Allozyme variation and evolutionary relationships of grain amaranths (Amaranthus spp.)

Summary Allozyme studies in amaranth provided useful assays of genetic variation in order to verify the patterns inferred from morphological traits, for elucidating the genetic structure of landraces, and for the studies of evolutionary relationships among wild, weedy and crop species. Thirty-four populations of cultivated New World amaranths were surveyed along with 21 weedy New World populations for allozyme variation at nine electrophoretic enzyme loci. Eleven populations of cultivated amaranths from the Indian State of Uttar Pradesh and six from Nepal were also surveyed for a comparison. In the New World populations, heterozygosity was low, and different populations ranged from 0 to 44% polymorphic loci. Adjacent populations were often fixed for different alleles or had very different allele frequencies at certain loci, with no apparent geographical patterns. Diversity index H was partitioned into the intra- and interpopulation as well as the interspecific components of variability. The crop versus weed genetic distances were the largest, whereas the intra- and interpopulation components of H were about equal. Genetic structure of all three species of the New World amaranths together can be described as a collection of distinct populations, each more or less a heterogeneous collection of highly homozygous individuals. The North Indian populations showed relatively less allozyme variability with the most common alleles same as those of Mexican landraces. Alleles at several loci proved to be diagnostic of the crop and weed groups, and of the three individual crop species. Genetic distances based on pooled gene frequencies showed the three crop species to be generally more closely related inter se than they were to their putative weedy progenitor species, respectively (with the exception of the weed-crop pair A. quitensis and A. caudatus). This implies a single domestication event involving A. hybridus as the common ancestor rather than three separate domestication events. Close similarity between A. caudatus and A. quitensis might have resulted from transdomestication based on a weedy or semi-domesticated species having migrated from Meso-America to South America. This preliminary report must now be expanded by further ecogeographical, cytogenetic and population studies on new extensive collections from the areas of early domestication. Some evidence of recent introgression and/or segregation of crop-weed hybrids between A. caudatus and A. retroflexus is available in the form of rare individuals in crop populations with crop allozyme genotypes except for a single homozygous weedy allele.     

The search for hidden enzymatic variation in the aphid Macrosiphum rosae (L.)

Summary Using two different buffer systems and up to 6 different electrophoretic polyacrylamide gel concentrations, hidden enzymatic variability was investigated in samples of the rose aphid Macrosiphum rosae. MDH1, PGM1, SDH, EST and LAP were found to be polymorphic. No additional variation was observed by changing the test conditions compared to those of earlier investigations using starch gel electrophoresis.     

Discovery of a diploid population of theHemidactylus garnotii-vietnamensis complex (Reptilia: Gekkonidae)

A diploid member of the parthenogenetic gekkonid species complexHemidactylus garnotii-vietnamensis was discovered for the first time from Thailand. This gecko, seemingly unisexual and parthenogenetic, possesses 2n=2x=38 chromosomes, showing distinct heteromorphisms. The absence of bisexual congeneric species with a combination of karyomorphs to produce this karyotype indicates the occurrence of chromosomal rearrangements after the initial estabilishment of a diploid clonal lineage of hybrid origin. Results of karyotypic comparisons of the present sample and the three known triploid species belonging to theH. garnotii-vietnamensis complex suggest that a triploid karyomorph similar to that ofH. vietnamensis has first emerged through an insemination of the diploid parthenogen's egg by the sperm from a bisexual species having 44 chromosomes (all telocentric), and that the karyomorph subsequently experienced some minor chromosomal aberrations to produce the karyomorphs ofH. vietnamensis andH. garnotii. The origin of theH. stejnegeri karyotype still remains an open question for future studies.     

Microgeographic differentiation in a stream population of Goodea atripinnis (Goodeidae) from the Mexican Plateau

Synopsis Significant genic differentiation occurred in samples of a stream population of Goodea atripinnis(Goodeidae) from a 1 km segment of the Rio Teuchitlan, Jalisco, Mexico. The lack of obvious selection gradients and physical barriers to migration over such short distances suggests that stochastic factors (seasonal reductions in stream flow, behavior) are involved in the differentiation. The extent of this phenomenon and its potential importance to the study of fish populations are discussed.To whom reprint should be sent.     

The biology of the stoat (Mustela erminea) in the National Parks of New Zealand III. Morphometric variation in relation to growth,geographical distribution,and colonisation

Abstract

A total of 1599 stoats were collected from 14 study areas (including all 10 National Parks) from 1972 to 1976. Samples were larger in summer, and contained more females. Young stoats are born in September-October, and females reach adult weight by the following March, though males not until after August. There was significant geographic variation in the body size of adult stoats sampled: males from lowland podocarp/broadleaved forests averaged 3% smaller than males from upland beech forests in skull length, and 4% smaller in head-and-body length. This pattern was repeated, less clearly, in females and in young (approximately 2–5 months old). In contrast with stoats in Britain, assumed to be still the same size as the colonising stock introduced into New Zealand in 1884 and subsequently, males from lowland podocarp forests were unchanged or possibly smaller, and males from upland beech forests were larger; females were larger in all habitats. In males, the extent of geographic variation is almost as great in New Zealand as in the whole of continental Europe. Possible explanations of this pattern are discussed.     

Cytological and Reproductive Studies of Japanese Diplazium (Woodsiaceae; Pteridophyta). III. The Cytological Complexity of Species Groups with Simply Pinnate to Bipinnatifid Leaves

Diplazium with simply pinnate or bipinnatifid leaves. Diplazium wichurae var. wichurae, D. wichurae var. amabile, D. okudairae, and D. pin-faense are sexual diploids (2n=82; n=41II); D.× kidoi and D. × okudairaeoides are sterile diploids (2n= 82; meiosis irregular); D. donianum var. donianum is an apomictic triploid (2n=123; n=123II); D. donianum var. aphanoneuron is a sterile triploid (2n=123; meiosis irregular); D. crassiusculum, D. cavalerianum, D. incomptum, D. longicarpum, and D. pullingeri are sexual tetraploids (2n= 164; n=82II); and D. lobatum is an apomictic tetraploid (2n=164; n=164II). This is the first report of the chromosome numbers of D. lobatum, D. crassiusculum, D. incomptum, D. longicarpum, D. pullingeri, and D. × okudairaeoides, as well as the mitotic chromosome numbers of D. wichurae var. amabile, D. okudairae, D. pinfaense, and D. ×kidoi. The mitotic chromosome number, meiotic behavior, sterility, and allozyme analysis confirm that D. × kidoi and D. × okudairaeoides are hybrids between D. pin-faense and D. wichurae var. wichurae and D. okudairae and D. wichurae var. wichurae, respectively. Diplazium with simply pinnate to bipinnatifid leaves displayed an extraordinary cytological and reproductive complexity: a polyploidal series with diploids to hexaploids, sexual and apomictic reproduction, and natural hybridization. Received 14 August 2001/ Accepted in revised form 1 October 2001     

Cytogenetics of the genus Arvicanthis (Rodentia,Muridae). 3. Comparative cytogenetics of A. neumanni and A. nairobae from Tanzania

The African rats of the genus Arvicanthis have been widely studied during recent years to clarify species boundaries and phylogenetic relationships. The wide chromosomal variability of the genus has been highlighted in several studies, with each accepted species characterised by its individual karyotypes and others being revealed as cryptic species. In the present paper we report the karyotype and the C- and G-banding patterns of the two species A. nairobae and A. neumanni from seven localities of Tanzania, an area of the range poorly studied. The two karyotypes were compared to that of A. niloticus, which is considered to be primitive. The karyotype of A. neumanni is characterised by 2n = 53–54 and NFa = 62. This karyotypic variability depends on a widespread Robertsonian polymorphism. The karyotype of A. nairobae shows 2n = 62 and NFa = 78; it diverges from that of A. niloticus through one reciprocal translocation, five inversions and three heterochromatic additions. The comparison with the karyotypes of other species of the genus showed that A. neumanni belongs to the east African lineage (with A. abyssinicus, A. blicki, A. niloticus), while A. nairobae is closer to the central and the west African representatives which were all previously under the name of A. niloticus (ANI-2, ANI-3, ANI-4). The distribution of A. nairobae in east Africa opens new scenarios in the biogeographical pattern of evolution of the genus.     

Population genetic study of allozyme variation in natural populations of Drosophila antonietae (Insecta, Diptera)

Drosophila antonietae is an endemic South American cactophilic species found in relictual xerophytic vegetation, mostly associated with Cereus hildmaniannus cactus. Low differentiation among populations of this species has been detected using several markers. In this work, we performed an allozyme genetic variability analysis of 11 natural populations of D. antonietae and included a discussion about the possible influences of several evolutionary processes that might be acting to maintain the pattern observed. The genetic variability of 14 isoenzyme loci was analysed and showed a high genetic diversity (average observed heterozygosity = 0.319) and a moderate genetic differentiation among populations ( F statistics = 0.0723). A correlation between genetic and geographical and ecological distances was detected among pairs of populations and the regional equilibrium analysis was thus applied. This analysis resulted in Nm (number of migrants) of approximately 3.21, indicating that moderate levels of both gene flow and genetic drift occur in this species, with gene flow overlapping genetic drift. However, considering ecological features of drosophilids, we propose a hypothesis to explain the moderate differentiation encountered as a result of three different processes, or a combination of them: (1) gene flow; (2) a short period of differentiation, i.e. maintenance of ancestral polymorphism; and (3) action of natural selection. Moreover, if gene flow is present, the high genetic diversity compared with other cactophilic and non-cactophilic species could be due to differential selection in different populations followed by gene exchange among them. These factors are discussed in the light of D. antonietae 's historical and evolutionary association with the host cactus.     

Patterns of evolution in Graomys griseoflavus (Rodentia,Muridae). IV. A case of rapid speciation

The South American group of rodents known as Graomys griseoflavus comprises two sibling species differing only in diploid chromosomal complement: G. griseoflavus (2n = 36, 37 and 38) and G. centralis (2n=42). Reproductive barriers comprising postzygotic as well as precopulatory mechanisms prevent gene exchange between these species. We have studied genetic polymorphism in two populations of G. centralis and four of G. griseoflavus by means of gel electrophoresis of enzymes and other proteins giving information on a total of 30 loci. Values of interspecific genetic identity were similar to those obtained for conspecific populations, suggesting that fixation of Robertsonian fusions would have occurred without significant bottlenecks. It would also indicate that the cladogenetic process must be relatively recent. F_IS values showed no evidence of inbreeding. Fixation indices (F_ST) for the ancestral species showed a tendency to form demes with very low gene flow among them, while in the derived species such tendency was not shown. However, because of the characteristics of the region they occupy, populations are of moderate size, and genic flow is low. Lack of correlation between gene flow levels and geographical distance between population pairs would indicate a recent and fast colonization of its distribution areas by the derived species. It is possible that fixation of Robertsonian fusions occurred in a marginal deme of the ancestral species, e.g. in a parapatric geographical context.     

Enzyme analysis of genetic variation and relationships in diploid and polyploid taxa ofGalium (Rubiaceae)

Allozyme variation at 11 loci (with 37 alleles) was studied electrophoretically in seven outbreeding, closely related diploid and tetraploid taxa, seven from sect.Leptogalium and two from sect.Leiogalium. Whereas the sections are clearly distinct by several different alleles, aggregates, species and subspecies differ only in the frequency or presence/absence of common alleles. The resulting dendrogram suggests phylogenetic relationships and is supported by other multidisciplinary evidence. Tetraploids have originated independently in several groups, and there is evidence for tetrasomic inheritance and thus for autopolyploidy in spite of normal meiotic bivalent pairing and partly suspected hybrid origin. Tetraploids differ from related diploids only little in number of alleles and expected heterozygosity within populations, but clearly exhibit higher numbers of genotypes. This often corresponds to their greater morphological variability, increased adaptive flexibility, and better colonizing capacity compared to related diploids.     

Genetic analysis of variation in micropropagated plants of Melia azedarach L.

Summary Plants were regenerated by shoot multiplication from four clones of Melia azedarach L. during 12 mo. of subculturing. One hundred and one of these plants were examined by randomly amplified polymorphic DNA analysis. All regenerated plants showed at least one polymorphism. However, no chromosome number alterations were observed. The pattern of variation obtained by principal coordinated analysis showed a random distribution of variation among regenerated plants and their controls, indicating that genetic alterations were not cumulative during in vitro culture. Similar results were found using Shannon's index, which revealed that 50% of the observed diversity resided among plants coming from the same subculture generation. This high intraclonal variation does not provide a clear scenario for predicting the amount of culture time required to preserve genetic fidelity in commercially micropropagated M. azedarach plants. Our work suggests that other mechanisms, such as chimerism, contribute to intraclonal heterogeneity in vitro.     

Patterns of genetic differentiation in two annual bromegrasses,Bromus lanceolatus andB. hordeaceus (Poaceae)

Infraspecific genetic differentiation was analysed in two tetraploid annual bromegrasses,Bromus lanceolatus (from N Africa) andB. hordeaceus (from N Africa and France). Genetic analysis of populations was based on allozyme polymorphisms at 17 loci. Different fixed heterozygous phenotypes were scored in both species, according to their allopolyploid origin. In N Africa, more variation occurred among populations ofB. lanceolatus than ofB. hordeaceus. The variation was not randomly distributed among populations of both species. InB. lanceolatus, differentiation was correlated with climatic variables rather than with geographic distance between populations. Higher correlation of genetic differentiation with geographic distance occurred inB. hordeaceus, particularly at large geographic scale, between French and N African populations. Within each region, the populations appeared weakly genetically differentiated, even when belonging to different subspecies.     

Population genetic analysis reveals a homoploid hybrid origin of Stephanomeria diegensis (Asteraceae)

Homoploid hybrid speciation has generally been viewed as a rare evolutionary phenomenon, with relatively few well-documented cases in nature. Here, we investigate the origin of Stephanomeria diegensis , a diploid flowering plant species that has been proposed to have arisen as a result of hybridization between S. exigua and S. virgata . Across the range of S. diegensis , all individuals share a common chloroplast haplotype with S. virgata while showing a greater affinity for S. exigua in terms of nuclear genetic diversity. A prinicipal coordinates analysis (PCO) based on the nuclear data revealed that S. diegensis is most similar to each parent along different axes. Moreover, a Bayesian clustering analysis as well as a hybrid index-based analysis showed evidence of mixed ancestry, with approximately two thirds of the S. diegensis nuclear genome derived from S. exigua . These results provide strong support for a homoploid hybrid origin of S. diegensis . Finally, contrary to the finding that homoploid hybrid species are typically multiply-derived, our results were most consistent with a single origin of this species.     

Patterns of morphological variation in the Acacia species (Mimosaceae) of northern Sudan

KORDOFANI, M. & INGROUILLE, M., 1991. Patterns of morphological variation in the Acacia species (Mimosaceae) of northern Sudan. A numerical taxonomic review has been carried out on the morphology of northern Sudanese Acacia species. Fifty-one characters were scored from 12 species sampled at 12 sites. There is evidence of large scale population variation. Within a single site species are distinct but a comparison of plants between different sites may obscure species differences. Each species has a peculiar local variant in each sampled site, even when sites are separated by only a few kilometres. The possible significance of this pattern of variation is discussed. Species complexes are delineated and useful species diagnostics described.     

The evolutionary origin of a novel karyotype in Timarcha (Coleoptera, Chrysomelidae) and general trends of chromosome evolution in the genus

In this work, we have analysed the karyotypes of six species of Timarcha for the first time and updated the cytological information for two additional taxa, for one of them confirming previous results ( Timarcha erosa vermiculata ), but not for the other ( T. scabripennis ). We describe the remarkable karyotype of T. aurichalcea , the lowest chromosome number in the genus (2 n  = 18), distinctive as well for the presence of an unusual chiasmatic sexual bivalent hitherto unreported for Timarcha . This study increases the number of species studied cytologically in this genus to forty. Additional cytogenetic analyses are performed on several species, including Ag-NOR staining and fluorescent in situ hybridization (FISH) studies with ribosomal DNA probes. Karyotype evolution is analysed by tracing different karyotype coding strategies on a published independent phylogenetic hypothesis for Timarcha based on the study of three genetic markers. The implementation of a likelihood model of character change optimized onto the phylogeny is tentatively used to detect possible drifts in chromosome changes. These analyses show that karyotype is conservative in the evolution of the genus and that there is an apparent trend to reducing chromosome number. Cytological and phylogenetic data are used to explain the evolutionary origin of the karyotype of T. aurichalcea by two centric fusions involving one pair of acrocentric autosomes and the sexual chromosomes.     

Genetic pollution and number of matings in a black honey bee (Apis mellifera mellifera) population

Summary In the south-east of France, local honey bees possess only the B allele at the MDH locus, whereas the races which are usually imported into this area do not have this allele. The proportion of non-B genes in a sample of drones was used to measure the genetic pollution in the local population. Within the course of a breeding scheme of local bees, 99 queens, whose genotypes are BB, were naturally mated between April 25 and June 10, 1985 at la Tave (Gard, France). Twenty daughters-workers of each queen were analysed at the MDH locus. The frequency of the B allele in drones that mated with these queens is estimated by the proportion of workers with genotype BB and the genetic pollution by the cumulated frequency of the other alleles. The sampling variances of these frequencies involve a coefficient which is a function of the average number of drones mated with a queen. This latter parameter is estimated through the maximum likelihood method. In addition to the three well-known alleles, a rare allele (frequency=0.0055), possibly equivalent to the S1 allele described by Badino et al. (1983), has been found in three different colonies. Cumulating the frequencies of the non-B alleles results in an estimation of the genetic pollution equal to 0.0394 (±0.0071). This low value allows us to proceed to the next step of the selection project. The mean number of drones mated to a queen is 12.4 with a (10.4–19.3) confidence interval at the 90% level.     

Patterns of morphometric variation and a new supraspecific classification of apomictic taxa of Hieracium (Asteraceae) from Denmark and southern Sweden

Patterns of variation among all micro-species of Hieracium sect. Hieracium and H. sect. Vulgata known from Denmark and southern Sweden are investigated. Forty-three, possibly independent morphological characters are used. Significant correlations were revealed among the majority of the characters. Multivariate analyses did not reveal any discontinuities in the variation or any discrete groups of species. However, there were obvious correlations between previous taxonomic classifications and the result of the multivariate analyses. Based on the statistical analyses, three sections and 38 informal species aggregates are recognized. H. sect. Bifidum T. Tyler is described anew. The characters that turned out to be most influential in the multivariate analyses, and thus most important for the classification, were the distribution of stellate tomentum on the phyllaries, the amount of glandular hairs and the amount and pigmentation of simple hairs on the phyllaries, the shape of the leaf-base and the regularity of the leaf dentation. The evolution of the group and the taxonomic treatment is thoroughly discussed in the light of the results.     

Aspartate aminotransferase allozyme variation in a germplasm collection of the domesticated lentil (Lens culinaris)

Summary Variation at a polymorphic Aspartate aminotransferase locus was assayed in a sample of 298 accessions from the ICARDA germplasm collection of the domesticated lentil (Lens culinaris). Two alleles Aat-1 ^F and Aat-1 ^S were detected with global frequencies of 0.51 and 0.49, respectively. Fifty-nine percent of accessions were polymorphic for both alleles. The frequency of outcrossing was estimated from the observed heterozygosity to be about 1%. This is higher than direct estimates of outcrossing and implicates selection in favour of heterozygous gene combinations. Significant variation in allele frequency and in the occurrence of polymorphic accessions was observed between countries or geographic areas. Significant associations were observed between the allozymes and agronomic characters. In particular high frequency of Aat-1 ^F appeared to be associated with late flowering and maturity and low yield.