Allozyme Analysis Research Articles

Patterns of morphological and genetic variability in UK populations of the shore crab, Carcinus maenas Linnaeus, 1758 (Crustacea: Decapoda: Brachyura)

Previous research has identified extensive inter-population variability in the morphology of the shore crab ( Carcinus maenas L.). To determine the source of this variation (genetic or environmental), morphological and genetic data were analysed from crabs collected from eight sites around the coast of the UK. Ten morphometric traits were measured from over 800 crabs and the degree of morphological similarity among sites was calculated using multivariate techniques. Allozyme electrophoresis was used to investigate patterns of genetic similarity. Extensive morphological variability was detected: eight out of the ten morphometric traits analysed were useful when discriminating between crabs from each site. Discriminant function analysis revealed that over 35% of individuals could be classified to their site of origin on the basis of their morphology. In contrast, the allozyme analysis revealed low levels of genetic variability, both within the meta-population and among the crab population at each site. Pairwise comparisons revealed a moderate correlation between the degree of morphological and genetic similarity of crabs at each site, which suggests that the observed phenotypic variability has a genetic component. However, only around 20% of the phenotypic variability detected was associated with the patterns of genetic similarity. This means that patterns of morphological variability in this species are largely determined by the local environmental conditions: local factors could have a within-generation selective influence on mean trait values or C. maenas may exhibit phenotypic plasticity.

Occurrence and cross-infection of Phytophthora infestans on hairy nightshade (Solanum sarrachoides) and potato (Solanum tuberosum) in Maine

Late blight, caused by Phytophthora infestans, is a significant disease in all potato-growing regions of the world. Identification of additional hosts is critical for understanding potential sources of inoculum. In 2004, late blight was observed on leaves and stems of hairy nightshade (Solanum sarrachoides), a common weed in many potato fields in Maine. Diseased nightshade plants were detected in 2 of 18 locations having potato late blight. Lesions from diseased nightshade leaves ranged from 0.25 to 9 cm2 and, on diseased stems, the range of lesion length was 4.5 to 13.8 cm. Isolations from diseased samples and microscopic observations confirmed the presence of P. infestans. Based on allozyme analysis, 27 representative isolates of P. infestans from hairy nightshade were identified as the US 8 genotype. Pathogenicity tests and Koch's postulates were satisfied by inoculating intact plant and detached nightshade leaves with P. infestans isolated from hairy nightshade. Cross-infection of nightshade, potato leaves (‘Shepody’), and potato tubers (‘Yukon Gold’) occurred when the inoculum source was either hairy nightshade or potato. When the inoculum source was hairy nightshade, the mean infection frequency at 18 °C was 50% and 67% on hairy nightshade and potato leaves, respectively. Inoculation with Phytophthora infestans isolated from potato resulted in average infection frequencies of 73% and 83% on nightshade and potato, respectively. These results suggest that hairy nightshade may be an inoculum source for late blight in potato fields. Management practices for controlling hairy nightshade would benefit potato production.

Rare recent natural hybridization in Hieracium s. str. – evidence from morphology, allozymes and chloroplast DNA

The first proven data on natural hybridization in the genus Hieracium s. str. are presented. Plants with intermediate morphological characters between the diploids H. alpinum and H. transsilvanicum were found in the Muntii Rodnei (Romanian Eastern Carpathians) in 2001 and in the Chornohora Mts (Ukrainian Eastern Carpathians) in 2003. While plants of intermediate morphology between usually so called basic species are usually tri- or tetraploid in Hieracium s. str., these plants were diploid (2n=18) like both parental species in this region. The Romanian plant did not produce fertile achenes in free pollination and in control backcrosses with H. transsilvanicum, two hybrids from Ukraine were completly seed sterile in free pollination and reciprocal crosses. Pollen stainability as an indirect measure of male fertility was quite high in the studied Ukrainian hybrid plants and similar to the parental taxa. Evidence from allozyme analysis also confirmed the hybrid origin of the studied plants. Sequencing and PCR-RFLP analyses of the trnT-trnL intergenic spacer revealed that all hybrid plants had the H. transsilvanicum chloroplast DNA haplotype. Maternal inheritance of chloroplast DNA in this particular cross was proved with artificial hybrids from reciprocal experimental crosses between H. alpinum and H. transsilvanicum. In both localities, the natural hybrid plants were found in disturbed habitats, exceptionally allowing contact of the otherwise ecologically vicariate parental species. Morphologically, the hybrid plants belong to H. × krasani Wol.

Genetic diversification among cytotypes of Ranunculus silerifolius Lév. (Ranunculaceae)

AbstractGenetic variations of the facultatively autogamous species Ranunculus silerifolius, which show intraspecific chromosomal polymorphisms (Karatsu‐cytotype, Matsuyama‐cytotype, Mugi‐cytotype and Otaru‐cytotype), were investigated in 95 populations using allozymic analysis. Sixteen loci of nine enzyme systems were resolved. Three loci were monomorphic for all populations. On average, 26% of the loci were polymorphic; the 16 loci resolved gave a total of 49 alleles with a mean number of 1.29 alleles per locus. We could not detect any genetic differentiation estimated from allozymic polymorphisms among cytotypes distinguished by chromosome structures in this species. The average genetic distance between populations was large (D = 0.129), indicating a high level of genetic differentiation and a low level of gene flow (Nm = 0.171) among the populations, whereas that between cytotypes was very small (D = 0.008), possibly a result of the relatively short period of time after the occurrence of cytotypes. The overall levels of genetic variation were low as with other facultatively autogamous species. The gene differentiation coefficient among populations, GST, was high (0.579), which probably reflected the inbreeding in this species. The absence of a correlation between genetic distance and geographic distance may also have resulted from inbreeding.

Is the last glaciation the only relevant event for the present genetic population structure of the meadow brown butterfly Maniola jurtina (Lepidoptera: Nymphalidae)?

Phylogeographical studies are available for a considerable number of European species, but few analyses exist for temperate species with very large and fairly continuous populations that are also absent from Northern Europe. Therefore, we studied the butterfly Maniola jurtina as a model for this group. The species has two major genetic lineages (mean genetic distance between lineages: 0.033; FCT: 0.052), most probably evolving in glacial differentiation centres in the western and eastern Mediterranean. The onset of this differentiation might have been the beginning of the last glacial stage maximum some 40 kyr bp. A hybrid zone between these two lineages exists in western Central Europe. No genetic substructures have been found within the two lineages (FSC: 0.017) and average genetic distances are very small. Therefore, it is highly probable that postglacial expansion was of the phalanx type. There is, at most, very limited differentiation at regional and local scales. However, the genetic diversity within populations is high (means: A: 2.68; HE: 17.2%; P: 78%), as would be predicted for such a common species. Comparison of these results with a published allozyme analysis revealed a similar phylogeographical pattern, but lower genetic diversity in the latter. Morphological patterns of wings and genitalia show similar geographical patterns as allozyme data. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85, 419–431.

Allozyme variations and classification of Trapa (Trapaceae) in Japan

Trapa L. (Trapaceae) is one of the most common aquatic plants in Japan. However, its taxonomic treatment has differed among authors. As a step toward a revision of Japanese Trapa, we analyzed allozymes in plant samples collected from 55 populations and tentatively classified into 6 taxa. Allozyme analysis indicated three distinct groups corresponding to the size class of the fruits: T. incisa (small), T. japonica group (medium), and T. natans group (large). The development of lower protuberances or spines and the presence or absence of tubercles had no correspondence to allozymic differentiation and thus are to be considered as variants within taxa. Fixed heterozygosity found in the T. japonica group indicates that the group might be of hybrid origin between T. incisa and plants of the T. natans group.

Maintenance of Phenotypic and Genotypic Diversity in Managed Populations of Stenocereus Stellatus (Cactaceae) by Indigenous Peoples in Central Mexico

The columnar cactus Stenocereus stellatus is used in Central Mexico for its edible fruits which are harvested in wild, managed in situ and cultivated populations. Management in situ of wild populations is conducted by selectively sparing and enhancing the abundance of plants with desirable phenotypes when fields are cleared for agricultural use. Cultivation of desirable phenotypes is carried out by vegetative propagation in homegardens. Effects of human management on morphological and genetic variation of S. stellatus were analyzed by comparing morphological diversity indices (MD, based on Simpson’s index) and expected (He) heterozygosity indices from allozyme analysis, in wild, managed in situ, and cultivated populations from La Mixteca and the Tehuacan Valley regions. Morphological diversity was similar among regions, but populations from the wetter La Mixteca region averaged higher genetic variation (He = 0.279) than populations from Tehuacan (He = 0.265). On average, populations manipulated by people had higher levels of variation (MD = 0.479 ± 0.012, He = 0.289 in cultivated populations; MD = 0.461 ± 0.014, He = 0.270 in managed in situ populations) than wild populations (MD = 0.408 ± 0.017, He = 0.253), which is apparently due to a continual introduction and replacement of plant materials in the manipulated populations. The results illustrate that human management may not only maintain but also increase both morphological and genetic diversity of manipulated plant populations in relation to that existing in the wild. Managed in situ and cultivated populations of S. stellatus are important reservoirs of variation, and are crucial for the general maintenance of diversity in wild populations. These populations may play a principal role in designing strategies for the conservation of variation of this cactus.

Isolation and characterization of two dinucleotide and four tetranucleotide polymorphic microsatellite loci in the Iberian midwife toad Alytes cisternasii

AbstractThe Iberian midwife toad Alytes cisternasii is an endemic species of the southwestern and central parts of the Iberian Peninsula. Allozyme analysis of Iberian midwife toads indicated no inter‐ or intrapopulation variation and a more sensitive method is required to quantify genetic differentiation and gene flow between populations of this species. We describe here the development of primers for the amplification by the polymerase chain reaction (PCR) of six polymorphic microsatellite loci in A. cisternasii.

Evolution of mosaic hybrid zone between invasive and endemic species of Cyprinidae through space and time

Hybridization phenomena can be considered in different ways. Hybridization studies can be used to elucidate some aspects of speciation and adaptation. However, hybridization may be a threat to endemic species. Here, we studied bidirectional introgression between two sympatric species of Cyprinidae: Chondrostoma toxostoma toxostoma and C. nasus nasus. Analysis of morphology, allozymes and mtDNA sequences revealed that the hybridization between these two cyprinids takes different forms in the same river. The mosaic hybrid zone (so called because of the absence of a simple cline) appeared to be partitioned due to the proportions of the two species along a spatial scale. The proportion of each hybrid group in this zone was unstable over a 5-year period. We propose various protection/conservation states for the C. t. toxostoma populations based on the level of introgressive hybridization and the genetic structure of both species in ‘pure’ populations.

Inheritance of amplified fragment length polymorphism markers and their utility in population genetic analysis of Plecoglossus altivelis

The reproducibility, mode of inheritance and polymorphism of amplified fragment length polymorphism (AFLP) markers were examined in ayu Plecoglossus altivelis(Salmoniformes: Plecoglossidae). The AFLP markers were highly reproducible, their inheritance following Mendelian expectations. The number of fragments amplified (34–134), polymorphic ratio (0·15–0·78) and average heterozygosity (0·02–0·25) of the AFLP markers showed significant variation among six primer pairs and among ayu populations, including a landlocked Lake‐Biwa population, two amphidromous populations (P. a. altivelis) and two Ryukyu‐ayu populations (P. a. ryukyuensis). Although AFLP analysis provided similar results in intra‐population diversity and relationships among populations to those found by analyses of allozymes, microsatellites and mitochondrial DNA sequences, AFLPs showed higher polymorphisms and hence greater distinction between genetically close populations.

Sistema de reprodução em Caesalpinia echinata Lam. implantada em arboreto experimental

The mating system of Caesalpinia echinata Lam. implanted in arboretum was studied by allozymes analysis of progeny arrays using the mixed-mating model and correlated-mating model. Deviations from mixed-mating model were observed from heterogeneity of pollen pools allele frequencies that fertilized different trees. The multilocus outcrossing rate was high (tm = 0.969), indicating that the species is predominantly allogamous. The high variation observed in the individual outcrossing rate (tranged from 0.77 to 1.00) shows that the species is not auto-incompatible. It was detected significant positive difference between multilocus and single locus outcrossing rate suggesting that biparental inbreeding has occurred (tm - ts = 0.078). High value of paternity correlation was detected (rp = 0.822), demonstrating that families are composed by full sibs, mainly. The coefficient of coancestry within families (qxy = 0.269) was higher than expected in half-sibs families (0.125). The results are discussed in the viewpoint of the sampling to genetic conservation and environmental recovering.

A long term lake-salinity record and its relationships to Daphnia populations

Sediment cores from the shallow, presently saline, volcanic maar lake of Tower Hill were collected in March 2000, dated using 210 Pb, and analysed for diatoms to infer changing salinity levels. Diatom inferred salinity was used to assess the hatching response of incorporated Daphnia ephippia. The early growth rate of Daphnia from different core depths, in media with two different salinities (0.5 g/L and 4 g/L) was also measured. Sediments have steadily accumulated in the Tower Hill basin over the past 50 years since the lake was last reported to have dried. The diatom record indicates a fairly stable salinity regime, with salt concentrations fluctuating between 1 and 2 g/L until 1990, followed by an exponential increase in salt concentrations peaking in the year 2000 at around 13 g/L. There were significant fluctuations in ephippia densities, with at least two large peaks and several periods of low ephippial accumulation. Ephippial densities were only weakly correlated with salinity changes. Maximum hatching of ephippia, all of the one species, Daphnia thomsoni, occurred in the top 7cm of the cores, corresponding to the past 10 years. The oldest eggs to hatch were from sediments dated around 37 years old. The body length after six days growth of 19 clones, from 3 core sections (0-2cm; 2-4cm; >4cm) was measured under conditions of low salinity (0.5 g/L) and high salinity (4 g/L). Surprisingly, all but one clone reached a larger size at high salinity. However, clones from the top 2cm, which were produced during the lake's recent period of high salinity showed the strongest growth response at 4 g/L. Analysis of allozymes at three polymorphic loci did not find any evidence of genetic differentiation based on allelic frequencies. In order to assess possible reasons for differences in hatching patterns observed in cores taken in 2000, two additional cores were collected in September 2002. One showed a similar hatching pattern to the 2000 cores, and the other exhibited a more even pattern of hatching over its length.

Genetic differentiations of Hynobius naevius (Amphibia, Hynobiidae) as revealed by allozyme analysis

A survey of genetic variation of lotic breeding salamander Hynobius naevius by starch gel electrophoresis using 26 populations from southwestern Japan revealed the presence of two genetically distinct groups (GROUP-A and B) which overlap distributional ranges in some parts of Kyushu. Degree of genetic differentiation between the two groups was larger in Kyushu, including sympatric area, than in allopatric areas. We surmise that the two groups first differentiated allopatrically and overlapped their distributions secondarily. The first genetic differentiation is considered to have occurred in the Pliocene as a result of isolation between northern (GROUP-A) and southern (GROUP-B) ancestral populations by the formation of the Seto Inland Sea, largely separating the present distributions of the two groups. Genetic diversities within the GROUP-A seem to have become complicated by isolations, disappearances of local populations, and subsequent range expansion of distributions in Chugoku and northern half of Kyushu regions. Within the GROUP-B, diversities first formed by isolation by distance have been retained and accelerated secondarily by the formations of the Kii and Bungo straits. Sympatric populations of the two groups in northern half of Kyushu seem to have overlapped their ranges by niche segregation.

A Genetic Assessment of Ohio River Walleyes

AbstractWalleyes Sander vitreus from nine Ohio River pools were examined by means of two independent restriction fragment length polymorphism (RFLP) analyses of mitochondrial DNA, allozyme analysis of nuclear DNA, and microsatellite analysis of nuclear DNA. The primary objective of this project was to document genetic variation and population structuring in walleyes among the nine pools analyzed. Both RFLP analyses revealed the presence of a distinct haplotype that was most abundant in walleyes collected from two tailwaters in the upper Ohio River (river miles 54 and 84), suggesting a remnant native population. The allozyme analysis also revealed differentiation between walleyes with the two haplotypes, even though there were no fixed differences. The microsatellite analysis indicated highly significant structuring among the nine pools analyzed. A lack of microsatellite differentiation between the two haplotypes detected in the same pool suggests that the fish are freely interbreeding. If the unique haplotype is from a remnant native stock of walleyes in the Ohio River, it could serve as a genetic marker to establish a broodstock for stocking walleyes in the upper Ohio River drainage. The second objective of the project was to evaluate the accuracy of field identifications of walleyes, saugers S. canadensis, and their hybrid, saugeyes, and to determine the direction of hybridization. Twenty‐seven percent of the fish identified as walleyes were misidentified (10% were FX hybrids and 17% F1 hybrids). All F1 hybrids were from walleye females and sauger males.

Origin and evolution of the Robertsonian populations of the house mouse (Rodentia, Muridae) in Tunisia based on allozyme studies

The central coastal region of Tunisia harbours two chromosomal races of the house mouse (2n = 22, 22Rb; 2n = 40, 40Std), which are genetically differentiated and show a high level of reproductive isolation. This study presents an allozyme analysis of house mice from the inland city of Kairouan 75 km from the coastal region. Results showed that the 22Rb and 40Std mice from Kairouan shared the same high degree of variability, and were not genetically differentiated. This contrasts with the genetic data registered for the two chromosomal races from the coastal towns, in which a particularly low genic diversity was observed in the 22Rb populations. As the two races in Kairouan show the same low hybridization rates as the populations in the coastal region, these results argue in favour of a local differentiation of the Rb race in Tunisia, most likely originating in Kairouan. The data further suggest that the decrease in variability observed in the coastal 22Rb populations is related to a founder effect or a bottleneck following the introduction of mice from Kairouan into one of these localities, prior to their dispersion throughout the coastal region.

Genetic variation among 11 Abies concolor populations based on allozyme analysis

In order to obtain information on the genetic structure of Abies concolor and the genetic variation among 11 populations introduced from America to China, allozyme analysis based on starch gel electrophoresis technology was used. 24 loci of 10 allozyme systems were mensurated, and the genetic structure and genetic diversity of the 11 populations of A. concolor evaluated. The results show that the genetic variation among is significant, and the genetic variation within A. concolor populations is more important. In contrast with other conifers, the variation of A. concolor is above the average level of conifers, and higher than the same level of Abies. The percentage of polymorphic loci (P) was 62.5%, the number of alleles per locus (A) 2.08, the number of effective alleles per locus (A e) was 1.37, the expected heterozygosity (H) 0.204, and the Shannon information index (I) 0.351 7. There is a short genetic distance (D=0.061) and a low gene flow (N m=0.839 4) among the 11 introduced populations of A. concolor with high genetic variation. The genetic differentiation coefficient (G st) was 0.229 5, which is higher than that of the mean in Abies or Pinus.

Clonal Diversity and Allelic Relationships between Two Closely Related Species of Columnar Cacti from the Sonoran Desert:Stenocereus erucaandStenocereus gummosus

Stenocereus eruca and Stenocereus gummosus are two closely related columnar cacti of the Sonoran Desert that are thought to be highly clonal. In addition, it has been suggested that S. eruca has recently been derived from an S. gummosus–like ancestor. We used allozymes analysis to test these hypotheses and to describe levels of genotypic diversity in populations of both taxa. Allelic composition in S. eruca was a subset of the composition found in S. gummosus, while polymorphism and expected heterozygosity were greater in S. gummosus, supporting the hypothesis that S. eruca is a recently derived species. The proportion of unique genotypes ($$G/N$$) and genotype diversity (D) varied from 0.42 to 0.68 and from 0.78 to 0.98, respectively, among populations of S. eruca and from 0.64 to 0.96 and from 0.96 to 1.00, respectively, among populations of S. gummosus. The evidence on clonal diversity indicates that both species combine clonal growth and sexual recruitment as mechanisms of regeneration and that S. eruca seems to rely more on clonal propagation than does S. gummosus. We hypothesize that the procumbent growth habit of S. eruca in the plains of Magdalena may have evolved in response to aeolian dune formation during the Pleistocene.

Allozyme analysis of geographical and seasonal variation of Illex coindetii (Cephalopoda: Ommastrephidae) from central Mediterranean and Iberian Atlantic

Previous morphological studies of Illex coindetii from the Mediterranean have shown both juvenile and mature individuals all year round suggesting an homogeneous population pattern, however, seasonal spawning variation seems to exist varying with geographical area. Present work analysed 240 individuals from the northern Tyrrhenian and Atlantic Iberian waters at the four year-round seasons using 33 presumptive enzyme-coding loci to compare geographical and temporal variances. Genetic variability was low (Ho=0·02–0·04). Moderate variation at some loci was found due to both temporal and geographical factors (12% of total genetic variance) and to temporal variance (FST=0·004–0·015). Unweighted pair-group method using arithmetric averages (UPGMA) and Multidimensional scaling–minimum spanning tree (MDS–MST) analyses after Cavalli-Sforza & Edwards (1967) chord genetic distances showed the summer Italian and the spring Atlantic samples as the most divergent among the whole.

Life history and allozyme diversification in regional ecomorphs of the Hyalella azteca (Crustacea: Amphipoda) species complex

In North America, several species in the freshwater amphipod genus Hyalella occur as one of two alternative phenotypic types, or ‘ecomorphs’, each possessing life history traits that allow success in alternative habitats that differ in predation regime. This study documents life history diversification, reproductive isolation and allozyme differentiation of Hyalella ecomorphs in Oklahoma, and compares these results to previously reported patterns of phenotypic and systematic diversification in Michigan. As in Michigan, two ecomorphs are common in Oklahoma, with an early maturing, small sized ecomorph found in habitats containing Lepomis sunfish, which prey on Hyalella, and a late reproducing, large sized ecomorph found in fishless habitats and in very shallow margins of large reservoirs. Allozyme analysis and laboratory interbreeding trials demonstrated that ecomorphs in Oklahoma are reproductively isolated species. Phenotypically, these species are very similar to species of the same ecomorph in Michigan. Large ecomorph species in the two regions differ substantially in allozyme allele composition in a pattern consistent with reproductive isolation, yet these species did not differ in a comparison of phenotype. The small ecomorph in Oklahoma is similar in phenotype to two of three small ecomorph species in Michigan. Overall, this study supports the hypothesis that Hyalella diversification in North America is characterized by the evolution of similar phenotypic solutions to comparable ecological challenges. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 84, 161–175.

Genetic variations in Lycoris radiata var. radiata in Japan

The genetic variations of Lycoris radiata var. radiata, a completely sterile triploid from Japan, were examined by comparing the nucleotide sequences of genomic DNA regions in 11 triploid strains sampled from Japan and four triploid strains sampled from China, and in two diploid strains of Lycoris radiata var. pumila, which is endemic to China and fertile. For this purpose, two genes were analyzed, the lectin gene in the nuclear genome and the maturase gene in the chloroplast genome. A clear genetic constancy was observed in their DNA nucleotide sequences. For both genes, completely identical nucleotide sequences were detected in the 11 Japanese and four Chinese triploid strains and also between the two Chinese diploid strains. However, some genetic variations were observed between the Japanese and Chinese triploid strains, and between the triploid and diploid strains. These results are consistent with the findings obtained from previous chromosome karyotype analyses and allozyme analyses. In addition, in our preliminary FISH analysis of the physical mapping of the rRNA gene family, the 18S-5.8S-26S rRNA and 5S rRNA loci were localized on six and four chromosomes, respectively. Regarding the 18S-5.8S-26S rRNA loci, two were associated with two SAT chromosomes. The remaining four were distinguished by having no secondary constriction. Localization of 5S rRNA loci to chromosome spreads revealed three sites on the proximal part of the long arm of three acrocentric chromosomes and one site on the distal part of the long arm of the SAT chromosome; the latter site was juxtaposed to the 18S-5.8S-26S rRNA loci. These findings indicate that L. radiata var. radiata is not a typical autotriploid. The present paper discusses the possible origin of L. radiata var. radiata from a diploid variety of L. radiata var. pumila, based on the molecular cytogenetic analysis and DNA sequence analysis.