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1.
Oriental beech (Fagus orientalis Lipsky) is a widespread monoecious and wind-pollinated tree species. It is one of the major components of the Hyrcanian forests
of Iran and it is of both ecological and economical importance. Twelve beech stands were surveyed at 9 chloroplast (cp) and
6 nuclear (n) polymorphic microsatellite loci (simple sequence repeats, SSR) to provide information on distribution of genetic
diversity within and among populations and on gene conservation and silvicultural management of this species. High levels
of genetic differentiation were detected for the chloroplast genome (F
ST = 0.80 and R
ST = 0.95), in sharp contrast to the nuclear genome (F
ST = 0.06, R
ST = 0.05). The analysis of molecular variance (AMOVA) showed that 48% of the total cpSSR variation was attributable to differences
among regions and 30% to differences among populations within regions, suggesting multiple origins of beech populations in
Hyrcanian forests. Nuclear SSRs confirmed the presence of significant differentiation among populations and among geographic
regions, even if, as expected, this was less pronounced than that found with cpSSRs (based on AMOVA, differences among regions
and among populations within regions each contribute 5% to total nSSR variance). A highly significant correlation between
genetic (nSSRs) and geographic distances (R
2 = 0.522) was estimated, thus showing an isolation by distance effect. The application of spatial analysis of molecular variance
(SAMOVA) using both marker data allowed identification of genetically homogeneous groups of populations. Possible applications
of these results for the certification of provenances and/or seed lots and for designing conservation programs are presented
and discussed. 相似文献
2.
Qiang Fan Sufang Chen Renchao Zhou Xu Xiang Wenbo Liao Suhua Shi 《Conservation Genetics》2011,12(3):753-760
Understanding the amount and distribution of genetic diversity in natural populations can inform the conservation strategy
for the species in question. In this study, genetic variation at eight nuclear microsatellite loci was used to investigate
genetic diversity and population structure of wild litchi (Litchi chinensis Sonn. subsp. chinensis). Totally 215 individuals were sampled, representing nine populations of wild litchi. All eight loci were polymorphic, with
a total of 51 alleles. The expected heterozygosity in the nine populations ranged from 0.367 to 0.638 with an average value
of 0.526. Inbreeding within wild litchi populations was indicated by a strong heterozygote defect. Significant bottleneck
events were detected in the populations from Yunnan and Vietnam, which could be responsible for lower levels of genetic diversity
in these populations. Measures of genetic differentiation (F
ST = 0.269) indicated strong differentiation among wild litchi populations. Significant correlation was found between genetic
differentiation and geographical distance (r = 0.655, P = 0.002), indicating a strong isolation by distance in these populations. Bayesian clustering suggested genetic separation
among three regional groups, namely, the western group, the central group and the eastern group. Some conservation strategies
for wild litchi populations were also proposed based on our results. 相似文献
3.
Jorge C. Pereira Raquel Chaves Alexandra Leitão Domitilia Matias Henrique Guedes-Pinto 《Helgoland Marine Research》2011,65(3):361-367
The clam Ruditapes decussatus is commercially important in the south of Portugal. The random amplified polymorphic DNA (RAPD) technique was applied to
assess the genetic diversity and population structure of two Portuguese populations occurring in the Ria Formosa (Faro) and
the Ria de Alvor, respectively. Twenty-five individuals of each population were investigated by RAPD profiles. Genetic diversity
within populations, measured by the percentage of polymorphic loci (%P), varied between 68.57% (Alvor) and 73.88% (Faro). Shannon’s information index (H) and Nei’s gene diversity (h) were 0.281 and 0.176, respectively, for the Alvor population and 0.356 and 0.234 for the Faro population. Overall, genetic
variation within R. decussatus populations was high. The total genetic diversity (H
T) was explained by a low variation between populations (G
ST = 0.145), which is consistent with high gene flow (N
m = 2.9). The analysis of molecular variance (AMOVA) showed that 65% of variability is within populations and 35% between populations
(ΦPT = 0.345; P ≥ 0.001). The value of Nei’s genetic distance was 0.0881, showing a low degree of population genetic distance, despite the
different geographic origin. This is the first study on the population genetics of R. decussatus by RAPD technique. The results may be useful for restocking programs and aquaculture. 相似文献
4.
Genetic variability in random amplified polymorphic DNA (RAPD) was studied in 90 individuals of Caragana microphylla, an outcrossing perennial shrub species, from five natural populations sampled in Inner Mongolia steppe of China on a small
scale. Nineteen selected primers were used to amplify DNA samples, and totally 225 bands were detected. The percentage of
polymorphic bands within populations ranged form 58.22% to 63.56%, with an average of 60% at the population level and 71.11%
at the species level, indicating relatively high genetic variations in C. microphylla species. Shannon’s information index (l) and Nei’s gene diversity (h) showed the similar trend with each other. According to the analysis of Nei’s gene diversity, the percentage of genetic variation
among populations was 7.13%, indicating a low level of genetic differentiation among populations. There existed a strong gene
flow (N
m
= 3.26) among populations. Although AMOVA analysis also revealed most variation was within populations (ΦST = 4.1%), a significant proportion was observed among populations (P < 0.001) in the present study, suggesting genetic differentiation occurred among populations at a certain extent. Based on
Mantel’s tests and the results of previous studies, the genetic structure pattern of C. microphylla accorded with the isolation-by-distance model on a very large scale, however, on a small scale, the significant genetic differentiation
among populations might be enhanced by the micro-environmental divergence among the sampling sites, rather than by geographic
factors. Analysis of the genetic variations of C. microphylla populations provided useful information for the adaptive strategy of Caragana species. 相似文献
5.
Yoshiaki Tsuda Haruo Sawada Takafumi Ohsawa Katsuhiro Nakao Hiroki Nishikawa Yuji Ide 《Tree Genetics & Genomes》2010,6(3):377-387
We evaluated the genetic structure of 16 Betula maximowicziana populations in the Chichibu mountain range, central Japan, located within a 25-km radius; all but two populations were at
altitudes of 1,100–1,400 m. The results indicate the effects of geographic topology on the landscape genetic structure of
the populations and should facilitate the development of local-scale strategies to conserve and manage them. Analyses involving
11 nuclear simple sequence repeat loci showed that most populations had similar intrapopulation genetic diversity parameters.
Population differentiation (F
ST = 0.021, G′ST = 0.033) parameters for the populations examined were low but were relatively high compared to those obtained in a previous
study covering populations in a much larger area with a radius of approximately 1,000 km (F
ST = 0.062, G′ST = 0.102). Three populations (Iriyama, Kanayamasawa, and Nishizawa) were differentiated from the other populations by Monmonier’s
and spatial analysis of molecular variance algorithms or by STRUCTURE analysis. Since a high mountain ridge (nearly 2,000 m)
separates the Kanayamasawa and Nishizawa populations from the other 14 populations and the Kanayamasawa and Nishizawa populations
are themselves separated by another mountain ridge, the genetic structure appears to be partly due to mountain ridges acting
as genetic barriers and restricting gene flow. However, the Iriyama population is genetically different but not separated
by any clear geographic barrier. These results show that the landscape genetic structure is complex in the mountain range
and we need to pay attention, within landscape genetic studies and conservation programs, to geographic barriers and local
population differentiation. 相似文献
6.
Zhou HF Zheng XM Wei RX Second G Vaughan DA Ge S 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2008,117(7):1181-1189
The cross compatible wild relatives of crops have furnished valuable genes for crop improvement. Understanding the genetics
of these wild species may enhance their further use in breeding. In this study, sequence variation of the nuclear Lhs1 gene was used to investigate the population genetic structure and gene flow of Oryza rufipogon and O. nivara, two wild species most closely related to O. sativa. The two species diverge markedly in life history and mating system, with O. rufipogon being perennial and outcrossing and O. nivara being annual and predominantly inbreeding. Based on sequence data from 105 plants representing 11 wild populations covering
the entire geographic range of these wild species, we detected significantly higher nucleotide variation in O. rufipogon than in O. nivara at both the population and species levels. At the population level the diversity in O. rufipogon (Hd = 0.712; θ
sil = 0.0017) is 2–3 folds higher than that in O. nivara (Hd = 0.306; θ
sil = 0.0005). AMOVA partitioning indicated that genetic differentiation among O. nivara populations (78.2%) was much higher than that among O. rufipogon populations (52.3%). The different level of genetic diversity and contrasting population genetic structure between O. rufipogon and O. nivara might be explained by their distinct life histories and mating systems. Our simulation using IM models demonstrated significant
gene flow from O. nivara to O. rufipogon, indicating a directional introgression from the annual and selfing species into the perennial and outcrossing species. The
ongoing introgression has played an important role in shaping current patterns of genetic diversity of these two wild species.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
7.
Kitt G. Payn William S. Dvorak Bernard J. H. Janse Alexander A. Myburg 《Tree Genetics & Genomes》2008,4(3):519-530
Eucalyptus urophylla (Timor mountain gum) is an economically important plantation species that occurs naturally in a series of disjunct populations
on the volcanic slopes of seven islands in eastern Indonesia. Twelve microsatellite markers were used to investigate the distribution
of nuclear genetic diversity among 19 geographically defined E. urophylla populations. High levels of gene diversity were observed throughout the geographic range (H
E = 0.703 to 0.776). The level of genetic differentiation among populations was low (F
ST = 0.031), but the amount of differentiation increased with geographic distance. A phenogram produced by a neighbor-joining
analysis illustrated that populations clustered according to islands. However, a Bayesian clustering approach revealed a more
cryptic population structure comprising two genetically homogeneous groups. Gene flow among the populations is likely responsible
for the apparent weak influence of geographic insularity on the genetic diversity and structure of the island species. These
findings provide direction for conservation and breeding strategies in E. urophylla.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
8.
Sal (Shorea robusta Gaertn., Dipterocarpaceae) is a wind-pollinated tropical tree species found in southern Asia. We investigated the genetic
diversity and structure at four microsatellites of 15 populations comprising continuous-peripheral and disjunct-peripheral
populations in Nepal. Estimates of genetic diversity (N
A = 8.98, H
O = 0.62, H
E = 0.69) were similar when compared with those of other tropical tree species. A higher level of genetic diversity was observed
in continuous-peripheral populations (N
A = 9.61, H
O = 0.67, H
E = 0.72) as compared to disjunct-peripheral (N
A = 8.04, H
O = 0.55, H
E = 0.64). Population differentiation was higher among disjunct-peripheral populations (F
ST = 0.043) than among continuous peripherals (F
ST = 0.012). There was a significant association between gene flow distances and genetic differentiation (r
2 = 0.128, P ≤ 0.007). No spatial arrangement of populations according to their geographical locations was found. Based on observed genetic
diversity protection of some populations in continuous-peripheral range are suggested for the sustainable conservation of
genetic resources of the species while protection of some disjunct-peripheral populations are also recommended for conserving
rare alleles. 相似文献
9.
Mao-feng Yue Ren-chao Zhou Ye-lin Huang Guo-rong Xin Su-hua Shi Li Feng 《Journal of Plant Biology》2010,53(2):165-171
High levels of genetic variation enable species to adapt to changing environments and provide plant breeders with the raw
materials necessary for artificial selection. In the present study, six AFLP primer pairs were used to assess the genetic
diversity of Desmodium triflorum (L.) DC. from 12 populations in South China. A high percentage of polymorphic loci (P = 76.16%) and high total gene diversity (H
T = 0.310) were found, indicating that the genetic diversity of D. triflorum is high at the species level. Genetic diversity was also relatively high at the population level (P = 55.85%, H
e = 0.230). The coefficient of gene differentiation among populations (G
ST) was 0.255, indicating that while most genetic diversity resided within populations, there was also considerable differentiation
among populations. AMOVA also indicated 24.29% of the total variation to be partitioned among populations (ΦST = 0.243). UPGMA clustering analysis based on genetic distances showed that the 12 populations could be separated into three
subgroups: an eastern, a western, and a central-southern subgroup. However, a Mantel test revealed no significant correlation
(r = 0.286, p = 0.983) between the geographical distances and genetic distances separating these populations; mountain barriers to gene
flow and human disturbance may have confounded these correlations. The present study has provided some fundamental genetic
data that will be of use in the exploitation of D. triflorum. 相似文献
10.
Population fragmentation is often correlated with loss of genetic diversity and reduced fitness. Obligate out-crossing (dioecy)
is expected to enhance genetic diversity, reduce genetic differentiation, and avoid inbreeding depression through frequent
gene flow. However, in highly fragmented populations dioecy has only diminishing effects upon genetic structure as pollination
limitations (e.g. flight distance of pollinators) most often restrict inter-population gene flow in insect pollinated species.
In fragmented dry grasslands in northeastern Germany, we analysed genetic structure, fitness, and habitat quality of the endangered
dioecious Silene otites (Caryophyllaceae). Using AFLP markers, a high level of differentiation among ten populations was found (F
st = 0.36), while the intra-population genetic diversities (H
E = 0.165–0.240) were similar as compared to hermaphroditic species. There was neither a correlation between geographic and
genetic distance nor between genetic diversity and population size, which indicates reduced gene flow among populations and
random genetic drift. Plant size was positively correlated with genetic diversity. Seed set and number of juveniles were positively
related to population size. Higher total coverage resulted in reduced plant fitness, and the number of juveniles was negatively
correlated to cryptogam cover. Additionally, we found a sex ratio bias towards more male plants in larger populations. Overall,
our results indicate that on a regional geographic scale dioecy does not necessarily prevent genetic erosion in the case
of habitat fragmentation, especially in the absence of long distance seed and pollen dispersal capacity. 相似文献
11.
Ipecac (Psychotria ipecacuanha) is a perennial, medicinal herb that grows in the understory of semi-deciduous tropical forests in the Neotropics. Ipecacs
present a widely disjunct distribution, with two of its three ranges occurring in Brazil. The Amazonian populations are at
least 1600 km from the nearest Atlantic populations. This work used ISSR markers to compare the genetic diversity and structure
of populations from the two Brazilian ranges. Lower genetic diversity in Amazon populations (P = 60.11%, Hs = 0.18) and higher
genetic diversity in Atlantic populations (P = 73.94%, Hs = 0.20) were detected. Differentiation between ranges were high
(θ
B = 0.6838, GST-B = 0.6665). AMOVA revealed that 65.3% of the total molecular variance can be attributed to regional differences between
the two ranges. Principal coordinate analyses and cluster analyses organized ipecacs at either individual or population level
into two exclusive groups that correspond each to one of the two disjunct ranges, without exception. The results do not support
a scenario that postulates human-mediated, long-distance dispersal events as a plausible origin for the distribution of the
Brazilian ipecacs, but indicate geographic isolation as a long-standing barrier to genetic exchange and connectivity among
populations from different ranges. Conservation implications are discussed. 相似文献
12.
In this study we evaluated the influence of recent landscape fragmentation on the dynamics of remnant fragments from the Brazilian
Atlantic Forest. This biome is one of the richest in the world and has been extensively deforested and fragmented. We sampled
five populations of the threatened Dalbergia nigra, a tree endemic to the Brazilian Atlantic Forest, two located in a large reserve of continuous forest and three in fragments
of different sizes and levels of disturbance. In order to assess historical changes, considering the longevity of the analyzed
species, 119 adults and 116 saplings were genotyped for six microsatellite loci. Lower levels of genetic diversity were found
in the most impacted fragments when compared to the most preserved population located inside the reserve, and there was significant
genetic structure among the populations studied (pairwise F
ST = 0.031–0.152; pairwise D
EST = 0.039–0.301). However, genetic structure among saplings (F
ST = 0.056; D
EST = 0.231) was significantly lower than among adults (F
ST = 0.088; D
EST = 0.275). Estimates of contemporary gene flow based on assignment tests corroborated this result, suggesting that fragmentation
led to an increase in gene flow. This connectivity among remnant fragments could mitigate the loss of genetic diversity through
a metapopulation dynamic, but the high rate of habitat loss and the unknown long-term genetic effects add uncertainty. These
results, taken together with the presence of private alleles in disturbed populations, highlight the importance of preserving
the extant fragments. 相似文献
13.
Cedrus libani of Lebanon is a valuable natural resource and the dominant species in its natural ecosystem. Intense and diverse anthropogenic
pressures over historical times raised concerns about its genetic vigor and continued survival. Our investigation of the genetic
diversity included samples from all remnant natural populations. Assessment of the genetic diversity using random amplified
polymorphic DNA markers revealed the persistence of considerable variation distributed within populations with low population
differentiation corroborated by Bayesian and analysis of molecular variance estimates (G
ST = 0.07, Φ
ST = 0.09). Individual assignment tests were carried out to investigate measures of gene flow. Inferences concluded that this
natural heritage is not currently threatened by inbreeding or by random genetic drift. Correlation studies investigated possible
effects of spatial distribution and environmental conditions on genetic structure. A climatic trend corresponding to a temperature–humidity
gradient correlated significantly with the level of genetic diversity, while the edaphic variation did not. 相似文献
14.
Satu Lampila Laura Kvist Ralf Wistbacka Markku Orell 《European Journal of Wildlife Research》2009,55(4):397-406
Siberian flying squirrel (Pteromys volans) has declined in Finland and it is considered an endangered species. We studied microsatellite variation in four flying squirrel
populations in a fragmented landscape in Finland to determine the amount of gene flow and genetic diversity in the populations.
Demographic data from these areas suggest that the populations are declining. All the populations are significantly differentiated
(F
ST = 0.23). The most notable result is the high degree of differentiation between two adjacent populations (F
ST = 0.11) and low genetic variability (number of alleles 3.0) in one of the populations. These findings suggest problems in
dispersal and possible fragmentation effects in the landscape where only 10–20% of habitat favorable for the flying squirrel
is left. Conservation ensuring dispersal should be urgently considered. Future studies should concentrate on the modeling
of the population viability and on the effects of inbreeding in these small populations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
15.
Tamarix chinensis, with its important ecological significance, is a vital dominant plant in the Yellow River Delta of China. To understand
its genetic structure and population dynamics, five populations of T. chinensis, consisting of 140 individuals, were analyzed in this study using inter simple sequence repeat markers. Seventy-eight polymerase
chain reaction fragments were scored, of which 62 were polymorphic. The mean percentage of polymorphic loci (P), the mean Nei’s gene diversity (h), and the mean Shannon’s information index (I) were 79.5%, 0.239, and 0.363, respectively. These indexes indicated that a moderate level of genetic diversity existed in
T. chinensis populations of the Yellow River Delta. Both analysis of molecular variance (AMOVA) (Φ
st = 0.169) and Popgene (G
st = 0.159) analyses revealed the low level of genetic differences among the five populations of T. chinensis. The results implied that relatively frequent gene flow existed among populations. However, slightly uneven genetic diversity
was also found among populations. Unweighted pair group method with arithmetic mean and principal component analysis showed
that populations with similar soil salinity had a close relationship, rather than populations with closer geographical distance.
A significant negative correlation between genetic diversity and soil salinity of the five populations (r = −0.958, p < 0.01) showed that soil salinity played an important role in shaping the population genetic structure of T. chinensis in the Yellow River Delta, China. 相似文献
16.
Dai-Chang Kuo Chia-Chia Lin Kuo-Chieh Ho Yu-Pin Cheng Shih-Ying Hwang Tsan-Piao Lin 《Conservation Genetics》2010,11(3):803-812
Cinnamomum kanehirae Hayata (Lauraceae), the most valuable subtropical and temperate broadleaf timber tree in Taiwan, is rapidly disappearing
from the wild. Taking advantage of a scion garden established by the Taiwan Forestry Research Institute, we examined patterns
of chloroplast DNA (cpDNA) variations in 19 populations including 94 individuals. By sequencing two cpDNA fragments using
universal primers (the trnL-trnF and petG-trnP intergenic spacers), we found eight polymorphic sites, six haplotypes, and extremely low nucleotide diversity (π = 0.00016) from 792 bp aligned sequences. The ancestral haplotype is widely distributed. Among the populations studied, three
separated populations, at Yungfeng, Fuli, and Tahu have high nucleotide diversity. No phylogeographical structures of haplotypes
were revealed because the tests of N
ST−G
ST for populations did not differ from zero in any situations; a ‘star-like’ genealogy is characteristic when all haplotypes
rapidly coalesce and is a general outcome of population expansion. The neutrality test also suggested demographic expansion.
The genetic divergence and diversity analyses suggested that two potential refugia existed during the last glaciation with
a major one located in southeastern Taiwan and a minor one located in Tahu in north-central Taiwan in the Hsuehshan Range,
west of the Central Mountain Range. 相似文献
17.
Previous studies have reached different discussions about the genetic variation and genetic structure of Quercus crispula populations in northeastern Japan. This is a common oak species in Eastern Asia. Some studies have suggested that the populations
in northeastern Japan were derived from those remaining in the southwest after the last glacial maximum (LGM), whilst other
studies have found evidence that populations persisted in northeastern Japan during the LGM. Using seven highly polymorphic
nuclear simple sequence repeat loci, we investigated the genetic structure of 16 Q. crispula populations along a latitudinal gradient in northeastern Japan (northern Honshu and Hokkaido), spanning about half of the
species’ biogeographic range in the country. Although the level of population differentiation was low (F
ST = 0.021;
G¢\textST G^{\prime}_{\text{ST}} = 0.090), two geographically differentiated clusters were detected by STRUCTURE analysis. The first cluster included most
of the populations in Hokkaido, and may indicate continued survival throughout past glacial periods. We found a significant
decrease in allelic richness with latitude, so the second cluster may represent an expansion of the lineage from Honshu during
the post-glacial period. These results should enhance our understanding of historical north–south migrations of this species
in northeastern Japan. 相似文献
18.
A combination of directed amplification of minisatellite DNA (DAMD) and random amplification of polymorphic DNA (RAPD) primes
were used to assess the genetic variation within and between three isolated populations of Indian sandalwood (Santalum album). Eleven primers used in this study amplified 65.99 % polymorphic bands. Analysis of molecular variance revealed a high genetic
variation among these populations (ϕST = 0.549). There are indications of clonality within the existing Indian sandalwood populations which can be attributed to
habitat fragmentation, isolation and vegetative reproduction. 相似文献
19.
Fengjuan Zhao Fuli Liu Jidong Liu Put O. AngJr. Delin Duan 《Journal of applied phycology》2008,20(2):191-198
Sargassum muticum is important in maintaining the structure and function of littoral ecosystems, and is used in aquaculture and alginate production,
however, little is known about its population genetic attributes. In this study, random amplified polymorphic DNA (RAPD) and
inter-simple sequence repeat (ISSR) markers were used to investigate the genetic structure of four populations of S. muticum and one outgroup of S. fusiforme (Harv.) Setchell from Shandong peninsula of China. The selected 24 RAPD primers and 19 ISSR primers amplified 164 loci and
122 loci, respectively. Estimates of genetic diversity with different indicators (P%, percentage of polymorphic loci; H, the expected heterozygosity; I, Shannon’s information index) revealed low or moderate level of genetic variations within each S. muticum population, and a high level of genetic differentiations were determined with pairwise unbiased genetic distance (D) and fixation index (F
ST
) among the populations. The Mantel test showed that two types of matrices of D and F
ST
were highly correlated whether from RAPD (r = 0.9706, P = 0.009) or ISSR data (r = 0.9161, P = 0.009). Analysis of molecular
variance (AMOVA) was conducted to apportion the variations among and within the S. muticum populations. It indicated that variations among populations were higher than those within populations, being 55.82% verse
44.18% by RAPD and 55.21% verse 44.79% by ISSR, respectively. Furthermore, the Mantel test suggested that genetic differentiations
among populations were related to the geographical distances (r > 0.6), namely, conformed to the IBD (isolation by distance)
model, as expected from UPGMA (unweighted pair group method with arithmetic averages) cluster analysis. On the whole, the
high genetic structuring among the four S. muticum populations along the distant locations was clearly indicated in RAPD and ISSR analyses (r > 0.9, P < 0.05) in our study. 相似文献
20.
The Oregon spotted frog (Rana pretiosa) is one of the most threatened amphibians in the Pacific Northwest. Here we analyzed data from 13 microsatellite loci and
298 bp of mitochondrial DNA in frogs collected from 23 of the remaining R. pretiosa populations in order to (1) assess levels of genetic diversity within populations of R. pretiosa, (2) identify the major genetic groups in the species, (3) estimate levels of genetic differentiation and gene flow among
populations within each major group, and (4) compare the pattern of differentiation among R. pretiosa populations with that among populations of R. cascadae, a non-endangered congener that also occurs in Oregon and Washington. There is a strong, hierarchical genetic structure in
R. pretiosa. That structure includes six major genetic groups, one of which is represented by a single remaining population. R. pretiosa populations have low genetic diversity (average H
e = 0.31) compared to R. cascadae (average H
e = 0.54) and to other ranid frogs. Genetic subdivision among populations is much higher in R. pretiosa than in R. cascadae, particularly over the largest geographic distances (hundreds of kilometers). A joint analysis of migration rates among populations
and of effective sizes within populations (using MIGRATE) suggests that both species have extremely low migration rates, and
that R. pretiosa have slightly smaller effective sizes. However, the slight difference in effective sizes between species appears insufficient
to explain the large difference in genetic diversity and in large-scale genetic structure. We therefore hypothesize that low
connectivity among the more widely-spaced R. pretiosa populations (owing to their patchier habitat), is the main cause of their lower genetic diversity and higher among-population
differentiation. Conservation recommendations for R. pretiosa include maintaining habitat connectivity to facilitate gene flow among populations that are still potentially connected,
and either expanding habitat or founding additional ‘backup’ populations to maintain diversity in the isolated populations.
We recommend that special consideration be given to conservation of the Camas Prairie population in Northern Oregon. It is
the most geographically isolated population, has the lowest genetic diversity (H
e = 0.14) and appears to be the only remaining representative of a major genetic group that is now almost extinct. Finally,
because the six major groups within R. pretiosa are strongly differentiated, occupy different habitat types, and are geographically separate, they should be recognized as
evolutionarily significant units for purposes of conservation planning. 相似文献