scholarly journals Genetic structure and long-distance dispersal in populations of the wingless pest springtail, Sminthurus viridis (Collembola: Sminthuridae)

2011 ◽  
Vol 93 (1) ◽  
pp. 1-12 ◽  
Author(s):  
JOHN M. K. ROBERTS ◽  
ANDREW R. WEEKS
Keyword(s):  
Population Structure ◽  
Genetic Structure ◽  
Cytochrome Oxidase ◽  
Isolation By Distance ◽  
Control Strategies ◽  
Single Species ◽  
Coi Gene ◽  
Effective Control ◽  
Long Distance Dispersal ◽  
Long Distance

SummaryThe lucerne flea, Sminthurus viridis (Collembola: Sminthuridae) (L.) is a major pest of broadacre agriculture across southern Australia. Few molecular studies have been conducted on S. viridis and none have examined its population genetics, despite the importance for developing effective control strategies. Here, we characterize the genetic structure of Australian populations using three allozyme and eight microsatellite loci, as well as sequencing a fragment of the mitochondrial DNA cytochrome oxidase I gene. We found that S. viridis in Australia are diploid, sexually reproducing and exhibit significant population structure as a result of limited gene flow. Despite significant differentiation between populations, there was very low cytochrome oxidase subunit I (COI) gene sequence variation, indicating the presence of a single species in Australia. The observed structure only marginally complied with an ‘isolation by distance’ model with human-mediated long-distance dispersal likely occurring. Allozymes and microsatellites gave very similar FST estimates, although differences found for novel alternative estimates of differentiation suggest that the allozymes did not capture the full extent of the population structure. These results highlight that control strategies may need to vary for locally adapted S. viridis populations and strategies aimed at limiting the spread of any future pesticide resistance will need to manage the effects of human-mediated dispersal.

scholarly journals Crawling to connectivity? The direct-developing journey of the spotted whelk (Cominella maculosa)

2021 ◽  
Author(s):  
◽  
Melanie Dohner
Keyword(s):  
Genetic Differentiation ◽  
Isolation By Distance ◽  
Alternative Methods ◽  
Coi Gene ◽  
Genetic Connectivity ◽  
Small Scale ◽  
Long Distance Dispersal ◽  
Long Distance ◽  
Ecological Scale ◽  
Genetic Patterns

<p>The exchange of individuals between populations influences demographic connectivity on the ecological scale and genetic connectivity on the evolutionary scale. In some circumstances there are similarities between demographic and genetic connectivity, but in others there are differences. Whenever genetic differentiation is found between populations demographic uncoupling can also be inferred, but when gene flow is found there is uncertainty about whether populations are demographically connected or not. Marine invertebrates typically have large population sizes and many opportunities for dispersal. However, species that have limited planktonic dispersal power are often characterized by genetically and demographically discrete populations that exhibit an isolation-by-distance (IBD) pattern of gene distribution. Alternative methods of dispersal, such as rafting or drifting, produce departures from this expected pattern for species lacking planktonic larvae. Examining genetic patterns at fine geographic scales can identify key dispersal barriers and may give clues to alternative dispersal methods influencing large scale processes.  The endemic, direct-developing spotted whelk, Cominella maculosa, is found in the intertidal rocky shores throughout most of New Zealand. This distribution makes it ideal for studying a species expected to exhibit low realized dispersal by crawling and is unlikely to experience dispersal by rafting. The first aim of this study was to investigate genetic patterns between two genetically distinct populations along the Wairarapa Coast of the North Island to determine if a barrier to dispersal was present or if the expected IBD pattern was observed. The second aim was to determine the likelihood of individual hatchlings undertaking long distance dispersal by drifting in the water column. The mitochondrial DNA COI gene was sequenced using 324 whelk samples collected at seven sites along 125 km of Wairarapa shoreline. No significant level of genetic isolation-by-distance or discontinuity in haplotype distribution was observed. Instead, two sites in the middle of the region form a contact area where the dominant northern and southern haplotypes coexist. To investigate dispersal by drifting in the water, three experimental trials were conducted with hatchlings obtained from field-collected egg capsules. When subjected to wave forces, or deposited directly in flow, hatchlings remained suspended and were carried a short distance. However, hatchlings circulated in currents and left for a longer period (12 hours) were rarely found drifting after this period. These trials indicate that wave dislodgement and local flow regime may result in small-scale displacement of hatchlings, but long-distance dispersal by drift is unlikely. Plankton sampling was also conducted at two sites with four nearshore traps. The rare capture of a related Cominella virgata hatchling supports the finding that hatchlings can be dislodged, but prolonged drift cannot be inferred. The findings from this study support the assumption that crawling is the dominant dispersal mechanism for C. maculosa. Crawling between sites best explains the blending of haplotypes in the middle of the Wairarapa and the genetic differentiation between populations. Crawling-mediated connectivity is unlikely to occur at the ecological scale; therefore populations are expected to be demographically isolated. The results of this research support the general findings in the literature that populations of direct developing species are often demographically isolated and have low levels of genetic connectivity.</p>

scholarly journals Crawling to connectivity? The direct-developing journey of the spotted whelk (Cominella maculosa)

2021 ◽  
Author(s):  
◽  
Melanie Dohner
Keyword(s):  
Genetic Differentiation ◽  
Isolation By Distance ◽  
Alternative Methods ◽  
Coi Gene ◽  
Genetic Connectivity ◽  
Small Scale ◽  
Long Distance Dispersal ◽  
Long Distance ◽  
Ecological Scale ◽  
Genetic Patterns

<p>The exchange of individuals between populations influences demographic connectivity on the ecological scale and genetic connectivity on the evolutionary scale. In some circumstances there are similarities between demographic and genetic connectivity, but in others there are differences. Whenever genetic differentiation is found between populations demographic uncoupling can also be inferred, but when gene flow is found there is uncertainty about whether populations are demographically connected or not. Marine invertebrates typically have large population sizes and many opportunities for dispersal. However, species that have limited planktonic dispersal power are often characterized by genetically and demographically discrete populations that exhibit an isolation-by-distance (IBD) pattern of gene distribution. Alternative methods of dispersal, such as rafting or drifting, produce departures from this expected pattern for species lacking planktonic larvae. Examining genetic patterns at fine geographic scales can identify key dispersal barriers and may give clues to alternative dispersal methods influencing large scale processes.  The endemic, direct-developing spotted whelk, Cominella maculosa, is found in the intertidal rocky shores throughout most of New Zealand. This distribution makes it ideal for studying a species expected to exhibit low realized dispersal by crawling and is unlikely to experience dispersal by rafting. The first aim of this study was to investigate genetic patterns between two genetically distinct populations along the Wairarapa Coast of the North Island to determine if a barrier to dispersal was present or if the expected IBD pattern was observed. The second aim was to determine the likelihood of individual hatchlings undertaking long distance dispersal by drifting in the water column. The mitochondrial DNA COI gene was sequenced using 324 whelk samples collected at seven sites along 125 km of Wairarapa shoreline. No significant level of genetic isolation-by-distance or discontinuity in haplotype distribution was observed. Instead, two sites in the middle of the region form a contact area where the dominant northern and southern haplotypes coexist. To investigate dispersal by drifting in the water, three experimental trials were conducted with hatchlings obtained from field-collected egg capsules. When subjected to wave forces, or deposited directly in flow, hatchlings remained suspended and were carried a short distance. However, hatchlings circulated in currents and left for a longer period (12 hours) were rarely found drifting after this period. These trials indicate that wave dislodgement and local flow regime may result in small-scale displacement of hatchlings, but long-distance dispersal by drift is unlikely. Plankton sampling was also conducted at two sites with four nearshore traps. The rare capture of a related Cominella virgata hatchling supports the finding that hatchlings can be dislodged, but prolonged drift cannot be inferred. The findings from this study support the assumption that crawling is the dominant dispersal mechanism for C. maculosa. Crawling between sites best explains the blending of haplotypes in the middle of the Wairarapa and the genetic differentiation between populations. Crawling-mediated connectivity is unlikely to occur at the ecological scale; therefore populations are expected to be demographically isolated. The results of this research support the general findings in the literature that populations of direct developing species are often demographically isolated and have low levels of genetic connectivity.</p>

scholarly journals Genetic Structure of Zymoseptoria tritici in Northern France at Region, Field, Plant, and Leaf Layer Scales

2018 ◽  
Vol 108 (9) ◽  
pp. 1114-1123 ◽  
Author(s):  
Ali Siah ◽  
Myriam Bomble ◽  
Benoit Tisserant ◽  
Thierry Cadalen ◽  
Maxime Holvoet ◽  
...  
Keyword(s):  
Genetic Structure ◽  
Gene Diversity ◽  
Isolation By Distance ◽  
Control Strategies ◽  
Spatial Scales ◽  
Regional Scale ◽  
Effective Control ◽  
Zymoseptoria Tritici ◽  
Northern France ◽  
Field Plant

Population genetic structure of the worldwide-distributed wheat pathogen Zymoseptoria tritici has been extensively studied at large geographical scales, but to a much less extent at small or local spatial scales. A total of 627 single-conidial fungal isolates were sampled from several locations in northern France (Hauts-de-France Region) to assess fungal genetic structure at region, field, plant, and leaf layer scales, using highly polymorphic microsatellite markers and mating type idiomorphs. Important and overall similar levels of both gene and genotype diversities (gene diversity values of ≥0.44 and haplotype frequencies of ≥94%) were found at all the examined scales. Such rates of diversity are likely due to an active sexual recombination in the investigated areas, as revealed by equal proportions of the two mating types scored in all sampled populations. Interestingly, a rare occurrence of clones among lesions from a same leaf, as well as among leaves from different plant leaf layers (e.g., upper versus lower leaves), was highlighted, indicating that ascospores contribute much more than expected to Z. tritici epidemics, compared with pycnidiospores. Population structure and analyses of molecular variance revealed significant genetic differentiation at the regional scale (GST = 0.23) and, as expected, not at the other more local scales (GST ≤ 0.01). Further analyses using Bayesian and unweighted neighbor-joining statistical methods detected six genetic clusters within the regional population, overall distributed according to the locations from which the isolates were sampled. Neither clear directional relative migration linked to the geographical distribution of the locations, nor isolation by distance, were observed. Separate evolutionary trajectories caused by selection and adaptations to habitat heterogeneity could be the main forces shaping such structuration. This study provides new insights into the epidemiology and the genetic structure of Z. tritici at small local and, for the first time, at single plant and leaf layer scales. Such findings would be helpful in implementing effective control strategies.

scholarly journals Genetic structure and dispersal patterns of the invasive psocid Liposcelis decolor (Pearman) in Australian grain storage systems

2010 ◽  
Vol 100 (5) ◽  
pp. 521-527 ◽  
Author(s):  
K.M. Mikac ◽  
N.N. FitzSimmons
Keyword(s):  
Genetic Structure ◽  
Isolation By Distance ◽  
Geographic Distance ◽  
Allelic Diversity ◽  
Mantel Test ◽  
Null Alleles ◽  
Dispersal Patterns ◽  
Long Distance ◽  
Population Comparisons ◽  
Low Levels

AbstractMicrosatellite markers were used to investigate the genetic structure among invasive L. decolor populations from Australia and a single international population from Kansas, USA to determine patterns of dispersal. Six variable microsatellites displayed an average of 2.5–4.2 alleles per locus per population. Observed (HO) heterozygosity ranged from 0.12–0.65 per locus within populations; but, in 13 of 36 tests, HO was less than expected. Despite low levels of allelic diversity, genetic structure estimated as θ was significant for all pairwise comparisons between populations (θ=0.05–0.23). Due to suspected null alleles at four loci, ENA (excluding null alleles) corrected FST estimates were calculated overall and for pairwise population comparisons. The ENA-corrected FST values (0.02–0.10) revealed significant overall genetic structure, but none of the pairwise values were significantly different from zero. A Mantel test of isolation by distance indicated no relationship between genetic structure and geographic distance among all populations (r2=0.12, P=0.18) and for Australian populations only (r2=0.19, P=0.44), suggesting that IBD does not describe the pattern of gene flow among populations. This study supports a hypothesis of long distance dispersal by L. decolor at moderate to potentially high levels.

scholarly journals Birds are islands for parasites

2014 ◽  
Vol 10 (8) ◽  
pp. 20140255 ◽  
Author(s):  
Jennifer A. H. Koop ◽  
Karen E. DeMatteo ◽  
Patricia G. Parker ◽  
Noah K. Whiteman
Keyword(s):  
Population Structure ◽  
Genetic Structure ◽  
Population Genetic Structure ◽  
Population Genetic ◽  
Evolutionary Biology ◽  
Isolation By Distance ◽  
Spatial Scales ◽  
Island Populations ◽  
Louse Species ◽  
Parasite Populations

Understanding the mechanisms driving the extraordinary diversification of parasites is a major challenge in evolutionary biology. Co-speciation, one proposed mechanism that could contribute to this diversity is hypothesized to result from allopatric co-divergence of host–parasite populations. We found that island populations of the Galápagos hawk ( Buteo galapagoensis ) and a parasitic feather louse species ( Degeeriella regalis ) exhibit patterns of co-divergence across variable temporal and spatial scales. Hawks and lice showed nearly identical population genetic structure across the Galápagos Islands. Hawk population genetic structure is explained by isolation by distance among islands. Louse population structure is best explained by hawk population structure, rather than isolation by distance per se , suggesting that lice tightly track the recent population histories of their hosts. Among hawk individuals, louse populations were also highly structured, suggesting that hosts serve as islands for parasites from an evolutionary perspective. Altogether, we found that host and parasite populations may have responded in the same manner to geographical isolation across spatial scales. Allopatric co-divergence is likely one important mechanism driving the diversification of parasites.

scholarly journals Population Structure of the Late Blight Pathogen Phytophthora infestans in a Potato Germplasm Nursery in Two Consecutive Years

2015 ◽  
Vol 105 (6) ◽  
pp. 771-777 ◽  
Author(s):  
Yuee Tian ◽  
Junliang Yin ◽  
Jieping Sun ◽  
Hongmei Ma ◽  
Yunfang Ma ◽  
...  
Keyword(s):  
Population Structure ◽  
Genetic Structure ◽  
Late Blight ◽  
Phytophthora Infestans ◽  
Plant Pathogens ◽  
Control Strategies ◽  
Northwestern China ◽  
Potato Seed ◽  
Low Level ◽  
Potato Germplasm

As the causal agent of late blight on potato, Phytophthora infestans is one of the most destructive plant pathogens worldwide and widely known as the Irish potato famine pathogen. Understanding the genetic structure of P. infestans populations is important both for breeding and deployment of resistant varieties and for development of disease control strategies. Here, we investigate the population genetic structure of P. infestans in a potato germplasm nursery in northwestern China. In total, 279 isolates were recovered from 63 potato varieties or lines in 2010 and 2011, and were genotyped by mitochondrial DNA haplotypes and a set of nine simple-sequence repeat markers. Selected isolates were further examined for virulence on a set of differential lines containing each resistance (R) gene (R1 to R11). The overall P. infestans population was characterized as having a low level of genetic diversity and resistance to metalaxyl, and containing a high percentage of individuals that virulent to all 11 R genes. Both A1 and A2 mating types as well as self-fertile P. infestans isolates were present but there was no evidence of sexual reproduction. The low level of genetic differentiation in P. infestans populations is probably due to the action of relatively high levels of migration as supported by analysis of molecular variance (P < 0.01). Migration and asexual reproduction were the predominant mechanisms influencing the P. infestans population structure in the germplasm nursery. Therefore, it is important to ensure the production of pathogen-free potato seed tubers to aid sustainable production of potato in northwestern China.

scholarly journals Restricted dispersal in a sea of gene flow

2021 ◽  
Vol 288 (1951) ◽  
pp. 20210458
Author(s):  
L. Benestan ◽  
K. Fietz ◽  
N. Loiseau ◽  
P. E. Guerin ◽  
E. Trofimenko ◽  
...  
Keyword(s):  
Genetic Structure ◽  
Population Genetic ◽  
Spatial Scales ◽  
Sampling Strategy ◽  
Biophysical Model ◽  
Long Distance Dispersal ◽  
Long Distance ◽  
Genetic Studies ◽  
Large Spatial Scale ◽  
Continuous Sampling

How far do marine larvae disperse in the ocean? Decades of population genetic studies have revealed generally low levels of genetic structure at large spatial scales (hundreds of kilometres). Yet this result, typically based on discrete sampling designs, does not necessarily imply extensive dispersal. Here, we adopt a continuous sampling strategy along 950 km of coast in the northwestern Mediterranean Sea to address this question in four species. In line with expectations, we observe weak genetic structure at a large spatial scale. Nevertheless, our continuous sampling strategy uncovers a pattern of isolation by distance at small spatial scales (few tens of kilometres) in two species. Individual-based simulations indicate that this signal is an expected signature of restricted dispersal. At the other extreme of the connectivity spectrum, two pairs of individuals that are closely related genetically were found more than 290 km apart, indicating long-distance dispersal. Such a combination of restricted dispersal with rare long-distance dispersal events is supported by a high-resolution biophysical model of larval dispersal in the study area, and we posit that it may be common in marine species. Our results bridge population genetic studies with direct dispersal studies and have implications for the design of marine reserve networks.

scholarly journals Genetic Structure of Cronartium ribicola Populations in Eastern Canada

1999 ◽  
Vol 89 (10) ◽  
pp. 915-919 ◽  
Author(s):  
K. Et-touil ◽  
L. Bernier ◽  
J. Beaulieu ◽  
J. A. Bérubé ◽  
A. Hopkin ◽  
...  
Keyword(s):  
Genetic Structure ◽  
Genetic Differentiation ◽  
Distribution Systems ◽  
Gene Diversity ◽  
Isolation By Distance ◽  
Random Amplified Polymorphic Dna ◽  
Cronartium Ribicola ◽  
Eastern Canada ◽  
Long Distance ◽  
Evolutionary Forces

The genetic structure of populations of Cronartium ribicola was studied by sampling nine populations from five provinces in eastern Canada and generating DNA profiles using nine random amplified polymorphic DNA markers. Most of the total gene diversity (Ht = 0.386) was present within populations (Hw = 0.370), resulting in a low level of genetic differentiation among populations in northeastern North America (Fst = 0.062). A hierarchical analysis of genetic structure using an analysis of molecular variance (AMOVA) revealed no statistically significant genetic differentiation among provinces or among regions. Yet, genetic differentiation among populations within regions or provinces was small (AMOVA φst = 0.078) but statistically significant (P < 0.001) and was several orders of magnitude larger than differentiation among provinces. This is consistent with a scenario of subpopulations within a metapopulation, in which random drift following migration and new colonization are major evolutionary forces. A phenetic analysis using genetic distances revealed no apparent correlation between genetic distance and the province of origin of the populations. The hypothesis of isolation-by-distance in the eastern populations of C. ribicola was rejected by computing Mantel correlation coefficients between genetic and geographic distance matrices (P > 0.05). These results show that eastern Canadian provinces are part of the same white pine blister rust epidemiological unit. Nursery distribution systems are controlled provincially, with virtually no seedling movement among provinces; therefore, infected nursery material may not play an important role in the dissemination of this disease. Long-distance spore dispersal across provincial boundaries appears to be an epidemiologically important factor for this pathogen.

Genetic structure of the rare and endangered moss Campylopus oerstedianus (Dicranaceae) in Europe

Biologia ◽  
2008 ◽  
Vol 63 (6) ◽  
Author(s):  
Marko Sabovljević ◽  
Jan-Peter Frahm
Keyword(s):  
Genetic Structure ◽  
Its Region ◽  
Long Distance Dispersal ◽  
Long Distance ◽  
Massif Central ◽  
Moss Species ◽  
The North ◽  
Rare And Endangered ◽  
The One ◽  
European Populations

AbstractThe genetic structure, diversity and phylogeography of the moss species Campylopus oerstedianus in Europe was studied, based on the ITS region of the nrDNA of nine selected European populations. Although this species is only known in sterile stage, long-distance dispersal and gene flow among populations seem to be present within Europe. High levels of genetic differentiation between the investigated Greek population and the western European populations indicate a long lasting isolation.The populations from France and Switzerland root together and supposedly have a common origin. From the French populations, the one from the Pyrenees is the most basal one and the populations in the Massif Central and the Vosges Mts can be derived from it. This indicates relatively recent dispersal of the species from the Mediterranean to the north, in spite of the lack of sporophytes and the fact that the type of the dispersed propagules and their vectors are not obvious.

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