Extinction and replacement in the Indo-West Pacific Ocean

Aim To provide evidence suggesting the existence of a dynamic system of extinction and replacement. Location The Indo-West Pacific Ocean. Methods Utilization of species distribution patterns produced by detailed systematic works. Results The distribution patterns appear to suggest a sequence of events that is consistent with the centre of origin hypothesis. The East Indies centre is considered to operate according to the centrifugal speciation model. Main conclusions Disjunct patterns appear to have originated in the East Indies and spread out from there. In cases where the vacated area is occupied by a sibling species, competitive (sympatric) speciation may have occurred. Over time the extinction pattern will gradually extend outward until it is played out among small populations far from their centre of origin     

The genus Herdmania Lahille, 1888 (Tunicata, Ascidiacea) in Australian waters

Revision of material from Australian waters previously assigned to Herdmania momus ( Savigny, 1816 ) has resulted in the recognition of five species (including two new indigenous species). A tropical Indo-West Pacific range is recorded for the type species ( H. momus ), although it is not recorded from Western Australia. A circum-continental range for the third and largest species, H. grandis ( Heller, 1878 ) is confirmed. Herdmania pallida (Heller, 1878), with a wide range in the western Pacific and Indian Ocean including the north-eastern and north-western coasts of Australia, is a different species from the Atlantic Ocean species (formerly thought to be conspecific). Herdmania fimbriae , a new species with a geographical range from southern to north-eastern Australia, is distinct from H. mentula , also a new species, from the north-western coast. The structure of the gonads and their ducts and accessory membranes and the arrangement and number of body wall muscles distinguish the species. Species differences are supported by the maximum size of individuals, nature of their test, number of branchial folds, number of internal longitudinal vessels on the folds and between the dorsal lamina and dorsal fold, the size and form of the dorsal tubercle and dorsal lamina, and the shape of the ciliated opening of the neural duct, although these characters are affected to some extent by growth. A variety of accessory membranes associated with both male and female gonoducal apertures are found in the majority of species in this genus. © 2002 The Linnean Society of London. Zoological Journal of the Linnean Society , 134 , 359–374.     

香港七纺蛛属（蜘蛛目：节板蛛科）一新种

记述采自香港的节板蛛科七纺蛛属一新种,定名为香港七纺蛛Ｈｅｐｔｙａｔｈｅｌａｈｏｎｇｋｏｎｇｓｐ．ｎｏｖ．,以庆贺香港回归祖国。     

Conservation evaluation of nine Hong Kong mangals

A comparative analysis of the conservation value of nine Hong Kong mangals spread across Hong Kong has been undertaken. The analysis is based on both biological and socio-economic attributes. Biological attributes used in the analysis include plant species richness, benthic and arboreal gastropod species richness, occurrence of rare species within each site, and site representativeness. A review of the past and present development and development plans around and within each site has been undertaken to assess the comparative degree of hazard to each mangal. The drastic decline of mangal habitats throughout Hong Kong highlights the need for conservation of what remains today. Priorities and strategies for conservation of these nine mangals are discussed with particular emphasis on the preservation of biodiversity and the management of these habitats as education and research sites.Department of Applied Biology & Chemical Technology, Hong Kong Polytechnic     

香港的两栖和爬行动物

香港及其附近水域已有纪录的两栖和爬行动物共4目23科70属107种。本文着重分析陆地与淡水产种类,计有4目21科63属98种,其中目前仅见于香港的特有种4种,物种密度高达897．4／104km2,东洋界种类占绝对优势,其中主要为南中国成分,其次为印度支那成分和印度马来成分,香港与我国东南沿海各省（区）具有很高的生物相似值（＞0．4）,在动物地理区划上属于东洋界华南区东南沿海亚区。香港地处北半球亚热带季风区,气候温暖湿润,雨量充沛,适合两栖爬行动物的生存和繁衍;但由于面积不大、地貌较不复杂,随着经济的发展和人口的增加,它们生存的地域越来越缩小,再加以人为的干扰,物种和数量有减少的趋势。     

A population-based study of Helicobacter pylori infection in Chinese children resident in Hong Kong: prevalence and potential risk factors

Background: Data of Helicobacter pylori prevalence in children and its risk factors provide clues to the health authority to estimate burden of H. pylori‐associated diseases usually encountered in adulthood and facilitate healthcare planning. Materials and Methods: A cross‐sectional population‐based study was conducted in Chinese children in elementary and high schools. Schools were selected from all three major areas of Hong Kong. H. pylori infection was defined by a positive ¹³C‐urea breath test. Study subjects were stratified into six age groups for estimation of prevalence. Potential risk factors were analyzed from data of self‐administered questionnaires. Results: A total of 2480 children (aged 6–19, male: 47.3%) participated in the study. Overall, 324 (13.1%) were positive for H. pylori. There was no difference in prevalence between sexes, and no statistical trend in the prevalence across the six age groups. Multivariate logistic regression identified lack of formal education of mother (OR = 2.43, 95%CI 1.36–4.34), family history of gastric cancer (OR = 2.19, 95%CI 1.09–4.41), and household member > 5 (OR = 1.57, 95%CI 1.12–2.19) to be positively associated with H. pylori infection in our children. Conclusions: The H. pylori prevalence of Hong Kong children is comparable to the data of developed countries. The association with family history of gastric cancer justifies further study to investigate the cost‐benefit of community screening program for such children to decrease the incidence of gastric cancer in adulthood.     

香港瓮缸群岛野生植物资源调查研究

香港瓮缸群岛共有维管植物166种,隶属于69个科138个属,其中蕨类植物7科8属10种,裸子植物2科2属2种,被子植物60科128属154种。瓮缸群岛为香港著名离岛,植被生境无人为干扰,野生植物资源利用度较低,本文通过对瓮缸群岛的植被类型和野生植物资源进行统计分析,结果表明,该群岛可供利用的植物资源共10类,分别为：药用植物103种、观赏植物107种、食用植物21种、牧草及饲用植物23种、材用植物17种、油脂植物22种、芳香精油植物25种、纤维植物13种、鞣料植物11种、有毒植物26种等,都有很高的开发利用潜力,在此基础上提出相应的保育及开发利用建议,旨在更好地保护和合理利用该群岛的野生植物资源。     

Indo-West Pacific patterns of genetic differentiation in the high-dispersal starfish Linckia laevigata

Genetic variation in four natural populations of the starfish Linckia laevigata from the Indo-West Pacific was examined using restriction fragment analysis of a portion of the mtDNA including the control region. Digestion with seven restriction enzymes identified 47 haplotypes in a sample of 326 individuals. Samples collected from reef sites within each location were not significantly differentiated based on Φ_ST or spatial distribution of haplotypes, indicating that dispersal is high over short to moderate distances. Evidence of gene flow is further supported by the low divergence among haplotypes and the lack of any clear geographical structuring among different haplotypes in the gene phylogeny. However, analysis of molecular variance ( AMOVA ), Φ_ST and contingency χ² analyses of the spatial distribution of haplotypes demonstrate the presence of significant broad scale population genetic structure among the four widespread locations examined. RFLP data are consistent with high gene flow between the Philippines and Western Australia and moderate gene flow between the Great Barrier Reef (GBR) and Fiji, but only limited gene flow between either the Philippines or Western Australia and either the GBR or Fiji. The presence of mtDNA structure contrasts with previous allozyme data which suggest that dispersal among widely separated locations is equivalent to dispersal among populations within the highly connected GBR studies. This discordance between patterns of gene flow inferred from these two markers cannot be fully accounted for by differences in effective population size for mtDNA. This might suggest that while mtDNA variation may represent contemporary patterns of gene flow, allozyme variation among populations is yet to reach equilibrium between drift and migration over the range surveyed.     

香港芒萁群落养分的研究

本文研究香港芒萁群落养分的分配、季节动态和循环。研究结果表明：(1)N、P、K浓度在活物质大于死物质,地上部分大于地下部分。(2)植物的养分贮量是活物质大于死物质,地下部分大于地上部分。(3)当年生芒萁地上部养分贮量随生物量的增加而增加,但是,干物质生产率超过养分吸收率,使得N、P、K浓度由于生物量的增加而降低。(4)虽然芒萁群落的净第一性生产力大于其邻近的草地和灌木林,但其净第一性生产量中的N和P量却小于灌木林。(5)以土壤中的总N和总P来计算,生态系统中的N和P主要贮存于土壤库中,但以土壤有效K来计算,则有大约36％～50％的K贮存于植被中。(6)在研究期间,立枯体和死地被物中的N、P、K贮量逐渐增加,这表明在火灾后生态系统的立枯体和死地被物养分库有一个累积过程。(7)N、P、K通过枯枝落叶的归还量分别占它们在地上部净第一性生产量中的49.1％、30.8％和13.1％,而地上部净第一性生产量中的N和P的31.2％和46.6％来自于养分的内部循环。     

香港润楠属植物的分类研究

本文记载了香港润楠属植物共１１种,其中包括２个香港新记录（Ｍ．ｌｅｐｔｏｐｈｙｌａＨａｎｄ．－Ｍａｚ．,Ｍ．ｒｏｂｕｓｔａＷ．Ｗ．Ｓｍ．）,改正了４个过去被误定的植物种名。     

Factors affecting the distribution of lignicolous marine fungi in Hong Kong

An investigation into the effect of environmental factors on the general distribution and occurrence of lignicolous marine fungi using submerged blocks of pine (Pinus massoniana Lamb.) and teak (Tectona grandis L.) was carried out for 18 months in the coastal waters of Hong Kong. Five test sites, with environmental conditions varying from estuarine to oceanic, and from polluted to non-polluted, were selected. During each collection, salinity, temperature, pH, dissolved oxygen, biochemical oxygen demand, nitrate-nitrogen, inorganic phosphate-phosphorus and light transmission were measured. A total of 51 species of fungi were recorded among which only 28 were either obligate or facultative marine forms. Neither the general distribution pattern nor the distribution of the more frequent fungi could be solely accounted for by differences in salinity at the test sites and it is suggested that other ecological factors such as heavy sediments in the waters, low pH, and the presence of an abundant source of inocula may be important.     

香港次生林下植物菌根的调查

本文报道了香港６４种野生植物根系天然感染菌根菌的状况：９８．４％的植物都不同程度地感染上了菌根菌,９８．１％的根样发现受内生菌根（ＶＡＭ）的感染,其中小叶青冈（Ｑｕｅｒｃｕｓｍｙｒｓｉｎａｅｆｏｌｉａ）同时受外生菌根（ＥＣＭ）和内生菌根的感染。该研究揭示了香港次生林植物在自然条件下受菌根菌感染的普遍性,为进一步探讨华南地区菌根与退化地区植物群落演替的关系提供了重要的本底资料。     

不受欢迎的生物多样性：香港的外来植物物种

香港早在19世纪中叶开始就有外来植物入侵的记录,迄今为止,已发现多达238种已归化的外来或怀疑为外来的植物,其中又以薇甘菊（Mikania micrantha)、五爪金龙（Ipomoea cairica)、假臭草（Eupatorium catarium)、大黍（Panicum maximum)等最常见,外来植物最常见于受人为干扰的生境,例如荒废农田及路旁等,而较少在天然林地生境及贫瘠的灌草丛中发现,外来植物的对本地生态系统的影响主要局限于低地生境,它们常形成单优种群,减少了生境及贫瘠的灌草丛中发现,外来植物对本地生态系统的影响主要局限于低地生境,它们常形成单优种群,减少少了生境及动植物的多样性,外来动物对香港原生植物影响最大的是于20世纪70年代入侵的松树线虫（Bur-saphelenchus xylophilus)。外来的脊椎动物也有可能对香港的植物被演替产生影响,目前香港的外来植物当中,有些在大陆较少分布或没有记录,作为华南最大的港口,香港对外来物种的引入扮演着重要的角色,因此制定控制外来种在香港及华南地区的引入及传播的政策及措施非常重要。     

香港瓮缸群岛植物物种多样性与植被的研究

通过野外实地调查以及相关资料的查阅,对香港瓮缸群岛植物种类、特点、分布区类型以及与邻近地区植物多样性的关系进行研究,结果表明,瓮缸群岛共有维管植物166种,隶属于69科138属,其中蕨类植物7科8属10种,裸子植物2科2属2种,被子植物60科128属154种。植物区系以热带性质占优势,具有向亚热带过渡的特点,植被类型以常绿阔叶灌丛、南亚热带灌丛草地为主,其次为南亚热带低山常绿阔叶林和崖壁植被,群岛各岛屿由于岛屿面积、海拔、隔离程度的差异,植物物种多样性各有特点,与邻近的果洲群岛植物区系有较高的相似性,而与蒲台群岛差异较大。     

Resurrection of New Caledonian maskray Neotrygon trigonoides (Myliobatoidei: Dasyatidae) from synonymy with N. kuhlii, based on cytochrome-oxidase I gene sequences and spotting patterns

The maskray from New Caledonia, Neotrygon trigonoides Castelnau, 1873, has been recently synonymized with the blue-spotted maskray, N. kuhlii (Müller and Henle, 1841), a species with wide Indo-West Pacific distribution, but the reasons for this are unclear. Blue-spotted maskray specimens were collected from the Indian Ocean (Tanzania, Sumatra) and the Coral Triangle (Indonesia, Taiwan, and West Papua), and N. trigonoides specimens were collected from New Caledonia (Coral-Sea). Their partial COI gene sequences were generated to expand the available DNA-barcode database on this species, which currently comprises homologous sequences from Ningaloo Reef, the Coral Triangle and the Great Barrier Reef (Coral-Sea). Spotting patterns were also compared across regions. Haplotypes from the Coral-Sea formed a haplogroup phylogenetically distinct from all other haplotypes sampled in the Indo-West Pacific. No clear-cut geographic composition relative to DNA-barcodes or spotting patterns was apparent in N. kuhlii samples across the Indian Ocean and the Coral Triangle. The New Caledonian maskray had spotting patterns markedly different from all the other samples. This, added to a substantial level of net nucleotide divergence (2.6%) with typical N. kuhlii justifies considering the New Caledonian maskray as a separate species, for which we propose to resurrect the name Neotrygon trigonoides.     

The distribution of mangrove-associated gastropod snails in Hong Kong

The distributions of mangal gastropod snails in Hong Kong were investigated by transect studies in nine mangals from around the coast. Fifty-one species of mangal associated were found, of which 25 were considered common. Gastropod faunas varied considerably between sites, both in terms of number of species and species composition. No one gastropod assemblage was found to be typical of the Hong Kong mangal. Local habitat differences were considered to have a major influence over species distributions, both within and between mangals. It is concluded that if species diversity is to be preserved then a representative sample of mangals needs protection.     

Population structure between environmentally transmitted vibrios and bobtail squids using nested clade analysis

Squids from the genus Euprymna (Cephalopoda: Sepiolidae) and their symbiotic bacteria Vibrio fischeri form a mutualism in which vibrios inhabit a complex light organ within the squid host. A host-mediated daily expulsion event seeds surrounding seawater with symbiotically capable V. fischeri that environmentally colonize newly hatched axenic Euprymna juveniles. Competition experiments using native and non-native Vibrio have shown that this expulsion/re-colonization phenomenon has led to cospeciation in this system in the Pacific Ocean; however, the genetic architecture of these symbiotic populations has not been determined. Using genetic diversity and nested clade analyses we have examined the variation and history of three allopatric Euprymna squid species (E. scolopes of Hawaii, E. hyllebergi of Thailand, and E. tasmanica from Australia) and their respective Vibrio symbionts. Euprymna populations appear to be very genetically distinct from each other, exhibiting little or no migration over large geographical distances. In contrast, Vibrio symbiont populations contain more diverse haplotypes, suggesting both host presence and unidentified factors facilitating long-distance migration structure in Pacific Vibrio populations. Findings from this study highlight the importance of how interactions between symbiotic organisms can unexpectedly shape population structure in phylogeographical studies.