Understory plant diversity is related to higher variability of vegetative mobility of coexisting species

Theoretical studies claim that if co-occurring species have very different mobilities this will result in greater small-scale species richness, but empirical evidence is still lacking. We measured horizontal vegetative mobility (VM) of 48 herbaceous understory species and estimated small-scale species richness in early and late successional boreonemoral herb-rich coniferous forests in central Estonia. VM of erosulate growth forms was significantly higher than that of hemi-rosette and rosette growth forms. Erosulate species exhibited higher mobility in young stands, but their relative and total cover was considerably higher in old stands. Local plant richness (in 1 × 1 m plots) correlated positively with the variability of VM of species in a plot—larger differences in VM resulted in a higher number of coexisting species. Our results thus suggest that species differences in VM can contribute to small-scale coexistence by providing different ways to colonise empty space. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Conservation of the Endemic Fern Lineage <Emphasis Type="Italic">Diellia</Emphasis> (Aspleniaceae) on the Hawaiian Islands: Can Population Structure Indicate Regional Dynamics and Endangering Factors?

We aimed to understand the regional population dynamics of the endemic fern lineage Diellia (D. erecta, D. erecta f. alexandri, D. falcata, D. mannii, D. pallida, and D. unisora) in mesic forests on the Hawaiian Islands. In particular, we were interested in whether studying life-stage structure would contribute to setting conservation management priorities and understanding regional dynamics. A repeated field survey of historically recorded population locations and most of the known populations were performed between 1999 and 2005. Distribution data available since 1838 show that these ferns have become extinct from 86% of the formerly recorded locations and the number of recorded extinction events exceeds the number of recorded appearance events. A significantly stronger cumulative impact of alien animals and plants distinguishes the habitats of extinct populations from other sites. The status of 19 local populations was assessed on the basis of stage structure as ‘dynamic’ (2 populations, sporelings predominate), ‘normal’ (8 populations), or ‘regressive’ (9 populations, mature plants predominate). Population size was negatively dependent on soil disturbance by alien animals. The existence of small regressive Diellia populations possibly indicates a delayed extinction process due to habitat deterioration. The study of life-stage structure, together with information about population size, is a useful tool to evaluate conservation management priorities and understand regional dynamics in conditions where demographic and precise distribution data are lacking. We conclude that the whole lineage is critically endangered and the impact of alien ungulates is obviously the main threat.     

Spatially-Explicit Estimation of Geographical Representation in Large-Scale Species Distribution Datasets

Much ecological research relies on existing multispecies distribution datasets. Such datasets, however, can vary considerably in quality, extent, resolution or taxonomic coverage. We provide a framework for a spatially-explicit evaluation of geographical representation within large-scale species distribution datasets, using the comparison of an occurrence atlas with a range atlas dataset as a working example. Specifically, we compared occurrence maps for 3773 taxa from the widely-used Atlas Florae Europaeae (AFE) with digitised range maps for 2049 taxa of the lesser-known Atlas of North European Vascular Plants. We calculated the level of agreement at a 50-km spatial resolution using average latitudinal and longitudinal species range, and area of occupancy. Agreement in species distribution was calculated and mapped using Jaccard similarity index and a reduced major axis (RMA) regression analysis of species richness between the entire atlases (5221 taxa in total) and between co-occurring species (601 taxa). We found no difference in distribution ranges or in the area of occupancy frequency distribution, indicating that atlases were sufficiently overlapping for a valid comparison. The similarity index map showed high levels of agreement for central, western, and northern Europe. The RMA regression confirmed that geographical representation of AFE was low in areas with a sparse data recording history (e.g., Russia, Belarus and the Ukraine). For co-occurring species in south-eastern Europe, however, the Atlas of North European Vascular Plants showed remarkably higher richness estimations. Geographical representation of atlas data can be much more heterogeneous than often assumed. Level of agreement between datasets can be used to evaluate geographical representation within datasets. Merging atlases into a single dataset is worthwhile in spite of methodological differences, and helps to fill gaps in our knowledge of species distribution ranges. Species distribution dataset mergers, such as the one exemplified here, can serve as a baseline towards comprehensive species distribution datasets.     

Telomere and telomerase in oncology

Telomere and cell replicative senescenceTelomeres, which are located at the end of chro-mosome, are crucial to protect chromosome againstdegeneration, rearrangment and end to end fusion[1].Human telomeres are tandemly repeated units of thehexanucleotide TTAGGG. The estimated length oftelomeric DNA varies from 2 to 20 kilo base pairs,depending on factors such as tissue type and hu-man age. The buck of telomeric DNA is double-stranded, but the end of telomeric DNA consists of3' overhang of…     

西藏色季拉山暗针叶林苔藓多样性及林窗干扰的影响

为了解西藏色季拉山暗针叶林苔藓多样性及林窗干扰的影响,在过去工作积累的基础上研究了色季拉山西坡5块样地内不同林内环境(林窗、林缘和林下)地面、腐木和树附生苔藓生物量特征。结果表明, 地面生单位面积苔藓植物生物量储量最高,平均910.10 g/m²,其次为腐木生(221.90 g/m²),树附生的最低(53.59 g/m²)。林窗地面生苔藓单位面积生物量最高,均值为360.47 g/m²,其次为林下(305.51 g/m²),最小为林缘(244.11 g/m²);林窗、林缘和林下间的地面生苔藓单位面积生物量差异显著(P＜0.05)。沿海拔梯度,林窗苔藓单位面积生物量表现出先增加后减少的趋势。因此,在西藏色季拉山暗针叶林内,林窗对地面生苔藓单位面积生物量有显著影响。