scholarly journals Response of xerophytic plants to glacial cycles in southern South America

2019 ◽  
Vol 124 (1) ◽  
pp. 15-26 ◽  
Author(s):  
Carmen G Ossa ◽  
Paz Montenegro ◽  
Isabel Larridon ◽  
Fernanda Pérez
Keyword(s):  
Genetic Diversity ◽  
Isolation By Distance ◽  
Population History ◽  
Arid Environments ◽  
Glacial Cycles ◽  
Niche Modelling ◽  
Climatic Niche ◽  
Range Contraction ◽  
Genetic Diversity And Structure ◽  
Semi Arid

Abstract Background and Aim Quaternary glaciations strongly affected the distribution of species from arid and semi-arid environments, as temperature drops were accompanied by strong fluctuations in rainfall. In this study, we examined the response of xerophytic species to glacial cycles, determining the genetic patterns and climatic niche of Echinopsis chiloensis var. chiloensis, an endemic columnar cactus of arid and semi-arid regions of Chile. Methods We analysed 11 polymorphic microsatellites for 130 individuals from 13 populations distributed across the entire distribution of the species. We examined genetic diversity and structure, identified possible patterns of isolation by distance (IBD) and tested two competing population history scenarios using Approximate Bayesian Computation. The first scenario assumes a constant population size while the second includes a bottleneck in the southern population. The latter scenario assumed that the southernmost populations experienced a strong contraction during glaciation, followed by a postglacial expansion; by contrast, the area of the northernmost populations remained as a stable refugium. We also used ecological niche modelling (ENM) to evaluate the location and extension of suitable areas during the Last Glacial Maximum (LGM) and the mid-Holocene. Key Results We found a decline in genetic diversity towards high latitudes and a significant IBD pattern that together with ENM predictions suggest that E. chiloensis var. chiloensis experienced range contraction northwards during wet–cold conditions of the LGM, followed by expansion during aridification of the mid-Holocene. In addition to IBD, we detected the presence of a strong barrier to gene flow at 32°30′S, which according to coalescence analysis occurred 44 kyr BP. The resulting genetic clusters differed in realized climatic niche, particularly in the variables related to precipitation. Conclusions Our results suggest that the cactus E. chiloensis var. chiloensis experienced range contraction and fragmentation during the wet–cold conditions of the LGM, which may have facilitated ecological differentiation between northern and southern populations, promoting incipient speciation.

scholarly journals Range reduction of the Oblong Rocksnail, Leptoxis compacta, shapes riverscape genetic patterns

2020 ◽  
Author(s):  
Aaliyah D. Wright ◽  
Nicole L. Garrison ◽  
Ashantye’ S. Williams ◽  
Paul D. Johnson ◽  
Nathan V. Whelan
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Human Impacts ◽  
Isolation By Distance ◽  
Extinction Risk ◽  
River System ◽  
High Genetic Diversity ◽  
Range Contraction ◽  
Genetic Patterns ◽  
Cahaba River

AbstractMany freshwater gastropod species face extinction, including 79% of species in the family Pleuroceridae. The Oblong Rocksnail, Leptoxis compacta, is a narrow range endemic pleurocerid from the Cahaba River basin in central Alabama that has seen rapid range contraction in the last 100 years. Such a decline is expected to negatively affect genetic diversity in the species. However, precise patterns of genetic variation and gene flow across the restricted range of L. compacta are unknown. This lack of information limits our understanding of human impacts on the Cahaba River system and Pleuroceridae. Here, we show that L. compacta has likely seen a species-wide decline in genetic diversity, but remaining populations have relatively high genetic diversity. We also report a contemporary range extension compared to the last published survey. Leptoxis compacta does not display an isolation by distance pattern, contrasting patterns seen in many riverine taxa. Our findings also indicate that historical range contraction has resulted in the absence of common genetic patterns seen in many riverine taxa like isolation by distance as the small distribution of L. compacta allows for relatively unrestricted gene flow across its remaining range despite limited dispersal abilities. Two collection sites had higher genetic diversity than others, and broodstock sites for future captive propagation and reintroduction efforts should utilize sites identified here as having the highest genetic diversity. Broadly, our results support the hypothesis that range contraction will result in the reduction of species-wide genetic diversity, and common riverscape genetic patterns cannot be assumed to be present in species facing extinction risk.

scholarly journals Range reduction of Oblong Rocksnail, Leptoxis compacta, shapes riverscape genetic patterns

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9789
Author(s):  
Aaliyah D. Wright ◽  
Nicole L. Garrison ◽  
Ashantye’ S. Williams ◽  
Paul D. Johnson ◽  
Nathan V. Whelan
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Human Impacts ◽  
Isolation By Distance ◽  
Extinction Risk ◽  
River System ◽  
High Genetic Diversity ◽  
Range Contraction ◽  
Genetic Patterns ◽  
Cahaba River

Many freshwater gastropod species face extinction, including 79% of species in the family Pleuroceridae. The Oblong Rocksnail, Leptoxis compacta, is a narrow range endemic pleurocerid from the Cahaba River basin in central Alabama that has seen rapid range contraction in the last 100 years. Such a decline is expected to negatively affect genetic diversity in the species. However, precise patterns of genetic variation and gene flow across the restricted range of L. compacta are unknown. This lack of information limits our understanding of human impacts on the Cahaba River system and Pleuroceridae. Here, we show that L. compacta has likely seen a species-wide decline in genetic diversity, but remaining populations have relatively high genetic diversity. We also report a contemporary range extension compared to the last published survey. Our findings indicate that historical range contraction has resulted in the absence of common genetic patterns seen in many riverine taxa like isolation by distance as the small distribution of L. compacta allows for relatively unrestricted gene flow across its remaining range despite limited dispersal abilities. Two collection sites had higher genetic diversity than others, and broodstock sites for future captive propagation and reintroduction efforts should utilize sites identified here as having the highest genetic diversity. Broadly, our results support the hypothesis that range contraction will result in the reduction of species-wide genetic diversity, and common riverscape genetic patterns cannot be assumed to be present in species facing extinction risk.

Genetic diversity patterns in an endangered desert shrub from north-western China: implications for conservation

2019 ◽  
Vol 67 (7) ◽  
pp. 571
Author(s):  
Zhihao Su ◽  
Liuqiang Wang ◽  
Li Zhuo ◽  
Xiaolong Jiang ◽  
Wenjun Li
Keyword(s):  
Genetic Diversity ◽  
Tarim Basin ◽  
Dna Sequences ◽  
Gene Diversity ◽  
Isolation By Distance ◽  
In Situ Conservation ◽  
Western China ◽  
Niche Modelling ◽  
Diversity Patterns ◽  
North Western

Tamarix taklamakanensis is an endangered shrub endemic to the Tarim Basin and adjacent Kumtag Desert in north-western China. Here, we used two chloroplast DNA sequences, namely, psbA-trnH and trnS-trnG, to examine the genetic diversity patterns of this species across its entire covered range. A total of nineteen haplotypes were detected. The total gene diversity within the species is high. Genetic variation mainly occurred among populations, SAMOVA groups, and geographic regions. The test for isolation-by-distance showed a significant correlation between genetic and geographical distances, and the genetic landscape shape analysis showed a significant genetic divergence between the Tarim Basin and Kumtag Desert. T. taklamakanensis likely had a potential geographic range during the Last Glacial Maximum period that was much smaller than the present range predicted by ecological niche modelling. The cold and dry climate during the glacial periods of the Quaternary might be a driver of the genetic isolation and divergence detected within T. taklamakanensis, and climatic oscillations might account for the habitat fragmentation of the species. Within the inner of the basin, populations have a higher level of genetic diversity and harbor most of this genetic diversity, thus a nature reserves should be set up in this area for the in situ conservation. In addition, five genetically distinct groups within T. taklamakanensis should be treated as different management units (MUs) when implementing conservation activities.

Consequences of long- and short-term fragmentation on the genetic diversity and differentiation of a late successional rainforest conifer

2011 ◽  
Vol 59 (4) ◽  
pp. 351 ◽  
Author(s):  
Rohan Mellick ◽  
Andrew Lowe ◽  
Maurizio Rossetto
Keyword(s):  
Genetic Diversity ◽  
New South ◽  
Demographic Stochasticity ◽  
Niche Modelling ◽  
Lag Effects ◽  
South Wales ◽  
Unique System ◽  
Genetic Diversity And Structure ◽  
Modelling Techniques ◽  
Diversity Estimates

The east Australian rainforests provide a unique system with which to study historic climate-driven habitat fragmentation. The long life span of rainforest conifers and consequent lag effects on genetic variation, offer insights into demographic stochasticity in small populations and persistence in increasingly fragmented systems. Microsatellite markers were used to investigate the genetic diversity and structure of Podocarpus elatus (Podocarpaceae), a long-lived rainforest conifer endemic to Australia. Twenty-seven populations throughout the east Australian rainforests were screened and two divergent regions separated by the dry Clarence River valley (New South Wales) were discovered. This biogeographic barrier may be referred to as the Clarence River Corridor. Niche modelling techniques were employed to verify the incidence of habitat divergence between the two regions. Significantly high inbreeding was detected throughout the species range with no evidence of recent bottlenecks. Most of the diversity in the species resides between individuals within populations, which suggest the species would be sensitive to the adverse effects of inbreeding, yet evidence suggests that these populations have been small for several generations. Slightly higher diversity estimates were found in the southern region, but it is likely that the species survived historic population contraction in dispersed refugia within each of these genetically differentiated regions.

Genetic diversity and structure of Jatropha curcas L. in its centre of origin

2014 ◽  
Vol 13 (1) ◽  
pp. 9-17 ◽  
Author(s):  
M. Salvador-Figueroa ◽  
J. Magaña-Ramos ◽  
J. A. Vázquez-Ovando ◽  
M. L. Adriano-Anaya ◽  
I. Ovando-Medina
Keyword(s):  
Genetic Diversity ◽  
Jatropha Curcas ◽  
Isolation By Distance ◽  
Random Mating ◽  
Mantel Test ◽  
Reproductive Pattern ◽  
Chain Reactions ◽  
Polymerase Chain Reactions ◽  
Centre Of Origin ◽  
Genetic Diversity And Structure

To investigate the genetic diversity and structure of Jatropha curcas L. oilseed plant, in this study, native populations from Chiapas, Mexico, were evaluated, using microsatellite DNA markers. A total of 93 representative samples were selected from seven sites in two regions in the state of Chiapas grouped by geographical proximity, where leaf samples were collected to isolate the genomic DNA. Individual polymerase chain reactions were carried out with ten pairs of specific oligonucleotides for the microsatellites of J. curcas, separating the products of amplification by acrylamide electrophoresis. Twenty-seven fragments were detected (77% polymorphic) with which heterozygous individuals were distinguished. The most informative microsatellite was Jcps20 (nine alleles, polymorphic index content 0.354). The average polymorphism per population was 58%. The Hardy–Weinberg tests revealed a reproductive pattern of non-random mating. The diversity descriptors and the analysis of molecular variance revealed that the populations were structured and moderately differentiated (FST 0.087) and that this differentiation was not due to isolation by distance, as the Mantel test was not significant (P= 0.137), but rather due to allopatry. Bayesian analysis revealed that the accessions belonged to only four genetic groups and confirmed the differentiation between the regions. Because some loci were in Hardy–Weinberg disequilibrium, it is proposed that differentiation is due to the clonal reproduction of J. curcas practised by farmers in Chiapas, along with the anthropogenic dispersion at regional levels. The results of this study reveal that J. curcas in Chiapas has genetic diversity that is greater than that reported in other parts of the world, which represents a potential germplasm pool for the selection of genotypes.

scholarly journals Does silvoagropecuary landscape fragmentation affect the genetic diversity of the sigmodontine rodent Oligoryzomys longicaudatus?

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3842 ◽  
Author(s):  
Daniela Lazo-Cancino ◽  
Selim S. Musleh ◽  
Cristian E. Hernandez ◽  
Eduardo Palma ◽  
Enrique Rodriguez-Serrano
Keyword(s):  
Genetic Diversity ◽  
Genetic Distance ◽  
Isolation By Distance ◽  
Landscape Fragmentation ◽  
Native Forest ◽  
Least Cost Path ◽  
Natural Habitats ◽  
Forest Patches ◽  
Genetic Diversity And Structure ◽  
Oligoryzomys Longicaudatus

Background Fragmentation of native forests is a highly visible result of human land-use throughout the world. In this study, we evaluated the effects of landscape fragmentation and matrix features on the genetic diversity and structure of Oligoryzomys longicaudatus, the natural reservoir of Hantavirus in southern South America. We focused our work in the Valdivian Rainforest where human activities have produced strong change of natural habitats, with an important number of human cases of Hantavirus. Methods We sampled specimens of O. longicaudatus from five native forest patches surrounded by silvoagropecuary matrix from Panguipulli, Los Rios Region, Chile. Using the hypervariable domain I (mtDNA), we characterized the genetic diversity and evaluated the effect of fragmentation and landscape matrix on the genetic structure of O. longicaudatus. For the latter, we used three approaches: (i) Isolation by Distance (IBD) as null model, (ii) Least-cost Path (LCP) where genetic distances between patch pairs increase with cost-weighted distances, and (iii) Isolation by Resistance (IBR) where the resistance distance is the average number of steps that is needed to commute between the patches during a random walk. Results We found low values of nucleotide diversity (π) for the five patches surveyed, ranging from 0.012 to 0.015, revealing that the 73 sampled specimens of this study belong to two populations but with low values of genetic distance (γST) ranging from 0.022 to 0.099. Likewise, we found that there are no significant associations between genetic distance and geographic distance for IBD and IBR. However, we found for the LCP approach, a significant positive relationship (r = 0.737, p = 0.05), with shortest least-cost paths traced through native forest and arborescent shrublands. Discussion In this work we found that, at this reduced geographical scale, Oligoryzomys longicaudatus shows genetic signs of fragmentation. In addition, we found that connectivity between full growth native forest remnants is mediated by the presence of dense shrublands and native forest corridors. In this sense, our results are important because they show how native forest patches and associated routes act as source of vector species in silvoagropecuary landscape, increasing the infection risk on human population. This study is the first approach to understand the epidemiological spatial context of silvoagropecuary risk of Hantavirus emergence. Further studies are needed to elucidate the effects of landscape fragmentation in order to generate new predictive models based on vector intrinsic attributes and landscape features.

Genetic differentiation between estuarine and open coast ecotypes of a dominant ecosystem engineer

2019 ◽  
Vol 70 (7) ◽  
pp. 977 ◽  
Author(s):  
M. A. Coleman ◽  
J. S. Clark ◽  
M. A. Doblin ◽  
M. J. Bishop ◽  
B. P. Kelaher
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Ecosystem Engineer ◽  
Isolation By Distance ◽  
Spatial Scales ◽  
Random Mating ◽  
Rocky Shores ◽  
Open Coast ◽  
Key Species ◽  
Genetic Diversity And Structure

Temperate intertidal shores globally are often dominated by habitat-forming seaweeds, but our knowledge of these systems is heavily biased towards northern hemisphere species. Rocky intertidal shores throughout Australia and New Zealand are dominated by a single monotypic species, Hormosira banksii. This species plays a key role in facilitating biodiversity on both rocky shores and estuarine habitats, yet we know little about the processes that structure populations. Herein we characterise the genetic diversity and structure of Hormosira and demonstrate strong restrictions to gene flow over small spatial scales, as well as between estuarine and open coast populations. Estuarine ecotypes were often genetically unique from nearby open coast populations, possibly due to extant reduced gene flow between habitats, founder effects and coastal geomorphology. Deviations from random mating in many locations suggest complex demographic processes are at play within shores, including clonality in estuarine populations. Strong isolation by distance in Hormosira suggests that spatial management of intertidal habitats will necessitate a network of broad-scale protection. Understanding patterns of genetic diversity and gene flow in this important ecosystem engineer will enhance the ability to manage, conserve and restore this key species into the future.

Genetic diversity and structure of the treeManilkara zapotain a naturally fragmented tropical forest

2017 ◽  
Vol 33 (4) ◽  
pp. 285-294 ◽  
Author(s):  
Daniela A. Martínez-Natarén ◽  
Víctor Parra-Tabla ◽  
Miguel A. Munguía-Rosas
Keyword(s):  
Genetic Diversity ◽  
Genetic Differentiation ◽  
Tropical Forest ◽  
Isolation By Distance ◽  
Allelic Diversity ◽  
Long Distance ◽  
Population Genetic Differentiation ◽  
Continuous Forest ◽  
Genetic Diversity And Structure ◽  
Degree Of Isolation

Abstract:Forest fragmentation, habitat loss and isolation may have a strong effect on biodiversity in tropical forests. This can include modification of the genetic diversity and structure of plant populations. In this study, we assessed the genetic diversity and structure of the treeManilkara zapotain 15 naturally formed fragments of semi-evergreen tropical forest, as well as in an adjacent continuous forest for comparison. Forest fragments were scattered within a matrix of wetlands and were highly variable in terms of size and degree of isolation. The naturally fragmented populations ofM.zapotahad slightly less allelic diversity (Ar: 3.4) than those of the continuous forest (Ar: 3.6), when corrected for sample size. However, populations in the fragments and continuous forest had very similar heterozygosity levels (HE: 0.59 in both cases). Low levels of genetic differentiation were observed among populations (FST: 0.026) and genetic structure was not consistent with isolation by distance, indicating high levels of gene flow. Genetic diversity was not explained by fragment size or degree of isolation. The relatively high genetic diversity and low inter-population genetic differentiation observed inM. zapotamay be the result of long-distance pollen and seed dispersal, as well as the high proximity among patches.

scholarly journals The impact of Pleistocene sea-level oscillations on plant genetic diversity: the case of the western Mediterranean endemic Carduncellus dianius (Asteraceae)

2019 ◽  
Vol 191 (3) ◽  
pp. 399-420
Author(s):  
Sonia Herrando-Moraira ◽  
Sergi Massó ◽  
Deborah Zani ◽  
Jordi López-Pujol ◽  
Roser Vilatersana
Keyword(s):  
Genetic Diversity ◽  
Sea Level ◽  
Plastid Dna ◽  
Western Mediterranean ◽  
Early Pleistocene ◽  
Niche Modelling ◽  
Long Distance ◽  
Sea Level Fluctuations ◽  
Genetic Diversity And Structure ◽  
The Impact

Abstract To what extent Pleistocene sea-level fluctuations have affected the genetic diversity of species is one of the current topics in biogeographical research. Carduncellus dianius is a Mediterranean narrow endemic species, restricted to < 20 populations distributed along coastal areas in Alicante (mainland eastern Iberian Peninsula) and on the island of Ibiza (Balearic Islands). To get insights into its evolutionary history and its genetic diversity and structure, we combined the analysis of molecular markers (three plastid DNA regions and AFLP) with ecological niche modelling. Results from dated phylogeographical analyses revealed that this species might have originated in the continental region during the early Pleistocene. The colonization of Ibiza could have occurred by a single long-distance dispersal event, with a subsequent back-colonization from the island to the same continental area of origin. These results corroborate the role of islands as sources for mainland colonization (biodiversity reservoirs) and as refugia during glacial periods. Notably, we detected that populations located on stable landmasses (i.e. not affected by sea rising during interglacial cycles) harboured significantly higher genetic diversity than those that were periodically submerged during the periods of marine transgressions. Our results point out sea-level fluctuations as a factor to be considered in phylogeographical studies focused on species distributed along coastlines.

Genetic diversity of butternut (Juglans cinerea) and implications for conservation

2008 ◽  
Vol 38 (4) ◽  
pp. 899-907 ◽  
Author(s):  
Amy Ross-Davis ◽  
Michael Ostry ◽  
Keith E. Woeste
Keyword(s):  
Genetic Diversity ◽  
Population Genetics ◽  
North America ◽  
Endangered Species ◽  
Isolation By Distance ◽  
Eastern North America ◽  
Native Range ◽  
Juglans Cinerea ◽  
Threatened And Endangered Species ◽  
Genetic Diversity And Structure

The management of threatened and endangered species can be improved by understanding their patterns of genetic diversity and structure. This paper presents the results of the first analysis of the population genetics of butternut ( Juglans cinerea L.) using nuclear microsatellites. Butternut once was an economically and ecologically valuable hardwood, but now its numbers are rapidly decreasing throughout its native range in eastern North America. By genotyping butternut trees (n = 157) from five populations at seven highly polymorphic loci, we determined that the remaining genetic diversity for the species is considerably higher than previously estimated (mean HE = 0.75). Populations were nearly genetically homogenous (FST = 0.025), with no evidence of isolation by distance. These results indicate that butternut retains a large amount of genetic diversity, and that it is not too late to implement strategies to conserve local butternut populations.

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