Temperature affects the repeatability of evolution in the microbial eukaryote Tetrahymena thermophila

Evolutionary biologists have long sought to understand what factors affect the repeatability of adaptive outcomes. To better understand the role of temperature in determining the repeatability of adaptive trajectories, we evolved populations of different genotypes of the ciliate Tetrahymena thermophila at low and high temperatures and followed changes in growth rate over 6,500 generations. As expected, growth rate increased with a decelerating rate for all populations; however, there were differences in the patterns of evolution at the two temperatures. The growth rates of the different genotypes tended to converge as evolution proceeded at both temperatures, but this convergence was quicker and more pronounced at the higher temperature. Additionally, over the first 4,000 generations we found greater repeatability of evolution, in terms of change in growth rate, among replicates of the same genotype at the higher temperature. Finally, we found limited evidence of trade‐offs in fitness between temperatures, and an asymmetry in the correlated responses, whereby evolution in a high temperature increases growth rate at the lower temperature significantly more than the reverse. These results demonstrate the importance of temperature in determining the repeatability of evolutionary trajectories for the eukaryotic microbe Tetrahymena thermophila and may provide clues to how temperature affects evolution more generally.     

Diversity of parental environments increases phenotypic variation in Arabidopsis populations more than genetic diversity but similarly affects productivity

Background and AimsThe observed positive diversity effect on ecosystem functioning has rarely been assessed in terms of intraspecific trait variability within populations. Intraspecific phenotypic variability could stem both from underlying genetic diversity and from plasticity in response to environmental cues. The latter might derive from modifications to a plant’s epigenome and potentially last multiple generations in response to previous environmental conditions. We experimentally disentangled the role of genetic diversity and diversity of parental environments on population productivity, resistance against environmental fluctuations and intraspecific phenotypic variation.MethodsA glasshouse experiment was conducted in which different types of Arabidopsis thaliana populations were established: one population type with differing levels of genetic diversity and another type, genetically identical, but with varying diversity levels of the parental environments (parents grown in the same or different environments). The latter population type was further combined, or not, with experimental demethylation to reduce the potential epigenetic diversity produced by the diversity of parental environments. Furthermore, all populations were each grown under different environmental conditions (control, fertilization and waterlogging). Mortality, productivity and trait variability were measured in each population.Key ResultsParental environments triggered phenotypic modifications in the offspring, which translated into more functionally diverse populations when offspring from parents grown under different conditions were brought together in mixtures. In general, neither the increase in genetic diversity nor the increase in diversity of parental environments had a remarkable effect on productivity or resistance to environmental fluctuations. However, when the epigenetic variation was reduced via demethylation, mixtures were less productive than monocultures (i.e. negative net diversity effect), caused by the reduction of phenotypic differences between different parental origins.ConclusionsA diversity of environmental parental origins within a population could ameliorate the negative effect of competition between coexisting individuals by increasing intraspecific phenotypic variation. A diversity of parental environments could thus have comparable effects to genetic diversity. Disentangling the effect of genetic diversity and that of parental environments appears to be an important step in understanding the effect of intraspecific trait variability on coexistence and ecosystem functioning.     

GENOTYPE‐BY‐TEMPERATURE INTERACTIONS MAY HELP TO MAINTAIN CLONAL DIVERSITY IN ASTERIONELLA FORMOSA (BACILLARIOPHYCEAE)

Marine and freshwater phytoplankton populations often show large clonal diversity, which is in disagreement with clonal selection of the most vigorous genotype(s). Temporal fluctuation in selection pressures in variable environments is a leading explanation for maintenance of such genetic diversity. To test the influence of temperature as a selection force in continually (seasonally) changing aquatic systems we carried out reaction norms experiments on co‐occurring clonal genotypes of a ubiquitous diatom species, Asterionella formosa Hassall, across an environmentally relevant range of temperatures. We report within population genetic diversity and extensive diversity in genotype‐specific reaction norms in growth rates and cell size traits. Our results showed genotype by environment interactions, indicating that no genotype could outgrow all others across all temperature environments. Subsequently, we constructed a model to simulate the relative proportion of each genotype in a hypothetical population based on genotype and temperature‐specific population growth rates. This model was run with different seasonal temperature patterns. Our modeling exercise showed a succession of two to several genotypes becoming numerically dominant depending on the underlying temperature pattern. The results suggest that (temperature) context dependent fitness may contribute to the maintenance of genetic diversity in isolated populations of clonally reproducing microorganisms in temporally variable environments.     

Association of loganin contents with the genetic characterization of natural populations of Palicourea rigida Kunth determined by AFLP molecular markers

Extracts of the medicinal plant Palicourea rigida Kunth, popularly known as douradinha, are widely used for treating urinary tract disorders. Unfortunately, nowadays this is one of the species endemic to Brazilian Cerrado that is at greatest risk of extinction.The aim of the this work was to use AFLP molecular markers to determine the genetic structure and diversity of eight natural populations of P. rigida and to associate their genetic characteristics with loganin production in order to obtain provide relevant information to promote programs for the conservation of this valuable medicinal plant.A total of 120 polymorphic bands were scored and higher proportion of genetic diversity was found in inter-populations (64%) rather than in intra-populations (36%). F_st value was found to be significantly greater than zero (0.3601), demonstrating the complex genetic structure of P. rigida populations. Accessions collected from Cristalina, GO, showed higher percentage of polymorphic loci (65.5%) and the highest genetic diversity. Analysis of Molecular variance (AMOVA) demonstrated 63.9% of intra-population genetic variation. The lowest genetic variability was detected among accessions from the population found in Sacramento, MG. No spatial standard was observed for P. rigida population, suggesting a partially isolated island model. It was observed a minor but significant positive correlation (r = 0.22) between chemical and genetic matrices. The association between chemical and genetic data indicated that environmental factors promoted the loganin production in populations growing in Luziânia, GO, and therefore accessions from those populations should be considered as prime material for initiating the conservation process of P. rigida.     

Genetic Diversity and Spatial Genetic Structure of Chamaedaphne calyculata (Ericaceae) at the Western Periphery in Relation to its Main Continuous Range in Eurasia

A previous phylogeography and genetic diversity study of Chamaedaphne calyculata (Ericaceae) showed that populations over its geographic range were strongly separated into two groups: a Eurasian/NW North American group and a NE North American one corresponding with the disjunct distribution of Sphagnum-dominated peatlands in north-western and central-eastern North America. Here, I have extended the survey and focused on the species’ detailed postglacial origin and the effect of isolation on genetic diversity patterns, particularly within island-like populations at the western periphery of its range in Europe. Using AFLP markers, estimates of genetic diversity within 16 C. calyculata populations in the Eurasian group were low (percentage of polymorphic loci P _PL=14.9–24.8 %, Nei’s gene diversity H=0.060–0.119). Genetic diversity patterns within this species did not support the hypothesis that genetic diversity decreases towards the periphery of the range. Bayesian clustering analysis showed that population-level admixture was present in almost all studied 16 populations, suggesting multi-directional gene flow. On the other hand, the majority of assigned individuals (ca. 98 % of individuals) were offspring of the original residents, confirming that C. calyculata populations in the present day acted as discrete genetic units both in its continuous range and at its western periphery, and that gene flow was historic rather than contemporary in Eurasia. There was no correlation between genetic and geographic distance in the Eurasian group (r=0.02, P>0.05, Mantel test) nor at the western periphery (r=0.15, P>0.05, Mantel test). The isolation-by-distance (IBD) scatterplot matched Hutchinson and Templeton’s interpretation (case III), and geographic distance between populations was not a reliable predictor of the degree of genetic differentiation between populations. It is suggested that the lack of IBD might be a result of random genetic drift in rather disconnected populations that have become increasingly fragmented relatively recently. Positive and significant relationships between genetic and geographic distance on a small population scale was the result of biparental inbreeding of C. calyculata and restricted seed rain. Despite sporadic generative reproduction and limited dispersal, the fine-scale genetic structure within populations has been maintained, even though population sizes have been reduced to small fragments in recent years.     

Genetic diversity of nine faba bean (Vicia faba L.) populations revealed by isozyme markers

Seven isozyme systems (Sod, 6-Pgd, Me, Est, Skdh, Fdh and Gdh) representing nine loci were used to study the genetic diversity of nine faba bean populations. Seven loci revealed polymorphic bands and showed the same quaternary structure as that found in several species. They revealed a high number of phenotypes. Indeed, from 3 to 9 phenotypes per locus were investigated in this study. The percentage of polymorphic loci (P = 59.3 %) was higher than that mentioned in the autogamous species (P = 20.3 %) and less than the optimum (P=96 %) indicated for allogamous plants. Total genetic diversity (H _T) and within population genetic diversity (H _S) were estimated with the isozyme markers. The contribution of among population genetic diversity (D _ST) to total genetic diversity was 22%. Enzyme markers pointed out an average inbreeding level for whole population (F _IT) and within population (F _IS). Within population genetic diversity represents 78% of total diversity. Intra-population genetic diversity (H _S = 0.206) was ranged with the respect of allogamous species and was clearly higher than that of among population genetic diversity (D _ST = 0.057) indicating an out-crossing predominance in the studied populations. The expected heterozygosity was higher than that observed heterozygosity at the allogamous species was confirmed in this study. Although, the mean estimated gene flow was less than 1(Nm=0.814), the dendrogram based on Nei’s genetic distance of the 9 populations using UPGMA method showed some genetic drift between populations.     

Intraspecific geographic variation in thermal limits and acclimatory capacity in a wide distributed endemic frog

Intraspecific variation in physiological traits and the standard metabolic rate (SMR) is common in widely distributed ectotherms since populations at contrasting latitudes experiences different thermal conditions. The climatic variability hypothesis (CVH) states that populations at higher latitudes presents higher acclimation capacity than those at lower latitudes, given the wider range of climatic variability they experience. The endemic four-eyed frog, Pleurodema thaul is widely distributed in Chile. We examined the variation in maximum and minimum critical temperatures (CT_max and CT_min), preferred temperature (T_Pref), SMR and their acclimatory capacity in two populations from the northern and center of its distribution. All the traits are higher in the warmer population. The capacity for acclimation varies between traits and, with the exception of CT_max and T_Pref, it is similar between populations. This pattern could be explained by the higher daily thermal variability in desert environments, that increases plasticity to the levels found in the high latitude population. However, we found low acclimatory capacity in all physiological traits, of only about 3% for CT_min, 10% for CT_max and T_Pref, and 1% for SMR. Thus, despite the fact that Pleurodema thaul possess some ability to adjust thermal tolerances in response to changing thermal conditions, this acclimatory capacity seems to be unable to prevent substantial buffering when body temperatures rise. The low acclimatory capacity found for P. thaul suggests that this species use behavioral rather than physiological adjustments to compensate for environmental variation, by exploiting available micro-environments with more stable thermal conditions.     

Evolutionary determinants of population differences in population growth rate × habitat temperature interactions in Chironomus riparius

Little is known about intraspecific variation in fitness performance in response to thermal stress among natural populations and how this relates to evolutionary aspects of species ecology. In this study, population growth rate (PGR; a composite fitness measure) varied among five natural Chironomus riparius populations sampled across a climatic gradient when subjected to three temperature treatments reflecting the typical range of summer habitat temperatures (20, 24 and 28 °C). The variation could be explained by a complex model including effects of genetic drift, genetic diversity and adaptation to average temperature during the warmest month, in addition to experimental temperature. All populations suffered a decrease in PGR from 20 to 28 °C and ΔPGR was significantly correlated with the respective average habitat temperature in the warmest month—populations from warmer areas showing lower ΔPGR. This implies that long-term exposure to higher temperatures in the warmest month (the key reproductive period for C. riparius) is likely to be a key selective force influencing fitness at higher temperatures. A comparison of phenotypic divergence and neutral genetic differentiation revealed that one phenotypic trait—the number of fertile egg masses per female—appeared to be under positive selection in some populations. Our findings support a role for response to temperature selection along a climatic gradient and suggest population history is a key determinant of intraspecific fitness variation. We stress the importance of integrating different types of data (climatic, experimental, genetic) in order to understand the effects of global climate change on biodiversity.     

Assessment of the genetic diversity among Glyptosternum maculatum, an endemic fish of Yarlung Zangbo River, Tibet, China using SSR markers

The genetic diversity of Glyptosternum maculatum populations from Nyang River, Lhasa River, and Shetongmon Reach of Yarlung Zangbo River was assessed using six microsatellite markers. Overall, the genetic diversity across the three populations was low. The Shetongmon population exhibited the highest level of genetic diversity in terms of number of alleles and effective alleles, heterozygosity, and polymorphic information content value, followed by the Nyang population and Lhasa population. The analysis of molecular variance demonstrated that almost the variation (86.64%) occurred within populations. The differentiation among populations was not significant, and population structure was weak. These results revealed that three natural populations of G. maculatum are not genetically differentiated and the large disparity of living altitude did not caused genetic differentiation between different populations. Our observations will help identify the genetic relationship among populations to understand the genetic diversity of G. maculatum.     

High genetic diversity detected in the endemic Primula apennina Widmer (Primulaceae) using ISSR fingerprinting

Primula apennina Widmer is endemic to the North Apennines (Italy). ISSR were used to detect the genetic diversity within and among six populations representative of the species distribution range. High levels of genetic diversity were revealed both at population percentage of polymorphic band (PPB = 75.92%, H _S = 0.204, H _pop = 0.319) and at species level (PPB = 96.95%, H _T = 0.242, H _sp = 0.381). Nei gene diversity statistics (15.7%), Shannon diversity index (16.3%) and AMOVA (14%) detected a moderate level of interpopulation diversity. Principal coordinate and Bayesian analyses clustered the populations in three major groups along a geographic gradient. The correlation between genetic and geographic distances was positive (Mantel test, r = 0.232). All together, these analyses revealed a weak but significant spatial genetic structure in P. apennina, with gene flow acting as a homogenizing force that prevents a stronger differentiation of populations. Conservation measures are suggested based on the observed pattern of genetic variability.     

Assessment of genetic diversity and population differentiation of Achyranthes bidentata (Amaranthaceae) in Dao Di and its surrounding region based on microsatellite markers

Identifying genetic diversity patterns is fundamentally important for effective species management and conservation. In this study, we used five microsatellite loci to investigate the genetic diversity and population differentiation of Achyranthes bidentata in Dao Di and its surrounding region. Our analysis of microsatellite data indicated the level of genetic diversity of A. bidentata (H_T = 0.333) was lower than other plants. The results showed no significant genetic diversity differences and population genetic differentiation between the Dao Di and surrounding region. Significant temperature differences (Bio2: mean diurnal range and Bio7: temperature annual range) were found between the Dao Di and surrounding region, which may improve the accumulation of medicinal ingredients of populations in the Dao Di. The populations of A. bidentata were divided into two genetic groups, which was caused by five temperature variables (Bio1, Bio4, Bio7, Bio9, and Bio11). This study thus provides an important case for over-collecting within limited ranges in affecting population diversity and bioclimate variables for different producing area in driving population differentiation.     

Genetic diversity of wild populations of Rheum tanguticum endemic to China as revealed by ISSR analysis

Rheum tanguticum is an important but endangered traditional Chinese medicine endemic to China. The wild resources have been declining. Establishing the genetic diversity of the species would assist in its conservation and breeding program. Inter-simple sequence repeats (ISSR) markers were used to assess the genetic diversity and population genetic structure in 13 wild populations of R. tanguticum from Qinghai Province. Thirteen selected primers produced 329 discernible bands, with 326 (92.94%) being polymorphic, indicating high genetic diversity at the species level. The Nei's gene diversity (He) was estimated to be 0.1724 within populations (range 0.1026–0.2104), and 0.2689 at the species level. Analysis of molecular variance (AMOVA) showed that the genetic variation was found mainly within populations (71.02%), but variance among populations was only 28.98%. In addition, Nei's differentiation coefficients (G_st) was found to be high (0.3585), confirming the relatively high level of genetic differentiation among populations. Mantel test revealed a significant correlation between genetic and geographic distances (r = 0.573, P = 0.002), and the unweighted pair-group method using arithmetic average (UPGMA) clustering and Principal coordinates analysis (PCoA) demonstrated similar results. Meanwhile, the genetic diversity of R. tanguticum positively correlated with altitude and annual mean precipitation, but negatively correlated with latitude and annual mean temperature. This result might be an explanation that the natural distribution of R. tanguticum is limited to alpine cold areas. We propose conservation strategy and breeding program for this plant.     

Rapid increase in southern elephant seal genetic diversity after a founder event

Genetic diversity provides the raw material for populations to respond to changing environmental conditions. The evolution of diversity within populations is based on the accumulation of mutations and their retention or loss through selection and genetic drift, while migration can also introduce new variation. However, the extent to which population growth and sustained large population size can lead to rapid and significant increases in diversity has not been widely investigated. Here, we assess this empirically by applying approximate Bayesian computation to a novel ancient DNA dataset that spans the life of a southern elephant seal (Mirounga leonina) population, from initial founding approximately 7000 years ago to eventual extinction within the past millennium. We find that rapid population growth and sustained large population size can explain substantial increases in population genetic diversity over a period of several hundred generations, subsequently lost when the population went to extinction. Results suggest that the impact of diversity introduced through migration was relatively minor. We thus demonstrate, by examining genetic diversity across the life of a population, that environmental change could generate the raw material for adaptive evolution over a very short evolutionary time scale through rapid establishment of a large, stable population.     

Genetic variability of the narrow endemic Rhamnus persicifolia Moris (Rhamnaceae) and its implications for conservation

Rhamnus persicifolia Moris is an endemic small tree belonging to the Rhamnus cathartica group, growing along mountainous streams of Central-Eastern Sardinia (Italy). ISSR markers were used to detect the genetic diversity within and among six populations representative of the species distribution range. In spite of the limited distribution of this endemic taxon, fairly high levels of genetic diversity were detected. Percentage of polymorphic bands (PPB), gene diversity (H_S and H_T) and Shannon information measure (Sh) were calculated both at population (PPB = 30.70%, H_S = 0.1105, Sh = 0.1646) and at species level (PPB = 68.42%, H_T = 0.2066, Sh = 0.3139).The existence of a spatial distribution of genetic diversity in R. persicifolia was revealed by a low gene flow, a fairly high level of genetic differentiation (G_ST = 0.4583) among populations and a positive correlation between genetic and geographic distances (Mantel test, r = 0.71, p = 0.016). The spatial genetic structure was also confirmed with BAPS analysis. Our results show that a certain level of isolation by distance and sex-ratio bias may explain the distribution of genetic diversity among populations.Conservation measures are suggested on the basis of the genetic diversity detected, by implementing an integrated in situ and ex situ conservation program for each population, in order to ensure effective protection for this endemic species.     

Variation at range margins across multiple spatial scales: environmental temperature,population genetics and metabolomic phenotype

Range margins are spatially complex, with environmental, genetic and phenotypic variations occurring across a range of spatial scales. We examine variation in temperature, genes and metabolomic profiles within and between populations of the subalpine perennial plant Arabidopsis lyrata ssp. petraea from across its northwest European range. Our surveys cover a gradient of fragmentation from largely continuous populations in Iceland, through more fragmented Scandinavian populations, to increasingly widely scattered populations at the range margin in Scotland, Wales and Ireland. Temperature regimes vary substantially within some populations, but within-population variation represents a larger fraction of genetic and especially metabolomic variances. Both physical distance and temperature differences between sites are found to be associated with genetic profiles, but not metabolomic profiles, and no relationship was found between genetic and metabolomic population structures in any region. Genetic similarity between plants within populations is the highest in the fragmented populations at the range margin, but differentiation across space is the highest there as well, suggesting that regional patterns of genetic diversity may be scale dependent.     

Chloroplast DNA-based genetic diversity and phylogeography of Pyrus betulaefolia (Rosaceae) in Northern China

Pyrus betulaefolia Bunge, considered as an intermediate between oriental and occidental pear groups, is one of the most important wild pear species. The number of its populations is decreasing because of habitat destruction, fragmentation, and continuous exploitation, so protection and conservation measures are urgently needed. Assessment of its genetic diversity and phylogeography are imperative for its efficient conservation. Two chloroplast DNA intergenic fragments were used to detect genetic diversity and phylogeography of 320 individuals from 18 wild P. betulaefolia populations. Haplotype variation, genetic differentiation, and historical events of the populations were estimated. The results showed that P. betulaefolia populations sampled in northern China contained a high level of genetic diversity (H _T?=?0.826). A significant isolation-by-distance value (r?=?0.587, P?<?0.001, 1,000 permutations) among all 18 populations indicated a correlation between genetic divergence and geographic distance. Four population groups were identified in a neighbor-joining tree based on the genetic distance. Analyses of molecular variation showed that the genetic variation mainly existed among population groups, representing 64.61 % of the total variation. Phylogeographic analyses indicated that the populations of P. betulaefolia experienced a scenario of rapid range expansion, which probably occurred between 608,000 and 204,580 years ago. Meanwhile, both the restricted gene flow with isolation by distance and allopatric fragmentation were crucial processes responsible for shaping the genetic patterns of P. betulaefolia. The occurrence of specific haplotypes might be ascribed to an ancestral introgression or joint retention of an ancestral polymorphism with other Pyrus species at the northern edge of the distribution of P. betulaefolia. Three populations displaying a high level of haplotype diversity and unique haplotypes were assumed to be relict populations of Quaternary glaciation and should have conservation priority. Three additional large populations should also be preferentially protected by building natural preservation zones.     

Conservation genetics and population diversity of Erigeron breviscapus (Asteraceae), an important Chinese herb

Erigeron breviscapus (Vant.) Hand.-Mazz. is an important Chinese herb in treating cerebral infarction and heart diseases, which is increasingly endangered because of over-harvesting and habitat fragmentation. We applied AFLP method to investigate its genetic diversity and population structure in order to make efficient conservation strategies. The results indicated a relatively low intraspecific genetic diversity and feeble genetic differentiation among populations, and no Evolutionarily Significant Units (ESUs) was detected. The relationships between population genetic diversity and populations' distributions (latitude, longitude and altitude) were tested, and the genetic diversity of each population (H_POP) positively correlated with the populations' distribution altitudes. The suitable germinating and growing conditions and less human disturbance at the higher latitude regions might be attributable for this phenomenon. For conservation purpose, an ex situ conservation measure for the populations of E. breviscapus with large size in higher altitude regions should be conserved in priority.     

Population structure and genetic diversity of Huperzia serrata (Huperziaceae) based on amplified fragment length polymorphism (AFLP) markers

The levels and pattern of the genetic variation within and among natural populations of Huperzia serrata were investigated using amplified fragment length polymorphism markers. Seven primer combinations used in the study amplified 615 discernible bands with 532 (86.5%) being polymorphic, indicating a considerable high level of genetic diversity at the species level. AMOVA analysis revealed a low level of genetic differentiation among the ten populations. The UPGMA cluster of all samples showed that individuals from the same population occasionally failed to cluster in one distinct group. A Mantel test showed no significant correlation between genetic distance and geographical distance (r = 0.278, P = 0.891), suggesting that the gene flow was not restricted geographically. A number of factors that might affect the genetic profiles of H. serrata included clonal growth, selective effect of niche and outcrossing, as well as the effective wind-dispersal of spores.     

Initial genetic diversity enhances population establishment and alters genetic structuring of a newly established Daphnia metapopulation

When newly created habitats are initially colonized by genotypes with rapid population growth rates, later arriving colonists may be prevented from establishing. Although these priority effects have been documented in multiple systems, their duration may be influenced by the diversity of the founding population. We conducted a large‐scale field manipulation to investigate how initial clonal diversity influences temporal and landscape patterns of genetic structure in a developing metapopulation. Six genotypes of obligately asexual Daphnia pulex were stocked alone (no clonal diversity) or in combination (‘high’ clonal diversity) into newly created experimental woodland ponds. We also measured the population growth rate of all clones in the laboratory when raised on higher‐quality and lower‐quality resources. Our predictions were that in the 3 years following stocking, clonally diverse populations would be more likely to persist than nonclonally diverse populations and exhibit evidence for persistent founder effects. We expected that faster growing clones would be found in more pools and comprise a greater proportion of individuals genotyped from the landscape. Genetic composition, both locally and regionally, changed significantly following stocking. Six of 27 populations exhibited evidence for persistent founder effects, and populations stocked with ‘high’ clonal diversity were more likely to exhibit these effects than nonclonally diverse populations. Performance in the laboratory was not predictive of clonal persistence or overall dominance in the field. Hence, we conclude that although laboratory estimates of fitness did not fully explain metapopulation genetic structure, initial clonal diversity did enhance D. pulex population establishment and persistence in this system.     

When landscape modification is advantageous for protected species. The case of a synanthropic tarantula, Brachypelma vagans

Landscape fragmentation usually has a considerable effect on the genetic and demographic viability of most species because it reduces population size and increases isolation among populations. This situation provokes loss of genetic diversity and increased inbreeding that can lead to population or species extinctions. Some studies also show that landscape fragmentation may have no effect on or even positive consequences for species genetic diversity. The protected tarantula, Brachypelma vagans, exhibits a particular situation in the Mexican Caribbean, which has experienced high lowland and coastal fragmentation because of recent increases in agricultural, urban and touristic development. This modified landscape structure creates favorable conditions for establishment of B. vagans populations in rural settlements. Populations of this tarantula have high densities of individuals, principally females and juveniles, and gene dispersion is assumed by the rare males. Within this context, we studied the influence of natural and anthropogenic fragmentation on the genetic diversity of six B. vagans populations (five continental, one insular), together with their spatial organization. Our approach used seven inter simple sequence repeat markers, which are highly polymorphic markers. The 76 loci selected revealed high genetic variability for continental populations and a low, but not critical situation, for the insular population. We detected a good level of gene exchange among continental populations, and an evident and recent isolation of the island population. This species exhibits a metapopulation structure in the lowlands with numerous local populations where mature females exhibit high birth site fidelity. We conclude that this protected species does not exhibit characteristics to warrant its current conservation status, and we propose complete revision of the ecological and genetic situation for B. vagans in particular, and for all species within the genus Brachypelma in general.