Effect of habitat structural complexity on collembolan communities

We investigated soil microarthropod communities in two physically dissimilar inorganic soil materials and in a mixture of these two materials to examine the effect of the structural complexity of a habitat on microarthropod abundance and communities, teasing it out from that of nutritional factors. Mesh boxes were filled with perlite (a highly porous material), similar size of granite gravels (no pores inside), or their mixture, and placed on a forest floor. The boxes were collected after 8 or 20 months, and the microarthropods were extracted and identified to the species level, with a focus on Collembola. We also evaluated fine-root biomass and the amount of organic matter in the boxes. It was found that the mixture of perlite and granite enhanced microarthropod abundance and root development. A partial redundancy analysis revealed that collembolan communities developed differently among the substrate materials. We also found that variation in the collembolan communities was related to fine-root development and the abundance of other microarthropods, implying that habitat structural complexity affects collembolan communities indirectly by affecting soil food webs

Soft Coral Sarcophyton (Cnidaria: Anthozoa: Octocorallia) Species Diversity and Chemotypes

Research on the soft coral genus Sarcophyton extends over a wide range of fields, including marine natural products and the isolation of a number of cembranoid diterpenes. However, it is still unknown how soft corals produce this diverse array of metabolites, and the relationship between soft coral diversity and cembranoid diterpene production is not clear. In order to understand this relationship, we examined Sarcophyton specimens from Okinawa, Japan, by utilizing three methods: morphological examination of sclerites, chemotype identification, and phylogenetic examination of both Sarcophyton (utilizing mitochondrial protein-coding genes MutS homolog: msh1) and their endosymbiotic Symbiodinium spp. (utilizing nuclear internal transcribed spacer of ribosomal DNA: ITS- rDNA). Chemotypes, molecular phylogenetic clades, and sclerites of Sarcophyton trocheliophorum specimens formed a clear and distinct group, but the relationships between chemotypes, molecular phylogenetic clade types and sclerites of the most common species, Sarcophyton glaucum, was not clear. S. glaucum was divided into four clades. A characteristic chemotype was observed within one phylogenetic clade of S. glaucum. Identities of symbiotic algae Symbiodinium spp. had no apparent relation to chemotypes of Sarcophyton spp. This study demonstrates that the complex results observed for S. glaucum are due to the incomplete and complex taxonomy of this species group. Our novel method of identification should help contribute to classification and taxonomic reassessment of this diverse soft coral genus

日本列島の冷温帯林における30年間の土壌動物相の変化とシカ類の影響の可能性

Feature : Impact on Ashiu forest ecosystem due to deerDeer overabundance affects many taxa and ecosystem functions in both aboveground and belowground systems. We investigated changes in soil macro fauna along a ridge and at the bottom of a slope in Ashiu Experimental Forest, a cool temperate natural forest in central Japan, in which the flora, fauna, microflora, and ecosystem functions were studied before the Sika-deer (Cervus nippon) population increased. The abundance and biomass of soil macrofaunal detritivores (earthworms, isopods, amphipods, and diplopods) and predators (opilionids, Araneae, and chilopods) were adversely affected both along the ridge and at the slope bottom. These results are consistent with prior studies conducted with deer exclosures or natural experiments. The soil organic matter distribution, the carbon-nitrogen ratio in the litter and mineral layers, and soil hardness along the slope also changed. These results suggest that deer overabundance affects ecosystem functions along the slope. The movement of litter and soil along the slope, and the reduction of soil macro fauna associated with decomposition possibly contributed to these changes.温帯におけるシカ類の密度の増大が、広範な植物相と動物相、生態系プロセスに影響することが示されてきた。我々はニホンジカ(Cervus nippon)の増加以前の土壌動物相の知見が蓄積されている京都大学芦生演習林(中部日本)において、斜面の尾根部と谷部において大型土壌動物相を調査して過去のデータと比較した。過去と現在の間の変化は尾根と谷とで類似しており、腐植食者のミミズ類、等脚類、端脚類、倍脚類と、捕食者であるイシムカデ類、ジムカデ類、クモ類、ザトウムシ類が個体数や現存量に負の影響を受けていた。尾根部で地表排徊性甲虫の密度が増加していた。我々の大型土壌動物に関する結果は排除柵や自然の実験を用いた、有蹄類が土壌動物に及ぼす影響に関する先行研究の結果によく一致するものであった。同じ期間に斜面における有機物土壌の分布と、表層リターおよび土壌におけるC/N比、土壌硬度が顕著に変化しており、シカが生態系機能に影響を与えていることが示唆された。斜面上の有機物の移動や分解者としての土壌動物相の減少がこの変化に寄与した可能性がある

Phylogenetic analyses of <i>Sarcophyton</i> species and relationship with chemotypes.

<p>Phylogentetic tree of an alignment of utilizing mitochondrial protein-coding genes MutS homolog <i>msh1</i> sequences for <i>Sarcophyton</i> specimens constructed by the maximum likelihood (ML) method. Values at branches represent ML, neighbor-joining (NJ) and maximum parsimony (MP) method bootstrap values, respectively. Monophylies with more than 95% Bayesian posterior probabilities are shown by thick branches. Sequences in bold without GenBank accession numbers are <i>msh1</i> sequences newly obtained in this study. Color dots indicate different chemotypes as described in this study. For chemotype information see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030410#pone-0030410-g002" target="_blank">Figure 2</a> and for specimen information see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030410#pone-0030410-t001" target="_blank">Table 1</a>.</p

Scatter plot and regression line of length and width of sclerites of each <i>Sarcophyton glaucum</i> clade.

<p>Horizontal axis: width of sclerites, vertical axis: length of sclerites.</p

Summary of field sites and chemotypes.

<p>For chemotype information see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030410#pone-0030410-g002" target="_blank">Figure 2</a>.</p><p>Specimens obtained from three field sites (April 2007-November 2007) were collected at depths of 5–20 m (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030410#s4" target="_blank">Materials and Methods</a>).</p

Structures of cembranes from <i>Sarcophyton</i> species identified in this study.

<p>Colored dots next to each cembrane are the same as in other figures.</p