Demography, Genetics, or Statistics: Comments on a Paper by Heschel and Paige

Ouborg, N. Joop; Groenendael, J.M. van

doi:10.1046/j.1523-1739.1996.10041290.x

Cited by 8 publications

(4 citation statements)

References 11 publications

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“…The reduced plasticity of offspring in small populations of P. veris , like their reduced performance, is therefore probably due to increased inbreeding, although effects of drift cannot be excluded. A reduced ability to tolerate changes in environmental conditions and simulated herbivory in plants from small populations has been claimed for Ipomopsis aggregata (Heschel & Paige 1995), although the validity of these results is questionable for statistical reasons (Ouborg & van Groenendael 1996).…”

Section: Discussionmentioning

confidence: 99%

Reduced fecundity and offspring performance in small populations of the declining grassland plantsPrimula verisandGentiana lutea

2000

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Summary 1We studied reproduction and o spring performance in relation to population size in the declining self-incompatible perennials Primula veris and Gentiana lutea. In both species, reproduction was strongly reduced in small populations, where plants produced fewer seeds per fruit and per plant. Total seed mass per plant was higher in large populations, but individual seeds were smaller, indicating a tradeo between seed number and size. Reproduction was depressed most strongly in populations consisting of less than c. 200 (P. veris) and c. 500 plants (G. lutea), respectively. 2 The inclusion of plant size (an integrated measure of habitat quality) in the statistical models did not change the relationships between fecundity and population size. Pollen limitation or inbreeding depression in small populations are therefore more likely explanations for these patterns than is habitat quality. 3 Germination rate and survival of seedlings in a common environment was not related to population size in either species, although P. veris developed into larger rosettes when seeds were derived from large populations. This suggests that inbreeding depression occurs in small populations of P. veris. 4 In a factorial fertilizer-by-competition experiment with P. veris, o spring from larger populations grew signi®cantly larger and responded more strongly to fertilizer. For this declining species genetic deterioration as a result of habitat fragmentation may therefore aggravate the e ects of environmental changes such as habitat eutrophication. 5 Our results suggest that small populations may face an increased short-term risk of extinction because of reduced reproduction, and an increased long-term risk because they are less able to respond to environmental changes.

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Section: Discussionmentioning

confidence: 99%

Reduced fecundity and offspring performance in small populations of the declining grassland plantsPrimula verisandGentiana lutea

2000

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“…Any effect observed might be attributable to the locus itself (Watt 1977) or ones linked to it, but individual loci are unlikely to be correlated directly with quantitative traits such as growth rates (Turelli and Ginzburg 1983, Burton 1990 a, b ). Understanding associations between heterozygosity and fitness in populations remains elusive (e.g., , , Ouborg and van Groenendael 1996, Sheffer et al 1997) and such association has been proven infrequently. Population‐level measures of genetic diversity including allele richness and the proportion of heterozygous individuals are likely to affect population success, as demonstrated in the field transplantation experiment.…”

Section: Discussionmentioning

confidence: 99%

Reduced Genetic Diversity in Eelgrass Transplantations Affects Both Population Growth and Individual Fitness

Williams

2001

Ecological Applications

220

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The transplantation of eelgrass (Zostera marina) for mitigation results in reduced genetic diversity among individuals and populations in southern California, the Chesapeake Bay, and New Hampshire. Although genetic variation determines the potential for eelgrass to adapt to the rapidly changing environment in its coastal and estuarine habitats, genetic considerations are not currently included in mitigation and restoration policy. I investigated where and how genetic diversity is lost during eelgrass transplantation. I then explored associations between genetic diversity and both vegetative propagation and sexual reproduction to evaluate the importance of genetic diversity for short‐term population growth. Eelgrass beds used as donor populations vary in genetic diversity, and some have little or no detectable genetic diversity. Genetic diversity is reduced upon transplantation because donor plants are collected from small areas, leading to random sampling errors in selecting stock. This loss can be minimized by using information from regional surveys of genetic diversity and structure in potential donor populations and by revising donor stock collection. There were significant positive associations between genetic diversity and the sexual reproduction of eelgrass, with a similar trend for vegetative propagation. Individuals heterozygous for glucose‐phosphate isomerase (GPI) developed flowering shoots more than did homozygotes. More seeds germinated from a genetically diverse, untransplanted population than from a transplanted population with low genetic diversity. A field transplantation of known multilocus genotypes revealed that leaf shoot density in high‐diversity eelgrass increased almost twice as fast as in low‐diversity eelgrass over 22 mo. In a mesocosm experiment under heat stress, eelgrass heterozygous for either GPI or malate dehydrogenase (MDH) produced almost twice as many leaf shoots as homozygotes. The difference between treatments in all experiments increased over time. Together, these results imply that there could be economic incentives to planting genetically diverse eelgrass, and that genetic diversity contributes to eelgrass population viability even over the short term.

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“…Any effect observed might be attributable to the locus itself (Watt 1977) or ones linked to it, but individual loci are unlikely to be correlated directly with quantitative traits such as growth rates (Turelli andGinzburg 1983, Burton 1990a, b). Understanding associations between heterozygosity and fitness in populations remains elusive (e.g., Heschel and Paige 1995, Paige and Heschel 1996, Ouborg and van Groenendael 1996, Sheffer et al 1997 and such association has been proven infrequently. Population-level measures of genetic diversity including allele richness and the proportion of heterozygous individuals are likely to affect population success, as demonstrated in the field transplantation experiment.…”

Section: What Are the Consequences Of Reduced Genetic Diversity For Ementioning

confidence: 99%

Reduced Genetic Diversity in Eelgrass Transplantations Affects both Population Growth and Individual Fitness

Williams¹

2001

Ecological Applications

125

207

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The transplantation of eelgrass (Zostera marina) for mitigation results in reduced genetic diversity among individuals and populations in southern California, the Chesapeake Bay, and New Hampshire. Although genetic variation determines the potential for eelgrass to adapt to the rapidly changing environment in its coastal and estuarine habitats, genetic considerations are not currently included in mitigation and restoration policy. I investigated where and how genetic diversity is lost during eelgrass transplantation. I then explored associations between genetic diversity and both vegetative propagation and sexual reproduction to evaluate the importance of genetic diversity for short-term population growth.Eelgrass beds used as donor populations vary in genetic diversity, and some have little or no detectable genetic diversity. Genetic diversity is reduced upon transplantation because donor plants are collected from small areas, leading to random sampling errors in selecting stock. This loss can be minimized by using information from regional surveys of genetic diversity and structure in potential donor populations and by revising donor stock collection.There were significant positive associations between genetic diversity and the sexual reproduction of eelgrass, with a similar trend for vegetative propagation. Individuals heterozygous for glucose-phosphate isomerase (GPI) developed flowering shoots more than did homozygotes. More seeds germinated from a genetically diverse, untransplanted population than from a transplanted population with low genetic diversity. A field transplantation of known multilocus genotypes revealed that leaf shoot density in high-diversity eelgrass increased almost twice as fast as in low-diversity eelgrass over 22 mo. In a mesocosm experiment under heat stress, eelgrass heterozygous for either GPI or malate dehydrogenase (MDH) produced almost twice as many leaf shoots as homozygotes. The difference between treatments in all experiments increased over time. Together, these results imply that there could be economic incentives to planting genetically diverse eelgrass, and that genetic diversity contributes to eelgrass population viability even over the short term.

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Demography, Genetics, or Statistics: Comments on a Paper by Heschel and Paige

Cited by 8 publications

References 11 publications

Reduced fecundity and offspring performance in small populations of the declining grassland plantsPrimula verisandGentiana lutea

Reduced fecundity and offspring performance in small populations of the declining grassland plantsPrimula verisandGentiana lutea

Reduced Genetic Diversity in Eelgrass Transplantations Affects Both Population Growth and Individual Fitness

Reduced Genetic Diversity in Eelgrass Transplantations Affects both Population Growth and Individual Fitness

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