Significant Loss Of Genetic Diversity Research Articles

Postglacial colonisation of western Central Europe by Polyommatus coridon (Poda 1761) (Lepidoptera: Lycaenidae): evidence from population genetics.

The genetic population structure of Polyommatus coridon (Poda 1761) over large regions of France, Italy and Germany was studied by allozyme electrophoresis. The genetic diversity within populations was high for all parameters analysed (number of alleles 2.72; observed and expected heterozygosity 19.6% and 20.3%, respectively; percentage of polymorphic loci: total: 76.4% and, with polymorphism if the frequency of the commonest allele is below 95%: 53.1%), whereas genetic differentiation between populations was comparatively low (FST = 0.021 +/- 0.002). The mean number of alleles declined significantly from southern to northern populations (r = -0.53, P = 0.0005). Similar effects were found also for other parameters of genetic diversity. This is interpreted as a loss of genetic diversity during postglacial expansion. However, samples from France and Italy had similar patterns of genetic diversity indicating no significant loss in this region. Populations from southern Germany were genetically uniform, well differentiated from French populations and showed a significant loss of genetic diversity. Probably, this is due to a bottleneck during passing through the Burgundian Gap, which is a migration corridor from north-eastern France to southern Germany. In contrast to southern German populations, western German populations were not well differentiated from French populations. Nevertheless, they were genetically impoverished, probably as a result from local bottlenecks and post-expansion phenomena.

Genetic diversity of PhilippineRubus moluccanusL. (Rosaceae) populations examined with VNTR DNA probes

ABSTRACTTwo synthetic DNA probes composed of tandemly repeated ‘core’ sequences (GACA and GATA) were used to examine genetic diversity at multiple variable-number-tandem-repeat (VNTR) loci within and among four spatially isolated Philippine populations ofRubus moluccanusL. (Rosaceae), an uncultivated bramble widely distributed throughout southeast Asia – Malesia. Central goals were to determine whether apomictic propagation was detectable inR. moluccanusand to examine whether populations isolated on separate islands, or on mountain tops on a single island, were genetically differentiated. Sampling 22 individuals per population, the findings include: (1) no two individuals shared identical VNTR band profiles and thus apomictic propagation was not detected; (2) the mean number of bands scored per individual was 24.3 (SD = 3.91) and the proportion of polymorphic loci within populations ranged from 0.69 to 1.00 (mean = 0.86 ± SD = 0.085); (3) the average proportion of bands shared between individuals within populations ranged from 0.39 to 0.67 (0.50 ± 0.067), while average interpopulation similarity ranged from 0.21 to 0.50 (0.32 ± 0.092); and (4) estimated heterozygosity within populations ranged from 0.42 to 0.79 (0.62 ± 0.083), while interpopulation heterozygosity ran from 0.62 to 0.81 (0.74 ± 0.062). Permutation tests were used to estimate the statistical significance of differences in similarity between populations. A Luzon population isolated by 1200 km was always significantly different in similarity tests when compared with each of the other three populations, all located on Mindanao (and separated by at least 100 km but less than 250 km). Of the latter three, only one population differed significantly from the other two in the degree of VNTR markers shared, possibly reflecting biogeographic partitioning suggested for the island. Across all populations, average estimated Fst was 0.154, although mean inter-island Fst (0.224) was significantly higher than mean intra-island Fst (0.085). These results suggest that, while intra-island gene flow is relatively high, significant differentiation of tropical species may occur even over short distances on individual islands. Preservation of only a limited number of populations may result in a significant loss of genetic diversity in such species.

Fish Resources; Threats and Protection

The status of fish species and fish resources is reviewed. Actual and potential threats are identified and, as far as possible, quantified in terms of their potential to cause local or general extinction. Excessive depletion by fishing alone has rarely, if ever, caused extinction, but the circumstances in which unrestrained fishing could potentially do so are identified. The harm to fish arising from deterioration of water quality caused by toxic pollutants and acidification is well documented and, for the most part, well understood. More subtle and potentially more dangerous conditions arise from excessive organic enrichment in low-energy systems such as deep lakes and semi-enclosed seas, which may lead to the creation or enhancement of an anoxic layer and its spead into shallower regions. The majority of introduced fish species have proved either non-viable or ecologically neutral. A small proportion have been beneficial, mainly in man-made water bodies. Some, notably general colonisers and powerful predators, have seriously harmed the native fish fauna. Most serious, because the fish have little or no natural protective response, is disruption of water flow or loss of habitat. Significant loss of genetic diversity can be caused even when these factors are not so serious as to cause total extinction. In reality, it is usual for two or more of the above threats to operate together; it is shown how the result may be more dangerous than the sum of their independent effects. In conclusion, it is suggested that a more rigorous and uniform definition of threat is needed. The established criteria and methodology of risk assessment could be used with advantage. Complete protection, except in special circumstances, is unattainable. A better strategy is to intensify efforts to convince the users of fish resources, whether for food, sport or the aquarium trade, that sustainable harvesting is to their long-term advantage as well as that of the fish. Above all, the need is to convince the general public that the conservation of fish is just as important as that of other more visible fauna and flora.

Management Options for Preserving Genetic Diversity: Reintroduction of Guam Rails to the Wild

Abstract: Population management programs recognize the importance of managing genetic diversity in species that are candidates for eventual reintroduction to natural habitats. The planned 1989 release of captive‐born Guam rails (Rallus owstoni), extinct in the wild since 1986, to the Northern Mariana island of Rota provides an opportunity to evaluate various management options for selecting breeders to produce young rails for release. Six options were compared to determine which one best replicated genetic diversity in the original captive founder population. Heterozygosity, allelic dimity, founder contribution, and founder genome equivalents were used as indicators of genetic diversity. Option 1: Randomly choose adults for breeding. Option 2: Choose the most fecund captive breeders. Option 3: Use allozyme data to choose parents that will produce the most genetically diverse chicks. Option 4: Choose pairs to equalize founder contribution in the population. Option 5: Choose pairs to maximize allelic diversity. Option 6: Choose pairs to maximize founder genome equivalents. Genetic management options based on pedigree analysis (#4, 5, 6) produced the most genetically diverse release populations for Rota. Managing founder genome equivalents produced a balance between equalizing founder contribution and maximizing allelic diversity, and provided the most genetically diverse population. Randomly selecting breeding pain, choosing the best captive breeding stock, or managing by allozyme data resulted in substantially reduced genetic diversity. Results illustrate that some of the most common approaches to population management or population reintroduction may produce significant loss of genetic diversity, whereas certain genetic management options may actually increase genetic diversity over current population levels.