Distyly and pollen dimorphism inLinum suffruticosum (Linaceae)

The Mediterranean distylousLinum suffruticosum has dimorphic pollen. That from short-styled plants has sub-monomorphic surface excrescences with minute papillae; that from long-styled plants has strongly dimorphic excrescences with conspicuous papillae. The differences are much like those described in species of other sections of the genus. Pollen of the related homostylousL. tenuifolium has monomorphic pollen. It combines characteristics of bothL. suffruticosum types but resembles that of the long-styled plants somewhat more closely. Ribbonlike styles of long-styled plants ofL. suffruticosum provide another feature which seems to be controlled by the S supergene thought to be associated with distylic incompatibility. The pollen ofL. suffruticosum andL. tenuifolium is very similar to that of some species of sectionLinastrum and would support their placement in that section.     

CHLOROPLAST DNA VARIABILITY AMONG LINUM SPECIES

We have compared the chloroplast DNA maps of a selection of Linum species, using recombinant DNA probes derived from L. usitatissimum chloroplast DNA. The heterologous probes have allowed us to construct physical maps for seven other Linum species. The chloroplast DNAs from two other species, L. flavum and L. tenuifolium, were so divergent that restriction maps could not be derived by this method. Analysis of the differences between the chloroplast DNAs has produced a phylogeny separating the species into two groups. These groups are coincident with previous taxonomic groupings and consist of L. perenne-related and non-related species. The major difference between the chloroplast DNAs of the two groups is a 13-kilobase pair segment near an inverted repeat/large single copy region boundary, which is present in the perenne-group species and absent from the non-perenne group species. In addition, we have identified a mutational hotspot analogous to that found in Nicotiana species chloroplast DNAs (Tassopulu and Kung, 1984). Among the species examined, the amount of base pair substitutions approaches 14% for the sites examined.     

Past forest cover explains current genetic differentiation in the Carpathian newt (Lissotriton montandoni), but not in the smooth newt (L. vulgaris)

Aim

Current genetic variation and differentiation are expected to reflect the effects of past rather than present landscapes due to time lags, that is, the time necessary for genetic diversity to reach equilibrium and reflect demography. Time lags can affect our ability to infer landscape use and model connectivity and also obscure the genetic consequences of recent landscape changes. In this work, we test whether past forest cover better explains contemporary patterns of genetic differentiation in two closely related but ecologically distinct newt species—Lissotriton montandoni and L. vulgaris.

Location

Carpathian Mountains and foothills.

Methods

Genetic differentiation between populations was related to landscape resistance optimized with tools from landscape genetics, for multiple timeframes, using forest-cover data from 1963 to 2015. Analyses were conducted for pairs of populations at distances from 1 to 50 km.

Results

We find evidence for a time lag in L. montandoni, with forest cover from 40 years ago (ca. 10 newt generations) better explaining current genetic differentiation. In L. vulgaris, current genetic differentiation was better predicted by present land-cover models with lower resistance given to open forests. This result may reflect the generalist ecology of L. vulgaris, its lower effective population sizes and exposure to habitat destruction and fragmentation.

Main Conclusions

Our study provides evidence for time lags in L. montandoni, showing that the genetic consequences of landscape change for some species are not yet evident. Our findings highlight the interspecific variation in time lag prevalence and demonstrate that current patterns of genetic differentiation should be interpreted in the context of historical landscape changes.     

Development of Linum flavum hairy root cultures for production of coniferin

Linum flavum hairy roots were initiated from leaf discs using Agrobacterium rhizogenes strains LBA9402 and TR105 though two other strains, 15834 and A4, were relatively ineffective for induction. Significant variation in coniferin accumulation was observed between hairy root lines originating from different L. flavum seedlings and/or A. rhizogenes strains. Coniferin reached 58 mg g^–1 dry wt by culturing the roots in Linsmaier and Skoog (LS) medium with 2,4-dichlorophenoxyacetic acid and naphthaleneacetic acid as growth regulators.     

Hunting and the fate of French breeding waterbirds

Capsule French breeding populations of hunted waterbirds have more negative long-term population trends than closely related non-hunted species.

Aims To assess the relative fate of breeding populations of hunted and non-hunted waterbird species in France.

Methods We compared long-term population growth rates of hunted versus non-hunted waterbirds using two large-scale and long-term national surveys.

Results Waterbirds globally displayed long-term increases in population sizes most likely driven by their positive response to the implementation of numerous protected areas over remnant wetlands across the country since the early 1970s. In contrast, hunted species revealed more negative trends compared to non-hunted species.

Conclusion A causal relationship between hunting and population dynamics is not demonstrated here, but the results are consistent with species' breeding populations being negatively affected, on average, if they are hunted.     

Contrasting effects of habitat discontinuity on three closely related fungivorous beetle species with diverging host‐use patterns and dispersal ability

Understanding how landscape structure influences biodiversity patterns and ecological processes are essential in ecological research and conservation practices. Forest discontinuity is a primary driver affecting the population persistence and genetic structure of forest‐dwelling species. However, the actual impacts on populations are highly species‐specific. In this study, we tested whether dispersal capability and host specialization are associated with susceptibility to forest discontinuity using three closely related, sympatric fungivorous ciid beetle species (two host specialists, Octotemnus assimilis and O. crassus; one host generalist, O. kawanabei). Landscape genetic analyses and the estimation of effective migration surfaces (EEMS) method consistently demonstrated contrasting differences in the relationships between genetic structure and configuration of forest land cover. Octotemnus assimilis, one of the specialists with a presumably higher dispersal capability due to lower wing loading, lacked a definite spatial genetic structure in our study landscape. The remaining two species showed clear spatial genetic structure, but the results of landscape genetic analyses differed between the two species: while landscape resistance appeared to describe the spatial genetic structure of the specialist O. crassus, genetic differentiation of the generalist O. kawanabei was explained by geographic distance alone. This finding is consistent with the prediction that nonforest areas act more strongly as barriers between specialist populations. Our results suggest that differences in host range can influence the species‐specific resistance to habitat discontinuity among closely related species inhabiting the same landscape.     

The evolutionary breakdown of distyly inLinum tenuifolium (Linaceae)

Distyly inLinum tenuifolium L. is associated with a high degree of self-incompatibility. Breakdown in this system has occurred without the morphological rearrangement expected as the result of cross-over within the distyly supergene. Pollen-flow in both distylous and monomorphic populations is leptokurtic. A high proportion of intra-flower pollination occurs. Pollen production per ovule is reduced in the self-compatible race. Mean seed-set is increased. Individuals of the self-compatible race produce less vegetative growth and require a shorter time to reach reproductive maturity under cultivation. Increased fecundity appears to provide the selective advantage promoting the breakdown of self-incompatibility in this species. This is achieved through a massive shift of resources toward female reproductive function in plants of the monomorphic race. Subsequent colonization by this race has led to its increased distribution in C. & S. Europe.     

Comparative Genome Analysis in Two Flax Species by C-Banding Patterns

C-banding patterns of the karyotypes of two closely related wild flax species, Linum austriacumL. (2n= 18) and Linum grandiflorumDesf. (2n= 16), were studied. The karyotypes of both species were similar in the chromosome morphology and size. In each species, metacentric and acrocentric chromosomes (1.7–4.3 m) and one satellite chromosome were observed. In the karyotypes of the species studied, all homologous chromosome pairs were identified, and quantitative idiograms were constructed. Eight chromosome pairs in the two species had similar C-banding patterns. A low level of intraspecific polymorphism in the intercalary and telomeric C-bands was shown in both species. The results indicate that the genomes of two flax species originated from one ancestral genome with the basic chromosome number of 8 or 9. Apparently, the duplication or loss of one chromosome with subsequent redistribution of the chromosome material in the ancestral form resulted in the divergence into two species,L. austriacumL. and L. grandiflorumDesf. A considerable similarity of chromosomes in these species provides evidence for their close phylogenetic relatedness, which makes it possible to place them in one section within the Linumgenus.     

The Effects of Landscape Modifications on the Long-Term Persistence of Animal Populations

Background

The effects of landscape modifications on the long-term persistence of wild animal populations is of crucial importance to wildlife managers and conservation biologists, but obtaining experimental evidence using real landscapes is usually impossible. To circumvent this problem we used individual-based models (IBMs) of interacting animals in experimental modifications of a real Danish landscape. The models incorporate as much as possible of the behaviour and ecology of four species with contrasting life-history characteristics: skylark (Alauda arvensis), vole (Microtus agrestis), a ground beetle (Bembidion lampros) and a linyphiid spider (Erigone atra). This allows us to quantify the population implications of experimental modifications of landscape configuration and composition.

Methodology/Principal Findings

Starting with a real agricultural landscape, we progressively reduced landscape complexity by (i) homogenizing habitat patch shapes, (ii) randomizing the locations of the patches, and (iii) randomizing the size of the patches. The first two steps increased landscape fragmentation. We assessed the effects of these manipulations on the long-term persistence of animal populations by measuring equilibrium population sizes and time to recovery after disturbance. Patch rearrangement and the presence of corridors had a large effect on the population dynamics of species whose local success depends on the surrounding terrain. Landscape modifications that reduced population sizes increased recovery times in the short-dispersing species, making small populations vulnerable to increasing disturbance. The species that were most strongly affected by large disturbances fluctuated little in population sizes in years when no perturbations took place.

Significance

Traditional approaches to the management and conservation of populations use either classical methods of population analysis, which fail to adequately account for the spatial configurations of landscapes, or landscape ecology, which accounts for landscape structure but has difficulty predicting the dynamics of populations living in them. Here we show how realistic and replicable individual-based models can bridge the gap between non-spatial population theory and non-dynamic landscape ecology. A major strength of the approach is its ability to identify population vulnerabilities not detected by standard population viability analyses.     

Lignans in seeds of Linum species

Mature seeds of 20 Linum species were analyzed for their content of lignans. The seeds of common flax (Linum usitatissimum L.) are known to contain as characteristic lignan sesoisolariciresinol diglucoside (SDG), whose presence in seeds of some other Linum species has also been reported. In order to investigate the material for the presence of such very polar lignans as well as for less polar non-glycosidic lignans as frequently found in aerial parts of Linum species, polar and non-polar extracts of each sample were analyzed by HPLC/ESI-MSMS.SDG was detected in 15 of 16 investigated seed samples of taxa representing sections Linum and Dasylinum. None of eight samples of taxa from sections Syllinum and Linopsis contained detectable amounts of SDG. Quite interestingly, most of the SDG-positive samples contained the 8R,8′R-isomer exclusively while only three (including L. usitatissimum) contained the 8S,8′S-stereoisomer as the predominant form. As a most noteworthy finding, the dichloromethane extracts obtained from seeds of several Linum species were found to contain significant concentrations of non-polar cyclolignans of the arylnaphthalene/-dihydronaphthalene lactone type or, alternatively of the aryltetralin lactone type. Thus, seeds of Linum perenne L. as well as those of several other representatives of sections Linum and Dasylinum were found to contain significant concentrations of the arylnaphthalene justicidin B along with further compounds of this type and some aryldihydronaphthalene-type lignans. On the other hand, seeds of Linum flavum and further representatives of section Syllinum were found to contain aryltetralin-type lignans, mainly in the form of esters with aliphatic carboxylic acids, such as 6-methoxypodophyllotoxin-7-O-n-hexanoate, whose occurrence in L. flavum seeds has very recently been reported by us for the first time.Various chemosystematic and biogenetic aspects are discussed in the light of these results.     

Comparative Population Dynamics of Two Closely Related Species Differing in Ploidy Level

Background

Many studies compare the population dynamics of single species within multiple habitat types, while much less is known about the differences in population dynamics in closely related species in the same habitat. Additionally, comparisons of the effect of habitat types and species are largely missing.

Methodology and Principal Findings

We estimated the importance of the habitat type and species for population dynamics of plants. Specifically, we compared the dynamics of two closely related species, the allotetraploid species Anthericum liliago and the diploid species Anthericum ramosum, occurring in the same habitat type. We also compared the dynamics of A. ramosum in two contrasting habitats. We examined three populations per species and habitat type. The results showed that single life history traits as well as the mean population dynamics of A. liliago and A. ramosum from the same habitat type were more similar than the population dynamics of A. ramosum from the two contrasting habitats.

Conclusions

Our findings suggest that when transferring knowledge regarding population dynamics between populations, we need to take habitat conditions into account, as these conditions appear to be more important than the species involved (ploidy level). However, the two species differ significantly in their overall population growth rates, indicating that the ploidy level has an effect on species performance. In contrast to what has been suggested by previous studies, we observed a higher population growth rate in the diploid species. This is in agreement with the wider range of habitats occupied by the diploid species.     

The viability of a plant “on the edge”: Glaucium flavum (Papaveraceae) in Norway

The prospects for persistence of Glaucium flavum in Norway were evaluated by integrating data concerning spatio‐temporal distribution, plant growth and development, reproduction, dispersal, seed bank and genetic variability. The distribution of Glaucium flavum in the Oslo Fjord region is much more restricted now than before. Out of the formerly recorded 35 populations, only eight populations were present in 1998, all in the outer parts of the fjord. The species is a short‐lived iteroparous perennial in Norway. This growth habit gives high reproductive output from fertile individuals. G. flavum is self‐compatible and can easily reproduce even in small populations. The ability to disperse long distances on water is limited. The observed seed bank will therefore enhance survival. No variation in isoenzymes was observed neither within nor among the G. flavum populations in the Oslo Fjord region. The species should be considered Endangered in Norway, according to the criteria given by IUCN.     

Genetic diversity,population structure and sex‐biased dispersal in three co‐evolving species

Genetic diversity and spatial structure of populations are important for antagonistic coevolution. We investigated genetic variation and population structure of three closely related European ant species: the social parasite Harpagoxenus sublaevis and its two host species Leptothorax acervorum and Leptothorax muscorum. We sampled populations in 12 countries and analysed eight microsatellite loci and an mtDNA sequence. We found high levels of genetic variation in all three species, only slightly less variation in the host L. muscorum. Using a newly introduced measure of differentiation (Jost’s D_est ), we detected strong population structuring in all species and less male‐biased dispersal than previously thought. We found no phylogeographic patterns that could give information on post‐glacial colonization routes – northern populations are as variable as more southern populations. We conclude that conditions for Thompson’s geographic mosaic of coevolution are ideal in this system: all three species show ample genetic variation and strong population structure.     

FOUNDER EFFECTS AND THE RATE OF MITOCHONDRIAL DNA EVOLUTION IN HAWAIIAN DROSOPHILA

The nearly-neutral-mutation theory predicts that populations with small effective sizes will undergo more rapid molecular evolution than populations with very large effective sizes. In particular, Ohta (1976) predicted that populations of Hawaiian Drosophila that are known to have small population sizes and to experience repeated population bottlenecks due to founder events should show a more rapid rate of molecular evolution relative to the rate of molecular evolution of species with large population sizes such as the continental Drosophila. In this paper we test this prediction by comparing the rate of molecular evolution in two closely related lineages of Hawaiian Drosophila that have experienced very different evolutionary histories. Both lineages belong to the planitibia subgroup of Hawaiian Drosophila. The beta lineage (which includes D. silvestris, D. planitibia, D. differens, and D. hemipeza) has undergone repeated founder events, as evidenced by their geographic distribution and behavioral biology. On the other hand, evidence on geographic distribution and behavior indicates that the alpha lineage (which includes D. melanocephala, D. cyrtaloma, and D. neoperkinsi) has arisen from large ancestral populations without founder effects. The mitochondrial DNA data reveal that, within a lineage, the rate of molecular evolution is rather uniform, while all comparisons between the two lineages show that the rate of molecular evolution in the beta lineage is three times that of the alpha lineage. This analysis strongly supports the predictions made by Ohta.     

Establishment of hairy root cultures of Linum flavum producing the lignan 5-methoxypodophyllotoxin

Hairy root cultures were induced from leaf explants of Linum flavum by infection with Agrobacterium rhizogenes. The transformed nature of tissue was confirmed by the production of opines. The cultures produced 1.5 to 3.5% of the lignan 5-methoxypodophyllotoxin (5-MPT) on a dry weight basis, which was 2 to 5 times higher than the 5-MPT content in untransformed root cultures and 5 to 12 times higher than in L. flavum cell suspensions. The 5-MPT production as a function of time was up to four times higher than that in cell suspensions.Abbreviations NAA 1-naphthaleneacetic acid - BAP 6-benzylaminopurine - 5-MPT 5-methoxypodophyllotoxin - DW dry weight - GC-MS gas-chromatography coupled electron impact mass spectrometry     

Syntopic frogs reveal different patterns of interaction with the landscape: A comparative landscape genetic study of Pelophylax nigromaculatus and Fejervarya limnocharis from central China

Amphibians are often considered excellent environmental indicator species. Natural and man‐made landscape features are known to form effective genetic barriers to amphibian populations; however, amphibians with different characteristics may have different species–landscape interaction patterns. We conducted a comparative landscape genetic analysis of two closely related syntopic frog species from central China, Pelophylax nigromaculatus (PN) and Fejervarya limnocharis (FL). These two species differ in several key life history traits; PN has a larger body size and larger clutch size, and reaches sexual maturity later than FL. Microsatellite DNA data were collected and analyzed using conventional (F_ST, isolation by distance (IBD), AMOVA) and recently developed (Bayesian assignment test, isolation by resistance) landscape genetic methods. As predicted, a higher level of population structure in FL (F_ST′ = 0.401) than in PN (F_ST′ = 0.354) was detected, in addition to FL displaying strong IBD patterns (r = .861) unlike PN (r = .073). A general north–south break in FL populations was detected, consistent with the IBD pattern, while PN exhibited clustering of northern‐ and southern‐most populations, suggestive of altered dispersal patterns. Species‐specific resistant landscape features were also identified, with roads and land cover the main cause of resistance to FL, and elevation the main influence on PN. These different species–landscape interactions can be explained mostly by their life history traits, revealing that closely related and ecologically similar species have different responses to the same landscape features. Comparative landscape genetic studies are important in detecting such differences and refining generalizations about amphibians in monitoring environmental changes.     

SPECIES RECOGNITION AND PATTERNS OF POPULATION VARIATION IN THE REPRODUCTIVE STRUCTURES OF A DAMSELFLY GENUS

The selection pressures imposed by mate choice for species identity should impose strong stabilizing selection on traits that confer species identity to mates. Thus, we expect that such traits should show nonoverlapping distributions among closely related species, but show little to no variance among populations within a species. We tested these predictions by comparing levels of population differentiation in the sizes and shapes of male cerci (i.e., the clasper structures used for species identity during mating) of six Enallagma damselfly species. Cerci shapes were nonoverlapping among Enallagma species, and five of six Enallagma species showed no population variation across their entire species ranges. In contrast, cerci sizes overlapped among species and varied substantially among populations within species. These results, taken with previous studies, suggest that cerci shape is a primary feature used in species recognition used to discriminate conspecific from heterospecifics during mating.     

Tree species dynamics and disturbance in three Swedish boreal forest stands during the last two thousand years

Abstract. Data from three forest stands for the past 2000 yr show how the shade-intolerant species Pinus sylvestris and Betula pubescens maintain significant populations in the Swedish boreal landscape. Age structure data from a northern stand close to the range limits of Picea abies and Pinus complement a local pollen diagram, and reveal cyclic population fluctuations which can be related to periods of climatic stress and fire. Pollen data from two southern stands show that high fire frequencies in the past prevented the expansion of Picea populations. Reduction of the fire frequency during the last 200 yr has favoured Picea. A long time perspective reveals the population dynamics of long-lived species and indicates the controlling factors. Such knowledge permits assessment of the current status and likely future of forest stands.     

The influence of stage-dependent dispersal on the population dynamics of three amphipod species

In metapopulations, the maintenance of local populations can depend on source–sink dynamics, where populations with positive growth rate seed populations with negative growth rate. The pattern and probability of successful dispersal among habitats can therefore be crucial in determining whether local populations will become rare or increase in abundance. We present here data on the dispersal strategy and population dynamics of three marine amphipods living in pen shells (Atrina rigida) in the Gulf of Mexico. The three amphipod species in this study disperse at different life stages. Neomegamphopus hiatus and Melita nitida disperse as adults, while Bemlos unicornis disperses as juveniles. The two species that disperse as adults have the highest initial population sizes when a new shell becomes available, likely caused by the arriving females releasing their brood into these recently occupied shells. This dispersal pattern results in initially higher population growth, but fewer occupied shells, as noted by their clumped distribution. In contrast, the species that disperses as juveniles accumulates more slowly and more evenly across habitats, eventually dominating the other two in terms of numerical abundance. The metapopulation dynamics of the three species seems to be highly dependent on the life history stage involved in dispersal. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.