Genetic variation in central and disjunct populations of Lilium parryi

1994 ◽  
Vol 72 (1) ◽  
pp. 79-85 ◽  
Author(s):  
Yan B. Linhart ◽  
Andrea C. Premoli
Keyword(s):  
Population Structure ◽  
Genetic Variation ◽  
Genetic Variability ◽  
The Other ◽  
Significant Genetic Differentiation ◽  
Isolated Populations ◽  
Disjunct Populations ◽  
Large Populations ◽  
Low Levels ◽  
Hawkmoth Pollination

We compared levels of genetic variability in small, isolated populations of Lilium parryi in Arizona with those found in large populations in California. Arizona populations were presumably derived from California populations; they were significantly less variable and showed evidence of much higher levels of inbreeding. One California locality whose population structure is similar to those found in Arizona also had relatively low levels of genetic variability. However, the other California populations were highly variable and showed lower levels of inbreeding than Arizona populations. There was significant genetic differentiation among all populations. In Arizona, there was no relationship between current population size and genetic variability. Arizona populations may be vulnerable to extinction, given the magnitude of environmental modifications in their habitats, their small sizes, and their low levels of variability. Key words: genetic structure, rare species, hawkmoth pollination, Lilium, disjunct populations.

High Levels of Genetic Variability in an Isolated Colony of Rock-wallabies (Petrogale assimilis): Evidence from Three Classes of Molecular Markers

1997 ◽  
Vol 45 (2) ◽  
pp. 199 ◽  
Author(s):  
Peter B. S. Spencer ◽  
Mark Adams ◽  
Helene Marsh ◽  
David J. Miller ◽  
Mark D. B. Eldridge
Keyword(s):  
Genetic Variation ◽  
Molecular Markers ◽  
Genetic Variability ◽  
Mating Systems ◽  
Selective Pressure ◽  
Multiple Mating ◽  
Dna Fingerprints ◽  
Average Heterozygosity ◽  
Low Levels ◽  
High Level

Estimates of genetic variation for a small (Ne = 39) colony of allied rock-wallabies (Petrogale assimilis) were calculated with three different categories of molecular marker. Average heterozygosity was estimated at 3·8% for allozymes, 47·3% for multilocus ‘DNA fingerprints’ and 85·5% for microsatellite markers. Overall these values indicate that this small isolated colony of rock-wallabies maintains a high level of genetic variation despite its relative isolation and the apparently low levels of migration between colonies. It is likely that mechanisms exist (such as kin avoidance, multiple mating systems, high and variable selective pressure in extreme and fluctuating environmental conditions) that promote the maintenance of high levels of genetic variation in isolated colonies of P. assimilis. These mechanisms are discussed in the context of the results obtained from the molecular markers.

scholarly journals How diverse can rare species be on the margins of genera distribution?

AoB Plants ◽  
2019 ◽  
Vol 11 (4) ◽  
Author(s):  
Alice Backes ◽  
Geraldo Mäder ◽  
Caroline Turchetto ◽  
Ana Lúcia Segatto ◽  
Jeferson N Fregonezi ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Population Structure ◽  
Genetic Variation ◽  
Genetic Variability ◽  
Habitat Loss ◽  
Evolutionary History ◽  
Founder Effects ◽  
Geographical Isolation ◽  
Genetic Diversity And Structure ◽  
Genetic Patterns

Abstract Different genetic patterns have been demonstrated for narrowly distributed taxa, many of them linking rarity to evolutionary history. Quite a few species in young genera are endemics and have several populations that present low variability, sometimes attributed to geographical isolation or dispersion processes. Assessing the genetic diversity and structure of such species may be important for protecting them and understanding their diversification history. In this study, we used microsatellite markers and plastid sequences to characterize the levels of genetic variation and population structure of two endemic and restricted species that grow in isolated areas on the margin of the distribution of their respective genera. Plastid and nuclear diversities were very low and weakly structured in their populations. Evolutionary scenarios for both species are compatible with open-field expansions during the Pleistocene interglacial periods and genetic variability supports founder effects to explain diversification. At present, both species are suffering from habitat loss and changes in the environment can lead these species towards extinction.

Isozyme diversity in large and isolated populations of Luma apiculata (Myrtaceae) in north-western Patagonia, Argentina

2005 ◽  
Vol 53 (8) ◽  
pp. 781 ◽  
Author(s):  
Mayra S. Caldiz ◽  
Andrea C. Premoli
Keyword(s):  
Genetic Variation ◽  
Isolated Populations ◽  
Isozyme Electrophoresis ◽  
Wahlund Effect ◽  
Rivers And Lakes ◽  
Large Populations ◽  
Vegetative Spread ◽  
Number Of Individuals ◽  
North Western ◽  
Isozyme Diversity

We evaluated the amount and distribution of genetic variation in large and small isolated populations of Luma apiculata (DC.) Burret (Myrtaceae) in north-western Patagonia. The hypothesis tested was that isolated smaller populations were more affected by drift and isolation than large stands. Higher genetic diversity was predicted in the latter. Fresh leaf material for isozyme electrophoresis was collected from 30 individuals in four isolated and two large and continuous stands (Quetrihue Peninsula and Punta Norte, Isla Victoria). Five subpopulations were sampled in both large stands, and in addition, three regeneration gaps in Punta Norte. Eleven loci were resolved; 91% were polymorphic in at least one population. Isolated and large populations had similar levels of genetic variation. Reduced observed heterozygosity and elevated inbreeding were measured in subpopulations and regeneration gaps within dense stands. Although small populations consist of a reduced number of individuals they are mostly coastal populations nearby rivers and lakes that may maintain considerable gene flow with other faraway populations counteracting the effects of drift. In addition to potential selfing, increased inbreeding within large populations and regeneration gaps may be due to an intra-population Wahlund effect from local seedling establishment and vegetative spread, resulting in clustered cohorts of similar genotypes.

Isonymy and population structure of Irish isolates during the 1890s

1982 ◽  
Vol 14 (2) ◽  
pp. 241-247 ◽  
Author(s):  
John H. Relethford
Keyword(s):  
Population Structure ◽  
Genetic Variation ◽  
Isolation By Distance ◽  
Breeding Population ◽  
Isolated Populations ◽  
Estimated Parameters ◽  
Distance Model ◽  
Local Breeding ◽  
And Migration ◽  
Close Fit

SummaryThe estimation of genetic similarity from correspondence of surnames (isonymy) allows investigation of historical population structure. This study uses surname data from seven isolates located along the west coast of Ireland during the 1890s to assess geographic and historic influences on population structure. Observed genetic variation among populations shows a close fit with the expected isolation by distance model, with estimated parameters of isolation and migration being similar to those obtained in other studies of isolated populations. Local genetic variation appears to be due primarily to the size of the local breeding population, with deviations being explained in terms of recent emigration.

Pollination biology and genetic variability of a giant perfumed flower (Aristolochia gigantea Mart. and Zucc., Aristolochiaceae) visited mainly by small Diptera

Botany ◽  
2012 ◽  
Vol 90 (9) ◽  
pp. 815-829 ◽  
Author(s):  
Juliana Hipólito ◽  
Blandina Felipe Viana ◽  
Alessandra Selbach-Schnadelbach ◽  
Leonardo Galetto ◽  
Peter G. Kevan
Keyword(s):  
Genetic Variability ◽  
The Other ◽  
Floral Traits ◽  
Pollination Syndrome ◽  
Chapada Diamantina ◽  
Species Characteristics ◽  
Structural Plan ◽  
Low Levels ◽  
Compatible Pollen ◽  
And Behavior

The genus Aristolochia presents conserved features in its basic structural plan of trap flowers and in its pollination syndrome. Visitors, usually flies, are attracted to the rotting-meat scented flowers and remain trapped until the second day, when the protogynous flowers release them. Aristolochia gigantea Mart. and Zucc showed many of these floral traits but display a citronella-like odour, giving the opportunity to study the reproductive ecology in this atypical species. Characteristics and behavior of pollinators, coupled with the distances between individual plants and populations, are important factors in patterns of genetic diversity. Thus, our objectives were to study the flower visitors, reproductive success, and gene flow in A. gigantea in the Chapada Diamantina, Bahia, Brazil. Results suggest that pollination by flies remains as a conserved interaction within the genus Aristolochia. The main pollinators appeared to be Megaselia spp. (Phoridae), evidenced primarily by the frequency of their occurrence within flowers and the transference of compatible pollen. On the other hand, the moderate to low levels of intrapopulation genetic variability found in A. gigantea, combined with low effective pollination and its reproductive dependence on biotic vectors, indicate that this species may be suffering gene erosion in the remaining populations located at Chapada Diamantina.

Morphological and genetic variation in disjunct populations of the avalanche lily Erythronium montanum

1996 ◽  
Vol 74 (3) ◽  
pp. 403-412 ◽  
Author(s):  
Geraldine A. Allen ◽  
Joseph A. Antos ◽  
Anne C. Worley ◽  
Terri A. Suttill ◽  
Richard J. Hebda
Keyword(s):  
Genetic Variation ◽  
Genetic Variability ◽  
Morphological Variability ◽  
Glacial Refugia ◽  
Long Distance Dispersal ◽  
Long Distance ◽  
Polymorphic Loci ◽  
Historical Factors ◽  
Disjunct Populations ◽  
Contrast Analysis

The genetic structure and morphological variability of species are influenced by both life-history traits and historical factors. We studied morphological and genetic variability in 12 populations of the avalanche lily, Erythronium montanum, representing the four disjunct regions of its geographic range in Oregon, Washington, and British Columbia. Floral traits exhibited significant differences among regions and among populations within regions, but these differences showed no clear geographic pattern, and for all traits there was substantial overlap among populations. In contrast, analysis of isozyme variation indicated a marked north–south gradient in genetic variability. The northernmost populations (from the B.C. Coast Range) had an average of 13% polymorphic loci and 1.13 alleles per locus, whereas southern populations (from the Cascade Mountains) averaged 48% polymorphic loci and 1.67 alleles per locus. The northern populations possessed no unique alleles but contained a subset of the alleles found in regions further south. We conclude that disjunct populations of E. montanum in B.C. probably arose through long-distance dispersal from more southern populations following deglaciation. Keywords: Erythronium montanum, genetic variation, glacial refugia, isozymes, long-distance dispersal, phytogeography.

Isozyme Variation in Eucalyptus nitens and E. denticulata

1998 ◽  
Vol 46 (1) ◽  
pp. 35 ◽  
Author(s):  
Ian O. Cook ◽  
Pauline Y. Ladiges
Keyword(s):  
Genetic Variation ◽  
Morphological Characteristics ◽  
Geographic Range ◽  
The Other ◽  
Isozyme Variation ◽  
Eucalyptus Nitens ◽  
Isolated Populations ◽  
Single Population ◽  
Central Victoria ◽  
Enzyme Systems

Seed samples from 22 populations across the geographic range ofE. nitens (Deane & Maiden) Maiden s. str. andE. denticulata I.O. Cook & P.Y. Ladiges wereanalysed for isozyme variation and estimation of the genetic distance betweenthe two taxa. Analysis of 12 enzyme systems in 3 buffer systems revealed 12polymorphic and 5 monomorphic loci. The results confirm the distinctiveness ofE. nitens and E. denticulatapreviously reported for morphological characteristics. A single population ofthe related species E. quadrangulata Deane & Maidenwas distinct from, and more heterogeneous than, populations of the other two taxa. The results also show regional genetic variation withinE. nitens that correlates with observed differences inmorphology. Three races were identified: northern and central NSW; southern NSW and Mt Kay in eastern Victoria; Baw Baw Ranges and Central Highlands inVictoria. Geographically isolated populations, particularly from central andnorthern NSW, showed the least genetic variation. Variation was highest in anequivocal population from Mt Gregory, central Victoria, where the distributionof E. nitens overlaps with that ofE. denticulata.

Microsatellite analysis reveals substantial levels of genetic variation but low levels of genetic divergence among isolated populations of Kaka (Nestor meridionalis)

2006 ◽  
Vol 106 (4) ◽  
pp. 329-338 ◽  
Author(s):  
James P. Sainsbury ◽  
Terry C. Greene ◽  
Ron J. Moorhouse ◽  
Charles H. Daugherty ◽  
Geoffrey K. Chambers
Keyword(s):  
Genetic Variation ◽  
Genetic Divergence ◽  
Microsatellite Analysis ◽  
Isolated Populations ◽  
Low Levels

scholarly journals Genetic variation, phylogenetic relationship and spatial distribution of ‘Candidatus Phytoplasma ulmi’ strains in Germany

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
B. Schneider ◽  
B. Hüttel ◽  
C. Zübert ◽  
M. Kube
Keyword(s):  
Phylogenetic Analysis ◽  
Genetic Variation ◽  
Spatial Distribution ◽  
Genetic Variability ◽  
Distribution Pattern ◽  
Phylogenetic Relationship ◽  
Regional Distribution ◽  
The Other ◽  
Flavescence Dorée ◽  
Regional Distribution Pattern

AbstractA recent survey in Germany revealed the wide presence of ‘Candidatus Phytoplasma ulmi’ in native elm stands. Accessions were studied for their genetic variability and phylogenetic relationship based on the conserved groEL and the variable imp gene. While the groEL sequences revealed a high intraspecific homology of more than 99%, the homology of the imp gene dropped to 71% between distantly related sequences. Twenty-nine groEL and 74 imp genotypes were distinguished based on polymorphic sites. Phylogenetic analysis of the groEL gene clustered all ‘Ca. P. ulmi’ strains and separated them from related phytoplasmas of the 16SrV group. The inferred phylogeny of the imp gene resulted in a different tree topology and separated the ‘Ca. P. ulmi’ genotypes into two clusters, one closely related to the flavescence dorée phytoplasma strain FD-D (16SrV-D), the other affiliated with the flavescence dorée phytoplasma strains FD-C and FD70 and the alder yellows phytoplasma (16SrV-C). In both phylograms, ‘Ca. P. ulmi’ genotypes from Scots elm trees formed a coherent cluster, while genotypes from European white elms and field elms grouped less strictly. The regional distribution pattern was congruent for some of the groEL and imp genotypes, but a strict linkage for all genotypes was not apparent.

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