加拿大-西北大西洋地区掌形藻的种群遗传结构与动态变化

探讨古气候波动(如更新世末期冰期)对典型生物的时空分布和有效种群大小变动的影响是生物地理学和进化遗传学的重要研究课题.本文利用线粒体cox2-3序列和RAPD两种分子标记,对分布于加拿大-西北大西洋地区8个地点(共138个个体)的掌形藻(Palmaria palmata)进行谱系地理学研究,试图阐明当更新世冰期来临时掌形藻如何衍生出适应性的进化机制,并形成当前的地理分布格局.结果表明,线粒体cox2-3间区序列共检测出11个单倍型,其中1个单倍型(C3)在所有种群中都有分布,并位于星状基因谱系的中心位置,可认为是祖先单倍型.St.Lawrence湾内北部的两个种群多样性最高,与其他地理种群分化最明显,这与基于RAPD数据的STRUCTURE聚类分析结果相一致.根据掌形藻遗传多样性及其单倍型谱系结构特征,推测掌形藻在加拿大-西北大西洋沿岸存在多个冰期避难所.分子多态性分析(AMOVA)显示掌形藻的遗传变异主要来自种群内,而St.Lawrence湾和Fundy湾群组间的遗传变异较小.cox2-3序列的Bayesian skyline plots分析结果反映出掌形藻种群在加拿大-西北大西洋沿岸经历了轻微的种群扩张,时间大概在0.18-0.13百万年前.St.Lawrence湾和Fundy湾群组间的K2P遗传距离为0.2％,相应的分化时间大约在0.36百万年前.由此推测,更新世末期的冰期及间冰期是影响掌形藻种群结构及变动的重要古气候环境因子.     

Corallivorous snail removal: evaluation of impact on Acropora palmata

With the continuing decline of Acropora palmata throughout the Caribbean region, impacts of the gastropod corallivore, Coralliophila abbreviata, are becoming more noticeable. A snail removal experiment was performed in remnant A. palmata populations in the Florida Keys National Marine Sanctuary to quantify the area of coral tissue consumed by ambient snail aggregations and to assess the possible effectiveness of snail removal in conserving live coral tissue. Corals where ambient snail aggregations were removed maintained significantly more live tissue area during the 2-month experiment than those where feeding snail aggregations were left in place. The corals with feeding snails left in place lost more than 3 cm² tissue day⁻¹ on average. Thus, removal of C. abbreviata may be an effective measure for conserving depressed A. palmata populations, though secondary effects of such a manipulation remain to be carefully evaluated. Accepted: 26 May 2000     

The Origin of Red Algae and Cryptomonad Nucleomorphs: A Comparative Phylogeny Based on Small and Large Subunit rRNA Sequences ofPalmaria palmata, Gracilaria verrucosa,and theGuillardia thetaNucleomorph

The complete large subunit rRNA sequences from the red algaePalmaria palmataandGracilaria verrucosa,and from the nucleomorph of the cryptomonadGuillardia theta,were determined in order to assess their phylogenetic relationships relative to each other and to other eukaryotes. Neighbor-joining, maximum-parsimony, and maximum-likelihood trees were constructed on the basis of small subunit rRNA, large subunit rRNA, and a combination of both molecules. Our results support the hypothesis that the cryptomonad plastid is derived from a primitive red alga, in that an ancient common ancestor of rhodophytes and cryptomonad nucleomorphs is indicated. This cluster shows some affinity with chlorobionts, which could point to a monophyletic origin of green and red plastids. However, the exact branching order of the crown eukaryotes remains uncertain and further research is required.     

用膨化柱填料的方法从红藻中规模分离纯化R-藻红蛋白

以Phenyl-sepharose作为柱填料,用streamline柱层析技术从红藻(Palmaria palmata (Lannaeus) Kuntze)中规模分离捕光色素蛋白--R-藻红蛋白.由于不是传统的从层析柱上方进样,而是用泵将样品从streamline层析柱的下方加样(从下至上),因而解决了用一般层析柱分离R-藻红蛋白时海藻抽提液中大量的粘性多糖堵塞层析柱的难题.用P.palmata粗提液上样后,分别用0.2 mol/L、 0.1 mol/L和0.05 mol/L的(NH4)2SO4溶液从相反的方向(即从上到下)洗脱层析柱,发现这些洗脱液中的藻红蛋白纯度已经较高.然后将洗脱液透析去盐,用阴离子交换柱层析(Q-sepharose)进一步纯化.经过这两次柱层析后,R-藻红蛋白的纯度(OD565/OD280)超过3.5,高于一般认可的R-藻红蛋白的纯度标准3.2;产率为每克冷冻P.palmata可纯化0.122 mg高纯度的R-藻红蛋白,比使用一般分离方法的产率要高10倍.这些结果表明,使用本文报道的方法纯化藻红蛋白,将会使作为生化检测试剂的藻红蛋白市场价格大幅度下降.     

Systematics and Biogeography of the Red Algal Genus Yonagunia (Halymeniaceae,Rhodophyta) from the Indo-Pacific Including the Description of Two New Species from Taiwan

Carpopeltis maillardii has been regarded as a widely distributed species in the Indo-Pacific region. In this study, we analyzed the genetic diversity of C. maillardii and related species collected from Taiwan and the Indian Ocean based on rbcL sequences, in order to elucidate species boundaries, diversity, and biogeographic patterns. Our analyses show that C. maillardii specimens are only distantly related to the genus Carpopeltis (type: C. phyllophora) but instead form a clade together with species of Yonagunia. We therefore propose the new combination Yonagunia maillardii comb. nov. In addition, two new species (Yonagunia palmata sp. nov. and Yonagunia taiwani-borealis sp. nov.) are described from Taiwan. The close relationship of Yonagunia to Grateloupia is corroborated by detailed observations of the female reproductive structures, which demonstrate that the development of auxiliary cell ampullae before and after diploidization is similar to that of Grateloupia sensu stricto. Namely, the ampullae are composed of only two orders of unbranched filaments in which only a few ampullar cells are incorporated into a basal fusion cell after diploidization of the auxiliary cell and the pericarp consists almost entirely of secondary medullary filaments. Of all Yonagunia species, Y. maillardii has the widest distribution in the Indo-Pacific, and can be identified in the field by its relatively thin, feathery, and highly branched morphology. Most other species, including those that occur in Taiwan, are seemingly more range-restricted. Our phylogenetic analyses resulted in a well-resolved phylogeny of Yonagunia, with an origin estimated in the Eocene–Oligocene, and diversification of species mainly in the Miocene.     

INORGANIC NITROGEN AND PHOSPHORUS UPTAKE KINETICS IN PALMARIA PALMATA (RHODOPHYTA)1

The N and P uptake responses were studied in a northern Spanish population of the edible red seaweed Palmaria palmata (Linnaeus) Kuntze. The fronds were incubated at different concentrations, and the nutrient depletion in the medium was measured at successive times to calculate uptake rates. Palmaria palmata uptake response was biphasic and nonsaturable for inorganic P. This would allow the species to exploit transient pulses of high P concentration in natural and fertilized conditions. Such a response is a common feature of algae avoiding nutrient deficiency. At average concentrations measured in the ocean, the response was nonsaturable for inorganic N sources, except for ammonium in autumn and winter when it is not the major N source. In contrast to the general rule of ammonium being taken at a higher rate than nitrate, we found similar affinity for both nutrients corresponding to the minor role of ammonium as N source for field populations over the year.     

Nine novel, polymorphic microsatellite markers for the study of threatened Caribbean acroporid corals

Caribbean reef-building corals in the genus Acropora have been declining dramatically since the 1980s and are now listed as threatened. The study of their complex reproductive system (mixed asexual and sexual) and their population structure requires highly polymorphic nuclear genetic markers. Of eight previously developed microsatellite loci for A. palmata, only five behaved in a Mendelian fashion and only four reliably amplified the sister species, A. cervicornis. Here, nine novel microsatellite markers are presented that dramatically increase the power to distinguish between asexual and sexual reproductive events and may help to refine population boundaries and gene flow across their ranges.     

SEASONAL VARIATION OF P CONTENT AND MAJOR N POOLS IN PALMARIA PALMATA (RHODOPHYTA)1

The annual variation of major nitrogen pools, phosphorus, carbon, ash, and thallus water content in relation to seasonal environmental changes was studied in two northern Spanish populations of the edible seaweed Palmaria palmata (Linnaeus) Kuntze. Observed patterns were investigated using Spearman rank order correlation coefficients. There were significant relationships between thallus nutrient content and nitrate and orthophosphate seawater concentration, irradiance, temperature, and wave force. The highest levels of total N and P and nitrogenous compounds were observed during autumn and winter because the thallus stored N‐ and P‐rich compounds in response to high nutrient seawater concentration when growth was limited by low light and temperature. Phycoerythrin and other proteins were the main N reserves. Thallus P content was higher in algae from the eutrophic site. During spring, reduced N and P thallus content and increased ash, water, and C content were observed in the growing fronds. N and P seawater concentrations were undetectable during summer when nutrient reserves were low and growth was reduced and eventually suppressed, suggesting nutrient limiting conditions. Palmaria palmata clearly could take advantage of elevated N and P concentrations to create storage reserves in winter to support early summer growth. This storage response reduced the dependence of algal nutrition on the external nutrient supply and supports the use of pulse fertilization to diminish summer nutrient limitation of cultured algae.