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.     

Molecular phylogeny of the genus<Emphasis Type="Italic">Hypericum</Emphasis> (Hypericaceae) from Korea and Japan: evidence from nuclear rDNA ITS sequence data

As part of our ongoing phylogenetic study of genusHypericum, nuclear ribosomal DNA internal transcribed spacer sequences were analyzed for 36 species ofHypericum as ingroup and two species ofThornea as outgroup. This sampling included most of the previously described species from both Korea and Japan. The ITS phylogeny suggested that the surveyedHypericum species belong to a monophyletic section,Trigynobrathys, and a polyphyletic section,Hypericum. In addition, two monotypic sections,Sampsonia andRoscyna, were identified. Members of sectionHypericum occur in four different lineages worldwide, which imply at least four independent origins. The Korean and Japanese species of sectionHypericum form a monophyletic group, except forH. vulcanicum. Instead, that particular species belongs to a distinct monophyletic group withH. scoreri andH. formosa from other geographic areas, and is a sister to sectionTrigynobrathys. The Korean and Japanese species of sectionTrigynobrathys show a monophyletic origin.H. sampsonii is now recognized as a distinct section rather than being a member of sectionsHypericum orDrosocarpium, as had been indicated previously. Our results differ somewhat from those of recent morphological and cytological studies. The phylogenetic relationships among Korean and Japanese species have now been mostly resolved via ITS phylogeny.     

Genetic diversity in Mediterranean diploid and tetraploid Bromus L. (section Bromus Sm.) populations.

The levels of genetic diversity assessed from allozyme data were investigated in 25 populations of Mediterranean Bromus intermedius, B. squarrosus, B. lanceolatus, and B. hordeaceus from Algeria. The geographically restricted diploids B. intermedius and B. squarrosus displayed less genetic diversity (the mean population gene diversity of Nei (Hu) ranged from 0.03 to 0.12) than the widespread tetraploid colonizers B. lanceolatus and B. hordeaceus (Hu = 0.07-0.27). Deviations from Hardy-Weinberg expectations in diploid populations of B. intermedius and B. squarrosus were observed owing to heterozygote excess at several loci and suggested that these self-fertilizing species may have substantial amounts of allogamy. Tetraploid populations of B. lanceolatus and B. hordeaceus were largely homozygous at homologous loci and frequently exhibited intergenomic fixed heterozygosity in accordance with their alloploid origin. Genetic variation at the infraspecific level was mostly distributed within populations in the four species, B. hordeaceus showing the lowest level of interpopulation differentiation (Gst = 0.06) and the highest level of gene flow (Nm = 3.75). Consistent gene flows are in agreement with the strongest intercontinental invasive behaviour of B. hordeaceus. Less differentiation was reported in the literature among later introduced B. hordeaceus populations from England and Australia, indicating reduced differentiation under the process of colonization. Moderate divergence occured among the four taxa, with interspecific genetic identities ranging from 0.87 to 0.93. In spite of substantial genetic similarity, species were clearly differentiated, with each tetraploid being more closely related to a diploid: B. hordeaceus to B. squarrosus and B. lanceolatus to B. intermedius.     

Genetic variation in Mediterranean Helichrysum italicum (Asteraceae; Gnaphalieae): do disjunct populations of subsp. microphyllum have a common origin?

The yellow‐flowered everlasting daisy Helichrysum italicum (Asteraceae, Gnaphalieae) is widely distributed in the Mediterranean basin, where it grows in continuous and widespread populations in diverse open habitats. Helichrysum italicum subsp. microphyllum has a disjunct distribution in the Balearic Islands (Majorca and Dragonera), Corsica, Sardinia, Crete and Cyprus. Numerous morphological intermediates between subsp. italicum and subsp. microphyllum are known from Corsica, where the two subspecies co‐occur. The aims of the study were to investigate if subsp. microphyllum has a common origin, constituting an independent gene pool from subsp. italicum, or if the morphological differences between subsp. microphyllum and subsp. italicum have arisen independently in different locations from a common wider gene pool. Our analyses of AFLP, cpDNA sequences and morphological characters show that there is geographic structure to the genetic variation within H. italicum, with eastern and western Mediterranean groups, which do not correspond with the division into subsp. microphyllum and subsp. italicum as currently circumscribed. Local selection on quantitative trait loci provides sufficient explanation for the morphological divergence observed and is consistent with genetic data. Within the western Mediterranean group of the species we found considerable polymorphism in chloroplast DNA sequences among and within some populations. Comparison with chloroplast DNA sequences from other Helichrysum species showed that some chloroplast haplotypes are shared across species.     

Genetic connectivity among osprey populations and consequences for conservation: philopatry versus dispersal as key factors

Genetic variability and population structure in osprey were studied using DNA microsatellite markers. Special emphasis was placed on the subspecies living in the Afro-Palearctic (Pandion haliaetus haliaetus). For comparative purposes, American osprey subspecies (P. h. carolinensis, P. h. ridgway) and Indo/Australian subspecies (P. h. cristatus) were included in this analysis. Twenty DNA microsatellite loci were analysed across a total of 200 individuals. Cluster analysis of genetic distances generally grouped populations of osprey in accordance with their subspecific designation and with previous results from mtDNA analysis. Ospreys from America and Australia were clearly separated from P. h. haliaetus suggesting a more ancient isolation which prevented recent gene flow across these groups. Within P. h. haliaetus, significant genetic differentiation was found between populations in northern and southern Europe, suggesting that the Afro-Palearctic group is structured into two interconnected entities (Mediterranean and continental Europe). Population structuring was supported by an assignment test and by analysis of allele-sharing among individuals. At the Mediterranean scale, no significant differences of allelic information were found between populations. Behaviours such as dispersal, migration and philopatry seem to have played simultaneously and in contrary directions in shaping the genetic structure and diversity of populations. Our results provide essential information for reconstructing gene flow and genetic variability among osprey populations at different scales, which call for caution in the proactive management and conservation of the species, namely in the Mediterranean area.     

Genetic differentiation and relationship of the dipodidsAllactaga andJaculus (Mammalia, Rodentia) in Egypt based on protein variation

Genetic differentiation among 14 populations representing all Egyptian dipodid (jerboa) species and subspecies was examined at 25 structural loci and interspecific relationships are discussed. Of the 25 loci, only 3 were monomorphic, with the same allele fixed in all taxa, 9 loci were monomorphic, but demonstrated intertaxon variation, and only 13 loci were polymorphic. The overall mean number of alleles per locus (A) was 1.23 ± 0.02 and the average percentage of polymorphic loci per taxon (P) was 23%. The overall mean of observed heterozygosity (H _o) was found significantly higher than that of expected heterozygosity (He); the overall means per taxon were 0.25 ± 0.017 and 0.085 ± 0.007. Mean levels of genetic identity (I) were 0.970 ± 0.003 among geographic populations, 0.718 ± 0.022 between subspecies, 0.590 ± 0.030 between congeneric species, and 0.368 ± 0.020 between genera. Phenetic analysis of genetic distance matrix produced a phenogram indicating a close association ofJaculus orientalis Erxleben, 1777 toJaculus jaculus (Linnaeus, 1758), particularly to its subspeciesJaculus jaculus butleri (Thomas, 1922), and indicating a distinct affinity between these latter two species andAllactaga tetradactyla (Lichtenstein, 1823). Estimates of genetic divergence demonstrated that J. orientalis appears to have shared a more recent common ancestor withJ. jaculus thanA. tetradactyla. Divergence of these species would have occurred by Miocene (ca 9.6 to 18.7 million years ago). The pattern of relationships of the dipodid species indicated in this study was closely consistent with the hypotheses derived from morphological and chromosomal data.     

Three new species of Dalechampia (Euphorbiaceae) from Venezuelan Guayana

Three new species ofDalechampia are described from the Guayanan region of Venezuela.Dalechampia attenuistylus belongs to sectionRhopalostylis and may be most closely related toD. parvibracteata Lanj.Dalechampia megacarpa belongs to sectionDioscoreifoliae, although it is not especially close to any species in the section.Dalechampia papillistigma is also an isolated member of sectionDioscoreifolieae.     

A new Madia (Compositae) from northwest California

A new species ofMadia sectionAnisocarpus from the serpentines of northwest California is described, illustrated and contrasted with its closest relatives. A key to the annual members of the section is presented.     

New species of Cuphea section Melvilla (Lythraceae) and an annotated key to the section

Three novelties inCuphea sectionMelvilla subsect.Pachycalyx are described from Brazil;C. andersonii andC. cylindracea from Pará, andC. sabulosa from Amazonas. An annotated key to the 47 species ofCuphea sectionMelvilla is provided, the first since the 1903 monograph of the family, which then included 27 species in the section. The key identifies those species ofCuphea with thick, dorsally convex, red- or yellow-tubed flowers distributed from Mexico to Argentina.     

Genetic Diversity inBrassica oleraceaL. (Cruciferae) and Wild Relatives (2n=18) using Isozymes

Genetic diversity in 36 populations of wild taxa of theBrassicaoleraceaL. group (2n=18) and two cultivated forms was studiedusing isozyme variation at 11 loci for five enzyme systems (IDH,6-PGD, PGM, PGI, MDH). Mean values for the percentage of polymorphicloci and expected heterozygosity were 54% and 0.224, respectively.Statistically significant differences among allele frequencieswere found with the 6-PGD isozyme system. Intrapopulationalgenetic diversity was 67% while interpopulational genetic diversitywas only 33%. The dendrogram obtained, using genetic distancesamong taxa, showed three different groups. With the exceptionofB. incana,they agree to the already accepted relationshipsamong the 14 taxa studied: the West Mediterranean group, withB.oleracea, B. alboglabra, B. bourgeauiandB. incana; another groupof species growing in the central Mediterranean area, whichincludesB. villosa, B. villosasubsp.drepanensis, B. rupestris,B. macrocarpa(the four taxa together withB. incanaare consideredtheB. rupestrisgroup) andB. montana; and finally the Aegeangroup, which includes the three subspecies ofB. cretica.Clearlyseparated wereB. insularisandB. hilarionis, showing the maximumgenetic distance. Separate dendrograms were also obtained forB.oleracea, B. montana, B. creticaandB. rupestrisgroup, and geneticdiversity parameters were estimated. Genetic distances amongB.oleraceapopulations are in the same range as populations oftheB. creticasubspecies. Highest genetic distances were foundamong populations of theB. rupestrisgroup.Copyright 1998 Annalsof Botany Company. Brassica oleraceaL., wild relatives, genetic diversity, genetic resources, isozymes.     

REPRODUCTIVE BIOLOGY OF SEVERAL BROMEGRASSES (BROMUS): BREEDING SYSTEM,PATTERN OF FRUIT MATURATION,AND SEED SET

Five species of Bromus were tested for self-fertility when bagged. Bromus inermis was self-incompatible. Bromus tectorum, B. kalmii, B. ciliatus, and B. latiglumis were capable of self-fertilization. Further evidence from flowering behavior suggested that B. tectorum almost always self-pollinated and that the remaining self-fertile species sometimes outcrossed. Florets in different positions on a spikelet varied in the proportion that set seed. Open-pollinated B. inermis plants had lower seed set than the self-fertile species, in agreement with the pattern in a variety of hermaphroditic plants.     

Aerobiological and phenological study of the main Poaceae species in Córdoba City (Spain) and the surrounding hills

This study reports on the flowering phenology of 12 Poaceae species in different types of plant cover (scrub, riverbank and pasture), with a view to creating a phenological calendar for the major species contributing most to airborne pollen concentrations. The study has been carried out from March to June between 2000 and 2013. Seventeen sampling sites in the study area were selected by accessibility, and predominantly, grasses grow in different land covers for phenological monitoring. Airborne pollen was collected using a Hirst-type volumetric spore trap. Results showed that longer phenological ranges were recorded in the wettest year and shorter ranges in the driest year. Over the study period, certain species displayed changes in the timing of flowering phenology. In pastureland and scrubland, a slight phenological delay over the study period has been recorded. In pastureland, some species—i.e., Bromus madritensis, B. diandrus and B. hordeaceus, Hordeum leporinum and Stipa capensis—displayed a delay in the timing of phenophases over the study period, including B. hordeaceus and B. madritensis on riverbank. Dactylis glomerata and Trisetaria panicea in scrub have been the only species with a clear advance; B. diandrus and B. madritensis a clear flowering delay. Lolium rigidum, Dactylis glomerata, Aegilops geniculata, in scrub, riverbank and pasture, and Arrhenatherum album, only in scrub, full flowering coincided with pollen peak in some populations during several years.     

Mortality of exotic and native seeds in invaded and uninvaded habitats

We examined seed survival in exotic- and native-dominated grasslands by placing seeds of a once-pervasive native grass species, Nassella pulchra, and two of the most common, widespread exotic grass species, Avena fatua and Bromus hordeaceus, in mesh bags in the field for 3 months. Compared to germination of unexposed seeds not placed in the field, exotic species experienced an approximately 40% reduction in viability, whereas the mortality experienced by the native species was <20%. Despite these differences, germination rates of exposed seeds were similar between native and exotic species because native N. pulchra seeds had lower initial viability prior to entering the seed bank. Seed mortality did not differ based on whether seeds were placed in habitats dominated by exotic or native grasses. Rather, our results suggest that re-establishment of native N. pulchra must focus on maximizing seed viability and survival, and that A. fatua and B. hordeaceus overcome relatively higher losses of viable seeds in the seed bank, potentially by producing large numbers of highly viable seeds.     

Hybridization in Capparis spinosa L.: Molecular and morphological evidence from a Mediterranean island complex

Inter-Simple Sequence Repeat (ISSR) molecular markers and morphological analysis were used in order to characterize wild populations and cultivated forms of orphan crop species Capparis spinosa L. in a Mediterranean island complex. Nineteen wild populations belonging to two different subspecies, C. spinosa subsp. spinosa and subsp. rupestris, were sampled in different environments in Sicily and the surrounding islets Lampedusa, Pantelleria and Salina. Different biotypes cultivated in Pantelleria and Salina were analysed. Six ISSR primers were selected for genetic characterization, and all clear and reproducible bands were scored and analysed. Among the 47 ISSR bands obtained, 97.5% were polymorphic. Results of AMOVA and STRUCTURE analysis suggested a clear genetic distinctness between subspecies at the regional level and suggested the existence of two taxonomic groups among wild populations, with different ecological preferences and distinctive morphological characters. Cultivated forms showed genetic affinity to subsp. rupestris. ISSR analysis not only provided specific molecular markers to discriminate the taxa, but also proved useful in supporting the hypothesis of a hybrid origin of the intermediate phenotypes found in overlapping distribution areas. The identified molecular markers provided a basic tool for the DNA fingerprinting of wild and commercial capers in the Mediterranean region and nearby territory.     

Molecular evidence for host-adapted races of the fungal endophyte Epichloë bromicola after presumed host shifts

Abstract.— Host shifts of plant‐feeding insects and parasites promote adaptational changes that may result in the formation of host races, an assumed intermediate stage in sympatric speciation. Here, we report on genetically differentiated and host‐adapted races of the fungal endophyte Epichloë bromicola, which presumably emerged after a shift from the grass Bromus erectus to other Bromus hosts. Fungi of the genus Epichloë (Ascomycota) and related anamorphs of Neotyphodium are widespread endophytes of cool‐season grasses. Sexually reproducing strains sterilize the host by formation of external fruiting structures (stromata), whereas asexual strains are asymptomatic and transmitted via seeds. In E. bromicola, strains infecting B. erectus are sexual, and strains from two woodland species, B. benekenii and B. ramosus, are asexual and seed transmitted. Analyses of amplified fragment length polymorphism fingerprinting and of intron sequences of the tub2 and tef1 genes of 26 isolates from the three Bromus hosts collected at natural sites in Switzerland and nearby France demonstrated that isolates are genetically differentiated according to their host, indicating that E. bromicola does not form a single, randomly mating population. Phylogenetic analyses of sequence data did not unambiguously resolve the exact origin of asexual E. bromicola strains, but it is likely they arose from within sexual populations on B. erectus. Incongruence of trees derived from different genes may have resulted from recombination at some time in the recent history of host strains. Reciprocal inoculations of host plant seedlings showed that asexual isolates from B. benekenii and B. ramosus were incapable of infecting B. erectus, whereas the sexual isolates from B. erectus retained the assumed ancestral trait of broad compatibility with Bromus host seedlings. Because all isolates were interfertile in experimental crosses, asexual strains may not be considered independent biological species. We suggest that isolates infecting B. benekenii and B. ramosus represent long‐standing host races or incipient species that emerged after host shifts and that may evolve through host‐mediated reproductive isolation toward independent species.     

Genetic divergence among species of the section Strombocarpa,genusProsopis (Leguminosae)

We studied degree of variability and relationships among populations belonging to five species of the section Strombocarpa of the family Leguminosae, namelyProsopis ferox, P. torquata, P. pubescens, P. strombulifera andP. reptans, by isozyme electrophoresis. The genetic similarity betweenP. reptans andP. strombulifera is high enough for the two to be considered subspecies or geographic races ofP. strombulifera instead of good taxonomic species. As expected these species cluster withP. pubescens, all belonging to series Strombocarpae. This group is different isoenzymatically from the remaining species,P. torquata andP. ferox. Comparison of our results with those obtained earlier for species of the section Algarobia showed that genetic variability in the section Strombocarpa is lower than in the section Algarobia, while the species divergence is much higher. These results suggest different adaptive strategies between these sections.     

Lack of congruence between morphometric evolution and genetic differentiation suggests a recent dispersal and local habitat adaptation of the Madeiran lizard Lacerta dugesii

Genetic differentiation among nine populations of the endemic lizard Lacerta dugesii Milne-Edwards 1829 (Lacertidae) from four groups of islands constituting the Archipelago of Madeira, was investigated by protein electrophoresis at 23 enzyme loci. Among twenty polymorphic loci, the total genetic diversity was due primarily to intra-population variation. The allele and genotypic frequencies among populations showed some heterogeneity, allowing the species to present a structuring pattern compatible with their geographical clustering. Some evidence suggests that selection acting on some loci in different ecological conditions may be responsible for the clustering of the populations studied. There was no apparent isolation effect expected under an "island" model of population divergence, and no correlation was found between genetic and geographic distances among populations. Morphological variation of the proposed three L. dugesii subspecies is not congruent with the allozyme analysis. This most probably suggests a rapid colonization of the islands followed by a strong effect of selection operating over the morphological characters used to define the subspecies.     

Evolvability of between‐year seed dormancy in populations along an aridity gradient

Under global climate change, adaptation to new conditions is crucial for plant species persistence. This requires the ability to evolve in traits that are correlated with changing climatic variables. We studied between‐year seed dormancy, which correlates with environmental variability, and tested for clinal trends in its evolvability along an aridity gradient in Israel. We conducted a germination experiment under five irrigation levels with two dryland winter annuals (Biscutella didyma, Bromus fasciculatus) from four sites along the gradient. Species differed in means and evolvability of dormancy. Biscutella had high dormancy, which significantly increased with aridity but decreased with higher irrigation. In Bromus, dormancy was low, similar among populations, and only marginally affected by irrigation. Evolvability in Biscutella was high and varied among populations, without a clinal trend along the gradient. Conversely, in Bromus, trait evolvability was low and declined with increasing aridity. We argue that changes in evolvability along climatic gradients depend on the relative intensity of stabilizing selection. This may be high in Bromus and not only depends on environmental stress, but also on variability. Our findings point to the importance of measuring evolvability of climate‐related traits across different natural and artificial environments and for many coexisting species. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 924–934.     

Arbuscular mycorrhizal fungal community differs between a coexisting native shrub and introduced annual grass

Arbuscular mycorrhizal fungi (AMF) have been implicated in non-native plant invasion success and persistence. However, few studies have identified the AMF species associating directly with plant invaders, or how these associations differ from those of native plant species. Identifying changes to the AMF community due to plant invasion could yield key plant–AMF interactions necessary for the restoration of native plant communities. This research compared AMF associating with coexisting Bromus tectorum, an invasive annual grass, and Artemisia tridentata, the dominant native shrub in western North America. At three sites, soil and root samples from Bromus and Artemisia were collected. Sporulation was induced using trap cultures, and spores were identified using morphological characteristics. DNA was extracted from root and soil subsamples and amplified. Sequences obtained were aligned and analyzed to compare diversity, composition, and phylogenetic distance between hosts and sites. Richness of AMF species associated with Artemisia in cultures was higher than AMF species associated with Bromus. Gamma diversity was similar and beta diversity was higher in AMF associated with Bromus compared to Artemisia. AMF community composition differed between hosts in both cultures and roots. Two AMF species (Archaeospora trappei and Viscospora viscosum) associated more frequently with Artemisia than Bromus across multiple sites. AMF communities in Bromus roots were more phylogenetically dispersed than in Artemisia roots, indicating a greater competition for resources within the invasive grass. Bromus associated with an AMF community that differed from Artemisia in a number of ways, and these changes could restrict native plant establishment.