Genetic Diversity and Population Size in Four Rare Southern Appalachian Plant Species

Genetic management of fragmented populations involves the application of evolutionary genetic theory and knowledge to alleviate problems due to inbreeding and loss of genetic diversity in small population fragments. Populations evolve through the effects of mutation, natural selection, chance (genetic drift) and gene flow (migration). Large outbreeding, sexually reproducing populations typically contain substantial genetic diversity, while small populations typically contain reduced levels. Genetic impacts of small population size on inbreeding, loss of genetic diversity and population differentiation are determined by the genetically effective population size, which is usually much smaller than the number of individuals.

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Small population size and low genomic diversity have no effect on fitness in experimental translocations of a wild fish

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2019.1989 ◽

2019 ◽

Vol 286 (1916) ◽

pp. 20191989 ◽

Cited By ~ 1

Author(s):

M. C. Yates ◽

E. Bowles ◽

D. J. Fraser

Keyword(s):

Genetic Diversity ◽

Body Size ◽

Population Size ◽

Brook Trout ◽

Habitat Degradation ◽

Species Conservation ◽

Empirical Work ◽

Genomic Diversity ◽

Effective Population ◽

Isolated Populations

Little empirical work in nature has quantified how wild populations with varying effective population sizes and genetic diversity perform when exposed to a gradient of ecologically important environmental conditions. To achieve this, juvenile brook trout from 12 isolated populations or closed metapopulations that differ substantially in population size and genetic diversity were transplanted to previously fishless ponds spanning a wide gradient of ecologically important variables. We evaluated the effect of genome-wide variation, effective population size ( N e ), pond habitat, and initial body size on two fitness correlates (survival and growth). Genetic variables had no effect on either fitness correlate, which was determined primarily by habitat (pond temperature, depth, and pH) and initial body size. These results suggest that some vertebrate populations with low genomic diversity, low N e , and long-term isolation can represent important sources of variation and are capable of maintaining fitness in, and ultimately persisting and adapting to, changing environments. Our results also reinforce the paramount importance of improving available habitat and slowing habitat degradation for species conservation.

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Large numbers of vertebrates began rapid population decline in the late 19th century

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1616804113 ◽

2016 ◽

Vol 113 (49) ◽

pp. 14079-14084 ◽

Cited By ~ 20

Author(s):

Haipeng Li ◽

Jinggong Xiang-Yu ◽

Guangyi Dai ◽

Zhili Gu ◽

Chen Ming ◽

...

Keyword(s):

Genetic Diversity ◽

Population Size ◽

Threatened Species ◽

Driving Forces ◽

Population Decline ◽

Cumulative Effect ◽

Extinction Time ◽

Time Period ◽

Large Numbers ◽

The Difference

Accelerated losses of biodiversity are a hallmark of the current era. Large declines of population size have been widely observed and currently 22,176 species are threatened by extinction. The time at which a threatened species began rapid population decline (RPD) and the rate of RPD provide important clues about the driving forces of population decline and anticipated extinction time. However, these parameters remain unknown for the vast majority of threatened species. Here we analyzed the genetic diversity data of nuclear and mitochondrial loci of 2,764 vertebrate species and found that the mean genetic diversity is lower in threatened species than in related nonthreatened species. Our coalescence-based modeling suggests that in many threatened species the RPD began ∼123 y ago (a 95% confidence interval of 20–260 y). This estimated date coincides with widespread industrialization and a profound change in global living ecosystems over the past two centuries. On average the population size declined by ∼25% every 10 y in a threatened species, and the population size was reduced to ∼5% of its ancestral size. Moreover, the ancestral size of threatened species was, on average, ∼22% smaller than that of nonthreatened species. Because the time period of RPD is short, the cumulative effect of RPD on genetic diversity is still not strong, so that the smaller ancestral size of threatened species may be the major cause of their reduced genetic diversity; RPD explains 24.1–37.5% of the difference in genetic diversity between threatened and nonthreatened species.

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