The genetic structure of the marine flatworm Stylochoplana pusilla (Rhabditophora: Polycladida) and its use of intertidal snails

2020 ◽  
Vol 100 (5) ◽  
pp. 713-717
Author(s):  
Daishi Yamazaki ◽  
Tomoki Aota ◽  
Satoshi Chiba
Keyword(s):  
Genetic Structure ◽  
Population Level ◽  
Mantle Cavity ◽  
Dispersal Ability ◽  
Snail Species ◽  
High Genetic Diversity ◽  
Local Populations ◽  
History Of ◽  
Invertebrate Taxon ◽  
Intertidal Snail

AbstractAlthough marine phylogeographers have accumulated knowledge of the evolutionary history of various invertebrates, there is a large bias among the taxa regarding genetic data. The order Polycladida is a typical example for which little genetic information at population level is available. Here, we focused on the polyclad flatworm Stylochoplana pusilla, distributed in the Japanese Pacific coastal area. Stylochoplana pusilla is known to have commensal relationships with certain intertidal snails, using snails (mainly Monodonta confusa) as a refugee house. During low tide, S. pusilla hides in the mantle cavity of snails to protect themselves from desiccation and predation. Here, we investigated the genetic structure of S. pusilla using a mitochondrial Cytochrome Oxidase I marker and the species diversity of snails used by it. We found that S. pusilla has high genetic diversity of its populations. While S. pusilla showed a significant genetic differentiation among populations, it was relatively low. In addition, we also showed that S. pusilla used several intertidal snail species which inhabit various coastal environments. The present study suggests S. pusilla has sufficient dispersal ability to connect among its local populations. Also, the range of available snails for S. pusilla may help the connectivity among local populations. We provide important knowledge about this invertebrate taxon with a unique ecology, which has been insufficiently studied.

scholarly journals High genetic diversity and presence of genetic structure characterise the Corso-Sardinian endemics Ruta corsica and Ruta lamarmorae (Rutaceae)

2018 ◽  
Author(s):  
Marilena Meloni ◽  
Caterina Angela Dettori ◽  
Andrea Reid ◽  
Gianluigi Bacchetta ◽  
Laetitia Hugot ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Genetic Structure ◽  
Biological Diversity ◽  
Taxonomic Status ◽  
Single Species ◽  
Dispersal Ability ◽  
Separate Species ◽  
High Genetic Diversity ◽  
History Of

SummaryCorsica and Sardinia form one of the ten areas with highest biodiversity in the Mediterranean and are considered one of the priority regions for conservation in Europe. In order to preserve the high levels of endemism and biological diversity at different hierarchical levels, knowledge of the evolutionary history and current genetic structure of Corso-Sardinian endemics is instrumental. Microsatellite markers were newly developed and used to study the genetic structure and taxonomic status of Ruta corsica and Ruta lamarmorae, rare endemics of Corsica and Sardinia, respectively, and previously considered a single species. Our analyses identified high levels of genetic variation within each species (P=0.883, He=0.543 for R. corsica; P=0.972, He=0.627 for R. lamarmorae). Intrinsic traits of the species (hermaphroditism, proterandry and polyploidy) and island-dependent factors (i.e. age, origin and history of the islands) might explain the detected high levels of genetic variation. We discovered differentiation between R. corsica and R. lamarmorae, and genetic structure within each species, which are consistent with the observation of low dispersal ability for both species. Our genetic results support the recent taxonomic classification of R. corsica and R. lamarmorae as separate species and suggest that they diverge at only few loci. One R. corsica population (SA) strongly differed from all other studied populations and appeared to be the product of hybridization between the two species in STRUCTURE analyses. Our results provide important insights for the conservation of the two rare endemics. Further genetic analyses are recommended for R. lamarmorae and for population SA (R. corsica).

scholarly journals Population Genetic Structure and Genetic Diversity in Twisted-Jaw Fish, Belodontichthys truncatus Kottelat & Ng, 1999 (Siluriformes: Siluridae), from Mekong Basin

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Surapon Yodsiri ◽  
Komgrit Wongpakam ◽  
Adisak Ardharn ◽  
Chadaporn Senakun ◽  
Sutthira Khumkratok
Keyword(s):  
Genetic Diversity ◽  
Genetic Structure ◽  
Demographic History ◽  
Hydropower Plant ◽  
Mekong River ◽  
Demographic Expansion ◽  
High Genetic Diversity ◽  
History Analysis ◽  
History Of ◽  
Important Food Source

The Mekong River and its tributaries possess the second highest diversity in fish species in the world. However, the fish biodiversity in this river is threatened by several human activities, such as hydropower plant construction. Understanding the genetic diversity and genetic structure of the species is important for natural resource management. Belodontichthys truncatus Kottelat & Ng is endemic to the Mekong River basin and is an important food source for people in this area. In this study, the genetic diversity, genetic structure, and demographic history of the twisted-jaw fish, B. truncatus, were investigated using mitochondrial cytochrome b gene sequences. A total of 124 fish specimens were collected from 10 locations in the Mekong and its tributaries. Relatively high genetic diversity was found in populations of B. truncatus compared to other catfish species in the Mekong River. The genetic structure analysis revealed that a population from the Chi River in Thailand was genetically significantly different from other populations, which is possibly due to the effect of genetic drift. Demographic history analysis indicated that B. truncatus has undergone recent demographic expansion dating back to the end of the Pleistocene glaciation.

Phylogeography of the black fly Simulium aureohirtum (Diptera: Simuliidae) in Thailand

Genome ◽  
2014 ◽  
Vol 57 (8) ◽  
pp. 411-417 ◽  
Author(s):  
Jiraporn Thaijarern ◽  
Piyamas Nanork Sopaladawan ◽  
Komgrit Wongpakam ◽  
Pairot Pramual
Keyword(s):  
Genetic Structure ◽  
Demographic History ◽  
High Genetic Diversity ◽  
Black Fly ◽  
History Of ◽  
Living Organisms ◽  
High Level ◽  
Genetic Structure And Diversity ◽  
Lineage Divergence ◽  
Population Demographic

The black fly Simulium aureohirtum Brunetti (Diptera: Simuliidae) is geographically widespread and utilizes diverse habitats. Previous studies revealed high genetic diversity, suggesting that this species could be a species complex. In this study, we used mitochondrial cytochrome c oxidase II sequences to examine genetic structure and demographic history of S. aureohirtum in Thailand. High level of genetic variation was observed due to the existence of genetically divergent lineages (A, B, and C). Lineages A and C were geographically widespread, while lineage B was geographically restricted to the eastern part of Thailand. The geographic localization of lineage B suggested limitations in gene flow, which is most likely a result of ecologically different habitats. Large genetic differences between individuals of lineages A and C, but geographically sympatric distributions of the members of these lineages, are considered to represent an admixture of the populations that have evolved allopatrically. Historical environmental change during the Pleistocene glaciations is possibly the factor that drove the lineage divergence. Population demographic history analyses revealed recent population expansions in the three lineages dating back to the last glaciations. These observations further highlight the significance of the Pleistocene climatic change on current genetic structure and diversity of living organisms of the Southeast Asian mainland.

Population stage structure of Hawaiian endemic fern taxa of Diellia (Aspleniaceae): implications for monitoring and regional dynamics

2004 ◽  
Vol 82 (10) ◽  
pp. 1438-1445 ◽  
Author(s):  
Ruth Aguraiuja ◽  
Mari Moora ◽  
Martin Zobel
Keyword(s):  
Census Data ◽  
Local Population ◽  
Hawaiian Islands ◽  
Stage Structure ◽  
Dispersal Ability ◽  
Local Populations ◽  
Regional Dynamics ◽  
The Status ◽  
History Of ◽  
Extinction Events

Single census data were used to investigate the stage structure within populations of the endemic fern genus Diellia in the Hawaiian Islands. Populations were classified as "dynamic" (sporelings predominate), "normal", or " regressive" (mature plants predominate). Six taxa were studied: Diellia erecta Brack., Diellia erecta f. alexandri (Hillebr.) W.H. Wagner, Diellia falcata Brack., Diellia mannii (D.C. Eaton) W.J. Rob., Diellia pallida W.H. Wagner, and Diellia unisora W.H. Wagner. There were significant differences between the population stage structures of different taxa. The populations of D. erecta f. alexandri, and D. unisora represented regressive cases. Diellia pallida was represented by two regressive and one dynamic local population. The status of local populations of D. erecta and D. falcata varied from dynamic to regressive. Diellia erecta f. alexandri, D. mannii, D. pallida, and D. unisora are probably near extinction. Variation in local population conditions of D. erecta, D. falcata, and D. pallida may represent the history of local colonization and subsequent extinction events. The regional dynamics of these taxa correspond with the metapopulation model, since pteridophytes have good dispersal ability, and recruitment of Diellia species takes place only in moist years and is influenced by local disturbances. We conclude that stage structure of local populations can indicate the regional dynamics of a species. All local Diellia populations have to be considered as priority candidates for future conservation efforts.Key words: conservation, Diellia, Hawaiian Islands, metapopulation, population stage structure, regional dynamics.

scholarly journals Diversity and Genetic Structure of Dioon holmgrenii (Cycadales: Zamiaceae) in the Mexican Pacific Coast Biogeographic Province: Implications for Conservation

Plants ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2250
Author(s):  
Mario Valerio Velasco-García ◽  
Carlos Ramírez-Herrera ◽  
Javier López-Upton ◽  
Juan Ignacio Valdez-Hernández ◽  
Higinio López-Sánchez ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Genetic Structure ◽  
Pacific Coast ◽  
Population Level ◽  
Fixation Index ◽  
High Genetic Diversity ◽  
Mexican Pacific ◽  
Biogeographic Province ◽  
Multiple Factors ◽  
F Statistics

Dioon holmgrenii De Luca, Sabato et Vázq.Torres is an endangered species; it is endemic and its distribution is restricted to the biogeographic province of the Mexican Pacific Coast. The aim of this work was to determine the diversity and genetic structure of nine populations. The genetic diversity parameters and Wright’s F statistics were determined with six microsatellite loci. The genetic structure was determined by using the Structure software and by a discriminant analysis. The genetic diversity of the populations was high. The proportion of polymorphic loci was 0.89, the observed heterogeneity was higher (Ho = 0.62 to 0.98) than expected (He = 0.48 to 0.78), and the fixation index was negative (IF = −0.091 to −0.601). Heterozygous deficiency (FIT = 0.071) was found at the species level and heterozygotes excess (FIS = −0.287) at the population level. The genetic differentiation between populations was high (FST = 0.287), with the number of migrants less than one. Three groups of populations were differentiated, and the variation within populations, between populations, and between groups was: 65.5, 26.3, and 8.2%, respectively. Multiple factors explain the high genetic diversity, while the genetic structure is due to geographic barriers. Community reserves are urgent in at least one most diverse population of each group.

scholarly journals Association between spatial genetic variation and potential distribution in tree fern Alsophila gigantea (Cyatheaceae) in Hainan Island, China

2021 ◽  
Vol 49 (3) ◽  
pp. 12407
Author(s):  
Ting WANG ◽  
Zhen WANG ◽  
Shufeng LI ◽  
Zhanming YING ◽  
Xiaoxian RUAN ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Genetic Variation ◽  
Genetic Structure ◽  
Spatial Genetic Structure ◽  
Geographic Distance ◽  
Population Level ◽  
Hainan Island ◽  
Mantel Test ◽  
High Genetic Diversity ◽  
Spatial Genetic Variation

Spatial genetic variation involves spatial genetic structure (SGS) and genetic diversity is important genetic features of plants. We first evaluated spatial genetic structure (SGS) and genetic diversity among four populations of Alsophila gigantea from Hainan Island, China, using inter-simple sequence repeat (ISSR) markers. Significant but weak FSGS was found in A. gigantea. High genetic diversity was identified at the species level and the population level. AMOVA analysis revealed a low level of genetic differentiation among the four populations with high gene flow. Mantel test showed no significant correlation between genetic distance and geographic distance. It was found that association between annual mean temperature and annual precipitation with FSGS. Combined with these spatial genetic variation, abundant precipitation and suitable temperature create a stable environment for A. gigantea in Hainan Island, which allows the fern to expand rapidly during the LGM. These results further emphasized the role of outcrossing, and history and environmental factors in the evolution of A. gigantea. This study also provided new insights on in local adaptation of A. gigantea to environmental fluctuations, and available genetic data to enhance the conservation for relict tree ferns.

scholarly journals Biological Control of Pest Non-Marine Molluscs: A Pacific Perspective on Risks to Non-Target Organisms

Insects ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 583
Author(s):  
Carl C. Christensen ◽  
Robert H. Cowie ◽  
Norine W. Yeung ◽  
Kenneth A. Hayes
Keyword(s):  
Biological Control ◽  
Environmental Impacts ◽  
Pacific Islands ◽  
Generalist Predators ◽  
Snail Species ◽  
Marine Mollusk ◽  
The Pacific ◽  
History Of ◽  
Ecosystem Level ◽  
Scientific Framework

Classic biological control of pest non-marine mollusks has a long history of disastrous outcomes, and despite claims to the contrary, few advances have been made to ensure that contemporary biocontrol efforts targeting mollusks are safe and effective. For more than half a century, malacologists have warned of the dangers in applying practices developed in the field of insect biological control, where biocontrol agents are often highly host-specific, to the use of generalist predators and parasites against non-marine mollusk pests. Unfortunately, many of the lessons that should have been learned from these failed biocontrol programs have not been rigorously applied to contemporary efforts. Here, we briefly review the failures of past non-marine mollusk biocontrol efforts in the Pacific islands and their adverse environmental impacts that continue to reverberate across ecosystems. We highlight the fact that none of these past programs has ever been demonstrated to be effective against targeted species, and at least two (the snails Euglandina spp. and the flatworm Platydemus manokwari) are implicated in the extinction of hundreds of snail species endemic to Pacific islands. We also highlight other recent efforts, including the proposed use of sarcophagid flies and nematodes in the genus Phasmarhabditis, that clearly illustrate the false claims that past bad practices are not being repeated. We are not making the claim that biocontrol programs can never be safe and effective. Instead, we hope that in highlighting the need for robust controls, clear and measurable definitions of success, and a broader understanding of ecosystem level interactions within a rigorous scientific framework are all necessary before claims of success can be made by biocontrol advocates. Without such amendments to contemporary biocontrol programs, it will be impossible to avoid repeating the failures of non-marine mollusk biocontrol programs to date.

scholarly journals Patterns of Weight Change in Aging and Dying

2020 ◽  
Vol 4 (Supplement_1) ◽  
pp. 491-491
Author(s):  
Stephen Thielke
Keyword(s):  
Older Adults ◽  
Weight Loss ◽  
Risk Factor ◽  
Weight Change ◽  
Population Level ◽  
Chronological Age ◽  
Average Weight ◽  
Remaining Life ◽  
Entire Cohort ◽  
History Of

Abstract Little research has characterized the natural history of weight change in older adults. Different changes may occur during aging and dying. We analyzed 18 years of weight measures from a cohort of 736,361 Veterans, all of whom had died at age 70 or older. We produced summary measures that accounted for both chronological age and number of years before death. Several clear population-level trends appeared. (1) The average weight of the sample declined across all ages at a rate of about 0.18 BMI points per year. (2) Starting about seven years before death, the amount of loss began to accelerate, reaching a decline of 0.75 BMI points in the year before death. (3) Changes in weight relative to years of remaining life were independent of chronologic age. People who died at age 70 experienced, on average, the same type and duration of terminal decline as did those who died at age 95. (4) The dying process involved a cumulative loss of about 1.3 BMI points. (5) The distribution of weights during advancing age both declined and narrowed. (6) Disproportionate deaths occurred at the lower BMI ranges (below a BMI of 24), and especially below 18, regardless of age. (7) The finding in #5 is explained by the entire cohort losing weight, with death of the thinnest members. These findings argue for examining survival time in studies of weight change. They indicate that weight loss may be a natural part of dying, rather than a risk factor for it.

scholarly journals Deep genetic structure at a small spatial scale in the endangered land snail Xerocrassa montserratensis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Cristina Català ◽  
Vicenç Bros ◽  
Xavier Castelltort ◽  
Xavier Santos ◽  
Marta Pascual
Keyword(s):  
Genetic Structure ◽  
Land Snail ◽  
Snail Species ◽  
Small Spatial Scale ◽  
Geographic Ranges ◽  
Genetic Groups ◽  
Species Of Conservation Concern ◽  
Conservation Actions ◽  
Conservation Concern ◽  
Single Locality

AbstractSpecies with small geographic ranges do not tend to have a high genetic structure, but some land snail species seem to be an exception. Xerocrassa montserratensis, an endangered land snail endemic to Catalonia (northeastern Iberian Peninsula), is an excellent model to study the processes affecting the phylogeography of specialized species of conservation concern. This species is restricted to xerophilous stony slopes and occurs within a small and fragmented area of ca. 500 km2. We sequenced the COI barcode region of 152 individuals from eight sites covering the entire range of the species. We found four genetic groups mostly coincident with their geographic distribution: a central ancestral group containing shared haplotypes among five localities and three groups restricted to a single locality each. Two of these derived groups were geographically and genetically isolated, while the third and most differentiated group was not geographically isolated. Geomorphologic and paleoclimatic processes during the Pleistocene can explain the divergence found between populations of this low dispersal species with historical fragmentation and secondary contacts. Nonetheless, recent passive large dispersal through streams was also detected in the central group. Overall, our study uncovered four evolutionary units, partially matching morphologically described subspecies, which should be considered in future conservation actions.

scholarly journals Effects of habitat structure and land-use intensity on the genetic structure of the grasshopper species Chorthippus parallelus

2014 ◽  
Vol 1 (2) ◽  
pp. 140133 ◽  
Author(s):  
Kerstin R. Wiesner ◽  
Jan Christian Habel ◽  
Martin M. Gossner ◽  
Hugh D. Loxdale ◽  
Günter Köhler ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Land Use ◽  
Genetic Structure ◽  
Sampling Site ◽  
Land Use Intensity ◽  
Habitat Size ◽  
Grasshopper Species ◽  
Chorthippus Parallelus ◽  
Landscape Characteristics ◽  
Local Populations

Land-use intensity (LUI) is assumed to impact the genetic structure of organisms. While effects of landscape structure on the genetics of local populations have frequently been analysed, potential effects of variation in LUI on the genetic diversity of local populations have mostly been neglected. In this study, we used six polymorphic microsatellites to analyse the genetic effects of variation in land use in the highly abundant grasshopper Chorthippus parallelus . We sampled a total of 610 individuals at 22 heterogeneous grassland sites in the Hainich-Dün region of Central Germany. For each of these grassland sites we assessed habitat size, LUI (combined index of mowing, grazing and fertilization), and the proportion of grassland adjoining the sampling site and the landscape heterogeneity (the latter two factors within a 500 m buffer zone surrounding each focal site). We found only marginal genetic differentiation among all local populations and no correlation between geographical and genetic distance. Habitat size, LUI and landscape characteristics had only weak effects on most of the parameters of genetic diversity of C. parallelus ; only expected heterozygosity and the grasshopper abundances were affected by interacting effects of LUI, habitat size and landscape characteristics. The lack of any strong relationships between LUI, abundance and the genetic structure might be due to large local populations of the species in the landscape, counteracting local differentiation and potential genetic drift effects.

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