Caracterización genética y morfológica de las poblaciones de Cyprinodon dearborni (Atherinomorpha: Cyprinodontidae) en Chacopata y Laguna de los Patos, Venezuela

The way that genetic variation is distributed geographically has important conservation and evolutionary implications. Here, we examined the distribution of genetic variation within and among populations of the montane perennial Ipomopsis aggregata. We sampled plants in western Colorado and examined (1) population genetic structure over a geographic area that spanned 130 km, including genetic variation within disturbed and undisturbed sites; (2) the relationship between genetic differentiation and geographic distance; and (3) the relationship between flowering time and genetic differentiation among plants within and among geographic areas. F IS was significantly higher (t test, P = 0.006), expected heterozygosity was significantly lower (t test, P = 0.04), and allelic richness was marginally significantly lower (t test, P = 0.078) among anthropogenically-disturbed sites compared to undisturbed sites. We found moderate genetic differentiation over the area sampled (average pairwise F ST = 0.04; average pairwise $$F^{\prime}_{ST} = 0.19$$ ), but no association of genetic and geographic distance (Mantel test P values 0.44 for F ST and 0.36 for $$F^{\prime}_{ST}$$ ). We found a strong association of flowering time and genetic differentiation over small and large spatial scales. Genetic differentiation between early and late flowering plants within a focal site was statistically significant (genic test for population differentiation combined P value <0.001; F ST = 0.05). There was a significant correlation between genetic distance ( $$F^{\prime}_{ST}$$ ) and distance in flowering time, when controlling for geographic distance, over the whole geographic area (Partial Mantel test R xy = 0.32, P = 0.013). A multiple regression with randomization further supported the inference that flowering time, but not geographic distance or elevation, predicted $$F^{\prime}_{ST}$$ (geographic distance: β = −0.03, P = 0.89; elevation: β = 0.01, P = 0.96; phenological distance: β = 0.30, P = 0.05), but not F st (geographic distance: β = −0.02, P = 0.92; elevation: β = 0.14, P = 0.38; phenological distance: β = 0.25, P = 0.11), unless elevation was left out of the model (geographic distance: β = −0.03, P = 0.9; phenological distance: β = 0.29, P = 0.03). The association of flowering time and genetic distance despite the lack of isolation by distance provides further evidence for the usefulness of incorporating this variable into plant landscape genetic studies when possible.

Characterization of genetic variance within and among five populations of Sperata seenghala (Skyes, 1839) revealed by random amplified polymorphic DNA markers

The Agave deserti complex, comprising A. deserti, A. cerulata and A. subsimplex, represents a group of species and subspecies with a near allopatric distribution and clear differences in morphology. Genetic differentiation and taxonomic status with respect to spatial distribution of 14 populations of the complex were analyzed in an effort to understand the evolution and speciation process within the genus. Allelic frequencies, levels of genetic variation, expected heterozygosity (H(S)), proportion of polymorphic loci (P), and genetic differentiation (theta and Nei's genetic distance) were estimated using 41 putative RAPD loci. All three species show high levels of genetic variation (H(S)=0.12-0.29, P=63.4-95.1), and low genetic differentiation between populations and species (theta populations=0.14+/-0.02 (SE); G(st)=0.11+/-0.02). Accordingly, gene flow among populations was estimated as high by three different methods (N(m)=2.91-6.14). Nei's genetic distances between the three species were low compared to the values obtained from other Agavaceae, and there was no clear correlation with taxonomic divisions. In a UPGMA analysis, A. subsimplex and A. cerulata formed exclusive monospecific clusters, whereas the A. deserti populations appear in more than one cluster together with other species. The results were consistent with a pattern of genetic isolation by distance.

Genetic divergence in bat communities was assessed on both sides of the Straits of Gibraltar and cryptic diversity was examined. Screening was carried out using partial sequences of the mitochondrial (mt)DNA cytochrome b gene on 399 individual bats belonging to the 18 species found on both sides of the Straits of Gibraltar. For those bats that showed important genetic discontinuities, molecular markers (ND1 and nuclear RAG2 genes) were added to expand the sampling process. Phylogenetic reconstructions were obtained using maximum parsinomy, genetic distances, maximum likelihood, and Bayesian criteria. As an estimate of bats’ flight performance, we measured for each species the wing aspect ratio and wing loading indexes, and correlated them with the maximum pairwise genetic distances obtained between southern Iberian and northern Moroccan populations. Genetic mtDNA distances between populations on both continents exceed 5% in seven out of 18 bat species analysed and unknown lineages were uncovered within the species complexes Myotis nattereri and Myotis mystacinus. We did not find a general pattern in the degree of permeability of the Straits of Gibraltar for bats. Genetic distances were not correlated with the ability to cross the Straits. Our study shows that the cryptic diversity uncovered among bats continues to increase as more regions are studied. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 434–450. ADDITIONAL KEYWORDS: community – cryptic diversity – cytochrome b – dispersal – genetic differentiation – mitochondrial DNA – ND1 – RAG2 – phylogeography – Pleistocene.

Analysis of genetic variation within and among samples of naturally produced Atlantic salmon (n = 372) from 7 Maine (U.S.A.) and one Canadian river were conducted based on 54 allozyme loci. Eight of the 54 loci proved polymorphic, and estimated heterozygosities (HS) based on all loci ranged from 0·012 to 0·026 (mean = 0·021, s.e. = 0·002). Only one of 56 tests revealed genotypic proportions that deviated significantly from Hardy–Weinberg expectations. Genetic distances (D) between samples ranged from 0·002 to 0·022. No obvious association existed between genetic and geographic distances. Cluster analysis of genetic distances revealed the Dennys River sample as the most differentiated when all samples were included in the analysis, though bootstrap support of the cluster analysis was generally weak. G‐tests revealed significant differences in allele frequencies among samples at five of the polymorphic loci, and the G‐value summed over all loci also indicated significant differences among samples. FST values indicated that 3·4% of the total genetic diversity was due to variability among samples, while 96·6% was due to variability within samples. These results indicate that the Atlantic salmon analyzed in this study had levels of genetic variability and differentiation among samples comparable to native populations from other areas collected across a similar geographic range.

RAPD technique was applied to study intraspecific genetic polymorphism and differentiation of Suaeda acuminata populations in oasis-desert transitional zone in Fukang, Xinjiang. By analysis of RAPD data, higher genetic variability was found in the populations of S. acuminata, with a percentage of polymorphic loci of 98.9%. Both estimations by Shannon diversity index and by Nei's gene diversity index from RAPD data, it was found identically that about 72% of molecular variation existed within the subpopulations, while about 28% of which existed among subpopulations. Analysis of genetic identity, genetic distance and cluster analysis showed that genetic differentiation has taken place in the populations of Suaeda acuminata in oasis-desert transitional zone in Fukang, Xinjiang, China. The correlation analytical result between the soil factures and the genetic diversity indicted that there was a significant positive relation between genetic diversity and concentrations of Mg++, conductivity (CO) and absorbed water(W) in soil, while there was no significant relation between genetic distance among subpopulations and geographical distance. Analysis of genetic identity, genetic distance and cluster analysis between the five subpopulations showed that genetic differentiation has taken place in the population of Suaeda acuminata in oasis-desert transitional zone in Fukang, Xinjiang. No correlation existed between genetic distance among subpopulations and their locations in oasis-desert transitional zone. Adaptation to its habitats and restricted gene flow among subpopulations may be a cause of genetic differentiation of Suaeda acuminata population in oasis-desert transitional zone in Fukang, Xinjiang.

The author carried out PCR-based genetic platform to investigate the hierarchical polar dendrogram of Euclidean genetic distances of one bastard halibut population, particularly for Paralichthys olivaceus, which was further connected with those of the other fish population, by involving with the precisely designed oligonucleotide primer sets. Eight oligonucleotides primers were used generating excessively alterating fragments, ranging in size of DNA bands from larger than approximately 100 bp to less than 2,000 bp. As regards average bandsharing value (BS) results, individuals from Hampyeong population (0.810) displayed lower bandsharing values than did individuals from Wando population (0.877). The genetic distance between individuals approved the existence of close relationship in the cluster II. Relatively, individuals of one bastard halibut population were fairly related to that of the other fish population, as shown in the polar hierarchical dendrogram of Euclidean genetic distances. The points of a noteworthy genetic distance between two P. olivaceus populations demonstrated this PCR procedure is one of the quite a few means for individuals and/or populations biological DNA investigates, for species security and proliferation of bastard halibut individuals in coastal region of the Korea.

Research on genetic differentiation among populations of Chromobotia macracanthus Bleeker from Sumatra, based on sequencing gene of mtDNA Cytochrome b and nucleus DNA RAG2 has been done. The objectives of the study were to obtain the representation of genetic differentiation among population of clown loach fishes or botia (Chromobotia macracanthus) from Sumatra and Kalimantan and to estimate the time divergence of both population group of botia. Samples of botia population were taken from 3 rivers in Sumatra namely Batanghari, Musi, and Tulang Bawang and one river from Kalimantan namely Kapuas. The genetic analysis was based on the sequencing of mtDNA Cytochrome b and nucleus DNA RAG2. The statistical analysis was done by using APE package on R language. The parameters observed were: nucleotide diversity, genetic distance, and neighbor-joining tree. The result showed that the highest nucleotide diversity was fish population of Musi, while the other two populations, Tulang Bawang (Sumatra) and Kapuas (Kalimantan), were considered as the lowest genetic diversity especially based on nucleus DNA RAG2 sequencing. Based on mtDNA Cytochrome-b sequencing, the most distinct population among those populations based on genetic distance were fish populations of Musi and Kapuas. According to the result of neighbor-joining tree analysis, the populations of botia were classified into two groups namely group of Sumatra and group of Kalimantan. The estimation of time divergence among group of population of Sumatra and Kalimantan based on mtDNA Cytochrome b was about 9.25—9.46 million years (Miocene era). The high genetic differences between groups of Sumatra and Kalimantan suggested that the effort of restocking botia from Sumatra into Kalimantan has to be done carefully, because it may disturb the gene originality of both botia populations.

Eleven weedy or wild species or subspecies of the genus Secale L. were compared with a set of cultivated rye accessions, based on inter-simple sequence repeat (ISSR) markers to analyze their phylogenetic relationships. A total of 846 bands were amplified from reactions using 12 screening primers, including 79 loci with a mean of 10.1 alleles per locus. The number of amplified bands for each primer ranged from 12 to 134, with a mean of 70.5 amplified bands per primer. The presence and distribution of amplified bands in different accessions demonstrate that a rapid evolutionary trend of microsatellite repeats occurred during the speciation process from the perennial wild form to annual cultivated rye. In addition, variation, amplification, and deletion of microsatellites in genomes revealed phylogenetic relationships in the genus Secale. Analysis of the presence, number, and distribution of amplified bands in genomes, as well as the comparison with genetic similarity (GS) indices based on ISSR, indicate that Secale strictum subsp. africanum (Stapf) Hammer, Secale strictum anatolicum (Boiss.) Hammer, Secale sylvestre Host, and Secale strictum subsp. strictum (C. Presl) Hammer emerged in succession from a common ancestor of Secale following geographic separation and genetic differentiation. The annual weedy rye evolved from S. strictum subsp. strictum, which was domesticated as present-day cultivated rye. Data from ISSR analyses separated all investigated accessions of the genus Secale into three distinct groups. These results support the division of the genus Secale into three species: the annual wild species S. sylvestre; the perennial wild species S. strictum, including several differential subspecies forms such as strictum, africanum, and anatolicum; and S. cereale, including cultivated and weedy rye as subspecies forms.

Genetic Differentiation and Similarity Degree Quantified by Statistical Parameters in the Romanian Sheep Breeds

Using starch gel and polyacrylamide gel electrophoresis, the genetic diversity of 19 populations of black locust (Robinia pseudoacacia L.) distributed in China has been evaluated based on seven allozyme systems. Among the 14 enzyme loci studied, 12 of them showed polymorphic, giving a total of 40 alleles. The average allelic number (A) and the average effective allelic number (Ae) were 3.004 and 2.178, whereas the average of expected heterozygosity (He) and the observed heterozygosity (Ho) were 0.525 and 0.440, respectively. The total genetic differentiation (HT) in the 19 populations tested was 0.536, including 0.515 within population (HS) and 0.021 among populations (DST). The mean coefficient of genetic differentiation (GST) was 0.038, indicating that 3.8% of genetic differentiation was resulted from the populations, and the rest from those within the population. The genetic distance among the 19 populations was small, ranging from 0.015 to 0.065. Cluster analysis based on AVERAGE showed that populations with closer geographical distribution had higher genetic similarity than that in populations with far away distribution. There was no evident geographic differentiation pattern in Chinese black locust populations at a biochemical level.

In this study, the levels of genetic variability were estimated in S.richadsonii fish populations from three different locations viz., Chirapani stream (pop 1), Gola (pop 2) and KosiRiver (pop 3) by using OPY Operon primers and 10 primers were produced distinct and repeatable amplification as well polymorphic loci. The higher proportion of polymorphic loci was observed in Champawat population as compared to other two populations and with the overall % polymorphisms were 14.76. The OPY 01, OPY 04, OPY 11 and OPY 16 primers were found to be the population specific banding patterns among these three populations. The Nei's genetic diversity (h) was found to be highest in pop1 andpop2 with 0.24 and 0.2 in pop3. The total gene diversity (Ht) in the population was 0.2962, within sample gene diversity (Hs) of 0.2321 and the genetic differentiation (GST) among the populations was 0.2164. The largest genetic distance (0.1565) was obtained between pop1 and pop2, whereas the smallest genetic distance was between pop1 and pop3 (0.1058), followed by pop3 and pop2 (0.1385). Further it is suggested that the levels of genetic identity and diversity obtained was very low and might be due to the less number of polymorphic loci and migration rate.

The level of genetic differentiation, gene flow and the relationship between geographical distance and genetic differentiation among six sheep populations of Mongolian group in China (Tong sheep, small-tailed Han sheep, Hu sheep, Tan sheep, Ujumuqin sheep and Bayinbuluk sheep) were analyzed using seven microsatellites. The trees were constructed from diversity coefficient (DC) distances among the six sheep populations. The overall heterozygote deficit across all the populations (Fit) was between 0.167 (OarAE101) and 0.044 (MAF33). The over-all significant deficit of heterozygote, because of inbreeding within breeds, (Fis) was between 0.089 (OarFCB304) and 0.005 (MAF33). The coefficient of genetic differentiation (Fst) was between 0.100 (OarAE101) and 0.022 (OarFCB48). It indicated that 3.9% of the total genetic variation could be explained by breed differences and the remaining 96.1% by differences among individuals for each population. This illustrated that most variations existed within breeds and genetic differentiation level were very low among sheep breeds of the Mongolian Group in China. The average number of effective migrants exchanged per generation (Nem) ranged from 2.7369 (Tan sheep and Bayinbuluk sheep) to 44.3928 (Tong sheep and Hu sheep), and the mean value was 11.25213. Significantly positive relationships between the level of genetic differentiation and geographical distance and genetic distances were detected. It is concluded that genetic differentiation of sheep breeds of Mongolian group in China is mainly the result of natural selection (different living conditions).

BIOGEOGRAPHY AND ORIGIN OF LILIUM LONGIFLORUM AND L. FORMOSANUM I - INTERSPECIFIC ISOLATING MECHANISMS AND POPULATION GENETIC STRUCTURE

Equilibrium models of isolation by distance predict an increase in genetic differentiation with geographic distance. Here we find a linear relationship between genetic and geographic distance in a worldwide sample of human populations, with major deviations from the fitted line explicable by admixture or extreme isolation. A close relationship is shown to exist between the correlation of geographic distance and genetic differentiation (as measured by F(ST)) and the geographic pattern of heterozygosity across populations. Considering a worldwide set of geographic locations as possible sources of the human expansion, we find that heterozygosities in the globally distributed populations of the data set are best explained by an expansion originating in Africa and that no geographic origin outside of Africa accounts as well for the observed patterns of genetic diversity. Although the relationship between F(ST) and geographic distance has been interpreted in the past as the result of an equilibrium model of drift and dispersal, simulation shows that the geographic pattern of heterozygosities in this data set is consistent with a model of a serial founder effect starting at a single origin. Given this serial-founder scenario, the relationship between genetic and geographic distance allows us to derive bounds for the effects of drift and natural selection on human genetic variation.