Genetic Diversity of Ostreopsis ovata (Dinophyceae) from Malaysia

The genus Ostreopsis is an important component of benthic and epiphytic dinoflagellate assemblages in coral reefs and seaweed beds of Malaysia. Members of the species may produce toxins that contribute to ciguatera fish poisoning. In this study, two species have been isolated and cultured, Ostreopsis ovata and Ostreopsis lenticularis. Analyses of the 5.8S subunit and internal transcribed spacer regions ITS1 and ITS2 of the ribosomal RNA gene sequences of these two species showed that they are separate species, consistent with morphological designations. The nucleotide sequences of the 5.8S subunit and ITS1 and ITS2 regions of the rRNA gene were also used to evaluate the interpopulation and intrapopulation genetic diversity of O. ovata found in Malaysian waters. Results showed a low level of sequence divergence within populations. At the interpopulation level, the rRNA gene sequence distinguished two groups of genetically distinct strains, representative of a Malacca Straits group (isolates from Port Dickson) and a South China Sea group (isolates from Pulau Redang and Kota Kinabalu). Part of the sequences in the ITS regions may be useful in the design of oligonucleotide probes specific for each group. Results from this study show that the ITS regions can be used as genetic markers for taxonomic, biogeographic, and fine-scale population studies of this species. Received September 15, 2000; accepted December 15, 2000     

Community Structure of Fishes and Habitat Complexity on a Tropical Rocky Shore

The relationship between the variables of reef fish community structure (fish richness, fish diversity and total number of fishes) and those of habitat complexity (total surface area, substratum diversity, topographic complexity, number of holes, percent cover of turf algae, zoanthids, millepores, massive corals, bare rock, encrusting calcareous algae, urchins, other sessile organisms and Sargassum) were examined on three different rocky shores (FA, FB and FT) at Arraial do Cabo, a tropical region located on Brazilian southeastern coast (23° S, 42° W). Fish abundance and vertical distribution were assessed by a visual census technique using strip transects. Percentage cover of benthic organisms and other substratum types were calculated by replicated transects using a chain laid down on the substratum. Topographic complexity was determined by the chain link method and number of holes were estimated by direct counts on replicated transects. More than 91 fishes belonging to 37 families were seen in all study sites during one year of visual census effort. FA and FB sites had similar fish community structure and habitat complexity characteristics, while FT showed different habitat characteristics and higher fish diversity and richness, plus total number of fishes. Vertical distribution of fishes along the rocky shores studied seemed to be predictable and was determined by factors such as feeding habits and behavior, availability of refuges and social interactions. The habitat variables that best explained the higher diversity and number of fishes observed in FT site were total surface area of rocky shores and the abundance of benthic sessile invertebrates; these conditions were typical of rocky shores more exposed to wave surge.     

Genetic diversity in the Japanese rosy bitterling, Rhodeus ocellatus kurumeus (Cyprinidae)

Comparison of meristic characters (pored lateral line scales, vertebrae, and fin rays), and PCR-RFLP analysis in the D-loop and ND1 regions of mitochondrial DNA were performed to estimate the genetic diversity in local populations of the Japanese rosy bitterling, Rhodeus ocellatus kurumeus. In terms of meristic characters, the Fukuoka population was the largest in both range and variance of the number of pored lateral line scales and vertebrae (abdominal and caudal), and Osaka was the second, whereas the Kagawa population showed the smallest range and variance in these characters. In PCR-RFLP analysis, 11 haplotypes (3 in Fukuoka, 2 in Okayama, 2 in Kagawa, and 4 in Osaka) were observed, and nucleotide sequence divergence (NSD) was approximately two times larger in ND1 (mean, 0.61%) than in D-loop (mean, 0.31%). In the neighbor-joining (NJ) tree, based upon the NSD value in ND1, haplotypes were arranged into four clades, which corresponded to the locality of each haplotype. The Fukuoka population was conspicuously apart from the other populations (mean, 0.90% in NSD), but the remaining three showed a similar genetic distance with each other (mean, 0.48%–0.52% in NSD). In haplotype diversity of mtDNA, half the stations in Osaka and all in Kagawa were monomorphic. Especially, two haplotypes endemic to Kagawa were randomly distributed, irrespective of drainages. Rhodeus o. kurumeus in Fukuoka inhabits small rivers and creeks (open water systems), while that in Kagawa and Osaka lives in small ponds (closed water systems). Taking the information of morphology, mtDNA, and habitat into consideration, the low genetic diversity in Kagawa and Osaka populations of R. o. kurumeus is thought to be mainly the result of the isolation of their habitat. Received: January 14, 2001 / Revised: June 14, 2001 / Accepted: July 1, 2001     

Diversity and palaeoecology of a highly diverse Late Triassic marine biota from the Cassian Formation of north Italy

A sample of marine invertebrates from the Late Triassic Cassian Formation (north Italy) yielded one of the most diverse Early Mesozoic fossil assemblages ever reported (c. 170 species). The assemblage was found in basin clays, but was transported from nearby carbonate platforms as indicated by fragmentation, microbial encrustation and the presence of coated grains and ooids. Most of the specimens are small (< 1 cm) reflecting both, small adult sizes and size sorting during transport. Rarefaction analysis suggests that diversity of surface collection and bulk sampling is the same. However, rank abundance, species richness and taxonomic composition differ strongly according to sampling method. Low‐grade lithification of the sediments is the main reason that high diversity can be recognized, because it facilitates disaggregation and finding of small molluscs. Sample standardization shows that the studied assemblage is much more diverse than known Early Triassic assemblages. However, its diversity is similar to that of Anisian assemblages. This suggests that recovery from the end‐Permian mass‐extinction was quite advanced in the Middle Triassic and alpha‐diversity remained high until the Late Triassic. According to current models, Early Triassic and Anisian faunas match the niche overlap phase of recovery during which diversity is built up by increasing alpha‐diversity, whereas beta‐diversity rises slowly. Subsequently, habitat width of species contracts because of increasing competition, making beta‐diversity the principal drive of overall diversity increase. The diversity pattern of various Late Triassic Cassian associations meets the predictions for the transition from the niche overlap to the habitat contraction phase.: Triassic, Cassian Formation, palaeoecology, diversity, mollusc dominance.     

Comparative Biogeography of Grasshoppers (Orthoptera: Acrididae) in North America and Siberia: Applications to the Conservation of Biodiversity

The objective of this study was to apply knowledge of holarctic grasshopper biogeography in representative, temperate ecosystems (Russia, South Siberia, Sayans region; 685,000km² and USA, Wyoming; 272,000km²) to develop a comparative basis for understanding and conserving insect biodiversity. Maps of species distributions and vegetation zones were digitized, and a Geographic Information System was used to identify habitats with the greatest biodiversity and to characterize this diversity as a function of selected attributes. With respect to subfamilies, the greatest differences were in cold, mesic zones, where gomphocerines and melanoplines were dominant in Sayans and Wyoming, respectively. In terms of mobility, the Sayans has more flightless species and individuals, with the taiga supporting the greatest frequency of flightless acridids in both countries. With regard to feeding types, the diversity and richness of graminivores and forbivores were similar in the two regions, but mixed feeders were much more frequent in Wyoming. In the Sayans and Wyoming, pest species were most common in boreal and prairie zones, respectively. Ecoregions with a high diversity of pests also supported a high diversity of rare species. Shrub and desert zones supported many rare species in both countries. Thus, in terms of conservation, the Sayans' acridofauna appears to be at greater risk in terms of ecological vulnerability; acridid biodiversity is dispersed among habitats, with high frequencies of flightless and oligophagous species. The acridofauna of Wyoming could be conserved in fewer habitats than in the Sayans, but these habitats are subject to considerable human disturbance.     

Commentary: Carbon Metabolism of the Terrestrial Biosphere: A Multitechnique Approach for Improved Understanding

Understanding terrestrial carbon metabolism is critical because terrestrial ecosystems play a major role in the global carbon cycle. Furthermore, humans have severely disrupted the carbon cycle in ways that will alter the climate system and directly affect terrestrial metabolism. Changes in terrestrial metabolism may well be as important an indicator of global change as the changing temperature signal. Improving our understanding of the carbon cycle at various spatial and temporal scales will require the integration of multiple, complementary and independent methods that are used by different research communities. Tools such as air sampling networks, inverse numerical methods, and satellite data (top-down approaches) allow us to study the strength and location of the global- and continental-scale carbon sources and sinks. Bottom-up studies provide estimates of carbon fluxes at finer spatial scales and examine the mechanisms that control fluxes at the ecosystem, landscape, and regional scales. Bottom-up approaches include comparative and process studies (for example, ecosystem manipulative experiments) that provide the necessary mechanistic information to develop and validate terrestrial biospheric models. An iteration and reiteration of top-down and bottom-up approaches will be necessary to help constrain measurements at various scales. We propose a major international effort to coordinate and lead research programs of global scope of the carbon cycle. Received 7 May 1999; accepted 28 September 1999.     

High genetic differentiation and low genetic diversity in Incarvillea younghusbandii, an endemic plant of Qinghai-Tibetan Plateau,revealed by AFLP markers

Incarvillea younghusbandii Sprague (Bignoniaceae) is a perennial herbaceous plant endemic to Qinghai-Tibetan Plateau. As a species of medical and horticulture importance, I. younghusbandii is threatened by over exploitation and habitat fragmentation. In this study, we analyze the genetic diversity and population structure of I. younghusbandii using amplified fragment length polymorphism (AFLP) markers. Our data reveal very low levels of genetic diversity in seven natural populations across Tibet. Specifically, at population level, the average Nei's genetic diversity index (H_E) and Shannon's diversity index (I) were 0.063 and 0.096, respectively. In contrast, high genetic differentiation among populations (Gst = 0.6238, Φ_ST = 0.614) is detected. The results of Neighbor-joining cluster, PCO, and STRUCTURE assignment reveal consistent pattern, suggesting seven well-defined genetic groups that are concordant with their geographical origins. The possible mechanisms and implications of these findings for conservation are discussed.     

基于高通量测序分析盐角草根部内生细菌多样性及动态规律

【目的】探讨盐角草根部内生细菌群落多样性特征,揭示内生细菌群落结构在宿主关键发育期动态变化规律。【方法】通过罗氏454高通量测序获得内生细菌16S r RNA片段,然后进行生物信息分析。【结果】共获得20363条16S r RNA基因序列。各样品中可操作分类单元(operational taxonomic units,OTUs)在552–941之间。根部内生细菌群落主要包括4个门,其中Proteobacteri门占主导地位,其余依次是Firmicutes,Actinobacteria,Bacteroidetes。在Proteobacteria门中,Gammaproteobacteria是第一大纲,其后是Betaproteobacteria纲。宿主5个发育时期共同拥有7个细菌属,包括Azomonas,Serratia,Pantoea,Serpens,Pseudomonas,Halomonas,Kushneria。整体上看,Gammaproteobacteria纲在宿主5个发育时期呈现增长趋势。优势菌属在5个发育期存在差异,分别为Delftia,Kushneria,Serratia,Pantoea,Erwinia。所有文库总共含2108个特异OTUs,共同拥有5个相同OTUs。花期OTUs数量最多,结种期内生细菌多样性降低。在宿主的5个发育时期中,土壤p H、月均温和土壤盐含量这3个环境因子组成的集合对其内生细菌群落变化具有显著影响。【结论】盐角草内生细菌群落多样性丰富,宿主发育期决定了内生细菌群落结构。     

Genetic diversity and population structure analysis of Qinghai-Tibetan plateau schizothoracine fish (Gymnocypris dobula) based on mtDNA D-loop sequences

Gymnocypris dobula is a commercially important fishery species and mostly distributed in the freshwater of Tibetan plateau. In this study, genetic diversity and intraspecific population differentiation were examined by using mitochondrial DNA D-loop sequences in 97 individuals sampled from three localities (Pali, Lasa and Yanghu) in the Tibetan plateau. Two hundred and fourteen polymorphic sites and 50 haplotypes were defined among the three localities. Genetic diversity analysis showed that the highest genetic diversity level was found in Pali population. Phylogenetic relationships analysis results indicated that closer phylogenetic relationships were found between the Yanghu and Lasa populations. Genetic population differentiation analysis indicated that the majority of variation (84.91%) was attributed to variations among populations and the largest differentiation was found between Pali and Lasa localities (F_st = 0.874, Nm = 0.036). Moreover, the historical demographic events were assessed by implementing the mismatch distribution analysis, Fajima's D test and Fu's Fs test. The results indicated that the Pali population had undergone a demographic expansion, possibly within the last 0.163 MYA (Million Years Ago). Our study firstly identified the population genetic structure of the G. dobula, which could be helpful for artificial breeding, fishery stock identification and resource conservation for this species.     

地理距离及环境差异对云南元江干热河谷植物群落beta多样性的影响

beta多样性反映了群落间物种组成的差异, 是生物多样性研究的热点之一。本研究通过对云南元江干热河谷41个植物群落样方进行调查, 用Jaccard相异系数表征物种beta多样性, 用样方之间的最近谱系距离(mean nearest taxon distance, MNTD)及平均谱系距离(mean pairwise distance, MPD)表征谱系beta多样性, 采用基于距离矩阵的多元回归和方差分解方法, 探讨了该区域干热河谷典型植物群落的物种beta多样性和谱系beta多样性与样方间环境差异(主要是气候)及地理距离之间的关系。结果表明: (1)群落间的地理距离和年平均温度差异对干热河谷植物群落的物种beta多样性和谱系beta多样性有显著影响; (2)地理距离对物种beta多样性和MNTD的影响最大; 地理距离和年平均温度差异对MPD的影响均较大; (3)样方间年平均温度与年平均降水量的差异和地理距离能够解释群落间beta多样性及谱系beta多样性11-13%的变异。以上结果表明, 生态位分化和扩散限制对该地区植物群落的beta多样性均有显著影响, 其中扩散限制的影响可能更大。此外, 人类活动等其他因素也很可能对元江干热河谷的群落组成具有非常重要的影响。