Evaluation of the extent of among-family variation in inbreeding depression in the perennial herb Scabiosa columbaria (Dipsacaceae)

Significantly different maternal line responses to inbreeding provide a mechanism for the invasion of a selfing variant into a population. The goal of this study was to examine the extent of family-level variation in inbreeding depression in the mixed-mating, perennial herb Scabiosa columbaria. Plants from one population were raised, and hand-pollinated to produce selfed and outcrossed progeny, and the effects of inbreeding depression on life-cycle traits were analyzed. Inbreeding depression significantly affected early life cycle traits. The pollination treatment by family interaction was significant for almost all traits, indicating a high family-level variation in inbreeding depression. The correlations between inbreeding depression values (e.g., percentage germination and flowering date, and flowering date and aboveground biomass) exhibited alternate signs, illustrating the type of association between inbreeding depression loci for different traits across the life cycle. Overall, it is concluded that the extent of among-family variation in inbreeding depression might allow a selfing variant of S. columbaria to invade an outcrossing population, though the pattern of correlations between inbreeding depression values might prevent effective purging of the deleterious genetic load.     

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.     

Molecular phylogenetic evidence for the origin of a diploid hybrid of Paeonia (Paeoniaceae)

There is growing evidence that hybridization not only by means of allopolyploidy but also at the homoploidy level was a major driving force of plant diversification. While allopolyploidy is known to be a common mode of speciation in Paeonia (Paeoniaceae), hybrid speciation at the diploid level needs further evaluation. Paeonia anomala was previously considered to be an interspecific hybrid but with an unknown ploidy level. In this study P. anomala is identified as a diploid (2n = 10). With increased sampling of populations and molecular markers, we showed that P. anomala is a homoploid hybrid that originated from a cross between P. veitchii and P. lactiflora. Five populations of P. anomala were sequenced for the following molecular markers: the matK gene and two intergenic spacers, psbA-trnH and rps16-trnQ, of the chloroplast genome; the internal transcribed spacers (ITS) of nuclear ribosomal DNA; and three low-copy nuclear genes, Adh1, Adh2, and Gpat. The populations of P. anomala were grouped together with P. veitchii on the ITS and Gpat phylogenies but with P. lactiflora on the chloroplast phylogeny. Sequence polymorphism was found at the Adh1 and Adh2 loci within individuals of P. anomala. These polymorphic sequences were grouped with P. veitchii and P. lactiflora, respectively. Phenetic analysis indicated that P. anomala is morphologically similar to P. veitchii. Phenotypic evolution resulting from the combination of two diverged genomes might have occurred primarily at the physiological level and allowed P. anomala to adapt to geographic regions different from those of its parents.     

The Rutilus alburnoides complex (Cyprinidae): evidence for a hybrid origin

A genetic survey of 18 presumptive enzyme loci was conducted on members of the diploid-triploid R. alburnoides complex in order to test the hypothesis of hybrid origin. Most specimens examined were heterozygous at a high proportion of loci, with seven loci showing virtually fixed heterozygosity in some or all populations. This observation strongly supports the hypothesized hybrid ancestry. Involvement in the origin of the R. alburnoides complex was examined by comparison of allels with those observed in the other diploid cyprinids that inhabit the same Portuguese drainages. Allelic composition at the homozygous loci IDDH* and LDH-B* seems to rule out the genus Chondrostoma and other members of the genus Rutilus as one of the ancestors, and supports Leuciscus sp. as one parental species involved in the putative hybrid origin of the R. alburnoides complex. Moreover, with few exceptions, all specimens exhibited at every locus one or two alleles also present in extant populations of Leuciscus. The indentity of the other parental taxon remains unclear. Five diploid males exhibited multilocus genotypes that fit to the hypothetical genotype(s) of the ‘missing’ ancestor. However, the possibility exists that a hybrid female could produce or re-create a genotype of a parental species.     

Genetic markers and morphometric analysis reveal past hybridization and introgression in putative Carex flava L. s.str. (Cyperaceae) hybrid populations

The affinities of taxonomically problematic populations are typically analyzed using molecular markers. However these are less subject to selection than morphological characteristics. Consequently both approaches may be required to obtain a fuller picture of the identity and history of populations. Three putative hybrid populations within the Carex flava agg. are examined using such a dual approach with a view to elucidate their taxonomic affinities. Analysis of 11 morphometric characters using principal component analysis and examination of 17 isozyme loci revealed a more complicated history than that suggested by morphometric analysis alone. Results from this study confirm the status of an additional British population of C. flava s.str. and also strongly suggest that a population morphologically resembling Carex lepidocarpa has experienced the introgression of C. flava genes in the past. An Irish population resembling C. flava in appearance but lacking typical C. flava allozymes may be a result of local selection.     

Systematic significance of seed coat morphology inSilene L. s. str. (sileneae-caryophyllaceae) from Korea

Seeds of eight species ofSilene s. str. in Korea were examined with a dissecting stereomicroscope and a scanning electron microscope (SEM) to evaluate the systematic significance of seed coat microstructure. The seeds ofSilene s. str. were characterized by triangular or reniform shape, planed or concave dorsal surface in outline, tuberculate or colliculate testa, and sinuated cell margin. Based on the degree of grooves and invagination at dorsal surface, the seeds of the examined taxa ofSilene s. str. fall into two distinct groups: (I) dorsal grooves inconspicuous, surface planed (Silene jenisseensis andS. repens), (II) dorsal grooves conspicuous, surface concave (six remaining taxa). Within each group, seeds of all species may be further distinguished based on shape, size, and testa surface sculpturing. A key to the different species or groups of species is provided, and the systematic significance between/among the taxa is also briefly discussed.     

Quinacrine fluorescence analysis of the chromosomes of Dipsacus fullonum L. (Dipsacaceae)

Abstract

Quinacrine fluorescence analysis of the chromosome complement of Dipsacus fullonum L. shows clear heterochromatic regions appearing as brightly fluorescent bands or clusters of fluorescent dots in most chromosomes. The resulting fluorescent pattern is chromosome specific.     

New species and records of Metriocnemus van der Wulp s. str. from China (Diptera,Chironomidae)

The Chinese species of Metriocnemus van der Wulp s. str., 1874 is reviewed. M. (M.) calcaneum sp. n. is described and illustrated as adult male. M. (M.) albolineatus (Meigen) is recorded from China for the first time. M. (M.) beringensis (Cranston & Oliver), M. (M.) bilobatus Makarchenko & Makarchenko, M. (M.) caudigus Sæther, M. (M.) intergerivus Sæther, M. (M.) tamaokui Sasa and M. (M.) tristellus Edwards are recorded from the Oriental Region for the first time. A key to the males of 17 Chinese Metriocnemus (Metriocnemus) species is given.     

Fruit micromorphology and anatomy of Valeriana officinalis s. str. (Valerianaceae)

Fruits of two varieties of Valeriana officinalis s. str. (var. officinalis , var. nitida ) are similar in general construction, but differ in details of external and internal structure. The outer cells of the pericarp form a regularly punctuated surface in both taxa. Scanning electron microscopy demonstrates variation in cuticular sculpturing of the outer epidermal cell walls and the presence of epicuticular wax. The surface of fruit hairs varies from micropapillate in var. officinalis to linear warty in var. nitida . In the mature rericarp there occur three distinct histological zones: an outer exocarp, a central mesocarp, and an inner endocarp. The seed is small, enclosed in the indehiscent fruit, with thin seed coat and a straight embryo. Endosperm is absent. The results of this carpological study, especially the SEM characters of pericarp surface, may provide criteria useful for delimitation of V officinalis varieties.     

Interspecific hybridization in the genus Hieracium s. str.: evidence for bidirectional gene flow and spontaneous allopolyploidization

Although reticulation has indisputably played an important role in the evolutionary history of the genus Hieracium s. str. (Asteraceae), convincingly documented cases of recent interspecific hybridization are very rare. Here we report combined evidence on recent hybridization between two diploid species, Hieracium alpinum and H. transsilvanicum. The hybrid origin of the plants from the Romanian Eastern Carpathians was supported by additive patterns of nuclear ribosomal DNA polymorphism (ITS), an intermediate position of hybrid plants in principal coordinate analysis based on amplified fragment length polymorphism phenotypes (AFLP), and additivity at one allozyme locus. Flow cytometric analyses and chromosome counting showed that two hybrids were diploid (2n ~ 2x ~ 18) while one was surprisingly tetraploid (2n = 4x = 36). To our knowledge, this is the first record of spontaneous polyploidization following interspecific crossing in the genus. Allozyme data, especially the presence of unbalanced heterozygosity at one locus, suggest the origin of this tetraploid via a triploid bridge with subsequent backcrossing to H. alpinum. According to PCR-RFLP analyses of the trnT-trnL intergenic spacer, all H. ×krasani hybrids examined had the H. alpinum haplotype while H. transsilvanicum served as a pollen donor. The hybrids occurred at the locality with abundant H. alpinum plants where paternal H. transsilvanicum was missing. Previously reported instances of interspecific hybridization between the same parental taxa showed an opposite direction of crossing and relative abundance of parental taxa. This suggests that the direction of hybridization might be influenced by the frequency of parental taxa at the locality.     

Pollen morphology of the genera Polygonum s. str. and Polygonella (Polygoneae: Polygonaceae)

The pollen of 30 taxa (27 species, one subspecies and two varieties) in two genera, viz Polygonum s. str. and Polygonella was investigated with LM and SEM, and some selected taxa with TEM. In all genera investigated the pollen is prolate to spheroidal, and the aperture is mostly tricolporate, rarely panto-hexacolporate (especially Polygonum section Polygonum). The exine sculpturing pattern is the most variable feature. Three types of exine can be recognized. Type 1 (Avicularia-Type, sensu Hedberg) - All species of section Polygonum and section Tephis share the smooth tectate exine with spinules, sometimes the surface is more or less rough (Polygonum afromontanum in section Tephis). Type 2 (Pseudomollia-Type, sensu Hong) - Pollen of Polygonum molliaeforme (section Pseudomollia) has the exine, which is verrucose on both poles and nearby the mesocolpium, and mostly psilate around the ectoaperture. Type 3 (Duravia-Type, sensu Hedberg) - Pollen grains of Polygonum section Duravia and Polygonella have the exine which is semitectate-reticulate at the mesocolpium and the poles, and rugulate/reticulate or sometimes foveolate with microspinules around the ectoapertures. The pollen grains in four taxa (viz Polygonum section Pseudomollia, P. section Duravia and genus Polygonella) have a well-marked dimorphism of the ektexine, which is considered to be a synapomorphic condition. The differences of pollen grain between the genus Polygonella and Polygonum section Duravia are almost non existent and clearly interrelated. It is therefore postulated that the similarity in pollen of both taxa is not the result of convergency, but is interpreted as a homology. It is noteworthy that the pollen of Polygonum molliaeforme (section Pseudomollia) appears as intermediate between the Avicularia-type and the Duravia-type, and is well supported the value of separated section for its own. Additionally, in TEM, some exine ultrastructures (e.g. columellae, foot layer, endexine) appear to be valuable characters for comparison between/among taxa. The systematic potentialities of the pollen data of the studied taxa at various systematic levels are also discussed.     

Morphological and molecular evidence for hybridization and introgression in Central European Arctium (Asteraceae)

Three species of burdock (Arctium lappa, A. tomentosum, and A. minus; Asteraceae), which commonly occur in sympatry in Central Europe, are thought to hybridize frequently, hence raising questions about their integrity. We surveyed mixed, monotypic, and/or single plant stands of these species in Central Germany to assess their extent of hybridization and introgression, and also the likelihood of insect host shifts between them. Individual plants were characterized by multivariate analyses of morphological and RAPD variation in combination with RAPD-based character-index-scores. All analyses recognized the three species as distinct units, but also identified a limited number of first (or early) generation hybrids between sympatric A. lappa and either A. tomentosum or A. minus, respectively, as well as one introgressant of A. tomentosum into A. lappa. While pre-zygotic isolation may partly account for the rarity of first generation crosses (F₁'s), the near absence of later generation hybrid segregants or introgressants likely reflects post-zygotic isolation due to the disruption of co-adapted gene complexes and/or habitat-mediated superiority shared by the ruderal parentals. As the tephritid fly Tephritis bardanae oviposits on both A. tomentosum (T) and A. minus (M), but not on A. lappa (L), the occurrence of L × M and L × T hybrids and/or introgressants may have important evolutionary consequences regarding the acquisition of a new host, i.e. A. lappa, by these insects.     

Allozyme evidence for the origin and diversification of Gossypium barbadense L.

Summary Gossypium barbadense L. is a commercially important cotton species of tropical South American origin presently grownin many regions of the world. The species is morphologically diverse, consisting of a wide range of wild (or feral), commensal, landrace, and highly improvedcommercial forms. We performed allozyme analysis on 153 accessions representing the spectrum of G. barbadense diversityto ascertain the geographic origin of the species, its patterns of diffusion subsequent to domestication, and to reveal infraspecific relationships. Levels ofgenetic variation in G. barbadense are moderate. Of 59 loci scored, 24 were polymorphic, with a mean number of alleles perlocus of 1.69 and an average panmictic heterozygosity of 0.062. Principal component analysis revealed geographic clustering of accessions into six relativelydiscrete regions. Gene frequencies at many loci are significantly heterogeneous among these regions, with an average G _STof 0.272. Northwestern South America contains the greatest genetic variability; we suggest that this region is the ancestral home of the species. The data indicate separate diffusion pathways from this region into Argentina-Paraguay and into eastern and northern South America east of the Andes. Caribbean Island and Central American forms appear to be derived from the latter. These diffusion pathways are in accordance with morphological evidence and historical record. In contrast to expectations based on geographic proximity, Pacific Island forms have their closest affinity to accessions from eastern South America. Advanced cultivated stocks seem largely derived from western Andean material, but also contain introgressed G. hirsutum germ plasm. Introgression was relatively high (22%–50% of accessions) in commercial stocks and in forms from Argentina-Paraguay and various Pacific Islands, but was conspicuously low or absent in material from Central America and the Caribbean, where commensal and commercial forms of both species are sympatric.     

New satellite DNA in Lacerta s. str. lizards (Sauria: Lacertidae): evolutionary pathways and phylogenetic impact

A new tandemly repeated (satellite) DNA family namely Agi160, from Lacerta agilis and Lacerta strigata (Lacerta sensu stricto (s. str.), Linnaeus 1758) have been cloned and sequenced. Agi160 is found in the above two species, as well as two other representatives of the same genus, L. viridis and L. media. DNA hybridization did not reveal it in Darevskia, Podarcis, Zootoca, Eremias, Ophisops, and Gallotia - the other genera of the family Lacertidae. The results suggest that Agi160 is a Lacerta s. str. specific family of tandem DNA repeats. However, a comparison between sequences of Agi160 and CLsat repeat units revealed 60 bp regions 62-74% identical. The latter is a satellite DNA family typical for Darevskia (syn. "L. saxicola complex") (Grechko et al., Molecular-genetic classification and phylogenetic relatedness of some species of Lacertidae lizards by taxonoprint data. Mol Biol 32:172-183, 1988.). Both Agi160 and CLsat tandem repeats share several common features (e.g., the same AT content and distribution of multiple short A-T runs, internal structure of repeated units, the presence of conservative regions). These data are indicative of their common origin and a possibly strong selective pressure upon conserving both satellites. A comparative analysis of structure, organization, and abundance of these two families of satDNA reveals evolutionary pathways that led to their formation and divergence. The data are consistent with the hypotheses of the concerted evolution of satellite DNA families. The possibility of use of Agi160 as a phylogenetic tool, defining relationships within Lacerta s. str., as well as within the whole family of Lacertidae is discussed.     

Evidence for the hybrid origin of Lathyrus plitmannii (Leguminosae)

ABSTRACT

The hypothesis that Lathyrus plitmannii may be of hybrid origin was tested on a morphological data set, derived from measurements of 50 herbarium specimens, by employing the computer program HYWIN. Results showed that all the specimens of L. plitmannii were putative hybrids and that the highest ranked pair of specimens that best matches the morphologies of its parents was L. gorgonei and L. pseudocicera. Examination of the distribution patterns of the three species shows that L. plitmannii is confined to regions common to both putative parents and that hybrids could be formed, assuming that genetic barriers were overcome. Additional supporting evidence includes overlaps in the edaphic requirements and the habitats of the three species. Lathyrus plitmannii is recognised as a distinct species that should be regarded as derivative of hybridisation between L. gorgonei and L. pseudocicera.     

Chromosome numbers and DNA ploidy levels of selected species ofHieracium s.str. (Asteraceae)

Chromosome numbers and /or ploidy levels are reported for 44 species and subspecies ofHieracium s.str. from the following European countries: Andorra, Austria, Bulgaria, Czech Republic, France, Italy, Montenegro, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland and Ukraine. The chromosome numbers/DNA ploidy levels ofH. bocconei (2n ～ 4x),H. bupleuroides subsp.leviceps (2n = 27),H. caesioides subsp.caesioides (2n = 27),H. basifolium (H. caesium agg., 2n = 36),H. plumbeum (H. caesium agg., 2n = 36),H. glaucum subsp.nipholepium (2n= 27),H.gouanii (2n = 18),H. gymnocerinthe (2n = 27),H. ramondii (2n = 27),H. recoderi (2n = 18),H. stelligerum (2n = 18), andH. tomentosum (2n = 18, 2n ～ 2x, 2n ～ 3x) were determined for the first time. New ploidy levels are reported forH. cerinthoides s.str. (2n = 27),H. humile (2n = 36), andH. tommasinianum (2n = 27).     

Ochthebius (s.str.) capicola (Coleoptera) re-discovered in the Cape Peninsula,South Africa

New distributional records and ecological observations are presented for the Cape endemic hydraenid Ochthebius capicola. Considered extinct on the Cape Peninsula, the species has been re-discovered at two adjacent locations as well as at a new site in Tsitsikamma National Park, Eastern Cape. New species associations are recorded, in conjunction with observations confirming this species' preference for algae-covered rock surfaces in the hypersaline pools of the supralittoral zone. Provisional internationally-endangered status for this species was examined but considered dependent on future data. It was considered likely that the beetle may be insufficiently recorded, due to its atypical habitat requirement. A synopsis of the taxonomic status of this species and Ochthebius rubripes is given. Notes on both species are provided, as well as a record of sympatric occurrence.