Plant succession in areas of scorched and blown-down forest after the 1980 eruption of Mount St. Helens,Washington

Abstract. Patterns of plant succession were studied in areas of scorched and blown-down forest resulting from the 1980 eruption of Mount St. Helens, Washington. Changes in species abundance were observed for 7 years in permanent sample plots representing four post-disturbance habitats, or site types. Total plant cover and species richness increased with time on all site types. In blown-down forests supporting snowpack at the time of eruption, understory recovery was dominated by the vegetative regeneration of species persisting through disturbance. In forests without snowpacks, plant survival was poorer. Increases in cover and diversity were dominated first by introduced grasses, then by colonizing forbs characteristic of early successional sites. Epilo-bium angustifolium and Anaphalis margaritacea showed widespread recruitment and clonal expansion throughout the devastated area. As a result, species composition on previously forested sites converged toward that on formerly clearcut sites, where early serai forbs resprouted vigorously from beneath the tephra. Total plant cover and species diversity were poorly correlated with post-disturbance habitat and general site characteristics (e.g. distance from the crater, elevation, slope, and aspect). However, distributions of several life-forms (e.g. low sub-shrubs and tall shrubs) were strongly correlated with depth of burial by tephra and with cover of tree rootwads. Thus, early community recovery may reflect microsite variation or chance survival and recruitment rather than broad-scale gradients in environment or disturbance. Recovery of pre-disturbance composition and structure will undoubtedly be much slower than after other types of catastrophic disturbance. The rate and direction of community recovery will largely depend on the degree to which original understory species survived the eruption.     

The influence of locus number and information content on species delimitation: an empirical test case in an endangered Mexican salamander

Perhaps the most important recent advance in species delimitation has been the development of model‐based approaches to objectively diagnose species diversity from genetic data. Additionally, the growing accessibility of next‐generation sequence data sets provides powerful insights into genome‐wide patterns of divergence during speciation. However, applying complex models to large data sets is time‐consuming and computationally costly, requiring careful consideration of the influence of both individual and population sampling, as well as the number and informativeness of loci on species delimitation conclusions. Here, we investigated how locus number and information content affect species delimitation results for an endangered Mexican salamander species, Ambystoma ordinarium. We compared results for an eight‐locus, 137‐individual data set and an 89‐locus, seven‐individual data set. For both data sets, we used species discovery methods to define delimitation models and species validation methods to rigorously test these hypotheses. We also used integrated demographic model selection tools to choose among delimitation models, while accounting for gene flow. Our results indicate that while cryptic lineages may be delimited with relatively few loci, sampling larger numbers of loci may be required to ensure that enough informative loci are available to accurately identify and validate shallow‐scale divergences. These analyses highlight the importance of striking a balance between dense sampling of loci and individuals, particularly in shallowly diverged lineages. They also suggest the presence of a currently unrecognized, endangered species in the western part of A. ordinarium's range.     

On Cannabis indica,Indian hemp

Background: The South Aegean Volcanic Arc (SAVA), one of the most notable geological structures of the Mediterranean Sea, is floristically well known. Nevertheless, the factors that contribute to shaping the plant species richness of the SAVA remain unclear.

Aims: To investigate the factors that affect plant species richness and identify plant diversity hotspots in the SAVA and other central Aegean islands.

Methods: We used stepwise multiple regression to test the relationship between a number of environmental factors and plant species richness in the SAVA, as well as the residuals from the species–area linear regressions of native, Greek and Cycladian endemic taxa as indicators of relative species richness.

Results: The area was confirmed to be the most powerful single explanatory variable of island species richness, while geodiversity, maximum elevation and mean annual precipitation explained a large proportion of variance for almost all the species richness measures. Anafi, Amorgos and Folegandros were found to be endemic plant diversity hotspots.

Conclusions: We have demonstrated that geodiversity is an important factor in shaping plant species diversity in the Cyclades, while mean annual precipitation, human population density and maximum elevation were significant predictors of the Greek endemics present in the Cyclades. Finally, Anafi was found to be a plant diversity hotspot in the South Aegean Sea.     

广东湛江火山沟植物与保育

由于火山岩特殊的自然地理条件,其植被的组成与分布也具有特殊性。野外调查表明,湛江火山沟共有维管束植物238种,含种类较多的科为菊科、大戟科、禾本科、蝶形花科、桑科和芸香科。较重要的物种有大果榕、对叶榕、樟树、幌伞枫、假苹婆、桃金娘、野牡丹、鸭脚木、厚皮树等,它们在植被的组成与演替中起着举足轻重的作用。值得注意的是,外来入侵种在本区占有较大比例,这与本区的地理位置和日益增长的外贸、旅游交流等密切相关。该文对植被的组成、外来入侵种的危害作了分析与探讨,并提出了相应的保育措施。     

A multilocus phylogeny of the fish genus Poeciliopsis: Solving taxonomic uncertainties and preliminary evidence of reticulation

The fish genus Poeciliopsis constitutes a valuable research system for evolutionary ecology, whose phylogenetic relationships have not been fully elucidated. We conducted a multilocus phylogenetic study of the genus based on seven nuclear and two mitochondrial loci with a thorough set of analytical approaches, that is, concatenated (also known as super‐matrix), species trees, and phylogenetic networks. Although several relationships remain unresolved, the overall results uncovered phylogenetic affinities among several members of this genus. A population previously considered of undetermined taxonomic status could be unequivocally assigned to P. scarlli; revealing a relatively recent dispersal event across the Trans‐Mexican Volcanic Belt (TMVB) or Pacific Ocean, which constitute a strong barrier to north–south dispersal of many terrestrial and freshwater taxa. The closest relatives of P. balsas, a species distributed south of the TMVB, are distributed in the north; representing an additional north–south split in the genus. An undescribed species of Poeciliopsis, with a highly restricted distribution (i.e., a short stretch of the Rio Concepcion; just south of the US‐Mexico border), falls within the Leptorhaphis species complex. Our results are inconsistent with the hypothesis that this species originated by “breakdown” of an asexual hybrid lineage. On the other hand, network analyses suggest one or more possible cases of reticulation within the genus that require further evaluation with genome‐wide marker representation and additional analytical tools. The most strongly supported case of reticulation occurred within the subgenus Aulophallus (restricted to Central America), and implies a hybrid origin for P. retropinna (i.e., between P. paucimaculata and P. elongata). We consider that P. balsas and P. new species are of conservation concern.     

Soluble Reactive Phosphorus Transport and Retention in Tropical, Rainforest Streams Draining a Volcanic and Geothermally Active Landscape in Costa Rica. : Long-Term Concentration Patterns, Pore Water Environment and Response to ENSO Events

Soluble reactive phosphorus (SRP) transport/retention was determined at four sites in three rainforest streams draining La Selva Biological Station, Costa Rica. La Selva is located at the base of the last remaining intact rainforest transect from 30 m above sea level to 3000 m along the entire Caribbean slope of Central America. Steam SRP levels can be naturally high there due to regional, geothermal groundwater discharged at ambient temperature. Monitoring since 1988 has revealed distinctive long-term differences in background SRP and total P (TP) for three streams in close proximity, and identified the impact of ENSO (El Nino Southern Oscillation) events on SRP-enriched reaches. Mean interannual SRP concentrations (± standard deviation) were 89 ± 53μg/l in the Salto (1988–1996), 21 ± 39μg/l in the Pantano (1988–1998), and 26 ± 35μg/l in the Sabalo (1988–1996). After January, 1997 the separate upland-lowland contributions to discharge and SRP load were determined monthly in the Salto. SRP in Upper Salto was low (19 ± 8μg/l, 1997–2002) until enriched at␣the upland-lowland transition by regional groundwater. Mean SRP concentration in Lower␣Salto (108 ± 104μg/l) was typically highest February–April, the driest months, and lowest July–September, the wettest. SRP concentration was positively correlated to the inverse of discharge in Lower Salto when ENSO data were omitted (1992 and 1998–1999), but not in the Upper Salto, Pantano, or Sabalo. TP was positively correlated to the inverse of discharge in all three streams when ENSO data were omitted. High SRP springs and seeps along the Lower Salto contributed 36% of discharge but 85% of SRP export 1997–2001. Annual SRP flux from the total Salto watershed (1997–2001) averaged 2.9 kg/ha year, but only 0.6 kg/ha year from the Upper Salto. A dye tracer injection showed that pore water environments were distinctly different between Upper and Lower Salto. Upper Salto had high surface water–pore water exchange, high dissolved oxygen, low SRP, and low conductivity similar to surface water, and Lower Salto had low surface water–pore water exchange, low dissolved oxygen, high SRP, and high conductivity reflecting geothermal groundwater influence. SRP export from the Salto was controlled by regional groundwater transfer, which in similar volcanic settings could be a significant P source. However, ENSO events modified the SRP concentration in the Salto suggesting that long-term monitoring is required to understand underlying SRP dynamics and P flux to downstream communities.     

日本三宅岛火山土壤中硫代硫酸盐氧化菌的分离、生物学特性及鉴定

【目的】利用培养法从日本三宅岛火山土壤(堆积年限131年)中分离到一株能氧化分解硫代硫酸盐的细菌MU2A-22T。【方法】用培养法对该菌株MU2A-22T进行了生理生化性质以及分类学位置上的确定。【结果】菌株MU2A-22T为革兰氏阴性,短杆状或球状。理化性质表明该菌株能利用葡萄糖、L-阿拉伯糖、葡萄糖酸盐、己二酸酯、dL-苹果酸钠、硫代硫酸钠(最适浓度为2.5 mmol/L)为唯一碳源进行自养生长。最适生长温度为25°C 30°C,最适pH为6.0 8.0。菌株MU2A-22T的16S rRNA序列与菌株Paracoccus solventivorans 6637T亲缘关系最近,序列相似性为97%,编码核酮糖-1,5-二磷酸羧化酶/加氧酶(Rubisco)的基因也被确定。对Paracoccus属内几种近缘菌的脂肪酸分析,证明菌株MU2A-22T中含有Paracoccus属的特征氨基酸,其中含量大于10%的分别为C18:1(74.7%)和C18:0(12.1%)。DNA-DNA杂交实验表明,菌株MU2A-22T与Paracoccus solventivorans 6637TDNA的相似度为49.3%。MU2A-22T菌株G+C含量为66.5%66.7%。【结论】菌株MU2A-22T为Paracoccus属内的一新种菌(登录号GQ452286),命名为Paracoccus scorialis sp.nov.。     

Mycorrhizal synthesis of four ectomycorrhizal fungi in potted <Emphasis Type="Italic">Populus maximowiczii</Emphasis> seedlings

Ectomycorrhizal (ECM) syntheses between four ECM fungi, Laccaria amethystina, Hebeloma mesophaeum, Thelephora terrestris, and Tomentella sp., and Populus maximowiczii seedlings that are known to form ECM at a denuded area of Mt. Usu were performed in volcanic debris in a controlled growth chamber. The percentage of ECM colonization and seedling growth were determined 3 months after inoculation. Seedlings were successfully colonized by the inoculated ECM fungi with low contamination ratios. Seedling height and biomass were larger in the inoculated seedlings than in the control, although the effects of inoculation on seedling growth varied with the ECM fungus.