Southern Peripheral Populations Research Articles

Lahaul-Zanskar-Sham Valley Corridor in Indian Trans Himalayan Region Facilitates Dispersal and Gene Flow in Himalayan Ibex.

Wildlife corridors that connect mosaic habitats in heterogeneous mountainous landscapes can be of high significance as they facilitate the genetic and demographic stability of free-ranging populations. Peripheral populations of widespread species are usually ignored in conservation planning. However, these populations retain locally common alleles and are genetic reservoir under the changing climatic conditions. Capra sibirica has widespread distribution, and its southern peripheral population is distributed in the Indian trans-Himalayan region (ITR). In the present study, we studied the spatial distribution and genetic make-up of Himalayan ibex from the ITR following the landscape genetics approach. We obtained 16 haplotypes at the mitochondrial d-loop region and found a stable demography in the past with a recent decline. With 10 nuclear microsatellites, we ascertained 111 unique individuals assigned into two clusters following Bayesian and non-Bayesian clustering analysis with several admixed individuals. We also recorded 25 first-generation migrants that reflected relatively high dispersal and gene-flow across the range. We identified a 19,835 sq.km suitable area with 13,311 sq.km in Ladakh and 6524 sq.km in Lahaul-Spiti. We identified a novel movement corridor for Himalayan ibex across the Lahaul-Zanskar-Sham valley (L-Z-SV) that displayed a fairly good conductance with low genetic divergence among the samples collected on the L-Z-SV corridor. We propose declaring a protected area in the Lahaul and Kargil districts to prioritize dedicated conservation efforts for the Himalayan ibex and other sympatric ungulates that impart a major role in the diet of large carnivore and balancing ecosystem services in the trans-Himalayan region.

A precarious future for distinctive peripheral populations of meadow voles (Microtus pennsylvanicus)

Abstract Conservation efforts rely on robust taxonomic assessments that should be based on critical assessment of interspecific boundaries, infraspecific variation, and potentially distinctive peripheral populations. The meadow vole (Microtus pennsylvanicus) is widely distributed across North America, including 28 morphologically defined subspecies and numerous isolated populations. Because some subspecies are of high conservation concern, we examined geographic variation across the range of the species to test existing infraspecific taxonomy in terms of local and regional diversification. We sequenced mitochondrial DNA (mtDNA) from 20 subspecies of M. pennsylvanicus and contextualized infraspecific variation through comparison of pairwise genetic distances derived from an extended data set of 63 species of Microtus. We found strong support for at least three divergent clades within M. pennsylvanicus, with observed intraspecific clade divergence exceeding that between several pairwise comparisons of sister species within Microtus. Six nuclear genes were then sequenced to test the validity of mtDNA structure and to further evaluate the possibility of cryptic, species-level diversity using Bayes factor species delimitation (BFD) analyses. BFD consistently and decisively supported multiple species based on the multilocus approach. We propose that taxonomic revision of the meadow vole is required, with the eastern clade now identified as M. pennsylvanicus (Ord 1815), the western clade as M. drummondii (Audubon and Bachman 1853), and the coastal Florida clade as M. dukecampbelli (Woods, Post, and Kilpatrick 1982). We suggest that such an arrangement would more closely reflect evolutionary history and provide critical context for further examination of distinctive southern peripheral populations that harbor novel evolutionary legacies and adaptive potential.

Sharp phylogeographical differentiation near the southern range edge of the silverside Odontesthes nigricans: Distinct peripheral populations and incipient speciation?

The silverside Odontesthes nigricans is the Atheriniform species that reach the southernmost latitude in Patagonia. Its wide distribution ranges from temperate waters in the Atlantic coast of South America (39°S, Buenos Aires Province, Argentina) to the Sub-Antarctic environment of Cape Horn (56°S). A previous study has shown significant intraspecific differences on growth parameters and otolith morphology between the southern peripheral population of O. nigricans in the Beagle Channel and the populations in the Atlantic coast of Tierra del Fuego. In this work, we report the first data on population genetics of O. nigricans along the southern part of its distributional range, including the peripheral populations of Beagle Channel. To examine the genetic variability, we analyzed 224 sequences of 815 bp of mitochondrial control region generated from individuals captured at two sites in the Beagle Channel and six sites at the Atlantic coast. The genetic structure assessment revealed a sharp phylogeographic division between Beagle Channel and the Atlantic coast of Patagonia with a 39.83% of variance among groups. The observed genetic diversity was lower in Beagle Channel than in the Atlantic coast sites and the demographic analyses are compatible with a scenario of past population expansion, especially in Beagle Channel. We hypothesize two possible scenarios: one is a recent colonization of the Beagle Channel from the Atlantic Coast followed by divergence promoted by adaptation to local conditions. On the other hand, population differentiation may have been attained or initiated in allopatric conditions during Quaternary glacial phases and the populations may now be experiencing a secondary contact near the eastern tip of Tierra del Fuego. These hypotheses should be addressed in the future with genomics tools. By now, these populations should be considered as different units for conservation and management purposes.

Experimental removals reveal dietary niche partitioning facilitates coexistence between native and introduced species.

Niche overlap between native species and ecologically similar invaders can lead to competitive exclusion of threatened native species, but if two such species also co‐occur naturally elsewhere, interactions between native and introduced populations may mirror coevolved niche partitioning that reduces competition and promotes coexistence.A single, insular population of Fremont's squirrel (Tamiasciurus fremonti) the Mount Graham red squirrel (MGRS; T. f. grahamensis) in the Pinaleño Mountains, Arizona, USA, is critically endangered and resource competition with introduced Abert's squirrels (Sciurus aberti) may threaten its long‐term persistence. The species are naturally synoptic in other mountain sites, and both consume diets comprised primarily of conifer seeds and fungi.We conducted experimental removals of introduced Abert's squirrels and used stable isotope analysis of diets before and after removals, and of diets in naturally syntopic populations to test the hypothesis that dietary niche partitioning can facilitate coexistence between native and introduced species. We also developed a novel approach to determine the influence of fluctuating food availability on carbon enrichment in consumers.Mount Graham red squirrels and introduced Abert's squirrels partitioned the dietary niche similarly to naturally syntopic populations. Removals had no apparent effect. Diet of MGRS was more closely linked to availability of resources than to presence of Abert's squirrels.Flexible dietary niche of introduced Abert's squirrels may have allowed them to exploit a resource opportunity in syntopy with MGRS. Variable food production of MGRS habitat may intensify competition in poor years, and territorial defense against non‐native Abert's squirrels likely imposes fitness costs on individual MGRS. Similarity in our model species’ diets may make MGRS more vulnerable to competition if climate change eliminates the advantages of larder‐hoarding. Where introduced populations of ecologically similar species are better adapted to changing conditions, they may ultimately replace southern peripheral populations of native species.

Reconciling differences in natural tags to infer demographic and genetic connectivity in marine fish populations

Processes regulating population connectivity are complex, ranging from extrinsic environmental factors to intrinsic individual based features, and are a major force shaping the persistence of fish species and population responses to harvesting and environmental change. Here we developed an integrated assessment of demographic and genetic connectivity of European flounder Platichthys flesus in the northeast Atlantic (from the Norwegian to the Portuguese coast) and Baltic Sea. Specifically, we used a Bayesian infinite mixture model to infer the most likely number of natal sources of individuals based on otolith near core chemical composition. Simultaneously, we characterised genetic connectivity via microsatellite DNA markers, and evaluated how the combined use of natural tags informed individual movement and long-term population exchange rates. Individual markers provided different insights on movement, with otolith chemistry delineating Norwegian and Baltic Sea sources, whilst genetic markers showed a latitudinal pattern which distinguished southern peripheral populations along the Iberian coast. Overall, the integrated use of natural tags resulted in outcomes that were not readily anticipated by individual movement or gene flow markers alone. Our ecological and evolutionary approach provided a synergistic view on connectivity, which will be paramount to align biological and management units and safeguard species’ biocomplexity.

Contrasting patterns of energy metabolism in northern vs southern peripheral European flounder populations exposed to temperature rising and hypoxia

A two months common garden experiment was carried out to explore the potential differences of energy metabolism in northern core (France, 50°N and 47°N) vs southern peripheral (Portugal, 41°N) populations of European flounder Platichthys flesus, submitted to cold condition (CC: water temperature = 10 °C) and to warm and hypoxic condition (WHC: water temperature = 22 °C, and moderate hypoxia with O2 saturation = 40% during the last 6 days). Convergent growth rates (in length) were observed in the different populations and conditions, when the southern peripheral population of Portugal did not grow under cold conditions. A general reduction in liver lipid storage was observed in all populations subjected to WHC when compared to CC, whereas muscle lipid storage was unaffected. The thermal and hypoxia treatment induced changes in muscle phospholipids (PL) ratios: phosphatidylserine/PL, phosphatidylinositol/PL, between northern and southern populations. Fish from northern estuaries displayed marked anaerobiosis in WHC (increased liver LDH activity) vs marked aerobiosis under CC (higher muscle CS and CCO activities). Contrariwise, fish from the southern estuary displayed equilibrium between anaerobiosis and aerobiosis activities in WHC. Flounders from the southern population exhibited generally lower G6PDH activity (proxy for anabolism and for defense against oxidative damage), tissue-specific anaerobiosis response (muscle LDH activity) and lower CS and CCO muscle activities (aerobiosis markers) when compared to northern populations. Globally, these inter-population differences in bioenergetics suggest that southern peripheral vs northern core populations have developed differential capacity to cope with interacting stressors and that much of this variation is more likely due to local adaptation.

Proteomic responses of European flounder to temperature and hypoxia as interacting stressors: Differential sensitivities of populations

In the context of global change, ectotherms are increasingly impacted by abiotic perturbations. Along the distribution area of a species, the populations at low latitudes are particularly exposed to temperature increase and hypoxic events. In this study, we have compared the proteomic responses in the liver of European flounder populations, by using 2-D electrophoresis. One southern peripheral population from Portugal vs two northern core populations from France, were reared in a common garden experiment. Most of the proteomic differences were observed between the two experimental conditions, a cold vs a warm and hypoxic conditions. Consistent differentiations between populations were observed in accumulation of proteins involved in the bioenergetics- and methionine-metabolisms, fatty acids transport, and amino-acid catabolism. The specific regulation of crucial enzymes like ATP-synthase and G6PDH, in the liver of the southern population, could be related to a possible local adaptation. This southern peripheral population is spatially distant from northern core populations and has experienced dissimilar ecological conditions; thus it may contain genotypes that confer resilience to climate changes.

Contrasting Population Dynamics in the Boreo-AlpineSilene acaulis(Caryophyllaceae) at Its Southern Distribution Limit

Classical theory predicts a high demographic vulnerability and diminished performance of peripheral plant populations, but recent studies highlight the fact that environmental factors may override that geographical pattern. In this study, we compare the density, population structure and population dynamics of the boreo-alpine Silene acaulis (Caryophyllaceae) in two locations at its southern European distribution limit, using matrix projection models. One population was close to the species' lower altitudinal limit, and thus exposed to more ecologically marginal conditions (higher intraspecific competition and temperature) than the population higher up. The low-altitude population was sparser and its members were older as a result of lower recruitment and survival of new individuals. Additionally, this population's growth rate was lower, mainly due to a shorter permanence of large plants. The contrasting demographic differences between two closely located, southern peripheral populations highlight the impo...

설악산 눈잣나무 천연집단의 침엽특성과 유전변이

설악산 눈잣나무 천연집단은 국내 유일하게 분포하는 남방한계 분포지 수종으로 유전자원보존을 위하여 침엽의 형태적 해부학적 특성과 I-SSR 표지자를 이용한 유전변이를 조사하였다. 8가지 침엽특성에 대한 ANOVA 분석결과 모든 특성에서 개체 간에 통계적인 유의성이 인정되었다. 조사된 66개체의 평균특성은 침엽길이 53.59 mm, 침엽폭 0.78 mm, 침엽지수 68.98 및 침엽두께 0.65 mm, 최대기 공열수 4.56개, 최소기공열수 3.80개, 전체기공열수 8.36개 및 수지구수 1.71개로 각각 나타났다. 특히, 수지구는 모두 바깥쪽에 위치하는 외위 형태의 1~3개 범위로 수지구 2개 유형이 69.47%을 나타낸 반면 1개 유형은 30.45%를 나타냈다. 선발된 9개 I-SSR Primer에서 총 78개의 증폭산물을 얻었으며, 다형적 유전자좌의 비율은 61.5%, 유효대립유전자의 수 1.698개, 이형접합도의 기대치 0.388 및 Shannon의 다양성지수 0.567로 각각 나타났다. This study was conducted to investigate the morphological and anatomical characteristics of needle and the genetic diversity of Pinus pumila Regel which is a unique and the southern peripheral population in South Korea. ANOVA test showed that there were significant differences among individuals within population in all 8 needle characteristics. Average characteristics of 66 individuals were 53.59 mm in needle length, 0.78 mm in needle width, 68.98 in needle index, 0.65 mm in needle thickness, 4.56 ea. in maximum stomata row, 3.80 ea. in minimum stomata row, 8.36 ea. in total stomata row and 1.71 ea. in resin canals, respectively. Resin canal per needle of this species ranged from one to three, depending on external type. Especially, arrangement types were 69.47% in two resin canals and 30.45% in a single resin canal. A total of 78 bands was generated from 9 selected I-SSR primers. The estimates of genetic variation were 61.5% in proportion of polymorphic bands (P), 1.698 in effective number of alleles (<TEX>$A_e$</TEX>), 0.388 in expected heterozygosity (<TEX>$H_e$</TEX>) and 0.567 in Shannon's information index (S.I.), respectively.

Divergent selection and heterogeneous migration rates across the range of Sitka spruce (Picea sitchensis).

Gene flow and effective population size (N(e)) should depend on a population's position within its range: those near the edges are expected to have smaller N(e) and lower relative emigration rates, whereas those nearer the centre should have larger N(e) and higher relative emigration rates. In species with continuous ranges, this phenomenon may limit the ability of peripheral populations to respond to divergent selection. Here, we employ Sitka spruce as a model to test these predictions. We previously genotyped 339 single nucleotide polymorphisms (SNPs) in 410 individuals from 13 populations, and used these data to identify putative targets of divergent selection, as well as to explore the extent to which central-peripheral structure may impede adaptation. Fourteen SNPs had outlier F(ST) estimates suggestive of divergent selection, of which nine were previously associated with phenotypic variation in adaptive traits (timing of autumn budset and cold hardiness). Using coalescent simulations, we show that populations from near the centre of the range have higher effective populations sizes than those from the edges, and that central populations contribute more migrants to marginal populations than the reverse. Our results suggest that while divergent selection appears to have shaped allele frequencies among populations, asymmetrical movement of alleles from the centre to the edges of the species range may affect the adaptive capacity of peripheral populations. In southern peripheral populations, the movement of cold-adapted alleles from the north represents a significant impediment to adaptation under climate change, while in the north, movement of warm-adapted alleles from the south may enhance adaptation.

Threatened freshwater pearl mussel Margaritifera margaritifera L. in NW Spain: low and very structured genetic variation in southern peripheral populations assessed using microsatellite markers

A genetic analysis of freshwater pearl mussel Margaritifera margaritifera populations from NW Spain, a peripheral area of its European distribution, was carried out using microsatellite markers. These populations were formerly reported as genetically differentiated on the basis of growth and longevity studies. Ten loci previously characterized in populations from central Europe were used to comparatively analyze the genetic variability at the southern edge of the species’ range. Iberian pearl mussel populations showed very low genetic variability and significant high genetic differentiation. Half of the total genetic diversity observed appeared to be distributed between populations, which suggested a highly structured adaptive potential in pearl mussel at the southern peripheral distribution of the species. Population distinctiveness was evidenced by assignment tests, which revealed a high accuracy of individual assignments to their population of origin. All data suggested low effective population size and major effects of genetic drift on population genetic structure. In order to avoid further loss of genetic variation in biologically distinctive populations from NW Spain, prioritization of genetic resources of this species is required for conservation and management.

Low levels of genetic variation among southern peripheral populations of the threatened herb, Leontice microrhyncha (Berberidaceae) in Korea

Levels of genetic variation and intrapopulation genetic structures of Leontice microrhyncha S. Moore (Berberidaceae) were assessed for six populations in South Korea, representing the southern most range of a species found in Northeast China and the Korean peninsula. Detected genetic diversity ( H es) was very low (0.024) and F IS values showed large heterozygote deficiencies. The small percentage of polymorphic loci and numbers of alleles per locus suggest that L. microrhyncha has a history of severe or long-lasting population bottlenecks that have eroded genetic diversity. This study suggests that the Korean population appears to consist of two historically isolated and independently evolving populations. It seems likely that these groups have been isolated and unstable for a significant period of time. However, the effects of recent habitat fragmentation on the historically disjunct and fragmented population system found in L. microrhyncha were not those predicted from the lack of significant relationships between population-level patterns of genetic variation and population sizes. Most non-unique genotypes were shared by most individuals and the lower level of diversity, high levels of inbreeding and population differentiation as well as high rate of seed production indicated that this species is autogamous and self-compatible and probably largely selfing. Therefore, to preserve extant genetic variation, all populations must be protected across the small geographic range of the species to retain both allelic and genotypic diversity.

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

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

BIOGEOGRAPHY AND ORIGIN OF LILIUM LONGIFLORUM AND L. FORMOSANUM II -INTRA- AND INTERSPECIFIC VARIATION IN STEM LEAF MORPHOLOGY, FLOWERING RATE AND INDIVIDUAL NET PRODUCTION DURING THE FIRST YEAR SEEDLING GROWTH

BIOGEOGRAPHY AND ORIGIN OF LILIUM LONGIFLORUM AND L. FORMOSANUM II -INTRA- AND INTERSPECIFIC VARIATION IN STEM LEAF MORPHOLOGY, FLOWERING RATE AND INDIVIDUAL NET PRODUCTION DURING THE FIRST YEAR SEEDLING GROWTH

Biogeography and origin of Lilium longiflorum and L. formosanum (Liliaceae) endemic to the Ryukyu Archipelago and Taiwan as determined by allozyme diversity

Allozyme diversity on 13 isozyme loci was investigated for two bulbous species, Lilium longiflorum and L. formosanum, endemic to the subtropical archipelago of continental origin located in East Asia. Degrees of allozyme variability and divergence for L. longiflorum were very high for insular endemic species, indicating relatively longtime persistence of the present widespread distribution across many islands in this phenotypically little-changed species. Lilium formosanum exhibited rather lower variability and divergence than did L. longiflorum and was genetically close to the southern peripheral populations of L. longiflorum with 0.978 as its highest genetic identity value. Combined with other biological and insular geohistorical information, our results suggest that L. longiflorum was established around the end of the Pliocene when the current distribution area was still a continuous part of the ancient Asian continent, and L. formosanum was derived from southern populations of L. longiflorum around the late Pleistocene when the mainland of Taiwan was completely separated from the adjacent islands and the main continent. Depauperization of allozyme variability in some L. longiflorum populations was found on islands with lower altitudes. This reflects bottleneck effects after the complete or almost complete submergence of such low islands during the archipelago's development.

Shell polymorphism in a southern peripheral population of Cepaea nemoralis (L.) (Pulmonata: Helicidae) in Spain

Populations of the land snail Cepaea nemoralis have been investigated at the southern limits of its range in Spain, the Upper Tajo region, in order to analyse the distribution of the species and the variation of polymorphism in relation to environmental conditions. For this purpose two natural subareas, which differ in topography, soil nature, climate and vegetation have been considered. Cepaea nemoralis is confined to the river banks of the area; it is found in open and shaded biotopes of subarea 1 where it is relatively common, and it is almost restricted to shaded biotopes of subarea 2 where it becomes progressively rarer towards the south. Relative abundance of the species may be related to the amount of calcareous soils and climate, the restriction in its southern distribution being probably the result of extreme solar radiation, high temperature and low humidity. The two subareas differ in the frequency of the main polymorphic characters. These differences may be related to the kind of biotope. Subarea 1 richer in more open and exposed biotopes have higher frequencies of yellow, 00000, 00300, and unfused bands, whereas the restriction to poplar groves because of the lack of suitable exposed biotopes in subarea 2 may account for the higher proportion of pink five-bandeds with the bands fused together. This kind of variation with biotope is consistent with an explanation in terms of differences in the temperature absorbance of different morphs and a metabolic response to differences in temperature amplitude of the biotopes. Other characters (lip colour, punctate bands, hyalozonate bands, etc.) are not polymorphic in this region, thus, suggesting that at the periphery environmental conditions are important not only in determining the distribution of the species but exerting a marked effect on the genetic structure of the populations.

The genetic structure of a southern peripheral population of the snail Cepaea nemoralis

The polymorphic land snail Cepaea nemoralis reaches the southern limit of its range in Yugoslavia. The overall frequency of yellow shells is much higher than in Britain (95% compared to 54%), while the frequencies of the genes controlling the number of bands on the shell do not differ as greatly from those found in British populations. Pink shells are found most commonly in one area which is known to be a frost hollow. The frequencies of the various phenotypes shows a great deal of microgeographical variation which does not appear to be related to topography. The existence of an apparent selective response at the colour locus to gross climatic differences from the north to the south of the species’ range suggests that microclimate may be important in affecting local differentiations (‘area effects’) in shell colour morph frequency found in central populations. It is possible that the absence of such a selective response in the frequency of the banding genes in Yugoslav peripheral populations indicates that climatic selection is also less important in controlling their microgeographical differentiation.