bluuebunny/crossref_metadata_2025 huggingface dataset:
Microevolution, low clonal diversity and genetic affinities of parthenogeneticSitobionaphids in New Zealand
Authors: Wilson A. C. C. , Sunnucks P. , Hales D. F.
Published: March 2003

In sharp contrast to their southeast Asian and European counterparts, Sitobion miscanthi andS.nearfragariaeaphids in Australia exhibit a complete absence of sexual reproduction. This demands an explanation within the context of the evolution and maintenance of sex and parthenogenesis. Accordingly, we executed a genetic analysis of the two species in neighbouring New Zealand. Microsatellites and single‐stranded conformation polymorphism/sequence analysis of the nuclear gene elongation factor 1α were used to identify aphid clones and confirm species identification, respectively. Karyotypic variation was also investigated. The New Zealand fauna showed few (nonrecombining) genotypes and appears to have received migrants from both Australia and Asia. Other genotypes have apparently arisenin situin New Zealand, exhibiting stepwise mutation of microsatellite alleles and also karyotypic change. Thus, these data represent rare evidence of evolution within wild‐living parthenogenetic lineages. Karyotypic changes appear to occur at a rate even greater than that of microsatellite evolution. Strong geographical partitioning of genotypes/karyotypes was found, with certain ones predominating over large areas. These data suggest that clonal selection could be important in the distribution and patterning of genetic variation. We present a model to explain the genetic patterns, with particular reference to the absence of sexual reproduction inSitobionaphids in New Zealand and Australia.
Influence of glaciation on divergence patterns of the endemic minnow, Zacco pachycephalus, in Taiwan
Authors: Wang Hurng‐Yi , Tsai Mung‐Pei , Yu Ming‐Jenn , Lee Sin‐Che
Published: March 2003

The genetic subdivision of the endemic minnow, Zacco pachycephalus, in 12 rivers of Taiwan was studied by allozyme electrophoresis. Among 26 loci surveyed, six were significantly differentiated among sites. Allozyme genotype frequencies within samples accord with Hardy–Weinberg expectations. A highly divergent genetic structure among sites (FST = 0.497) with low genetic variability within samples (H = 0.006–0.062, mean = 0.03) suggests that local populations originated from a small number of founders. upgma and Fitch trees derived from Nei’s genetic distance and hierarchical analysis of FST values reveal that samples of Z. pachycephalus can be divided into northern, middle, and southern subgroups and that most genetic variation (87%) is distributed among rather than within groups. It is proposed that there were two isolated refugia during the most recent glacial period, and that populations of the southern group (Group I) originated from a southern refugium in Taiwan below the boundary of the Kaoping River, and other groups (Group II), including northern and middle subgroups, originated from a refugium located on the extinct landbridge between Taiwan and mainland China. The postglacial division between northern and middle subgroups may be due to hydrological differences between these two regions.
Genetic variation within a fragmented population ofSwietenia humilisZucc.
Authors: White G. M. , Boshier D. H. , Powell W.
Published: March 2003

With large tracts of once continuous forest now modified by human use to leave reduced and highly fragmented stands of trees, the determination of the genetic consequences of forest fragmentation is a priority for ascertaining the conservation value of resultant stands, and in formulating sustainable management strategies. The levels and distribution of genetic diversity over 10 microsatellite loci were investigated within a fragmented population of the neotropical treeSwietenia humilisZucc. High levels of genetic variation, typical of a highly outcrossing species, were found in all fragments at all loci (meanHE = 0.548). The majority of the variation was within rather than between fragments (RST = 0.032), giving high indirect estimates of gene flow (Nm = 8.9), probably reflecting the genetic structure of the trees present under more continuous forest. A high proportion of loci also showed significant departures from Hardy–Weinberg equilibrium with associated significant levels ofFIS. The initial effects of fragmentation were, however, seen in the fragments through the loss of low‐frequency alleles present in the continuous ‘control’ stand. The percentage of this allelic loss increased with a decrease in fragment size.
Patterns of microsatellite polymorphism in the range‐restricted bonobo (Pan paniscus): considerations for interspecific comparison with chimpanzees (P. troglodytes)
Authors: Reinartz G. E. , Karron J. D. , Phillips R. B. , Weber J. L.
Published: March 2003

The endangered great ape,Pan paniscus(bonobo) has the smallest range of the African apes. Virtually nothing is known about the genetic diversity or genetic structure of this species, while substantial amounts of polymorphism have been reported for the bonobo’s widespread congener, the chimpanzee (P. troglodytes). Given its restricted range, what is the extent of genetic variation in the bonobo relative to the chimpanzee, and is the bonobo genetically depauperate? To investigate patterns of genetic polymorphism, bonobos of wild origin were genotyped for 28 microsatellite loci. The mean number of alleles per locus (5.2) and the mean observed heterozygosity (0.52) in bonobos were similar to variation observed in a wild chimpanzee community (P. t. schweinfurthii). The rarer bonobo is not genetically depauperate and may have genetic diversity comparable to the eastern chimpanzee subspecies. Bonobos have approximately 55% of the allelic diversity and 66% of the observed heterozygosity exhibited by all three chimpanzee subspecies sampled across equatorial Africa. Resampling techniques were used to quantify the effects of sample size differences and number and choice of loci between bonobos and chimpanzees. The examination of these variables underscores their importance in accurately interpreting interspecific comparisons of diversity estimates.
Multiple paternity increases effective size of southern Atlantic salmon populations
Authors: Martinez J. L. , Moran P. , Perez J. , De Gaudemar B. , Beall E. , Garcia‐Vazquez E.
Published: March 2003

Genetic analyses were performed on the progeny of Atlantic salmon (Salmo salar L.) sampled in natural redds of three rivers flowing into the Bay of Biscay, the Nivelle, the Mandeo and the Sella. These rivers are at the southern limit of the European distribution of the species and their populations are small and endangered by human activities. Nine variable number of tandem repeat (VNTR) loci (five minisatellites and four microsatellites) were used for parentage analysis. Multiple male participation was recognized in the fertilization of eggs. A large proportion was fertilized by precociously mature parr. We demonstrate that multiple paternity derived from mature parr is crucial for the conservation of genetic variability in small populations of Atlantic salmon.
Higher impact of female than male migration on population structure in large mammals
Authors: Tiedemann Ralph , Hardy Olivier , Vekemans Xavier , Milinkovitch Michel C.
Published: March 2003

We simulated large mammal populations using an individual‐based stochastic model under various sex‐specific migration schemes and life history parameters from the blue whale and the Asian elephant. Our model predicts that genetic structure at nuclear loci is significantly more influenced by female than by male migration. We identified requisite comigration of mother and offspring during gravidity and lactation as the primary cause of this phenomenon. In addition, our model predicts that the common assumption that geographical patterns of mitochondrial DNA (mtDNA) could be translated into female migration rates (Nmf) will cause biased estimates of maternal gene flow when extensive male migration occurs and male mtDNA haplotypes are included in the analysis.
The molecular population genetics of regulatory genes
Authors: Purugganan Michael D.
Published: March 2003

Regulatory loci, which may encode both trans acting proteins as well as cis acting promoter regions, are crucial components of an organism’s genetic architecture. Although evolution of these regulatory loci is believed to underlie the evolution of numerous adaptive traits, there is little information on natural variation of these genes. Recent molecular population genetic studies, however, have provided insights into the extent of natural variation at regulatory genes, the evolutionary forces that shape them and the phenotypic effects of molecular regulatory variants. These recent analyses suggest that it may be possible to study the molecular evolutionary ecology of regulatory diversification by examining both the extent and patterning of regulatory gene diversity, the phenotypic effects of molecular variation at these loci and their ecological consequences.
Genetic variability among endangered Chinese giant salamanders, Andrias davidianus
Authors: Murphy Robert W. , Fu Jinzhong , Upton Darlene E. , De Lema Thales , Zhao Er‐Mi
Published: March 2003

The endangered Chinese giant salamander (Andrias davidianus) is endemic to mainland China. Genetic divergence among six populations of the species was investigated by means of isozyme electrophoresis and mitochondrial DNA (mtDNA) sequences. Forty allozyme loci were resolved for all populations; the amount of genetic divergence among populations was comparable to that in other amphibians. mtDNA sequences showed a similar level of divergence. The population from Huangshan is distinct from other populations, indicating the existence of localized divergence. Both allozyme and mtDNA data failed to associate the populations into a pattern corresponding to the three Chinese river systems, which may be the consequence of human relocation. Conservation policies should emphasize the protection of localized populations and cessation of human‐facilitated introductions. Future studies should focus on investigating the divergence among localized populations from isolated mountain regions, particularly using more fine‐grained techniques such as microsatellite DNA.
Maternal control of sex ratio in Rana rugosa: evidence from DNA sexing
Authors: Sakisaka Y. , Yahara T. , Miura I. , Kasuya E.
Published: March 2003

Parental control of primary sex ratio has been reported in a mammal (red deer), some birds, and a snake. However, it remains uncertain whether other vertebrates including Amphibia can control sex ratio. In this paper, we examined the possibility in a wild population of the Japanese frog Rana rugosa which has female heterogamety. Sex ratios of their eggs were determined using DNA markers. The eggs were sampled in the field from May to August in 1998. Each egg was then sexed by polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) using a sex‐specific DNA marker. The result showed a male bias early in the season which changed to a female bias later, suggesting that females of R. rugosa can control the primary sex ratio.
Genetic lineages and postglacial colonization of grayling (Thymallus thymallus, Salmonidae) in Europe, as revealed by mitochondrial DNA analyses
Authors: Koskinen M. T. , Ranta E. , Piironen J. , Veselov A. , Titov S. , Haugen T. O. , Nilsson J. , Carlstein M. , Primmer C. R.
Published: March 2003

In stark contrast to other species within the Salmonidae family, phylogeographic information on European grayling, Thymallus thymallus, is virtually nonexistent. In this paper, we utilized mitochondrial DNA polymerase chain reaction–restriction fragment length polymorphism (mtDNA PCR–RFLP) and sequence variation to infer the postglacial dispersal routes of T. thymallus into and within northern Europe, and to locate geographically, potential evolutionarily distinct populations. Mitochondrial analyses revealed a total of 27 T. thymallus haplotypes which clustered into three distinct lineages. Average pairwise interlineage divergence was four and nine times higher than average intralineage divergence for RFLP and sequence data, respectively. Two European grayling individuals from the easternmost sample in Russia exhibited haplotypes more genetically diverged from any T. thymallus haplotype than T. arcticus haplotype, and suggested that hybridization/introgression zone of these two sister species may extend much further west than previously thought. Geographic division of the lineages was generally very clear with northern Europe comprising of two genetically differentiated areas: (i) Finland, Estonia and north‐western Russia; and (ii) central Germany, Poland and western Fennoscandia. Average interpopulation divergence in North European T. thymallus was 10 times higher than that observed in a recent mtDNA study of North American T. arcticus. We conclude that (i) North European T. thymallus populations have survived dramatic Pleistocene temperature oscillations and originate from ancient eastern and central European refugia; (ii) genetic divergence of population groups within northern Europe is substantial and geographically distinct; and (iii) the remainder of Europe harbours additional differentiated assemblages that likely descend from a Danubian refugium. These findings should provide useful information for developing appropriate conservation strategies for European grayling and exemplify a case with a clear need for multinational co‐operation for managing and conserving biodiversity.
Mitochondrial DNA variation in rainbow trout (Oncorhynchus mykiss) across its native range: testing biogeographical hypotheses and their relevance to conservation
Authors: McCusker Megan R. , Parkinson Eric , Taylor Eric B.
Published: March 2003

North‐western North America has been repeatedly glaciated over most of the past two million years, with the most recent glaciation occurring between 60 000 and 10 000 years ago. Intraspecific genetic variation in many species has been shaped by where they survived glaciation and what postglacial recolonization routes were used. In this study, molecular techniques were used to investigate biogeographical, taxonomic and conservation issues in rainbow trout, Oncorhynchus mykiss. Mitochondrial DNA (mtDNA) variation was assessed using a restriction fragment length polymorphism (RFLP) analysis, focusing mainly on the previously understudied northern extent of the species’ range. Two phylogenetically distinct mitochondrial lineages were found that differed from each other by up to 1.8% in sequence. Although the geographical distributions of the two clades overlap extensively, diversity and distributional analyses strongly suggest that trout survived glaciation in both coastal and inland refugia followed by postglacial gene flow and secondary contact. Postglacial dispersal into British Columbia most likely occurred from the Queen Charlotte Islands and the Columbia River. Although trout most likely also survived glaciation along the coast of Washington, Oregon and California, as well as near the Bering Strait, evidence suggests that dispersal into British Columbia from these areas was limited. Sequence analysis of mitochondrial haplotypes revealed higher diversity in California than in the northern part of the species’ range, indicating an ancient presence of the species in the south. Phylogeographic divergence probably predates adaptive variation in the species as suggested by evidence for parallel evolution of life history types across the range of O. mykiss.
Partial nucleotide sequences, and routine typing by polymerase chain reaction–restriction fragment length polymorphism, of the brown trout (Salmo trutta) lactate dehydrogenase, LDH‐C1*90 and *100 alleles
Authors: McMeel O. M. , Hoey E. M. , Ferguson A.
Published: March 2003

The cDNA nucleotide sequences of the lactate dehydrogenase alleles LDH‐C1*90 and *100 of brown trout (Salmo trutta) were found to differ at position 308 where an A is present in the *100 allele but a G is present in the *90 allele. This base substitution results in an amino acid change from aspartic acid at position 82 in the LDH‐C1 100 allozyme to a glycine in the 90 allozyme. Since aspartic acid has a net negative charge whilst glycine is uncharged, this is consistent with the electrophoretic observation that the LDH‐C1 100 allozyme has a more anodal mobility relative to the LDH‐C1 90 allozyme. Based on alignment of the cDNA sequence with the mouse genomic sequence, a local primer set was designed, incorporating the variable position, and was found to give very good amplification with brown trout genomic DNA. Sequencing of this fragment confirmed the difference in both homozygous and heterozygous individuals. Digestion of the polymerase chain reaction products with BslI, a restriction enzyme specific for the site difference, gave one, two and three fragments for the two homozygotes and the heterozygote, respectively, following electrophoretic separation. This provides a DNA‐based means of routine screening of the highly informative LDH‐C1* polymorphism in brown trout population genetic studies. Primer sets presented could be used to sequence cDNA of other LDH* genes of brown trout and other species.
Use of amplified fragment length polymorphism markers to assess genetic diversity of Lolium species from Portugal
Authors: Cresswell A. , Sackville Hamilton N. R. , Roy A. K. , Viegas B. M. F.
Published: March 2003

We evaluated the use of amplified fragment length polymorphism (AFLP) markers to distinguish genotypes, populations and species of Lolium. Accessions of two species Lolium perenne and Lolium multiflorum and their hybrid Lolium × hybridum, collected by the Institute of Grass and Environmental Research in 1995 from locations across Portugal, were used. The genetic variation within and between populations from the extremes of latitude and altitude was determined and assessed. Three primer pair combinations generated 765 polymorphic bands. Principal coordinate analysis of similarities between 127 plants showed high dimensionality in the data. Axes 1–3 were associated primarily with species differences, axes 4–14 with population differences within species and axis 15 onwards with within population differences. UPGMA analysis confirmed the groupings. The three populations of L. perenne formed a discrete cluster widely separated from all other populations. There were two distinct groups of L. × hybridum, of which one was similar to and overlapped with L.multiflorum and the second formed a distinct cluster. Analyses of individual bands showed that every inter‐ and intraspecific contrast involved a different sets of bands, again confirming the high dimensionality of the data. No single band was strictly diagnostic of any population or species. Nevertheless, the UPGMA analysis showed little or no overlap between populations. Thus, despite the high ratio of within‐to‐between population genetic variance, the full AFLP banding pattern of each genotype is a relatively reliable fingerprint diagnostic of its parent population. The high dimensionality implies that many different factors contribute to the differences observed. This adds to the potential value of the methodology, since it implies that there is a reasonably high likelihood of finding bands relevant to a given environmental gradient or other factor influencing the distribution of genetic diversity.
Low reproductive success in territorial male Antarctic fur seals (Arctocephalus gazella) suggests the existence of alternative mating strategies
Authors: Gemmell Neil J. , Burg Theresa M. , Boyd Ian L. , Amos William
Published: March 2003

Microsatellites were used to conduct an analysis of paternity of Antarctic fur seals (Arctocephalus gazella) from Bird Island, South Georgia. At most, only 28% of pups at our study site could be assigned a father, even though the majority (~90%) of candidate males within this colony were sampled. The behavioural and genetic evidence from this study suggests that a number of alternative mating strategies may exist within this fur seal population. Holding a land‐based territory conferred an advantage to male reproductive success. However, this advantage was much smaller than expected from behavioural observations. At least 70% of fur seal pups born at our study site in a given year are not fathered by males who held a territory or were observed copulating with females in the previous year, implying that there exists a pool of males that seldom venture ashore at this site. To explain this discrepancy we suggest that female choice is an integral component of the Antarctic fur seal mating system and that aquatic mating may play a much larger role in the Antarctic fur seal than previously thought.
Raciation and speciation in house mice from the Alps: the role of chromosomes
Authors: Piálek Jaroslav , Hauffe Heidi C. , Rodríguez‐Clark Kathryn M. , Searle Jeremy B.
Published: March 2003

There are at least 24 different karyotypic races of house mouse in the central Alps, each characterized by a different complement of ancestral acrocentric and derived metacentric chromosomes; altogether 55 different metacentric chromosomes have been described from the region. We argue that this chromosome variation largely arosein situ. If these races were to make contact, in most cases they would produce F1hybrids with substantial infertility (sometimes complete sterility), due to nondisjunction and germ cell death associated with the formation of long‐chain and/or ring configurations at meiosis. We present fertility estimates to confirm this for two particular hybrid types, one of which demonstrates male‐limited sterility (in accordance with Haldane’s Rule). As well as a model for speciation in allopatry, the Alpine mouse populations are of interest with regards speciation in parapatry: we discuss a possible reinforcement event. Raciation of house mice appears to have happened on numerous occasions within the central Alps. To investigate one possible source of new karyotypic races, we use a two‐dimensional stepping stone model to examine the generation of recombinant races within chromosomal hybrid zones. Using field‐derived ecological data and laboratory‐derived fertility estimates, we show that hybrid karyotypic races can be generated at a reasonable frequency in simulations. Our model complements others developed for flowering plants that also emphasize the potential of chromosomal hybrid zones in generating new stable karyotypic forms.
Spawning success in Atlantic salmon (Salmo salar L.): a long‐term DNA profiling‐based study conducted in a natural stream
Authors: Taggart J. B. , McLaren I. S. , Hay D. W. , Webb J. H. , Youngson A. F.
Published: March 2003

Spawning success of Atlantic salmon (Salmo salar L.) was investigated, under near‐natural conditions, in the Girnock Burn, an 8‐km long tributary of the River Dee in Scotland. Employing minisatellite‐based DNA profiling, mating outcomes were resolved over three spawning seasons by assigning parentage to progeny samples removed from spawning nests (‘redds’). While individual spawning patterns differed markedly, consistent trends were present over the 3 years studied. Multiple spawning was found to be prevalent. More than 50% of anadromous spawners of both sexes contributed to more than one redd. Up to six redds for a single female and seven for a single male were detected. Both sexes ranged extensively. Distance between redds involving the same parent varied from a few metres to > 5 km. Distances > 1 km were common. Both males and females ranged to a similar extent. Range limit was not correlated to fish size. Pairs were not monogamous, both males and females mating with different partners at different sites. Size assortative mating was apparent among 1991 spawners but was not detected for 1992 or 1995. Redd superimposition was found to be common (17–22% of redds over the 3 years), although it was not correlated to the number of anadromous spawners present. High levels of nonanadromous mature parr mating success (40–50% of total progeny sampled) were recorded, and these likely contribute greatly to the effective population size. The relevance of these findings at the individual and population level is discussed, with particular reference to management implications.
Breeding origin and migration pattern of dunlin (Calidris alpina) revealed by mitochondrial DNA analysis
Authors: Wennerberg L.
Published: March 2003

The large‐scale migration of birds has been studied extensively by recoveries of ringed birds. However, there is very little ringing data from the arctic breeding grounds of waders. Here, the migration pattern of the dunlin, Calidris alpina, is studied with population genetic markers, using haplotype frequencies to estimate the breeding origin of migrating and wintering populations. Polymerase chain reaction (PCR) and restriction analysis of DNA from the mitochondrial control region was used to study the breeding origins of morphologically similar winter populations in the western Palaearctic, and to describe the population structure of the dunlin during winter. Also migrating dunlin from various stopover sites in Europe, Africa and Asia, were analysed with respect to their mitochondrial DNA (mtDNA) haplotypes. The genetic markers clearly show that the dunlin has a parallel migration system, with populations breeding in the western Palaearctic wintering mainly in the western part of the wintering range, and dunlin populations breeding further east wintering further east. The results also show that the distance between breeding and wintering area increases eastwards in this region.
Assignment of paternity groups without access to parental genotypes: multiple mating and developmental plasticity in squid
Authors: Emery A. M. , Wilson I. J. , Craig S. , Boyle P. R. , Noble L. R.
Published: March 2003

We present a novel approach to investigating sibling relationships and reconstructing parental genotypes from a progeny array. The Bayesian method we have employed is flexible and may be applicable to a variety of situations in addition to the one presented here. While mutation rates and breeding population allele frequencies can be taken into account, the model requires relatively few loci and makes few assumptions. Paternity of 270 veined squid (Loligo forbesi) hatchlings from three egg strings collected from one location was assigned using five microsatellite loci. Paternal and maternal genotypes reconstructed for each of the three strings were identical, strongly indicating that a single female produced the strings that were fertilized by the same four males. The proportion of eggs fertilized was not equal between males in all three strings, with male 1 siring most offspring (up to 68% in string 1), through to male 4 siring the least (as low as 2.4% in string 1). Although temperature had a profound effect on incubation time, paternity did not affect this trait at 12 °C or 8 °C.
Demic structure and its relation with the distribution of an adaptive trait in Danish flea beetles
Authors: De Jong P. W. , De Vos H. , Nielsen J. K.
Published: March 2003

The flea beetlePhyllotreta nemorumis an oligophagous species using crucifers as host plants. In Denmark two populations have been found which useBarbarea vulgarisssp.arcuata(G‐type) as a host plant, whereas this plant is unsuitable for the survival of the majority ofP. nemorum. In the locations in which these two populations occur, alternative host plants are also present. The plants occur in patches, some of which contain a mixture of host plants. In this study of allozyme variation, genetic differentiation betweenP. nemorumusing different host plants in patches in the two different localities was studied hierarchically to assess substructuring of the populations. Evidence was found for low, but significant, amounts of genetic differentiation between (sub)populations using spatially separated plant patches at a distance of ≈100 m to 1 km (θ = 0.009) and between localities ≈ 44 km apart (θ = 0.026), and there was an association between genetic differentiation and geographical distance. No genetic differentiation was found between beetles from different host plants with overlapping local distributions. No evidence was thus found for sympatric host race formation. The geographical distribution of genes enablingP. nemorumto useB. vulgarisas a host plant (100%‘resistant’ beetles in samples fromB. vulgaris, but much fewer on patches containing only alternative host plants) contrasts with the relatively low amount of genetic differentiation at the neutral allozyme loci. This distribution of ‘resistant’ beetles (toB. vulgarisdefence) is likely to be influenced by local differences in selection and asymmetric gene flow.
Microsatellite diversity associated with ecological factors in Hordeum spontaneum populations in Israel
Authors: Turpeinen Timo , Tenhola Teija , Manninen Outi , Nevo Eviatar , Nissilä Eero
Published: March 2003

Microsatellite diversity at 18 loci was analysed in 94 individual plants of 10 wild barley, Hordeum spontaneum (C. Koch) Thell., populations sampled from Israel across a southward transect of increasing aridity. Allelic distribution in populations was not distributed randomly. Estimates of mean gene diversity were highest in stressful arid‐hot environments. Sixty‐four per cent of the genetic variation was partitioned within populations and 36% between populations. Associations between ecogeographical variables and gene diversity, He, were established in nine microsatellite loci. By employing principle component analysis we reduced the number of ecogeographical variables to three principal components including water factors, temperature and geography. At three loci, stepwise multiple regression analysis explained significantly the gene diversity by a single principal component (water factors). Based on these observations it is suggested that simple sequence repeats are not necessarily biologically neutral.
Y chromosome haplotyping in Scandinavian wolves (Canis lupus) based on microsatellite markers
Authors: Sundqvist A.‐K. , Ellegren H. , Olivier M. , Vilà C.
Published: March 2003

The analysis of mitochondrial DNA sequences has for a long time been the most extensively used genetic tool for phylogenetic, phylogeographic and population genetic studies. Since this approach only considers female lineages, it tends to give a biased picture of the population history. The use of protein polymorphisms and microsatellites has helped to obtain a more unbiased view, but complementing population genetic studies with Y chromosome markers could clarify the role of each sex in natural processes. In this study we analysed genetic variability at four microsatellite loci on the canid Y chromosome. With these four microsatellites we constructed haplotypes and used them to study the genetic status of the Scandinavian wolf population, a population that now contains 60–70 animals but was thought to have been extinct in the 1970s. In a sample of 100 male wolves from northern Europe we found 17 different Y chromosome haplotypes. Only two of these were found in the current Scandinavian population. This indicates that there should have been at least two males involved in the founding of the Scandinavian wolf population after the bottleneck in the 1970s. The two Scandinavian Y chromosome haplotypes were not found elsewhere in northern Europe, which indicates low male gene flow between Scandinavia and the neighbouring countries.
Introgressive hybridization inRorippa(Brassicaceae): gene flow and its consequences in natural and anthropogenic habitats
Authors: Bleeker W. , Hurka H.
Published: March 2003

Introgressive hybridization between threeRorippaspecies (R. amphibia,R. palustrisandR. sylvestris) in northern Germany has been studied using isozymes and noncoding chloroplast DNA (trnL/F spacer). Our results provide substantial evidence for different patterns of gene flow in natural and in anthropogenic environments. Hybridization and bi‐directional introgression (chloroplast DNA and allozymes) betweenR. amphibiaandR. sylvestriswere detected at the river Elbe, which is one of the last rivers in Central Europe showing a natural dynamic of erosion and sedimentation. The natural dynamic of the Elbe leads to periodic habitat disturbance and the temporal breakdown of ecological isolation barriers betweenR. amphibiaandR. sylvestris. However, the high dynamic does not provide the opportunity for persistence of the morphologically intermediate hybridR. × anceps(R. amphibia × R. sylvestris). We did not find hybrid zones betweenR. amphibiaandR. sylvestrisin the more anthropogenic landscape of northwest Germany. However, contact zones betweenR. amphibiaandR. palustriswere detected in drainage ditches in northwest Germany. We found substantial evidence for unidirectional introgression ofR. palustrismarkers (chloroplast DNA and allozymes) intoR. amphibiain the man‐made habitats. TheR. amphibiaintrogressants in the drainage ditches often showed strongly serrate upper cauline leaves instead of the entire upper cauline leaves typical forR. amphibia. We argue that landscape melioration in northwest Germany, particularly the creation of drainage ditches, favoured both hybrid‐zone formation and ecotypic differentiation withinR. amphibia.
Fine‐scale genetic structure, estuarine colonization and incipient speciation in the marine silverside fishOdontesthes argentinensis
Authors: Beheregaray Luciano B. , Sunnucks Paul
Published: March 2003

The idengification of incipient ecological species represents an opportunity to investigate current evolutionary process where adaptive divergence and reproductive isolation are associated. In this study we analysed the genetic structure of marine and estuarine populations of the silverside fishOdontesthes argentinensisusing nine microsatellite loci and 396 bp of the mitochondrial DNA (mtDNA) control region. Our main objective was to investigate the relationship among estuarine colonization, divergent selection and speciation in silversides. Significant genetic structure was detected among all marine and estuarine populations. Despite the low phylogeographic structure in mtDNA haplotypes, there was clear signal of local radiations of haplotypes in more ancient populations. Divergence among marine populations was interpreted as a combined result of homing behaviour, isolation by distance and drift. On the other hand, ecological shifts due to the colonization of estuarine habitats seem to have promoted rapid adaptive divergence and reproductive isolation in estuarine populations, which were considered as incipient ecological species. This conclusion is supported by the existence of a set of environmental factors required for successful reproduction of estuarine ecotypes. The pattern of genetic structure indicates that phenotypic and reproductive divergence evolved in the face of potential gene flow between populations. We suggest that the ‘divergence‐with‐gene‐flow’ model of speciation may account for the diversification of estuarine populations. The approach used can potentially idengify ‘incipient estuarine species’, being relevant to the investigation of the evolutionary relationships of silversides in several coastal regions of the world.
A generalized heterozygote deficiency assessed with microsatellites in French common ash populations
Authors: Morand M.‐E. , Brachet S. , Rossignol P. , Dufour J. , Frascaria‐Lacoste N.
Published: March 2003

Common ash is a temperate forest tree with a colonizing behaviour, a discontinuous spatial distribution and a peculiar and poorly known mating system. Microsatellite markers were used to study the genetic structure in natural populations of common ash. Twelve populations located in northeastern France were analysed at five loci. Levels of genetic variability within and among stands were estimated for the seedling and adult stages. As expected for a forest tree, our results reveal high levels of intrapopulation diversity and a low genetic differentiation between stands. However, a general and significant heterozygote deficiency was found, with a mean FIS of 0.163 for the seedlings and of 0.292 for the adult trees. The different explanations for such an excess homozygosity are discussed: a nonMendelian inheritance of alleles, the presence of null alleles, a Wahlund effect and assortative mating.
Islands within an island: phylogeography and conservation genetics of the endangered Hawaiian tree snail Achatinella mustelina
Authors: Holland Brenden S. , Hadfield Michael G.
Published: March 2003

Mitochondrial DNA (mtDNA) sequences were used to evaluate phylogeographic structure within and among populations of three endangered Hawaiian tree snail species (n = 86). The primary focus of this investigation was on setting conservation priorities for Achatinella mustelina. Limited data sets for two additional endangered Hawaiian tree snails, A. livida and A. sowerbyana, were also developed for comparative purposes. Pairwise genetic distance matrices and phylogenetic trees were generated, and an analysis of molecular variance was performed on 675‐base pair cytochrome oxidase I gene sequences from multiple populations of Hawaiian tree snails. Sequence data were analysed under distance‐based maximum‐likelihood, and maximum‐parsimony optimality criteria. Within the focal species, A. mustelina, numbers of variable and parsimony informative sites were 90 and 69, respectively. Pairwise intraspecific mtDNA sequence divergence ranged from 0 to 5.3% in A. mustelina, from 0 to 1.0% in A. livida and from 0 to 1.9% in A. sowerbyana. For A. mustelina, population genetic structure and mountain topography were strongly correlated. Maximum genetic distances were observed across deep, largely deforested valleys, and steep mountain peaks, independent of geographical distance. However, in certain areas where forest cover is presently fragmented, little mtDNA sequence divergence exists despite large geographical scales (8 km). Genetic data were used to define evolutionarily significant units for conservation purposes including decisions regarding placement of predator exclusion fences, captive propagation, re‐introduction and translocation.
Transgenic potatoes with enhanced levels of nematode resistance do not have altered susceptibility to nontarget aphids
Authors: Cowgill S. E. , Wright C. , Atkinson H. J.
Published: March 2003

Cysteine proteinase inhibitors (cystatins) confer resistance to plant‐parasitic nematodes when expressed in transgenic plants. The survival and growth of nymphs of the peach‐potato aphid, Myzus persicae, were adversely affected when cystatins were added to artificial diets. When aphids were clip‐caged onto transgenic plants expressing chicken egg white cystatin (CEWc) there was no adverse effect on aphid fitness. Field populations of aphids on transgenic Desiree potatoes, expressing CEWc or a modified version of oryzacystatin I, were not significantly different from populations on control Desiree plants. The effect of other nematode management options on aphid numbers was also studied. A conventionally bred cultivar, with partial nematode resistance, supported higher populations of aphids than the transgenic lines at the beginning of the sampling period. Peak aphid densities on the untreated control and untreated transgenic lines were 7 and 5.2 aphids per plant. Aldicarb, commonly used to control nematodes on potatoes, reduced the value to less than 0.2 aphids per plant. The results demonstrate that levels of expression in the plant tissue actually consumed are important in determining the risk of cystatins to nontarget invertebrates. The study also highlights the importance of including currently used management options in any assessment of the impact of transgenic plants on nontarget organisms.
Maternal lineages ofPinus densata, a diploid hybrid
Authors: Song Bao‐Hua , Wang Xiao‐Quan , Wang Xiao‐Ru , Sun Lan‐Ju , Hong De‐Yuan , Peng Pei‐Hao
Published: March 2003

Previous morphological, allozyme and chloroplast DNA data have suggested thatPinus densataoriginated through hybridization betweenP.tabuliformis andP.yunnanensis. In the present study, sequence and restriction site analyses of maternally inherited mitochondrialnad1 intron were used to detect variation patterns in 19 populations ofP.tabuliformis,P.yunnanensisandP.densata. A total of three mitotypes (A, B, C) were detected. All but one of the populations ofP.yunnanensispossessed mitotype B while all populations ofP.tabuliformishad mitotype A.Pinus densatapopulations, on the other hand, harboured both mitotypes A and B, which are characteristic ofP.tabuliformisandP.yunnanensis, respectively.This result gives strong additional evidence supporting the hybrid origin of this diploid pine. The distribution of mitotypes indicated very different mating compositions and evolutionary history amongP.densatapopulations. It seems that local founder populations and backcrosses may have played important roles in the early establishment ofP.densatapopulations. The uplift of the Tibetan Plateau had a significant impact on the distribution of maternal lineages ofP.densatapopulations.
The phylogeography and connectivity of the latitudinally widespread scleractinian coralPlesiastrea versiporain the Western Pacific
Authors: Rodriguez‐Lanetty M. , Hoegh‐Guldberg O.
Published: March 2003

Whereas terrestrial animal populations might show genetic connectivity within a continent, marine species, such as hermatypic corals, may have connectivity stretching to all corners of the planet. We quantified the genetic variability within and among populations of the widespread scleractinian coral,Plesiastrea versiporaalong the eastern Australian seaboard (4145 km) and the Ryukyu Archipelago (Japan, 681 km) using sequences of internal transcribed spacers (ITS1‐2) from ribosomal DNA. Geographic patterns in genetic variability were deduced from a nested clade analysis (NCA) performed on a parsimony network haplotype. This analysis allowed the establishment of geographical associations in the distribution of haplotypes within the network cladogram, therefore allowing us to deduce phylogeographical patterns based under models of restricted gene flow, fragmentation and range expansion. No significant structure was found among Ryukyu Archipelago populations. The lack of an association between the positions of haplotypes in the cladogram with geographical location of these populations may be accounted for by a high level of gene flow ofP. versiporawithin this region, probably due to the strong Kuroshio Current. In contrast, strong geographical associations were apparent among populations ofP. versiporaalong the south‐east coast of Australia. This pattern of restricted genetic connectivity among populations ofP. versiporaon the eastern seaboard of Australia seems to be associated with the present surface ocean current (the East Australian Current) on this side of the south‐western Pacific Ocean.
The genetic structure of natural and reintroduced roe deer (Capreolus capreolus) populations in the Alps and central Italy, with reference to the mitochondrial DNA phylogeography of Europe
Authors: Vernesi C. , Pecchioli E. , Caramelli D. , Tiedemann R. , Randi E. , Bertorelle G.
Published: March 2003

The first hypervariable fragment (HVI) of the mitochondrial DNA control region was sequenced in 90 individuals of the European roe deer (Capreolus capreolus) from the Alps, central Italy and Spain. Pooling these data with 70 published sequences from several European regions, we were able to identify patterns of divergence within the Italian peninsula, and in Europe in general. The results we obtained can be summarized as follows. First, the genetic structure of European roe deer populations is substantial (ΦST values around 0.6). Second, the divergence between some central Italian populations, the Alpine group (which is genetically close to the French, the Spanish and the Norwegian samples) and the Eastern European populations seems to reflect Upper Pleistocene subdivisions, possibly related to three southern European refugia. Third, a different group of central Italian individuals probably diverged more recently from the Alpine group, and their attribution to the subspecies C. c. italicus does not appear justified. Fourth, the analysis of mitochondrial DNA in the roe deer can be used to identify recently reintroduced animals in the western Alps which clearly cluster within the Eastern European group, thus providing an important tool for conservation and management strategies for this species.
Applications of selective neutrality tests to molecular ecology
Authors: Ford Michael J.
Published: March 2003

This paper reviews how statistical tests of neutrality have been used to address questions in molecular ecology are reviewed. The work consists of four major parts: a brief review of the current status of the neutral theory; a review of several particularly interesting examples of how statistical tests of neutrality have led to insight into ecological problems; a brief discussion of the pitfalls of assuming a strictly neutral model if it is false; and a discussion of some of the opportunities and problems that molecular ecologists face when using neutrality tests to study natural selection.
Investigation of the population genetic structure and mating system in the antPheidole pallidula
Authors: Fournier Denis , Aron Serge , Milinkovitch Michel C.
Published: March 2003

The origin of eusociality in haplo‐diploid organisms such as Hymenoptera has been mostly explained by kin selection. However, several studies have uncovered decreased relatedness values within colonies, resulting primarily from multiple queen matings (polyandry) and/or from the presence of more than one functional queen (polygyny). Here, we report on the use of microsatellite data for the investigation of sociogenetic parameters, such as relatedness, and levels of polygyny and polyandry, in the antPheidole pallidula. We demonstrate, through analysis of mother–offspring combinations and the use of direct sperm typing, that each queen is inseminated by a single male. The inbreeding coefficient within colonies and the levels of relatedness between the queens and their mate are not significantly different from zero, indicating that matings occur between unrelated individuals. Analyses of worker genotypes demonstrate that 38% of the colonies are polygynous with 2–4 functional queens, and suggest the existence of reproductive skew, i.e. unequal respective contribution of queens to reproduction. Finally, our analyses indicate that colonies are genetically differentiated and form a population exhibiting significant isolation‐by‐distance, suggesting that some colonies originate through budding.
The influence of mating system, demography, parasites and colonization on the population structure ofBiomphalaria pfeifferiin Madagascar
Authors: Charbonnel N. , Angers B. , Rasatavonjizay R. , Bremond P. , Debain C. , Jarne P.
Published: March 2003

Current evolutionary forces and historical processes interact to shape the distribution of neutral genetic variability within and among populations. Focusing on the genetics of recently introduced organisms offers a good opportunity to understand the relative importance of these factors. This study concerns variation at 8 polymorphic microsatellite loci in 30 populations ofBiomphalaria pfeifferi. The sampling area spans most of the species’ range in Madagascar where it was probably introduced recently. Extremely low variation was found within all populations studied, which may partly result from high selfing rates. However, this cannot account for the variance of variation across populations, which is better explained by habitat openness (that reflects environmental stochasticity), the prevalence of the parasitic trematodeSchistosoma mansoniand historical demography (colonization and subsequent bottlenecks). Large global differentiation was also observed, suggesting that current gene flow among populations is limited to small distances, within watersheds and to few individuals. Our data set also allowed us to test several hypotheses regarding colonization, based on bottleneck and admixture tests. The observed pattern requires at least two independent introductions from slightly differentiated genetic sources in the western part of Madagascar. Another introduction, from a very different genetic origin, should also be postulated to explain the genetic composition of eastern populations. That this introduction occurred recently suggests that the colonization of Madagascar byB. pfeifferiis an ongoing process.