen and/or seed dispersal, despite evidence that strong selection can re-create genetic differentiation within a single generation even after gene flow has occurred (Jain and Bradshaw 1966;McNeilly 1968;Antonovics and Bradshaw 1970).…”

Section: Natural Selection and Effective Gene Flow Across Ecological mentioning

confidence: 99%

“…If most gene dispersal is local, then genetic substructure should develop within populations due to the actions of genetic drift (Turner et al 1982;Sokal and Wartenburg 1983;Bos and van der Haring 1988), localized selection (Wright 1943(Wright , 1969Levin and Kerster 1974;Loveless and Hamrick 1984), or their interaction (Dickinson and Antonovics 1973;Sokal and Oden 1978a,b). Many empirical studies have documented spatial genetic heterogeneity within contiguous natural plant populations (e.g., Epling and Dobzhansky 1942;Schoen and Latta 1989;Argyres and Schmitt 1991;Campbell and Dooley 1992;Williams 1994), while other studies have found little or no genetic differentiation at micro geographic scales (Dewey and Heywood 1988;Epperson and Allard 1989;Knowles et al 1992;reviewed in Waser 1993).…”

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confidence: 99%

POPULATION STRUCTURE ALONG A STEEP ENVIRONMENTAL GRADIENT: CONSEQUENCES OF FLOWERING TIME AND HABITAT VARIATION IN THE SNOW BUTTERCUP, RANUNCULUS ADONEUS

1997

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Few studies have determined how gene flow and selection interact to generate population genetic structure in heterogeneous environments. One way to identify the potential role played by natural selection is to compare patterns of spatial genetic structure between different life cycle stages and among microenvironments. We examined patterns of spatial structure in a population of the snow buttercup (Ranunculus adoneus), using both adult plants and newly emerged seedlings. The study population spans a steep environmental gradient caused by gradual melting of snow within a permanent snowbed. Early-melting sites are characterized by denser vegetation, more fertile soils, and a longer growing season than late-melting sites tens of meters away. The flowering time of R. adoneus is controlled entirely by time of snowmelt, so the contiguous population is phenologically substructured into a series of successively flowering cohorts, reducing the opportunity for direct pollen transfer between early- and late-melting sites. For four highly polymorphic enzyme loci in this tetraploid species, there was subtle, but statistically significant, genetic differentiation between early, middle, and late-melting cohorts; adults usually showed greater differentiation among snowmelt zones than did seedlings. At two loci in adults and one locus in seedlings, homozygotes were more common than predicted at Hardy-Weinberg equilibrium, even when assuming maximum levels of double reduction during meiosis. This pattern suggests the occurrence of self-fertilization and/or population substructure. To determine how spatial isolation and phenological separation each contribute to genetic substructure, we used bivariate regression models to predict the numbers of allele differences between randomly paired individuals as a function of meters separation in space and days separation in flowering time. For newly emerged seedlings, we found that spatial separation was positively associated with genetic difference, but that the additional contribution of phenological separation to genetic difference was not significant. This implies that seeds and/or pollen move effectively across the snowmelt gradient, despite differences in flowering time. As was true for seedlings, spatial separation between paired adults contributed to greater genetic difference, but for a given spatial separation, the genetic difference between adult plants was reduced by phenological separation. This result implies that postemergence selection is favoring at least some seeds that migrate across the snowmelt gradient. Directional gene flow across the snowmelt gradient probably results from a genetic source-sink interaction, that is, the colonization of ecologically marginal late-melting sites by high quality seeds produced by the larger subpopulation in early-melting sites. Effective gene flow from high to low quality microenvironments is likely to impede adaptation to late-melting locations.

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“…By the mid-1990s, the focus of autocorrelation studies turned to the analysis of 'fine-scale genetic structure' within populations, using multi-allele, multilocus genotypes for individuals (e.g. Heywood 1991;Knowles et al 1992;Berg & Hamrick 1995;Epperson 1995;Loiselle et al 1995;Streiff et al 1998;Hardy & Vekemans 1999;Smouse & Peakall 1999;Rousset 2000;Vekemans & Hardy 2004).…”

Section: Introductionmentioning

confidence: 99%

A heterogeneity test for fine‐scale genetic structure

2008

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For organisms with limited vagility and/or occupying patchy habitats, we often encounter nonrandom patterns of genetic affinity over relatively small spatial scales, labelled fine-scale genetic structure. Both the extent and decay rate of that pattern can be expected to depend on numerous interesting demographic, ecological, historical, and mating system factors, and it would be useful to be able to compare different situations. There is, however, no heterogeneity test currently available for fine-scale genetic structure that would provide us with any guidance on whether the differences we encounter are statistically credible. Here, we develop a general nonparametric heterogeneity test, elaborating on standard autocorrelation methods for pairs of individuals. We first develop a 'pooled within-population' correlogram, where the distance classes (lags) can be defined as functions of distance. Using that pooled correlogram as our null-hypothesis reference frame, we then develop a heterogeneity test of the autocorrelations among different populations, lag-by-lag. From these single-lag tests, we construct an analogous test of heterogeneity for multilag correlograms. We illustrate with a pair of biological examples, one involving the Australian bush rat, the other involving toadshade trillium. The Australian bush rat has limited vagility, and sometimes occupies patchy habitat. We show that the autocorrelation pattern diverges somewhat between continuous and patchy habitat types. For toadshade trillium, clonal replication in Piedmont populations substantially increases autocorrelation for short lags, but clonal replication is less pronounced in mountain populations. Removal of clonal replicates reduces the autocorrelation for short lags and reverses the sign of the difference between mountain and Piedmont correlograms.

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SPATIAL GENETIC STRUCTURE IN TWO TAMARACK [LARIX LARICINA(DU ROI) K. KOCH] POPULATIONS WITH DIFFERING ESTABLISHMENT HISTORIES

Cited by 66 publications

References 21 publications

Pursuing glacier retreat: genetic structure of a rapidly expanding Larix decidua population

Pursuing glacier retreat: genetic structure of a rapidly expanding Larix decidua population

POPULATION STRUCTURE ALONG A STEEP ENVIRONMENTAL GRADIENT: CONSEQUENCES OF FLOWERING TIME AND HABITAT VARIATION IN THE SNOW BUTTERCUP, RANUNCULUS ADONEUS

A heterogeneity test for fine‐scale genetic structure

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