bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sustaining genetic variation in a small population: evidence from the Mauritius kestrel
Authors: Nichols Richard A. , Bruford Michael W. , Groombridge Jim J. 
Published: March 2003

AbstractWe obtained measures of genetic diversity in 10 kestrel species at a suite of 12 microsatellite loci. We estimated the relative effective size (Ne) of the species using a Markov chain Monte Carlo (MCMC) approach, which jointly estimated the locus specific mutation rates as nuisance parameters. There was surprisingly high genetic diversity found in museum specimens of the Mauritius kestrel. Being an endemic species on a small island, it is known to have a long history of small population size. Conversely, kestrels with a continental distribution hadNeestimates that were only one order of magnitude larger and similar to each other, despite having current population sizes that were between one and three orders of magnitude larger than the Mauritius kestrel. We show how many of the theoretical results describing the effective size of a subdivided population can be captured in terms of three rates which describe the branching pattern of the gene genealogy, and that they are useful in estimating the time to migration‐drift and mutation‐drift equilibrium. We use this approach to argue that population subdivision has helped retain genetic diversity in the Mauritius kestrel, and that the continental species’ genetic diversity has yet to reach equilibrium after the range changes following the last ice age. We draw parallels with Hewitt’s observation that genetic variation seems to survive species’ range compression and is rather vulnerable to range expansion.
The role of hybridization in evolution
Authors: Barton N. H. 
Published: March 2003

AbstractHybridization may influence evolution in a variety of ways. If hybrids are less fit, the geographical range of ecologically divergent populations may be limited, and prezygotic reproductive isolation may be reinforced. If some hybrid genotypes are fitter than one or both parents, at least in some environments, then hybridization could make a positive contribution. Single alleles that are at an advantage in the alternative environment and genetic background will introgress readily, although such introgression may be hard to detect. ‘Hybrid speciation’, in which fit combinations of alleles are established, is more problematic; its likelihood depends on how divergent populations meet, and on the structure of epistasis. These issues are illustrated using Fisher’s model of stabilizing selection on multiple traits, under which reproductive isolation evolves as a side‐effect of adaptation in allopatry. This confirms a priori arguments that while recombinant hybrids are less fit on average, some gene combinations may be fitter than the parents, even in the parental environment. Fisher’s model does predict heterosis in diploid F1s, asymmetric incompatibility in reciprocal backcrosses, and (when dominance is included) Haldane’s Rule. However, heterosis arises only when traits are additive, whereas the latter two patterns require dominance. Moreover, because adaptation isviasubstitutions of small effect, Fisher’s model does not generate the strong effects of single chromosome regions often observed in species crosses.
Spatial structure of lemming populations (Dicrostonyx groenlandicus) fluctuating in density
Authors: Ehrich D. , Jorde P. E. , Krebs C. J. , Kenney A. J. , Stacy J. E. , Stenseth N. C. 
Published: March 2003

AbstractThe pattern and scale of the genetic structure of populations provides valuable information for the understanding of the spatial ecology of populations, including the spatial aspects of density fluctuations. In the present paper, the genetic structure of periodically fluctuating lemmings (Dicrostonyx groenlandicus) in the Canadian Arctic was analysed using mitochondrial DNA (mtDNA) control region sequences and four nuclear microsatellite loci. Low genetic variability was found in mtDNA, while microsatellite loci were highly variable in all localities, including localities on isolated small islands. For both genetic markers the genetic differentiation was clear among geographical regions but weaker among localities within regions. Such a pattern implies gene flow within regions. Based on theoretical calculations and population census data from a snap‐trapping survey, we argue that the observed genetic variability on small islands and the low level of differentiation among these islands cannot be explained without invoking long distance dispersal of lemmings over the sea ice. Such dispersal is unlikely to occur only during population density peaks.
Genetic and ecological divergence of a monophyletic cichlid species pair under fully sympatric conditions in Lake Ejagham, Cameroon
Authors: Schliewen Ulrich , Rassmann Kornelia , Markmann Melanie , Markert Jeff , Kocher Thomas , Tautz Diethard 
Published: March 2003

AbstractAlthough there is mounting evidence that speciation can occur under sympatric conditions, unambiguous examples from nature are rare and it is almost always possible to propose alternative allopatric or parapatric scenarios. To identify an unequivocal case of sympatric speciation it is, therefore, necessary to analyse natural settings where recent monophyletic species flocks have evolved within a small and confined spatial range. We have studied such a case with a cichlid species flock that comprises five Tilapia forms endemic to a tiny lake (Lake Ejagham with a surface area of approximately 0.49 km2) in Western Cameroon. Analysis of mitochondrial D‐Loop sequences shows that the flock is very young (approximately 104 years) and has originated from an adjacent riverine founder population. We have focused our study on a particular pair of forms within the lake that currently appears to be in the process of speciation. This pair is characterized by an unique breeding colouration and specific morphological aspects, which can serve as synapomorphic characters to prove monophyly. It has differentiated into a large inshore and a small pelagic form, apparently as a response to differential utilization of food resources. Still, breeding and brood care occurs in overlapping areas, both in time and space. Analysis of nuclear gene flow on the basis of microsatellite polymorphisms shows a highly restricted gene flow between the forms, suggesting reproductive isolation between them. This reproductive isolation is apparently achieved by size assortative mating, although occasional mixed pairs can be observed. Our findings are congruent with recent theoretical models for sympatric speciation, which show that differential ecological adaptations in combination with assortative mating could easily lead to speciation in sympatry.
Shared parentage and incest avoidance in the cooperatively breeding acorn woodpecker
Authors: Haydock J. , Koenig W. D. , Stanback M. T. 
Published: March 2003

AbstractSocial groups of acorn woodpeckers (Melanerpesformicivorus) range in size from unaided pairs to 15 adults. Behavioural indicators of mate guarding, assumed incest avoidance and observations of egg‐laying indicate that social organization ranges from monogamous pairs to groups with up to seven male and three female putative cobreeders plus up to 10 nonbreeding helpers. In addition, groups occasionally lack a putative breeder throughout the breeding season. Here we report results from multilocus DNA fingerprinting of 372 nestlings from 123 nests in groups with putative cobreeders of one or both sexes. No extra‐group fertilizations were found. Putative cobreeding males within social groups shared paternity. However, the most reproductively successful male was, on average, almost three times as successful as the next most successful and additional males only occasionally sired offspring. In contrast, cobreeding females shared parentage equally. Helpers never bred incestuously when their opposite‐sex parent (or another relative, such as their uncle) held breeding status in the group. However, during breeding male vacancies, 14 nestlings were produced when helper males bred incestuously with their mother. Both male and female helpers usually became successful cobreeders with their same‐sex parent following replacement of the opposite‐sex breeder(s) by unrelated individuals.
Spatial patterns of genetic diversity in Posidonia oceanica, an endemic Mediterranean seagrass
Authors: Procaccini G. , Orsini L. , Ruggiero M. V. , Scardi M. 
Published: March 2003

Abstract Posidonia oceanica is an endemic seagrass species in the Mediterranean Sea. In order to assess levels of genetic structure in this species, the microsatellite polymorphism was analysed from meadows collected in several localities, along the coasts of the Tyrrhenian Sea (Mediterranean Sea). The existence of single population units and the recruitment of seedlings collected in some localities were investigated. Moreover, genetic structure at different spatial scales and biogeographic relationships among populations were also assessed. Our analysis showed the existence of clear patterns of genetic structure in P. oceanica in the area considered in the analysis. P. oceanica, in fact, is present in separate meadows that represent discrete populations, characterized by low genetic diversity. Comparable levels of genetic variability between mature meadows and seedlings were found. Patterns of genetic relatedness among populations seem to be in accord with direction of dominant current flux in the whole area, separating South Tyrrhenian from North Tyrrhenian populations. Moderate levels of gene flow between populations and genetic substructure within populations, together with the finding of the limited role of sexual reproduction in increasing genetic variability, should be a cause for concern for the persistence of this essential resource in the Mediterranean basin.
Genetic structure of populations of the human hookworm, Necator americanus, in China
Authors: Hawdon J. M. , Li T. , Zhan B. , Blouin M. S. 
Published: March 2003

AbstractTwenty‐one to 58 individual Necator americanus were sampled from each of four villages in south‐western China. Each nematode was sequenced for 588 bp of the mitochondrial cytochrome oxidase I gene. Allelic and nucleotide diversity varied two‐fold among villages. Overall FST among populations was ≈ 0.28, but this large value resulted from one low‐diversity population that had a large genetic distance to the other three populations (FST = 0.10 without that population). There was no correlation between geographical and genetic distance among sites. Thus, the genetic structure of this species in China may be characterized by variable effective sizes and uneven movement among sites. We discuss the implications of this genetic structure for vaccine development and the spread of drug resistance in human hookworms, and compare the genetic structure of hookworms with that of other nematodes.
Allozyme and microsatellite loci provide discordant estimates of population differentiation in the endangered dusky grouper (Epinephelus marginatus) within the Mediterranean Sea
Authors: De Innocentiis S. , Sola L. , Cataudella S. , Bentzen P. 
Published: March 2003

AbstractThe dusky grouper, Epinephelus marginatus, inhabits coastal reefs in the Mediterranean Sea and Atlantic Ocean. A decline in the abundance of this long‐lived protogynous hermaphrodite has led to its listing as an endangered species in the Mediterranean, and heightened management concerns regarding its genetic variability and population substructure. To address these concerns, we analysed genetic variation at seven microsatellite and 28 allozyme loci in dusky groupers sampled from seven areas (for microsatellites) and three areas (for allozymes) in the west‐central Mediterranean. Levels of genetic variability were higher for microsatellites than for allozymes (mean HE = 0.78 and 0.07, respectively), but similar to those observed in other marine fishes with comparable markers. Both microsatellites and allozymes revealed significant genetic differentiation among all areas analysed with each class of marker, but the magnitude of differentiation revealed by allozymes over three locales (FST = 0.214) was greater than that detected with microsatellites over seven areas, or over the three areas shared with the allozyme analysis (FST = 0.018 and ~0, respectively). A large proportion of the allozyme differentiation was due to a single locus (ADA*) possibly influenced by selection, but allozyme differentiation over the three areas was still highly significant (FST = 0.06, P < 0.0001), and the 95% confidence intervals for allozyme and microsatellite FST did not overlap when this locus was excluded. There was no evidence of isolation by distance with either class of markers. Our results lead us to conclude that dusky groupers are not panmictic in the Mediterranean Sea and suggest that they should be managed on a local basis. However, more work is needed to elucidate genetic relationships among populations.
DNA from bird‐dispersed seed and wind‐disseminated pollen provides insights into postglacial colonization and population genetic structure of whitebark pine (Pinus albicaulis)
Authors: Richardson B. A. , Brunsfeld S. J. , Klopfenstein N. B. 
Published: March 2003

AbstractUniparentally inherited mitochondrial (mt)DNA and chloroplast (cp)DNA microsatellites (cpSSRs) were used to examine population genetic structure and biogeographic patterns of bird‐dispersed seed and wind‐disseminated pollen of whitebark pine (Pinus albicaulis Engelm.). Sampling was conducted from 41 populations throughout the range of the species. Analyses provide evidence for an ancestral haplotype and two derived mtDNA haplotypes with distinct regional distributions. An abrupt contact zone between mtDNA haplotypes in the Cascade Range suggests postglacial biogeographic movements. Among three cpSSR loci, 42 haplotypes were detected within 28 cpSSR sample populations that were aggregated into six regions. Analysis of molecular variance (amova) was used to determine the hierarchical genetic structure of cpSSRs. amova and population pairwise comparisons (FST) of cpSSR, and geographical distribution of mtDNA haplotypes provide insights into historical changes in biogeography. The genetic data suggest that whitebark pine has been intimately tied to climatic change and associated glaciation, which has led to range movements facilitated by seed dispersal by Clark’s nutcracker (Nucifraga columbiana Wilson). The two hypotheses proposed to explain the genetic structure are: (i) a northward expansion into Canada and the northern Cascades in the early Holocene; and (ii) historical gene flow between Idaho and the Oregon Cascades when more continuous habitat existed in Central Oregon during the late Pleistocene. Genetic structure and insights gained from historical seed movements provide a basis on which to develop recovery plans for a species that is at risk from multiple threats.
Genetic variation across the historical range of the wild turkey (Meleagris gallopavo)
Authors: Mock K. E. , Theimer T. C. , Rhodes O. E. , Greenberg D. L. , Keim P. 
Published: March 2003

AbstractGenetic differences within and among naturally occurring populations of wild turkeys (Meleagris gallopavo) were characterized across five subspecies’ historical ranges using amplified fragment length polymorphism (AFLP) analysis, microsatellite loci and mitochondrial control region sequencing. Current subspecific designations based on morphological traits were generally supported by these analyses, with the exception of the eastern (M. g. silvestris) and Florida (M. g. osceola) subspecies, which consistently formed a single unit. The Gould’s subspecies was both the most genetically divergent and the least genetically diverse of the subspecies. These genetic patterns were consistent with current and historical patterns of habitat continuity. Merriam’s populations showed a positive association between genetic and geographical distance, Rio Grande populations showed a weaker association and the eastern populations showed none, suggesting differing demographic forces at work in these subspecies. We recommend managing turkeys to maintain subspecies integrity, while recognizing the importance of maintaining regional population structure that may reflect important adaptive variation.
Molecular identification of prey in predator diets
Authors: Symondson W. O. C. 
Published: March 2003

AbstractIn many situations prey choice by predators in the field cannot be established or quantified using direct observation. The remains of some prey may be visually identified in the guts and faeces of predators but not all predators ingest such hard remains and even those that do consume them may also ingest soft‐bodies prey that leave no recognizable remnants. The result is, at best, a biased picture of prey choice. A range of molecular techniques and applications are reviewed that allow prey remains to be identified, often to the species and even stage level. These techniques, all of which are still in use, include enzyme electrophoresis, a range of immunological approaches using polyclonal and monoclonal antibodies to detect protein epitopes, and recently developed polymerase chain reaction (PCR)‐based methods for detecting prey DNA. Analyses may be postmortem, on invertebrate and vertebrate predators collected from the field, or noninvasive assays of the remains in regurgitated bird pellets or vertebrate faeces. It was concluded that although monoclonal antibodies are currently the most effective method in use today, PCR‐based techniques have proved to be highly effective and versatile in recent laboratory trials and are likely to rapidly displace all other approaches.
Reconciling genetic expectations from host specificity with historical population dynamics in an avian brood parasite, Horsfield’s Bronze‐CuckooChalcites basalisof Australia
Authors: Joseph L. , Wilke T. , Alpers D. 
Published: March 2003

AbstractMitochondrial DNA (mtDNA) is being used increasingly to explore the evolution of host specificity in avian brood parasites. A stable coevolutionary equilibrium between multiple phylogenetically unrelated hosts and a brood parasitic species predicts that mtDNA diversity in the parasite should be relatively deep and phylogenetically structured. Also, the different intraspecific clades resulting from parasitism to multiple sympatric hosts should themselves occur sympatrically. However, mtDNA diversity in brood parasites is as susceptible to effects of historical population dynamics as in any species. We demonstrate the relevance of these dynamics to the use of mtDNA in understanding coevolution between an Australian brood‐parasite, Horsfield’s Bronze‐CuckooChalcites basalisand its hosts,Malurusfairy‐wrens andAcanthizathornbills. Previous ecological and behavioural analyses argue thatMalurus‐ andAcanthiza‐specific host races exist inC. basalis. Yet mtDNA diversity inC. basalisis low and phylogenetically unstructured (mean sequence divergence 0.15 ± 0.07%, range 0.00%–0.31%) and tests of mtDNA neutrality and range expansion vs. population stability (Tajima’s D, Fu & Li’s F* and D*, Fu’sFS, mismatch analyses) all indicate thatC. basalishas expanded its range very recently, probably within the last few tens of thousands of years following climatic amelioration after a peak of aridity in the late Pleistocene. The low mtDNA diversity and its lack of phylogenetic structure inC. basalisdeny the existence of evolutionarily long‐term stable host races inC. basalisbut not the possibility of recently evolved ones. They highlight the need for renewed behavioural and ecological study of the relationship betweenC. basalisand its hosts. Our findings illustrate the need to understand the evolutionary context in which a brood parasite and its hosts have evolved if mtDNA data are to be used in testing hypotheses concerning the origin and maintenance of host specificity. They also add to the growing body of work illustrating the use of mismatch analyses and Fu’sFSin detecting range expansions.
The Mediterranean fruit fly in California: evidence for multiple introductions and persistent populations based on microsatellite and mitochondrial DNA variability
Authors: Meixner M. D. , McPheron B. A. , Silva J. G. , Gasparich G. E. , Sheppard W. S. 
Published: March 2003

AbstractMicrosatellite and mitochondrial DNA (mtDNA) variability data were used to study outbreaks of Mediterranean fruit fly in California in the years 1992–94 and 1997–99. A total of 359 flies caught in monitoring traps during these years were examined at three polymorphic mtDNA restriction sites and two microsatellite loci. Composite genotypes obtained through analysis of these markers indicate at least five independent introductions of medflies into California between 1992 and 1998. Whereas the majority of specimens displayed a single mtDNA haplotype (AAA), variation of microsatellite alleles among these flies suggests at least one additional introduction in 1993 into southern California. Flies displaying the AAB haplotype sampled in 1992 both in northern and southern California shared microsatellite alleles absent in AAA flies although lacking others commonly found in AAA specimens, thus supporting the hypothesis of an independent introduction of these flies from a different source. In contrast to earlier infestations, a few specimens caught in southern California in 1993 and again in 1998 showed both mtDNA and microsatellite patterns consistent with a Hawaiian origin. Single flies collected in Santa Clara County in 1997 and in El Monte, Los Angeles County & in 1999 most likely represent a sixth and seventh distinct introduction, respectively.
Population genetic structure of two rare tree species (Colubrina oppositifoliaandAlphitonia ponderosa, Rhamnaceae) from Hawaiian dry and mesic forests using random amplified polymorphic DNA markers
Authors: Kwon J. A. , Morden C. W. 
Published: March 2003

AbstractHawaiian dry and mesic forests contain an increasingly rare assemblage of species due to habitat destruction, invasive alien weeds and exotic pests. Two rare Rhamnaceae species in these ecosystems,Colubrina oppositifoliaandAlphitonia ponderosa, were examined using random amplified polymorphic DNA (RAPD) markers to determine the genetic structure of the populations and the amount of variation relative to other native Hawaiian species. Relative variation is lower than with other Hawaiian species, although this is probably not a consequence of genetic bottleneck. Larger populations of both species contain the highest levels of genetic diversity and smaller populations generally the least as determined by number of polymorphic loci, estimated heterozygosity, and Shannon’s index of genetic diversity. Populations on separate islands were readily discernible for both species as were two populations ofC. oppositifoliaon Hawai’i island (North and South Kona populations). Substructure among Kaua’i subpopulations ofA. ponderosathat were ecologically separated was also evident. Although population diversity is thought to have remained at predisturbance levels, population size continues to decline as recruitment is either absent or does not keep pace with senescence of mature plants. Recovery efforts must focus on control of alien species if these and other endemic dry and mesic forest species are to persist.