Revision of Lyonothamnus A. Gray (Rosaceae) from the Neogene of Western North America

Lyonothamnus Gray is a monotypic genus of evergreen trees endemic to California's Channel Islands. There is one species, L. floribundus, with two subspecies, ssp. floribundus and ssp. asplenifolius. Subspecies floribundus has simple and entire-margined leaves, while leaves of ssp. asplenifolius are pinnate and composed of three to seven primary segments. Despite its restricted modern occurrence, three fossil species have been described from Neogene paleofloras in the far western United States. Lyonothamnus mohavensis Axelrod is known from California; L. parvifolius (Axelrod) Wolfe and L. cedrusensis Axelrod, from Nevada. However, the size ranges used to segregate these species were all found to fall within the range of L. parvifolius from Stewart Valley, Nevada. Study of intact leaves reveals that the combination of (1) number of primary segments, (2) length of primary segments, (3) number of medial secondary segments per primary segment, and (4) lengths and widths of medial secondary segments is important in segregating species. Using these characters, L. parvifolius and L. wolfei Erwin et Schorn sp. nov. are recognized from Nevada and Oregon, and two species, L. mohavensis and L. axelrodii Erwin et Schorn sp. nov., from California. This renewed taxonomy within an updated temporal framework provides an important first step toward understanding the evolution, diversity, paleoecology, and paleobiogeographic history of this unusual member of the Rosaceae.     

Correlated evolution of self-incompatibility and clonal reproduction in Solanum (Solanaceae)

It has been suggested that clonality provides reproductive assurance in cross-fertilizing species subject to pollen limitation, relieving one of the main selective pressures favoring the evolution of self-fertilization. According to this hypothesis, cross-fertilizing species subject to pollen limitation should often be clonal. Here, we investigated the association between clonality and a genetic mechanism enforcing outcrossing, self-incompatibility, in Solanum (Solanaceae). We collected self-incompatibility and clonality information on 87 species, and looked for an association between these two traits. To account for the contribution of shared evolutionary history to this association, we incorporated phylogenetic information from chloroplast (NADH dehydrogenase subunit F) sequence data. We found that self-incompatibility is strongly associated with clonal reproduction: all self-incompatible species reproduce clonally, while the absence of clonality is widespread among self-compatible taxa. The observed correlation persists after taking into account shared phylogenetic history, assumptions about the evolutionary history of self-incompatibility, uncertainty associated with phylogeny estimation, and associations with life history (annual/perennial). Our results are consistent with the hypothesis that clonality provides reproductive assurance, and suggest that the consequences of clonal growth in the evolution of plant reproductive strategies may be more significant than previously thought.     

Leptographium pruni, sp. nov. from bark beetle-infested Prunus jamasakura in Japan

Leptographium species are anamorphs of Ophiostoma, commonly isolated from conifer. There are, however, a small number of these fungi that have been collected from angiosperm hosts. In this study, we describe Leptographium pruni, sp. nov. isolated from the bark of Prunus jamasakura infested by the bark beetle Polygraphus ssiori. This new species is unusual in having a distinct Sporothrix synanamorph with ramoconidia. No evidence of a teleomorph was found, but a high level of tolerance to the antibiotic cycloheximide and the presence of a Sporothrix synanamorph suggest that L. pruni is an Ophiostoma anamorph. Analysis of sequence data for the domain 1 region of the LSUrDNA operon also supports the phylogenetic relationship of L. pruni with Ophiostoma. In addition, sequence data suggest that L. pruni is related to other species of Leptographium rather than Pesotum species with distinct Sporothrix synanamorphs.     

Standardizing methods to address clonality in population studies

Although clonal species are dominant in many habitats, from unicellular organisms to plants and animals, ecological and particularly evolutionary studies on clonal species have been strongly limited by the difficulty in assessing the number, size and longevity of genetic individuals within a population. The development of molecular markers has allowed progress in this area, and although allozymes remain of limited use due to their typically low level of polymorphism, more polymorphic markers have been discovered during the last decades, supplying powerful tools to overcome the problem of clonality assessment. However, population genetics studies on clonal organisms lack a standardized framework to assess clonality, and to adapt conventional data analyses to account for the potential bias due to the possible replication of the same individuals in the sampling. Moreover, existing studies used a variety of indices to describe clonal diversity and structure such that comparison among studies is difficult at best. We emphasize the need for standardizing studies on clonal organisms, and particularly on clonal plants, in order to clarify the way clonality is taken into account in sampling designs and data analysis, and to allow further comparison of results reported in distinct studies. In order to provide a first step towards a standardized framework to address clonality in population studies, we review, on the basis of a thorough revision of the literature on population structure of clonal plants and of a complementary revision on other clonal organisms, the indices and statistics used so far to estimate genotypic or clonal diversity and to describe clonal structure in plants. We examine their advantages and weaknesses as well as various conceptual issues associated with statistical analyses of population genetics data on clonal organisms. We do so by testing them on results from simulations, as well as on two empirical data sets of microsatellites of the seagrasses Posidonia oceanica and Cymodocea nodosa. Finally, we also propose a selection of new indices and methods to estimate clonal diversity and describe clonal structure in a way that should facilitate comparison between future studies on clonal plants, most of which may be of interest for clonal organisms in general.     

Life history traits as predictors of plant rarity, with particular reference to hemiparasiticOrobanchaceae

We made a comparison between life history and reproductive characteristics of a group of Dutch rare (30) and common (105) plant species, all dicotyledonous and insect-visited forbs. The traits life span, clonality, breeding system, seed production, seed dispersal, and soil seed bank longevity are considered. All trait values have been ranked according to their possible effect on the vulnerability of a species for extinction, where low values indicate a low risk and high values a high risk for a species. Rare and common plants differed significantly in four traits: seed production, breeding system, seed bank longevity and clonality. The discriminant analysis showed that 79% of the 135 species was correctly classified in the group they presently belong to. Especially species that are rare now but were much more common 50–100 years ago were classified as being common species, pointing at the detrimental effect of habitat loss these species encountered at which they have not yet been able to adapted to. The data set include eight hemiparasitic plant species (familyOrobanchaceae), of which six are endangered in The Netherlands and two more common. Both rare and common hemiparasites scored high traits values, indicating that they are vulnerable for extinction. The hemiparasites had several characteristics in common: they are all annuals or biennials that have no means of clonal reproduction. They all have non-clustered, zygomorphic flowers that produce nectar and have a precise pollen presentation and are mainly visited by (bumble) bees. Mean life span was significantly shorter in the eight hemiparasiticOrobanchaceae than in the non-hemiparasiticScrophulariaceae used for comparison (4 species). Overall, we concluded that hemiparasitic plants have a special combination of life history traits which makes them vulnerable for local and regional extinction.     

海草克隆性及其种群遗传效应

海草是适应在海洋环境中生存和繁殖的单子叶植物,由于所处环境常存在潮汐、风暴等的干扰,海草形成了一系列适应特征,克隆性是其中突出的一个.所有的海草都具有水平根状茎,许多海草也具有垂直根状茎,在一些海草中,也观察到无性生殖(无融合生殖).与克隆生长有关的参数(如节间长度、间隔子长度、分枝角度以及延伸速率和分枝率等)对于海草的克隆生长有着决定性影响,但繁育系统对克隆斑块大小也有较大影响.强烈的克隆性影响着海草的遗传变异.总体来看,海草种群内遗传多样性比陆生植物低,也低于另一类海洋高等植物-红树植物,利用DNA标记观察到的多样性高于等位酶标记.在一些海草植物种群中观察到较高的克隆多样性,但也有一些种群由单一基因型或少量基因型组成,其原因主要是由于奠基者效应和克隆生长.通常克隆植物中基因流有限,但是海草的克隆片段可能远距离扩散,从而提高种群间的基因流.就克隆生长对种群空间结构和交配系统的影响进行了综述.     

Extensive clonality of the endemic Calamagrostis pseudopurpurea Gerstl. ex O.R. Heine in central Germany revealed by RAPD markers

Calamagrostis pseudopurpurea is one of only a few endemic species in Germany and is confined to the catchment area of the River Mulde in the states of Saxony and Saxony-Anhalt. We studied the genetic structure and seed viability across its entire distribution area. Patterns of random amplified polymorphic DNA (RAPD) variation were analysed using 183 individuals from 43 stands in order to assess the overall genetic structure and the extent of clonality. In addition, four related Calamagrostis species ( C. canescens , C. epigejos , C. phragmitoides and C. villosa ) were included in our study to consider the probable phylogenetic origin of C. pseudopurpurea . We detected two clearly different RAPD phenotypes of C. pseudopurpurea , each distributed along the river banks of two spatially isolated stream courses. Both phenotypes are present downstream of the confluence. Our results indicate that C. pseudopurpurea originates from two distinct periods of hybridisation between the same parental taxa, and that clonal propagation is most likely the main reproduction method. In line with its hybrid origin, embryos of sampled C. pseudopurpurea caryopses were found to be mostly degraded or unviable over several years. Calamagrostis pseudopurpurea is genetically closer to C. canescens and C. phragmitoides than it is to other studied species, but C. canescens and C. phragmitoides have not been proven to be direct parental taxa of C. pseudopurpurea . Calamagrostis pseudopurpurea should therefore still be treated as a separate species that needs special attention from a conservation point of view.     

Polymorphism in the Aegean "five-loculed" species of the genus Campanula, Section Quinqueloculares (Campanulaceae)

Population variation in species of Campanula Section Quinqueloculares and related taxa has been studied. 19 species and 48 populations from the Aegean region have been sampled. There are few distinct character states available for analysis so that metric variables have been scored. 11 leaf variables and 19 flower variables have been measured in up to 683 plants. Regressions of variables with overall size have been calculated and where significant allometric variation has been detected residual scores have been used as variables. Hierarchical analysis of variance has indicated that a large part of the total variation is found between populations within species rather than within populations. Between the 10 most closely related species there is a considerable overlap in population means of variables. Multivariate analysis also fails to identify distinct species clusters. In particular principal components analysis provides additional evidence of overlap between species. It is suggested that a detailed study of genetic variation within and between species is required in order to establish the presence of any distinct phylogenetic lineages.     

Extreme gender flexibility: using a phylogenetic framework to infer the evolution of variation in sex allocation, phylogeography, and speciation in a genus of bidirectional sex changing fishes(Lythrypnus, Gobiidae)

The genus Lythrypnus is a group of marine gobies that exhibit extreme gender flexibility as bidirectional sex changers. The genus consists of 20 described species and several undescribed species that are distributed in the Americas. Five species have been characterized with respect to sex allocation and gonad morphology. The hormonal, morphological, and behavioral aspects of sex change have been studied extensively for one species, L. dalli. These data, however, have not been interpreted in an evolutionary context because a phylogenetic hypothesis has not previously been proposed for the genus Lythrypnus. We propose the first phylogenetic hypothesis for the genus based on molecular data from three mitochondrial genes (12s, ND2, and Cytb), one nuclear gene (Rag1) and one nuclear intron (S7). We also include three previously undescribed Lythrypnus species. Our results support the monophyly of the genus with L. heterochroma, an Atlantic species, as the basal taxon. After the divergence of L. heterochroma, there are two main clades, one comprised of species distributed in the Atlantic, the other comprised of species distributed in the Pacific. These data indicate an Atlantic origin for the genus, followed by divergence after the closure of the Isthmus of Panama. Our data also support the monophyly of three previously described species complexes, the L. rhizophora complex and L. dalli complex in the Pacific, and the L. mowbrayi complex in the Atlantic. We mapped patterns of sex allocation within this genus onto the fully resolved and supported topology, and found that sexual plasticity and gender flexibility is likely a synapomorphy for the genus. Overall our results create a well-supported framework to understand the phylogeography of the genus, and to interpret the evolution of sex allocation in Lythrypnus gobies.     

Parallel speciation or long‐distance dispersal? Lessons from seaweeds (Fucus) in the Baltic Sea

Parallel evolution has been invoked as a forceful mechanism of ecotype and species formation in many animal taxa. However, parallelism may be difficult to separate from recently monophyletically diverged species that are likely to show complex genetic relationships as a result of considerable shared ancestral variation and secondary hybridization in local areas. Thus, species' degrees of reproductive isolation, barriers to dispersal and, in particular, limited capacities for long‐distance dispersal will affect demographical structures underlying mechanisms of divergent evolution. Here, we used nine microsatellite DNA markers to study intra‐ and interspecific genetic diversity of two recently diverged species of brown macroalgae, Fucus radicans (L. Bergström & L. Kautsky) and F. vesiculosus (Linnaeus), in the Baltic Sea. We further performed biophysical modelling to identify likely connectivity patterns influencing the species' genetic structures. For each species, we found intraspecific contrasting patterns of clonality incidence and population structure. In addition, strong genetic differentiation between the two species within each locality supported the existence of two distinct evolutionary lineages (F_ST = 0.15–0.41). However, overall genetic clustering analyses across both species' populations revealed that all populations from one region (Estonia) were more genetically similar to each other than to their own taxon from the other two regions (Sweden and Finland). Our data support a hypothesis of parallel speciation. Alternatively, Estonia may be the ancestral source of both species, but is presently isolated by oceanographic barriers to dispersal. Thus, a limited gene flow in combination with genetic drift could have shaped the seemingly parallel structure.     

A Battle Lost? Report on Two Centuries of Invasion and Management of Lantana camara L. in Australia,India and South Africa

Recent discussion on invasive species has invigorated the debate on strategies to manage these species. Lantana camara L., a shrub native to the American tropics, has become one of the worst weeds in recorded history. In Australia, India and South Africa, Lantana has become very widespread occupying millions of hectares of land. Here, we examine historical records to reconstruct invasion and management of Lantana over two centuries and ask: Can we fight the spread of invasive species or do we need to develop strategies for their adaptive management? We carried out extensive research of historical records constituting over 75% of records on invasion and management of this species in the three countries. The records indicate that governments in Australia, India and South Africa have taken aggressive measures to eradicate Lantana over the last two centuries, but these efforts have been largely unsuccessful. We found that despite control measures, the invasion trajectory of Lantana has continued upwards and that post-war land-use change might have been a possible trigger for this spread. A large majority of studies on invasive species address timescales of less than one year; and even fewer address timescales of >10 years. An understanding of species invasions over long time-scales is of paramount importance. While archival records may give only a partial picture of the spread and management of invasive species, in the absence of any other long-term dataset on the ecology of Lantana, our study provides an important insight into its invasion, spread and management over two centuries and across three continents. While the established paradigm is to expend available resources on attempting to eradicate invasive species, our findings suggest that in the future, conservationists will need to develop strategies for their adaptive management rather than fighting a losing battle.     

Alkaloid profile of leaves and seeds of Lupinus hintonii C. P. Smith

L. hintonii C. P. Smith grows in the Central Highland forests of Mexico at altitudes between 2800 m to 3200 m above see level. Members of the genus Lupinus produce quinolizidine alkaloids as main chemical defensive compounds against herbivores. Surprisingly alkaloid profiles are rather constant within this species, while substantial variation was found when compared to morphologically closely related other taxa. As part of a phytochemical project on Mexican wild lupins, we report on the alkaloid profiles of seeds and leaves of L. hintonii. 19 alkaloids could be identified by capillary GLC-MS. Six major alkaloids occurred in leaves and seeds: 13-hydroxylupanine (28% and 45% respectively), tetrahydrorhombifoline (31% and 23% respectively), angustifoline (2% and 4% respectively), lupanine (7% and 5% respectively), 13alpha-tigloyloxylupanine (19% and 5% respectively) and 4alpha-angeloyl-3beta-hydroxylupanine (9% and 2%). This chemical pattern resembles that of the North American lupin L. floribundus.     

126 Porphyra Birdiae Neefus et Mathieson (Bangiales, Rhodophyta): A New Species from the Northwest Atlantic

Recent studies combining biochemical, molecular, and traditional morphological and ecological traits have shown that some currently recognized species of the red algal genus Porphyra are actually "form species" or "complexes" comprising several morphologically similar but genetically distinct taxa. Conflicting reports of chromosome numbers and differences in DNA sequences reported for Porphyra purpurea (Roth) C. Agardh have raised suspicion that more than one taxon has been confused under this name in the Northwest Atlantic. We have identified one of these cryptic taxa and have recently described it as a new species, Porphyra birdiae . Like P. purpurea (Roth) C. Agardh, it has an ovate to broadly elongate, foliose blade with reproductive areas segregated by a distinct line into male and female sectors. While reproductive specimens have historically been confused with P. purpurea , non-reproductive specimens of P. birdiae have been incorrectly identified as P. umbilicalis Kützing. Although P. birdiae is morphologically similar to both of these species, sequences of SSU (nuclear small subunit rRNA gene) and rbc L (plastid ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit gene) indicate that it is not closely related to either one. Based on rbc L sequences, P. birdiae is closely related to P. aestivalis Lindstrom et Fredericq, a proposed new species from Alaska.     

Species density and associations in Caribbean reef corals

The density of scleractinian corals on portions of two reefs in the Grenadine Islands, W. I. has been investigated by direct observation by SCUBA divers. Grid, transect, and random quadrat methods were compared with total samples to determine the precision and accuracy of these techniques. Transect methods were generally satisfactory provided at least 15% of a 400 m² total grid area was included in the sample. The data strongly indicated clumped distributions of all species, although numerical analysis does not indicate the distinct zones reported by other workers. Species associations based on Jaccard's coefficient and cluster analysis showed possible similarities in physical requirements, although few strong associations were found. Data based on 4 m² quadrats generally provided a more reliable estimate of species associations than did data based on 1 m² quadrats. It is suggested that surveys of these reef types may be better based on a number of parallel transects rather than a single transect, and that well-defined zones are more likely to be the exception than the rule.     

Genetic differentiation in the African malaria vector, Anopheles gambiae s.s., and the problem of taxonomic status

Of the seven recognized species of the Anopheles gambiae complex, A. gambiae s.s. is the most widespread and most important vector of malaria. It is becoming clear that, in parts of West Africa, this nominal species is not a single panmictic unit. We found that the internal transcribed spacer (ITS) of the X-linked rDNA has two distinct sequences with three fixed nucleotide differences; we detected no heterozygotes at these three sites, even in areas of sympatry of the two ITS types. The intergenic spacer (IGS) of this region also displays two distinct sequences that are in almost complete linkage disequilibrium with the distinct ITS alleles. We have designated these two types as S/type I and M/type II. These rDNA types correspond at least partly to the previously recognized chromosomal forms. Here we expand the geographic range of sampling to 251 individuals from 38 populations. Outside of West Africa, a single rDNA type, S/type I, corresponds to the Savanna chromosomal form. In West Africa, both types are often found in a single local sample. To understand if these findings might be due to unusual behavior of the rDNA region, we sequenced the same region for 46 A. arabiensis, a sympatric sibling species. No such distinct discontinuity was observed for this species. Autosomal inversions in one chromosome arm (2R), an insecticide resistance gene on 2L, and this single X-linked region indicate at least two genetically differentiated subpopulations of A. gambiae. Yet, rather extensive studies of other regions of the genome have failed to reveal genetic discontinuity. Evidently, incomplete genetic isolation exists within this single nominal species.     

Is Lutzomyia serrana (Diptera, Psychodidae, Phlebotominae) present in Ecuador?

We describe a multivariate metric comparison of three sandfly species showing strong differences in size, which questions the geographical distribution of one of them. Two species are represented by a single population (L. robusta and L. guilvardae) and one by two populations (L. serrana). All of them belong to the series serrana (Diptera, Psychodidae, Phlebotominae). The morphometric data confirm that L. guilvardae is a distinct species. However, they suggest that L. robusta and L. serrana in Ecuador are the same taxon, and that it is distinguishable from the population of L. serrana in Bolivia. A multilocus enzyme electrophoresis analysis comparing L. serrana in Bolivia and L. robusta in Ecuador adds further evidence that these two populations are distinct species. Thus, our data seem to indicate that, in Ecuador, the population previously identified as L. serrana is actually the same species as the allopatric population previously identified as L. robusta. Accepting L. serrana in Ecuador as small-sized L. robusta, the resulting geographic distribution of this latter becomes in closer agreement with ecology and epidemiology.     

Phylogeographic analysis reveals a deep lineage split within North Atlantic Littorina saxatilis

Phylogeographic studies provide critical insight into the evolutionary histories of model organisms; yet, to date, range-wide data are lacking for the rough periwinkle Littorina saxatilis, a classic example of marine sympatric speciation. Here, we use mitochondrial DNA (mtDNA) sequence data to demonstrate that L. saxatilis is not monophyletic for this marker, but is composed of two distinct mtDNA lineages (I and II) that are shared with sister species Littorina arcana and Littorina compressa. Bayesian coalescent dating and phylogeographic patterns indicate that both L. saxatilis lineages originated in the eastern North Atlantic, around the British Isles, at approximately 0.64 Ma. Both lineages are now distributed broadly across the eastern, central and western North Atlantic, and show strong phylogeographic structure among regions. The Iberian Peninsula is genetically distinct, suggesting prolonged isolation from northeastern North Atlantic populations. Western North Atlantic populations of L. saxatilis lineages I and II predate the last glacial maximum and have been isolated from eastern North Atlantic populations since that time. This identification of two distinct, broadly distributed mtDNA lineages further complicates observed patterns of repeated incipient ecological speciation in L. saxatilis, because the sympatric origins of distinct ecotype pairs on eastern North Atlantic shores may be confounded by admixture of divergent lineages.     

Cryptic species in an endangered pondweed community (Potamogeton, Potamogetonaceae) revealed by AFLP markers

Cryptic species are morphologically indistinguishable, yet reproductively isolated. Morphological boundaries between species can also be obscured by hybridization and clonality. Determining the roles of reproductive isolation, hybridization, and clonality in morphologically indistinguishable taxa is essential to determining appropriate species-level taxonomic rankings for conservation purposes. The taxonomic status of the endangered Little Aguja pondweed of west Texas, Potamogeton clystocarpus, is uncertain due to a lack of fixed morphological differences between it and two sympatric congeners. Morphology, amplified fragment length polymorphisms (AFLPs), and sequences of the internal transcribed spacer (ITS) region and trnL-F intron and spacer were used to determine the degree of genetic distinctiveness, hybridization and clonality for this rare species. AFLPs indicate that P. clystocarpus is a genetically distinct lineage compared to P. pusillus and P. foliosus. No hybrids involving P. clystocarpus were detected, but two putative hybrids involving P. pusillus and P. foliosus were identified. Clonal growth was only detected in P. pusillus. A combination of morphological and molecular markers was successful in determining the genetic distinctiveness of an endangered cryptic species, Potamogeton clystocarpus. Further sampling in this and adjacent drainages is necessary to assess the degree of endemism of P. clystocarpus and confidently rule out hybridization and clonality in this taxon.