Experimental Feeding of Hydrilla verticillata Colonized by Stigonematales Cyanobacteria Induces Vacuolar Myelinopathy in Painted Turtles (Chrysemys picta)

Vacuolar myelinopathy (VM) is a neurologic disease primarily found in birds that occurs when wildlife ingest submerged aquatic vegetation colonized by an uncharacterized toxin-producing cyanobacterium (hereafter “UCB” for “uncharacterized cyanobacterium”). Turtles are among the closest extant relatives of birds and many species directly and/or indirectly consume aquatic vegetation. However, it is unknown whether turtles can develop VM. We conducted a feeding trial to determine whether painted turtles (Chrysemys picta) would develop VM after feeding on Hydrilla (Hydrilla verticillata), colonized by the UCB (Hydrilla is the most common “host” of UCB). We hypothesized turtles fed Hydrilla colonized by the UCB would exhibit neurologic impairment and vacuolation of nervous tissues, whereas turtles fed Hydrilla free of the UCB would not. The ability of Hydrilla colonized by the UCB to cause VM (hereafter, “toxicity”) was verified by feeding it to domestic chickens (Gallus gallus domesticus) or necropsy of field collected American coots (Fulica americana) captured at the site of Hydrilla collections. We randomly assigned ten wild-caught turtles into toxic or non-toxic Hydrilla feeding groups and delivered the diets for up to 97 days. Between days 82 and 89, all turtles fed toxic Hydrilla displayed physical and/or neurologic impairment. Histologic examination of the brain and spinal cord revealed vacuolations in all treatment turtles. None of the control turtles exhibited neurologic impairment or had detectable brain or spinal cord vacuolations. This is the first evidence that freshwater turtles can become neurologically impaired and develop vacuolations after consuming toxic Hydrilla colonized with the UCB. The southeastern United States, where outbreaks of VM occur regularly and where vegetation colonized by the UCB is common, is also a global hotspot of freshwater turtle diversity. Our results suggest that further investigations into the effect of the putative UCB toxin on wild turtles in situ are warranted.     

Bacterial community structure in freshwater springs infested with the invasive plant species Hydrilla verticillata

The phylogenetic composition and physiological profiles of bacterial communities in freshwater springs were evaluated during the blooming and non-blooming stages of the invasive plant species, Hydrilla verticillata. Community-level physiological profiles (CLPPs) and pyrosequencing of 16S rRNA gene amplicons were used to study potential Hydrilla mediated shifts in the physiological potential and phylogenetic composition of the bacterial community in infested systems. The results of CLPP revealed that the microbes in the Hydrilla invaded sites utilized less substrates during blooming periods than during non-blooming periods of the plant. Spearman’s rank correlation analysis showed some relationships between the relative abundances of bacterial taxa and the Biolog substrate utilization pattern. The relative abundance of the identified taxa showed some striking differences based on the blooming status of Hydrilla and to a lesser extent on site variation. The relative abundance of Actinobacteria, Bacteriodetes, and Verrucomicrobia was generally higher during Hydrilla blooms, while Deltaproteobacteria was generally higher during non-blooming stages of Hydrilla. The detected genera also varied based on the blooming stages of the plant. Based on the findings, it appears that Hydrilla alters the phylogenetic composition and structure of the bacterial community during the blooming stage.     

Effects of light and spermine on senescence of hydrilla and spinach leaves

Light treatment markedly accelerated chlorophyll loss in Hydrilla (Hydrilla verticillata [L.f.] Royle) over dark treatment whereas such acceleration could not be observed in spinach (Spinacia oleracea L.) leaf segments. Spermine, a polyamine, retarded the loss of chlorophyll in the dark but markedly accelerated this loss in the light during senescence of Hydrilla leaves. However, such effect of spermine in the dark was not so pronounced in spinach. The loss of protein was slower in the light than in the dark in both the species. Spermine arrested the loss of protein (as in spinach) or even raised the protein level over initial (as in Hydrilla). Loss of both soluble and insoluble protein was slower in light than in darkness. Spermine treatment, either in light or darkness, markedly accelerated the loss of soluble protein but raised the level of insoluble protein over initial in both the species. The pattern of change in α-amino nitrogen in either species could be correlated well with that of protein level. In Hydrilla, light increased the soluble protein fraction over initial and this rise was prevented by cycloheximide and not by chloramphenicol. Also, spermine augmented the protease activity (both acid and neutral) while light retarded the rise in protease activity during senescence of either species. Although spermine treatment reduced the leaching of α-amino nitrogen and electrolytes in Hydrilla, it augmented the same in spinach.     

Leaves and pollen of bamboos from the Polish Neogene

Recently discovered fossil bamboo leaves and pollen are described from the Neogene of Poland. Morphological analysis of fossil leaves from the Late Miocene deposits of the Bełchatów Lignite Mine, Central Poland have allowed them to be determined as “Bambusa” lugdunensis Saporta. It is the first record of this species in the Cenozoic of Poland. The fossils have been compared with other records of bamboos from the Cenozoic of Europe. Pollen grains from the Middle Miocene (Badenian) deposits from the Legnica brown coal deposit (Lower Silesia) provide additional evidence of bamboos. These are assigned to Graminidites bambusoides Stuchlik, and are similar to those of recent Arundinaria. We infer that plant (plants?) that produced the pollen of G. bambusoides could have grown in swamp forests and/or reed marshes. This report provides a general survey of the occurrence of bamboos in the European Neogene, from which the leaves and pollen documented here present important data on the distribution of this group of monocots in Poland and eastern Europe.     

Environmental conditions and phosphorus removal in Florida lakes and wetlands inhabited by Hydrilla verticillata (Royle): implications for invasive species management

Hydrilla verticillata is considered the most problematic aquatic plant in the United States. In south Florida, Hydrilla dominance has also been documented in treatment wetlands. This paper characterizes (1) environmental conditions which favor Hydrilla growth and (2) understand its nutrient removal capability. Despite its occurrence over a wide range of environmental conditions, Hydrilla abundance increased with increasing pH, alkalinity, total P and total N, and decreased with water depth in selected Florida lakes. No relationship was found between color, Secchi depth and Hydrilla abundance. In several Hydrilla-dominated lakes, mean total P concentration (126 μg/l) at inflow was reduced to 106 μg/l at outflow. The maximum inflow total P concentration in a lake with positive nutrient reduction was 148 μg/l. Total P removal efficiency by Hydrilla-dominated lakes and wetlands was comparable to or higher than systems dominated by emergent and other submerged plants. Mean total P settling rates for lakes and a constructed wetland dominated by Hydrilla were estimated at 19 and 34 m/year, respectively, which were higher than or comparable to similar systems dominated by other aquatic plants. Results from this study suggest that reduction of Hydrilla from constructed wetlands will not likely improve nutrient removal performance.     

Two photosynthetic mechanisms mediating the low photorespiratory state in submersed aquatic angiosperms

The submersed angiosperms Myriophyllum spicatum L. and Hydrilla verticillata (L.f.) Royal exhibited different photosynthetic pulse-chase labeling patterns. In Hydrilla, over 50% of the ¹⁴C was initially in malate and aspartate, but the fate of the malate depended upon the photorespiratory state of the plant. In low photorespiration Hydrilla, malate label decreased rapidly during an unlabeled chase, whereas labeling of sucrose and starch increased. In contrast, for high photorespiration Hydrilla, malate labeling continued to increase during a 2-hour chase. Thus, malate formation occurs in both photorespiratory states, but reduced photorespiration results when this malate is utilized in the light. Unlike Hydrilla, in low photorespiration Myriophyllum, ¹⁴C incorporation was via the Calvin cycle, and less than 10% was in C₄ acids.

Ethoxyzolamide, a carbonic anhydrase inhibitor and a repressor of the low photorespiratory state, increased the label in glycolate, glycine, and serine of Myriophyllum. Isonicotinic acid hydrazide increased glycine labeling of low photorespiration Myriophyllum from 14 to 25%, and from 12 to 48% with high photorespiration plants. Similar trends were observed with Hydrilla. Increasing O₂ increased the per cent [¹⁴C]glycine and the O₂ inhibition of photosynthesis in Myriophyllum. In low photorespiration Myriophyllum, glycine labeling and O₂ inhibition of photosynthesis were independent of the CO₂ level, but in high photorespiration plants the O₂ inhibition was competitively decreased by CO₂. Thus, in low but not high photorespiration plants, glycine labeling and O₂ inhibition appeared to be uncoupled from the external [O₂]/[CO₂] ratio.

These data indicate that the low photorespiratory states of Hydrilla and Myriophyllum are mediated by different mechanisms, the former being C₄-like, while the latter resembles that of low CO₂-grown algae. Both may require carbonic anhydrase to enhance the use of inorganic carbon for reducing photorespiration.

     

Allelopathic influence of Hydrilla verticillata (L.F.) Royle on the distribution of Ceratophyllum species

Ceratophyllum demersum L. and C. muricatum Chamisso are not found to grow together with Hydrilla verticillata (L.f.) Royle in India. An experimental study shows that Hydrilla is allelopathic to the two species of Ceratophyllum and inhibits their growth. Thus, the distribution of Ceratophyllum species is limited by the presence of Hydrilla.     

New insights on postglacial colonization in western Europe: the phylogeography of the Leisler's bat (Nyctalus leisleri)

Despite recent advances in the understanding of the interplay between a dynamic physical environment and phylogeography in Europe, the origins of contemporary Irish biota remain uncertain. Current thinking is that Ireland was colonized post-glacially from southern European refugia, following the end of the last glacial maximum (LGM), some 20 000 years BP. The Leisler''s bat (Nyctalus leisleri), one of the few native Irish mammal species, is widely distributed throughout Europe but, with the exception of Ireland, is generally rare and considered vulnerable. We investigate the origins and phylogeographic relationships of Irish populations in relation to those across Europe, including the closely related species N. azoreum. We use a combination of approaches, including mitochondrial and nuclear DNA markers, in addition to approximate Bayesian computation and palaeo-climatic species distribution modelling. Molecular analyses revealed two distinct and diverse European mitochondrial DNA lineages, which probably diverged in separate glacial refugia. A western lineage, restricted to Ireland, Britain and the Azores, comprises Irish and British N. leisleri and N. azoreum specimens; an eastern lineage is distributed throughout mainland Europe. Palaeo-climatic projections indicate suitable habitats during the LGM, including known glacial refugia, in addition to potential novel cryptic refugia along the western fringe of Europe. These results may be applicable to populations of many species.     

Genetic variation in zinc-tolerant populations of Glyceria fluitans

Amplified fragment length polymorphism (AFLP) was used to conduct a study of the genetic diversity of zinc-tolerant populations of Glyceria fluitans from 10 sites from across Europe. Six different primer combinations were used on five to nine plants from each of the 10 sites to generate a total of 796 bands, of which 670 were polymorphic. These data were then used to calculate a dendrogram by agglomerative clustering using the unweighed pair group method with average linkage (UPGMA). The dendrogram contained two distinct clusters, with little overlap between populations. Genetic diversity between populations of G. fluitans did not always correlate with geographical distances, for example, plants from the Navan population from Ireland were more genetically similar to populations from Poland than other populations from Ireland. In other instances, geographical origin was significant, for example, all Polish populations were genetically similar to each other. Populations from two English sites only 160 km apart, showed such a high degree of genetic diversity that they were placed in different clusters in the dendrogram. They were more closely related to Irish and Polish populations than to each other. Plants from different zinc-contaminated sites were found not to cluster together. The conclusion was that the cluster groupings were not related to exposure to zinc at the sites of origin, and that the drive to generate distinct metal-tolerant populations may not occur in this species due to the existence of a constitutive tolerance to metals.     

Hydrilla verticillata (Hydrocharitaceae), a recent invader threatening Brazil’s freshwater environments: a review of the extent of the problem

Hydrilla verticillata (Hydrocharitaceae) is a highly prolific, rooted submerged macrophyte native to Asia that has invaded aquatic systems worldwide, causing many ecological and human-related problems. Hydrilla recently invaded the Paraná River basin in Brazil, making other ecologically and socially important Brazilian watersheds more susceptible to invasion by this plant. Here, I summarize the relevant information about Hydrilla, focusing on its biotic attributes, abiotic tolerance and effects on ecosystems. The aim of this review is to provide background information to assist with planning for the potential impacts of this species in the Neotropical region (particularly in Brazil) and the development of research, monitoring and management strategies. A wide ecological amplitude, resistance organs, and high growth rates and dispersion ability provide Hydrilla with great potential to invade and infest a variety of habitats, often resulting in important physico-chemical and biotic effects on the environment. Hydrilla is similar in its morphological and ecological aspects to Egeria najas and Egeria densa (South American Hydrocharitaceae), but this non-native species is a superior competitor and can be expected to exert significant pressure in habitats colonized by these native Hydrocharitaceae. Socially important rivers (such as the S?o Francisco River) have a high risk of being infested with Hydrilla, especially in stretches affected by dams, which could prejudice important human activities like hydropower generation. Important wetlands for biodiversity conservation (such as the Pantanal) may also be invaded, but they seem to be more resistant to infestations as long as their natural hydrologies are preserved. Before investing substantial effort to control Hydrilla, managers should weigh the potential costs and benefits of available techniques and consider the potential benefits of Hydrilla in providing ecosystem services.     

Use of DNA sequences for Rickettsia identification in Ixodes ricinus ticks: the first detection of Rickettsia monacensis in Poland

The cosmopolitan tick Ixodes ricinus inhabiting Europe, including Poland, is a vector for many pathogens, such as various Rickettsia species, which spread to new territories. They are present mainly in the Mediterranean countries, but have also been found in Central Europe at increasing frequency. In the present study, the gltA gene, encoding citrate synthase, and an internal transcribed spacer (ITS) were employed to detect the DNA and identify the species of tick-borne pathogens of the Rickettsia genus. The presence of bacterial DNA was detected in 9.5% of the examined I. ricinus individuals. Based on the nucleotide sequences of the analysed genomic fragments, most pathogens were identified as Rickettsia helvetica, while Rickettsia monacensis was revealed in one case. We have described for the first time, to our knowledge, the occurrence of this species in Poland. Both markers employed in the experiments were successful in species identification of R. helvetica. The newly described species R. monacensis may be identified by the protein-coding gene, but the ITS nucleotide sequences proved insufficient.     

Possible mechanisms of light-induced chlorophyll degradation in senescing leaves of Hydrilla verticillata

Light treatment markedly accelerated the chlorophyll loss in senescing leaves of Hydrilla verticillata [(L.f.) Royle] as compared to dark treatment, whereas such acceleration could not be observed in senescing spinach (Spinacia oleracea L.) leaves. The light-induced cholorophyll loss in Hydrilla was retarded slightly by chloramphenicol and markedly by cycloheximide. Catalase (EC 1.11.1.6) activity did not change appreciably in Hydrilla leaves either in light or in darkness, while in spinach it declined markedly in the dark, and light retarded such decline. Peroxidase activity in Hydrilla showed faster increase in light than in darkness, while in spinach it increased only in light during senescence. The activity of phenol(pyrogallol)-specific peroxidase increased markedly in light, and that of ascorbate-specific peroxidase decreased slightly both in light and darkness during senescence of Hydrilla leaves. This rise in phenolspecific peroxidase activity was prevented by cycloheximide treatment. Pretreatment of Hydrilla leaves with monophenol (2,4-dichlorophenol) and o-diphenol (hydroquinone) accelerated and retarded, respectively, the light-induced cholorophyll loss. Pretreatment of Hydrilla leaves with H₂O₂ augmented the chlorophyll loss more markedly in light than in darkness. The endogenous level of H₂O₂ increased more in light than in dark during senescence of Hydrilla leaves. Treatment of Hydrilla leaves with 3-(3.4-dichlorophenyl)-l,l-dimethylurea. a photosystem II inhibitor, prevented both light-induced rise in H₂O: level and chlorophyll loss, but it was without effect in the dark. Retardation of light-induced chlorophyll loss occurred during senescence of Hydrilla leaves when light was given in different photoperiods in a 24-h daily cycle for 6 days instead of as continuous irradiance. There was a negative correlation between the length of the photoperiod and the extent of cholorophyll loss.     

Prevalence and phenology of white-nose syndrome fungus Pseudogymnoascus destructans in bats from Poland

Pseudogymnoascus destructans (Pd), a parasitic fungus (being responsible for a disease known as white-nose syndrome, WNS) that caused mass mortality of cave-dwelling, hibernating bats in North America, appears to be native of Europe, where it also occurs on wintering bats, but no similar outbreaks of WNS have been recorded. Herein, we provide the first account on prevalence and phenology of P. destructans in Poland. Bats were counted once per month, from October or January to May (2010-2013), in an abandoned ore mine in southern Poland. Presence of P. destructans in two samples was confirmed by sequencing of isolated fungal DNA. Observations of phenotypically identical mycosis on bats hibernating at this site in March 2006 are likely to be the first known records of P. destructans from Poland. All Pd-suspected individuals were Myotis myotis with an exception of one Myotis daubentonii. The first Pd-suspected bats were noted in mid-February, but their number was the highest in March, what overlapped with maximum numbers of hibernating M. myotis. The prevalence in March was 7%–27% of M. myotis individuals. No mass mortality of bats was observed in the mine, with only three dead individuals found in the hibernaculum which hosted up to 130 bats, representing 6–7 species.     

The oldest nautiloid recorded from the Triassic Germanic Basin and the first ammonoid from the Aegean (Middle Triassic) of Poland

During the Triassic in Europe, the Germanic Basin extended from England in the west to the eastern border of Poland in the east. Although cephalopods are common in some Middle Triassic (Muschelkalk) horizons, there still persists a gap in the palaeontological record of the eastern part of the Germanic Basin, notably in the lowermost parts of the Lower Muschelkalk, spanning the latest Olenekian-Aegean interval. The present contribution attempts to fill this gap by presenting the first ammonoid (ceratitid Beneckeia sp.) and nautiloids (Germanonautilus cf. dolomiticus and G. cf. salinarius) from the Lower Gogolin Beds (Upper Silesia, Poland). These Germanonautilus are the oldest nautiloids found in the entire Germanic Basin.     

Genetic variability of central–western European pine marten (Martes martes) populations

Recent studies highlighted the potential role of cryptic glacial refugia for temperate taxa in Europe beyond the Mediterranean peninsulas. To further investigate phylogeographic features of the European pine marten (Martes martes) in previously identified cryptic refugia located in central–western Europe, we analysed the hyper-variable diagnostic fragment of the mitochondrial control region in a total of 134 specimens, allowing for reliable comparisons with previous genetic studies of the species. We included samples from eight different European countries in central–western Europe (Belgium, France, Luxembourg and the Netherlands), in south–western Europe (Spain), in north–central Europe (Denmark) and in central Europe (Germany and Poland). The sequences collapsed in 17 haplotypes, which allowed us to determine the genetic composition of the pine marten populations throughout central–western Europe. Overall, our results showed that the population genetic variation, estimated by the standardised haplotype diversity, was high (0.400?≤?Hs?≤?0.762), and it was considerably higher in Germany (0.762) and the Netherlands (0.722) compared to the other countries. The nucleotide diversity was relatively low (0.002?≤?π?≤?0.016) even in Germany and the Netherlands (0.016 and 0.014, respectively), suggesting relatively small, long-term effective population sizes or severe bottlenecks. Out of the 17 haplotypes found in our study area, 13 were unique and limited to a single country: one in Denmark, one in Spain, four in Poland and seven in the Netherlands. The pairwise genetic distance ranged from 0.001 to 0.032 and did not show any evident correlation with the geographic distances between the populations. A genealogical relationship network was constructed, which provided evidence for a recent origin of many of the unique haplotypes. Approximately 82 % of the samples analysed in this study belonged to haplotypes grouped into a previously identified central–northern European phylogroup of the species. Our results support previous findings, indicating low contribution of southern refugial populations to the postglacial recolonization of central–western Europe and a predominant contribution of pine marten populations that survived the Last Glacial Maxima in cryptic northern refugia.     

Spatial variation in the recruitment of the intertidal barnacles Chthamalus montagui Southward and Chthamalus stellatus (Poli) (Crustacea: Cirripedia) over an European scale

Spatial variation in the recruitment of the intertidal barnacles Chthamalus montagui and Chthamalus stellatus was examined over an European scale. The study was carried out using standardised protocols at a series of locations. The five locations chosen (SW Ireland, NW Spain, SW Portugal and NW and NE Italy) span a large part of the range of these species in Europe. The spatial scales were location (hundreds of kilometres) and shore (thousands of metres).Estimates of total cumulative recruitment (cyprids and metamorphs) summed over the year (April 1997 to March 1998) showed substantial variation between locations which was dependent on the species. Recruitment was highest in SW Portugal for C. montagui and in SW Ireland and NW Spain for C. stellatus. Overall recruitment of C. montagui was higher than that of C. stellatus at all locations except SW Ireland, where recruitment of the two species was not significantly different. There were significant differences among shores in each location.The recruitment period of both species varied with location, with recruitment beginning earlier further south. In general, recruitment of C. montagui and C. stellatus was recorded in 8 months in NW Spain and NE Italy, while only in 7 months in SW Ireland. Recruitment of C. montagui occurred in 10 months in SW Portugal, but no recruits of C. stellatus were found. In all locations there was at least one distinct peak of recruitment. In SW Ireland both species showed only one peak of recruitment, a month after initiation. At the more southerly Atlantic locations, as well as in the Mediterranean, two unequal peaks of recruitment were generally seen. During recruit census, the number of cyprids, in comparison to metamorphs, found at any location was very low. In SW Ireland and NW Spain cyprids of both species were found, while in SW Portugal and in the Mediterranean, only cyprids of C. montagui were found.     

Propagule type influences competition between two submersed aquatic macrophytes

Summary Glasshouse competition experiments with Hydrilla verticillata (L.f.) Royle indicate that plants grown from turions are weaker competitors than those grown from tubers, when compared to the widely distributed macrophyte, Potamogeton pectinatus L. These results support an earlier hypothesis about the importance of propagule size for predicting the outcome of plant competition (Grace 1985; Schaffer and Gadgil 1980). Results of outdoor growth experiments indicate that even though Hydrilla plants from turions are relatively weaker competitors, they are able to grow succesfully in an existing macrophyte bed composed of either, P. pectinatus or P. gramineus. During the early stages of Hydrilla invasion into an area of existing macrophytes, native plants may coexist with Hydrilla. However, once the abundance of Hydrilla tubers in the sediment increases, Hydrilla may displace existing plants.     

Tidal rates of settlement of the intertidal barnacles Chthamalus stellatus and Chthamalus montagui in western Europe: the influence of the night/day cycle

Chthamalus montagui and Chthamalus stellatus are abundant barnacles in western Europe. Tidal settlement of Chthamalus in SW Ireland and SW Portugal was studied in relation to a night and day factor and at different temporal (dates) and spatial (shores and sites) scales. Based on the identifiable cyprids and metamorphs, Chthamalus settlement in SW Ireland was comprised mainly of C. stellatus but was composed of C. montagui only in SW Portugal.In SW Ireland and SW Portugal, settlement rates of Chthamalus (mean number of settlers per 25 cm²±S.E.) were higher after one day tidal cycle (597±158.7 in SW Ireland, 144±23.6 in SW Portugal) than one night tidal cycle (55±12.1 in SW Ireland, 13±2.2 in SW Portugal), but significant differences were only detected in SW Portugal. Different models were proposed for explaining this pattern related to night and day variability of the physical processes responsible for transporting cyprids to shore (1), and/or of pre-settlement behaviour (2) and/or of settlement behaviour of cyprids (3).Spatial patterns of tidal settlement of both species or at both locations seem similar with small scale variability (between sites, 5 to 30 m apart) in settlement of Chthamalus being the only spatial scale at which variability was detected in both locations.The composition of Chthamalus cohorts settling during one tidal cycle differed considerably between locations/species: settlers of C. stellatus were mainly cyprids; settlers of C. montagui during the day (when most settlement occurred) were essentially metamorphs.     

Irish Cepaea nemoralis Land Snails Have a Cryptic Franco-Iberian Origin That Is Most Easily Explained by the Movements of Mesolithic Humans

The origins of flora and fauna that are only found in Ireland and Iberia, but which are absent from intervening countries, is one of the enduring questions of biogeography. As Southern French, Iberian and Irish populations of the land snail Cepaea nemoralis sometimes have a similar shell character, we used mitochondrial phylogenies to begin to understand if there is a shared “Lusitanian” history. Although much of Europe contains snails with A and D lineages, by far the majority of Irish individuals have a lineage, C, that in mainland Europe was only found in a restricted region of the Eastern Pyrenees. A past extinction of lineage C in the rest of Europe cannot be ruled out, but as there is a more than 8000 year continuous record of Cepaea fossils in Ireland, the species has long been a food source in the Pyrenees, and the Garonne river that flanks the Pyrenees is an ancient human route to the Atlantic, then we suggest that the unusual distribution of the C lineage is most easily explained by the movements of Mesolithic humans. If other Irish species have a similarly cryptic Lusitanian element, then this raises the possibility of a more widespread and significant pattern.     

Chloroplast DNA variation of Betula humilis Schrk. in Poland and Belarus

Betula humilis is an endangered plant species in Central Europe. In order to protect this species, it is necessary to document its genetic diversity in this region and to identify areas for conservation prioritisation. As molecular investigations conducted throughout the ranges of many plant species have shown that the highest genetic diversities are found within former glacial refugia and/or within the contact zones of different phylogenetic lineages, we investigated the reasons underlying the considerable genetic variation of B. humilis in northeastern Poland revealed previously using nuclear microsatellites. We analysed 365 individuals of B. humilis from 19 populations and 67 specimens of Betula pendula and Betula pubescens sampled in four geographical regions in Poland and Belarus for polymorphism in chloroplast PCR-restriction fragment length polymorphism markers. Genetic data strongly suggested that B. humilis could have survived the Last Glacial Maximum at higher latitudes, but the hypothesis of a refugium in southeastern Poland was rejected. Chloroplast DNA analysis confirmed high genetic diversity in some populations in northeastern Poland. This phenomenon can likely be explained in terms of a suture zone, as the high haplotypic richness was followed by h _T????v _T. Similar patterns of haplotype distributions in the birches under study and high introgression ratio (IG?=?0.71) among B. humilis and congeneric trees suggested that postglacial recolonisation of the shrub birch was complicated by haplotype sharing with other birches.