The significance of genetic erosion in the process of extinction. I. Genetic differentiation in Salvia pratensis and Scabiosa columbaria in relation to population size

Treuren, R. van; Bijlsma, Rob G.; Delden, W. van; Ouborg, N. Joop

doi:10.1038/hdy.1991.23

Cited by 221 publications

(156 citation statements)

References 24 publications

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“…As a consequence, small populations are expected to show lower allelic diversity and heterozygosity within populations and higher genetic differentiation among populations than large populations (Lande, 1988;Hamrick & Godt, 1989). Genetic erosion has recently been observed in populations of a few endangered plant species, which have become small and isolated owing to habitat destruction and fragmentation by human activities Van Treuren et al, 1991;Raijmann et al, 1994).…”

Section: Introductionmentioning

confidence: 99%

Allozyme variation in relation to ecotypic differentiation and population size in marginal populations of Silene nutans

et al. 1997

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In Belgium, at the north-western margin of its geographical range, Silene nutans is a rare species, which has evolved a silicicolous (Si) and a calcicolous (Ca) ecotype, with contrasting morphometric traits. Genetic diversity and population genetic structure were examined for seven allozyme loci in 16 Si and 18 Ca populations (a total of 567 individuals). High genetic variation was found at both the ecotypic and population level, and no significant correlation was found between population size and any measure of genetic variation. The maintenance of high levels of genetic diversity in small, marginal populations might be explained by the perennial, long-lived life form and the outcrossing breeding system of the species. Additionally, low F ST -values suggested that efficient gene flow was occurring within both ecotypes. Genetic distance measures and cluster analysis using UPGMA on the distance matrix revealed that the populations were differentiated according to their ecotypic property in two distinct gene pools. It is argued that the congruence of allozymic and morphometric differentiation between edaphic races is unusual for an outcrossing species. This finding, together with previous observations of isolating mechanisms between ecotypes, strongly suggests that incipient speciation is occurring within Silene nutans at the margin of its geographical range.

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Section: Introductionmentioning

confidence: 99%

Allozyme variation in relation to ecotypic differentiation and population size in marginal populations of Silene nutans

et al. 1997

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“…For example, in a series of studies of the genetic diversity and population measures of growth rate and fecundity of the threatened perennial plant Scabiosa columbaria in the Netherlands, allozyme diversity decreased in the smaller populations. However, early fitness estimates based on seed set, seed size, and seedling size were mostly influenced by nongenetic maternal effects rather than by population origin (van Treuren et al, 1991). Similarly, in populations in the long-lived perennial Gentiana pneumonanthe, measures of early fitness were positively correlated with population size; however, correlations between population sizes with fitness traits later in the life cycle were not significant Raijman et al, 1994).…”

Section: Discussionmentioning

confidence: 79%

“…Studies of genetic erosion and demographic decline in natural populations often compare classes of populations that differ in size, age, or degree of isolation (Menges, 1991;van Treuren et al, 1991;Oostermeijer et al, 1994;Ouborg and van Treuren, 1995). For example, we might predict that smaller populations would contain relatively low levels of genetic diversity, and that their component individuals would be less fit than would be the case in large populations.…”

Section: Introductionmentioning

confidence: 99%

“…While the relation between the loss of genetic variation and population decline has been studied in experimental and natural populations (Menges, 1991;van Treuren et al, 1991;Oostermeijer et al, 1994;Heschel and Paige, 1995;Newman and Pilson, 1997;Fischer and Matthies, 1998;Hanski and Ovaskainen, 2000), the dynamical relation between genetic diversity and demography is less well-documented (but see Westemeier et al, 1998). Studies of genetic erosion and demographic decline in natural populations often compare classes of populations that differ in size, age, or degree of isolation (Menges, 1991;van Treuren et al, 1991;Oostermeijer et al, 1994;Ouborg and van Treuren, 1995).…”

Section: Introductionmentioning

confidence: 99%

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Genetic and demographic dynamics of small populations of Silene latifolia

2003

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Small local populations of Silene alba, a short-lived herbaceous plant, were sampled in 1994 and again in 1999. Sampling included estimates of population size and genetic diversity, as measured at six polymorphic allozyme loci. When averaged across populations, there was very little change between samples (about three generations) in population size, measures of within-population genetic diversity such as number of alleles or expected heterozygosity, or in the apportionment of genetic diversity within and among populations as measured by F st . However, individual populations changed considerably, both in terms of numbers of individuals and genetic composition. Some populations doubled in size between samples, while others shrank by more than 75%. Similarly, expected heterozygosity and allele number increased by more than two-fold in individual populations and decreased by more than threefold in others. When population-specific change in number and change in measures of genetic diversity were considered together, significant positive correlations were found between the demographic and genetic variables. It is speculated that some populations were released from the demographic consequences of inbreeding depression by gene flow.

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“…That is, they reflect the genetic resources necessary for short-term ecological adaptation and for long-term evolutionary change. Significant positive correlations between isozyme variation and quantitative morphological traits that affect fitness have been demonstrated in plants (e.g., Ouborg, van Treuren, and van Damme, 1991;van Treuren et al, 1991). Therefore, to preserve extant variation in H. cumulicola, many populations must be protected from across the small geographic range of the species to ensure retention of allelic and genotypic diversity.…”

Section: General Patterns Of Isozyme Variation-allmentioning

confidence: 99%

Conservation implications of genetic variation in three rare species endemic to Florida rosemary scrub

Dolan

Yahr

Menges

et al. 1999

American J of Botany

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Habitat conversion and fire suppression during the last 50 yr have greatly reduced and altered Florida scrub vegetation, resulting in threats to the persistence of its unique flora. As part of a larger conservation project, we investigated patterns of isozyme variation in three rare perennial scrub plants with overlapping ranges endemic to Florida rosemary scrub on the Lake Wales Ridge. All three species have low levels of genetic variation, comparable to or lower than those generally reported for rare plants with restricted geographic ranges. Liatris ohlingerae has more than twice the expected heterozygosity of the other two species, with little population differentiation. In contrast, Hypericum cumulicola has highly differentiated populations with little apparent interpopulation gene flow and heterozygote deficiencies indicative of inbreeding. Eryngium cuneifolium, the species with the narrowest range and fewest populations, has intermediate values for genetic parameters. Although the three species have narrow and overlapping geographic ranges and similar habitat specificity, we discuss how optimal conservation of each species differs.

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The significance of genetic erosion in the process of extinction. I. Genetic differentiation in Salvia pratensis and Scabiosa columbaria in relation to population size

Cited by 221 publications

References 24 publications

Allozyme variation in relation to ecotypic differentiation and population size in marginal populations of Silene nutans

Allozyme variation in relation to ecotypic differentiation and population size in marginal populations of Silene nutans

Genetic and demographic dynamics of small populations of Silene latifolia

Conservation implications of genetic variation in three rare species endemic to Florida rosemary scrub

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