How can geographic isolation occur

Geographic isolation is a term that refers to a population of animals, plants, or other organisms that are separated from exchanging genetic material with other organisms of the same species. Typically geographic isolation is the result of an accident or coincidence. Geographic isolation can be caused by many factors and can result in a variety of results. Here are some examples:. Now you have some examples of geographic isolation and can better understand what this concept means and how it exists in the real world.

All rights reserved. Cheetah in the wild as examples of geographic isolation. Geographic Isolation Geographic isolation can be caused by many factors and can result in a variety of results. Isolation by Barriers The people of Finland, who are secluded to some degree from the rest of the world by water, develop certain diseases due to the lack of genetic material from other ethnicities and races. Barrett, S. Evolutionary processes in aquatic plant populations.

Why are most aquatic plants widely distributed? Dispersal, clonal growth and small-scale heterogeneity in a stressful environment. Acta Oecol.

Wright, S. Isolation by distance. Genetics 28, — Genetic structure is correlated with phenotypic divergence rather than geographic isolation in the highly polymorphic strawberry poison-dart frog. De Meester, L. The monopolization hypothesis and the dispersal—gene flow paradox in aquatic organisms. Storfer, A. Landscape genetics: where are we now? Zhao, Y. Are habitat fragmentation, local adaptation and isolation-by-distance driving population divergence in wild rice Oryza rufipogon?

Couch, R. Myriophyllum spicatum in North America. Anderson, L. Reed, C. History and distribution of Eurasian watermilfoil in United States and Canada. Phytologia 36, — Google Scholar. Aiken, S. The biology of Canadian weeds.

Myriophyllum spicatum L. Plant Sci. Yu, D. Taxonomic revision of the genus Myriophyllum Haloragaceae in China. Rhodora , — Lacoul, P. Environmental influences on aquatic plants in freshwater ecosystems. Viana, D. Environment and biogeography drive aquatic plant and cladoceran species richness across Europe. Freshwater Biol. Suren, A. Aquatic bryophytes in Himalayan streams: testing a distribution model in a highly heterogeneous environment.

Aquatic macrophyte distribution in response to physical and chemical environment of the lakes along an altitudinal gradient in the Himalayas, Nepal. Figuerola, J. Dispersal of aquatic organisms by waterbirds: a review of past research and priorities for future studies. Olney, P. The food and feeding habits of teal Anas crecca.

Brochet, A. Plant dispersal by teal Anas crecca in the Camargue: duck guts are more important than their feet. MacKinnon, J. A biodiversity review of China. Sibley, C. Distribution and taxonomy of birds of the world. Yale University Press, New Haven Wang, Y. Population genetic structure of an aquatic herb Batrachium bungei Ranuculaceae in the Hengduan Mountains of China. Chen, J. Chloroplast DNA phylogeography reveals repeated range expansion in a widespread aquatic herb Hippuris vulgaris in the Qinghai-Tibetan Plateau and adjacent areas.

Ohsawa, T. Global patterns of genetic variation in plant species along vertical and horizontal gradients on mountains. Global Ecol. Shi, M. Isolation by elevation: genetic structure at neutral and putatively non-neutral loci in a dominant tree of subtropical forests. Castanopsis eyrei.

Frei, E. Plant population differentiation and climate change: responses of grassland species along an elevational gradient. Global Change Biol. Wang, Z. Low-temperature induced leaf elements accumulation in aquatic macrophytes across Tibetan Plateau. Hirao, A. Landscape genetics of alpine-snowbed plants: comparisons along geographic and snowmelt gradients.

Heredity 93, — Heredity 98, — Moody, M. Evidence of hybridity in invasive watermilfoil Myriophyllum populations. USA 99, — Invasions 9, — Wu, Z. Influence of niche similarity on hybridization between Myriophyllum sibiricum and M.

Development of microsatellite markers in the hexaploid aquatic macrophyte, Myriophyllum spicatum Haloragaceae. Nei, M. Molecular evolutionary genetics. Columbia University Press, New York Meirmans, P. Notes 4, — Bruvo, R. A simple method for the calculation of microsatellite genotype distances irrespective of ploidy level. Lynch, M. The similarity index and DNA fingerprinting. Samadi, S.

Microsatellite and morphological analysis of population structure in the parthenogenetic freshwater snail Melanoides tuberculata : insights into the creation of clonal variability. Clark, L.

Dufresne, F. Recent progress and challenges in population genetics of polyploid organisms: an overview of current state-of-the-art molecular and statistical tools. Ortego, J. Climatically stable landscapes predict patterns of genetic structure and admixture in the Californian canyon live oak. Pritchard, J. Inference of population structure using multilocus genotype data. Genetics , — Falush, D. Inference of population structure using multilocus genotype data: linked loci and correlated allele frequencies.

Inference of population structure using multilocus genotype data: dominant markers and null alleles. Notes 7, — Evanno, G. Detecting the number of clusters of individuals using the software structure: a simulation study.

During this rainy period, water levels increase, which, in some years, could generate corridors that allow dispersion between different sectors and gene flow among some of the populations that are otherwise isolated Morales et al.

However, a limitation of the study by Morales et al. The present study seeks to evaluate the diversity and genetic structure of O. The results are discussed in relation to the distribution patterns and the geography of the salt pan. This area has little annual precipitation, approximately mm per year Risacher et al. The salt pan extends for approximately 30 km; it has twelve springs on its eastern side that originate from subterranean water and are separated by evaporative surfaces.

The populations of O. Individuals were collected between the years and The fish were captured using scoop nets. The mtDNA control region data set comprised sequenced individuals Table 1 , which included the sequences Genbank accession numbers: JN — JN obtained in Morales et al.

The 18 new sequences were obtained using the primers described in Morales et al. PCR products were purified and sequenced in both directions by Macrogen Inc. South Korea. We amplified nine microsatellite loci using the primers described by Esquer-Garrigos et al. The conditions for the thermal cycling were the same as those used by Esquer-Garrigos et al.

The number of polymorphic sites, number of haplotypes, haplotype diversity, nucleotide diversity, and pairwise differences were calculated using ARLEQUIN, version 3. The pairwise F ST Wright, values were calculated using the differences between pairs of sequences to examine the differentiation between pairs of springs. The significance of each pairwise value was obtained using 10 permutations of the haplotypes between sites.

SAMOVA defines groups of populations that are geographically homogeneous and maximally differentiated from each other. Before the analysis, the excess of homozygotes or heterozygotes was reviewed to correct alleles with large peaks and the presence of stutters that generate reading errors, as well as to detect the presence of null alleles for each locus using MICRO-CHECKER, version 2. The number of individuals with missing data is indicated in the Supporting information Table S1.

The genetic diversity is expressed as the mean number of alleles and allele diversity in the population, measured as the number of alleles across loci. The observed heterozygosity H O was obtained from genotype counts, and deviations from Hardy—Weinberg equilibrium F IS were evaluated using the expected heterozygosity H E.

The significance of each comparison was obtained using 10 permutations of the allele frequencies between sites. We analyzed from one to 12 groups, with 20 Markov chain Monte Carlo MCMC runs of 1 iterations with the first discarded as burn-in ; these parameters were calculated for each value of K under the no admixture model, with correlated allele frequencies among groups clusters and the locprior setting, which has been suggested for species with discrete population distributions Pritchard et al.

The most probable number of populations K was determined using the mean logarithm of the likelihood of the observed data, ln P Pritchard et al. S1, Table S2. These analyses used the microsatellite data. For each population, MCMC chains were run once for 3 generations burn in with a sampling frequency of For this, we determined the significance of correlations between matrices of pairwise distances between populations, with 10 randomizations.

With these matrices, we estimated the correlations shown in Results Table 4. We determined the altitude patterns in the salt pan using a digital elevation model. The altitude ranges were classified by zones in accordance with information obtained in the field, identifying low zones as those with altitudes from to m a. We selected this longitude because it is close to all springs, and also allowed the characterization of the total extension of the salt pan. The altitude was graphed every kilometer from the northern limit.

We added a contour line m a. A, median-joining network inferred from the mtDNA control region sequences. The positions of the springs are indicated. The dashed line indicates the probable maximum water level.

The mtDNA haplotype sequences of samples from springs V9 and V12 were added to the data set reported by Morales et al. The indices of genetic diversity are shown in Table 1. The pattern observed by Morales et al. Each of the springs also showed high genetic diversity; the haplotype diversity ranged from 0.

Springs V1 and V11 showed the lowest values 1. The haplotype network Fig. The number of pairwise differences ranged between one and 25 mean 6.

However, all the haplotypes found in V1 and V11 were specific to these springs except for one haplotype that was shared between V1 and V7 , forming two clear haplogroups. The haplotypes in these haplogroups were closely related there are four mutational steps maximum between haplotypes from V1, and six mutational steps maximum between haplotypes from V It is worth noting that spring V12 showed a different pattern of genetic diversity than the rest of the springs.

The haplotypes from this spring are specific to it except one that is shared with V7 and V8 , although they do not form a haplogroup as V1 and V11 do; most of them are closely related to the more abundant haplotypes of V8, V9, and V10 Fig. This spring showed a large number of polymorphic sites 15 , which was in the observed range 7—27 , even though its sample size was much smaller Table 1.

The pairwise comparisons between populations Table 2 showed a similar pattern to that reported by Morales et al. Significant corrected P -values are shown in bold. Three of these groups were composed of individuals from only one spring: V1, V11, and V The fourth group was composed of individuals from V2 to V7 and springs V8, V9, and V10 formed the last group.

The discordances between the analyses are a result of the south-centre springs, V8, V9, V10, and V the pairwise F ST analysis differentiated all of them, although the SAMOVA analysis grouped springs V8, V9, and V10 together and V12 was still differentiated, even though four out of five haplotypes are closely related to the south-centre group springs V8, V9, and V Genotypes were obtained for individuals of the 12 localities Table 1 using eight loci of the nine analyzed microsatellites locus B showed null alleles in seven of the 12 analyzed localities and was excluded from the analyses.

All individuals included in the analyses amplified at least four loci, and out of individuals Genetic diversity varied among localities, showing the same pattern as the mtDNA control region; those of the centre of the salt pan V2—V10 showed high diversity H O ranged between 0. Three springs, V1, V7, and V11, were significantly different from all of the others.

S1, Table S3. Table 3 and the Supporting information Table S4 show the migration rates between the genetic groups estimated in the previous analyses and between springs, respectively. Migration rates estimated for each genetic group based on the microsatellite dataset.

The columns correspond to the locality of origin of the individuals and the rows are the locality of destination. The auto-recruitment rate local origin is shown in bold. This result is congruent with the similar pattern of differentiation found in the pairwise F ST analysis for the mtDNA control region and microsatellites Table 2 ; of the 66 total pairwise comparisons, 48 were significant for the mtDNA control region, whereas 51 were significant for microsatellites.

Mantel tests to compare genetic distances and physical distances geographical distance and altitude difference. By contrast, there was no significant relationship using geographical distance as covariate.

Spring V11 was located in this zone. Altitude decreased toward the north of the salt pan; however, the northern extreme where spring V1 is located was above m a. The lowest zone of the salt pan is the north-west and currently contains several bodies of water but is without O. Finally, we observed that Fig. Springs V2 and V3 in the northern centre and V10 in the southern centre are at higher altitudes than their neighbours V4—V7 and V8—V9, respectively , althogh with a difference of no more than 2 m.

The analyses of genetic structure coincided in determining four genetic groups in the O. Although there were a few variations in the best grouping, they were exclusively a result of the mitochondrial genetic diversity of the south-centre springs; these four springs share haplotypes, although to a lesser extent than V2—V7.

For this same reason, V12 is a differentiated group in some analyses. Additionally, the mitochondrial marker did not indicate differences between the individuals of springs V2—V7, whereas the F ST pairwise analysis with microsatellites showed that the individuals of spring V7 are different in terms of everything else Table 2.

This result suggests that the mtDNA control region reflects an ancient connection between spring V7 and the more northern springs, which would have allowed gene flow, whereas the microsatellite variation suggests that this spring has been isolated recently.

The contemporary migration rates suggested low gene flow among groups and that most of the individuals were of local origin Table 3. This pattern could be a result of the geographical location of this spring, separated by 9. The altitude and geographical distance could also affect the migration rate among springs within genetic groups: in group G2, spring V3 provided a significant number of migrant individuals to the rest of the springs of that group, and, in group G3, a similar trend was observed, with spring V10 acting as a source of migrants see Supporting information, Table S4.

This pattern could have been facilitated by the closeness between springs of the same genetic group and the higher altitude at which these source springs are located Table 1 and Fig. The geographical distance could be the most significant factor explaining this migration pattern because the large extensions of evaporative surfaces between springs represent geographical barriers that would accentuate the isolation-by-distance pattern.

The environmental changes that occurred in this area during the Pleistocene may have influenced the genetic structure of O. During this time, one large population would have existed, allowing the generation of the high genetic diversity that is currently observed. In the Holocene 8. The springs slowly became isolated. Based on the microsatellite results and the altitude of the springs, we may infer the way in which the isolation of the different populations was generated.

The first spring to become disconnected may have been V11 because it is at a greater altitude. Then, V1 would have become isolated and, finally, those of the north-centre V2—V7 and south-centre V8—V10 would have separated. The temporal connection of these springs would facilitate dispersion of individuals between them, allowing gene flow. Thus, both groups would behave as metapopulations Morales et al. This temporal connection between springs would have been repeated at least over the last years, a time period that has shown fluctuations in the precipitation in this region with dry and wet periods of different durations Morales et al.

Such dynamics would allow high diversity to be maintained in these central groups of the salt pan and decrease the effect of genetic drift. Therefore, altitude could have been a key factor that facilitated spring isolation in the past when the water level dropped.

However, currently, the geographical distance would be a key factor involved in the temporal connections or disconnections of the springs because the extensive evaporitic areas between springs and areas of higher elevation are the barriers that cannot be surpassed. Similar genetic diversity and structure results have been reported in other species of the same family Cyprinodontidae; for example, currently, populations of the genus Cyprinodon inhabit isolated springs in an elevation gradient in the Ash Meadows Wildlife Refuge Mojave Desert , although they were part of a single, larger population in the past.

The populations of this species are patchy, fragmented and small, and are present in several isolated alkaline lagoons in Lake Magadi in Kenya. As in the present study, the populations of A. Although these cases represent good examples in which hydrological mechanisms can explain genetic differentiation, O.

In the present study, we provide evidence of the existence of high genetic structure in the species O. These patterns would be highly associated with a fragmentation process of this species and the salt pan aquatic system that began after the Last Maximum Glacial and that continues in the present, which has been modulated by geography altitude and distance between springs and hydrographical history.

This microscale model may reflect the process that occurred during the late Pleistocene in the Altiplano and could be useful for understanding the patterns of differentiation in the genus Orestias and other aquatic taxa. We also thank the anonymous reviewers for their valuable comments and suggestions for improving the quality of the manuscript.

Aljanabi SM , Martinez I.