The phytosociology of British sea-cliff vegetation with special reference to the ecophysiology of some maritime cliff plants

The major factors thought to control the distribution of associations on the sea cliffs in Britain are discussed in relation to the zonation of cliff vegetation, and some experiments to investigate the effects of these factors are described.The seeds of the maritime cliff species are able to germinate in higher salinities than those of closely related inland species.Relative growth rates of maritime cliff species indicate stimulation at low salinities over non-saline conditions, and less reduction in growth at higher salinities than those of closely related inland species.Increasing salinity reduces both photosynthesis and dark respiration in Lavatera arborea. Mesophyll and stomatal resistances are increased while transpiration is reduced.The distribution of ions within Lavatera arborea grown at different salinities indicates differential accumulation between young leaves, old leaves and roots.Nomenclature follows Clapham, Tutin & Warburg (1962).     

Urbanisation versus agriculture: a comparison of local genetic diversity and gene flow between wood mouse Apodemus sylvaticus populations in human‐modified landscapes

Urbanisation and agriculture dramatically modify the landscapes available for use by wildlife, affecting key aspects of their ecology such as survival, foraging, predation, competition and reproductive success. Relatively little is known about the effects of urbanisation and agriculture on the genetic structure, gene flow and genetic diversity of wild species. Here, landscape genetic techniques were applied to compare local genetic diversity and gene flow between wood mouse populations in urban and arable landscapes. Using nine microsatellite markers, individuals were genotyped from six arable and seven urban sample sites. Inter‐population genetic differentiation was significantly greater in urban than arable habitat, while allele richness, private allele richness and heterozygosity were higher for arable sample sites, with varying degrees of significance. These suggest that urban habitat was sufficiently fragmented to limit gene flow. To test the effect of landscape features on gene flow, several cost‐distance measures were generated. Overland distance and Euclidean distance correlated best with inter‐population genetic differentiation in arable habitat, whereas distances that accommodated differences in habitat quality better explained differentiation in urban habitat. There was no evidence that margins adjacent to roads, rivers or railways facilitated gene flow. Together, the results indicate that urban landscapes expose wood mice to greater fragmentation in habitat quality than arable areas, leading to greater population isolation that is not mitigated by the presence of dispersal corridors.     

Vegetation gradients in Atlantic Europe: the use of existing phytosociological data in preliminary investigations on the potential effects of climate change on British vegetation

• 1 This paper aims to demonstrate the use of available vegetation data from the phytosociological literature in preliminary analyses to generate hypotheses regarding vegetation and climate change.
  • 2 Data for over 3000 samples of calcareous grassland, mesotrophic grassland, heath and woodland vegetation were taken from the literature for a region in the west of Atlantic Europe and subjected to ordination by detrended correspondence analysis in order to identify the main gradients present.
    • 3 Climate data were obtained at a resolution of 0.5° from an existing database. The relationship between vegetation composition and climate was investigated by the correlation of the mean scores for the first two ordination axes for each 0.5° cell with the climate and location variables.
      • 4 The ordinations resulted in clear geographical gradients for calcareous grasslands, heaths and woodlands but not for mesotrophic grasslands. Significant correlations were shown between some of the vegetation gradients and the climate variables, with the strongest relationships occurring between the calcareous grassland gradients and July temperature, latitude and oceanicity. Some of the vegetation gradients were also inferred to reflect edaphic factors, management and vegetation history.
        • 5 Those gradients that were related to temperature were hypothesized to reflect the influence of a progressively warmer climate on species composition, providing a baseline for further studies on the influence of climate change on species composition.
        • 6 The validity of the literature data was assessed by the collection of an original set of field data for calcareous grasslands and the subsequent ordination of a dataset containing samples from both the literature and the field. The considerable overlap between the samples from the literature and the field suggest that literature data can be used, despite certain limitations. Such preliminary analyses, using readily available data, can thus achieve useful results, thereby saving lengthy and costly field visits.

     

A multi-gene phylogeny for Stachybotrys evidences lack of trichodiene synthase (tri5) gene for isolates of one of three intrageneric lineages

Members of the mitosporic fungal form-genus Stachybotrys, including common indoor contaminants Stachybotrys chartarum, Stachybotrys echinata and Stachybotrys chlorohalonata, are capable of producing potent, protein synthesis-inhibiting, trichothecene mycotoxins. A combined multi-gene approach was used to investigate relationships among species of Stachybotrys against which the presence/absence of the trichothecene biosynthetic pathway gene, trichodiene synthase (tri5), was evaluated. Phylogenetic analyses partitioned species of Stachybotrys into three strongly supported lineages, two of which contained common indoor taxa. No tri5 PCR product was amplified from members of the third clade, which included the only member of the group with a known sexual state, Stachybotrys albipes. Isolates grouped with S. albipes also tested negative for tri5 in Southern analyses. The phylogenetic distribution of tri5 was consistent with known toxin production for the group. For isolates with tri5 product, Bayesian analysis suggested that signal from amino acid determining sites conflicted with the combined phylogeny. Incongruence however, was not supported by either SH-test results or maximum likelihood analyses. Moreover, sites rates analysis showed that tri5 was highly conserved at the amino acid level suggesting that identity at variable sites, among otherwise divergent taxa, might be the result of chance events.     

Recent changes in the distribution of carboxylesterase genes and associated chromosomal rearrangements in Greek populations of the tobacco aphid Myzus persicae nicotianae

We present data on the frequency of amplified E4 and FE4 carboxylesterase genes in Myzus persicae s.l. clones collected during the years 2002–2007 and 2012 in Greece. Most clones were of the tobacco aphid, Myzus persicae nicotianae. Samples from 2012 were genotyped with microsatellite DNA markers and a number of them were karyotyped. Aphid clones with amplified FE4 genes predominated in all years, whereas E4 was present in only 3.5% of all samples and always occurred in clones with FE4. Most of the clones examined showed high carboxylesterase activity levels (R2 resistant category). The results showed marked changes in the frequencies of the two carboxylesterase genes in the tobacco aphid populations compared to published data that were collected in Greece in the mid 1990s, when E4 was recorded on its own in 20% of all samples and in 32% of samples from tobacco. A parallel change in karyotype was also observed because the A1,3 translocation, which had a worldwide association with amplified E4 genes in the 1990s, was not detected in the clones analyzed in 2012. Possible causes for these changes are discussed, although selection as a result of pest management practices appears to be the major one. Novel chromosomal rearrangements were also found in M. persicae nicotianae clones. These rearrangements could be a result of clastogenic effects of nicotine, which could persist because of the holocentric nature of aphid chromosomes. The results are discussed in relation to rapid evolution events that have taken place in the tobacco aphid in Greece during the last two decades. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 455–470.     

Spatial and temporal dynamics of Myzus persicae clones in fields and suction traps

1 The population of peach‐potato aphid Myzus persicae in Scotland is comprised almost entirely of long‐term asexual clones. 2 Over a ten year period, M. persicae from Scottish fields and suction traps were analysed with six microsatellite markers. 3 Out of 1497 individuals analysed, 14 clones (denoted A–N) comprised over 98% of the collection. 4 Some clones were particularly abundant but most clones had a widespread distribution on all available plants. 5 Clones E and L had distinct features in their distributions as clone L was geographically totally restricted to the north east of Scotland and clone E showed a marked preference for brassica crops. 6 Clones E and L provide direct evidence of a role for local adaptations in the distribution of M. persicae clones.