Cluster analysis of potomac river survey stations based on protozoan presence-absence data

Four high-water and six low-water limnological surveys of a portion of the Potomac River were made from 1956 to 1965; samples were collected at three stations on each survey to determine the effects of operation of the PEPCO Dickerson Power Station on the aquatic biota. Cluster analyses were made of various combinations of Jaccard coefficients relating 46 aggregations of 647 protozoan species.Similarities of aggregations of species within a survey were nearly always greater than similarities among aggregations from different surveys, indicating linear or along-stream environmental influences. Within-survey similarities for the early and late surveys were usually higher than similarities within middle-year surveys, a possible indication of environmental change at all stations, including the control, and subsequent biotic readjustment. Clustering of the 1956 aggregations, taken under high-water conditions before plant operations began, with aggregations from other surveys for any one station indicate that 1956 may have been different from other survey years. One explanation is that increased urbanization upstream from the power station after 1956 caused some environmental change. No changes in aquatic biota could be attributed to thermal pollution as a direct result of operation of the electric power generating station.     

Individual growth and reproductive behavior in a newly established population of northern snakehead (<Emphasis Type="Italic">Channa argus</Emphasis>), Potomac River,USA

Northern snakehead (Channa argus) were first found in the Potomac River in 2004. In 2007, we documented feeding and reproductive behavior to better understand how this species is performing in this novel environment. From April to October, we used electrofishing surveys to collect data on growth, condition, and gonad weight of adult fish. Growth rates of young were measured on a daily basis for several weeks. Mean length-at-age for Potomac River northern snakehead was lower than for fish from China, Russia, and Uzbekistan. Fish condition was above average during spring and fall, but below average in summer. Below-average condition corresponded to periods of high spawning activity. Gonadosomatic index indicated that females began spawning at the end of April and continued through August. Peak spawning occurred at the beginning of June when average temperatures reached 26°C. Larval fish growth rate, after the transition to exogenous feeding, was 2.3 (SD ± 0.7) mm (total length, TL) per day. Although Potomac River northern snakehead exhibited lower overall growth rates when compared to other populations, these fish demonstrated plasticity in timing of reproduction and rapid larval growth rates. Such life history characteristics likely contribute to the success of northern snakehead in its new environment and limit managers’ options for significant control of its invasion.     

Cluster analysis of occurrence and distribution of insect species in a portion of the Potomac River

Summary Limnological surveys of a portion of the Potomac River were made from 1956 to 1965 to determine the effects of operation of the PEPCO Dickerson Power Station on the aquatic biota. Samples were collected at three stations on each of four high-water and six-low-water surveys. Cluster analyses were made of various combinations of Jaccard coefficients relating 50 aggregations of 370 insect species.Similarities of aggregations of species with a survey were in all cases greater than similarities among aggregations from different surveys, indicating relatively strong within-year or along-stream environmental influences. Clusters of aggregations from middle-year survey show a greater similarity to each other than to the earlier or later surveys. This may indicate environmental change at all stations, including the control. The marked dissimilarity of aggregations from the last survey to all others suggests biotic change in the river. One explanation is that increased urbanization upstream from the power station after 1956 caused some environmental change. No changes in aquatic biota can be attributed to thermal loading as a direct result of operation of the electric power generating station.The clustering method used provides a convenient quantitative analysis of limnological survey data and a comparison of environmental information derived from the study of distribution and ocurrence of different groups or organisms. The significance of this is that similarities and differences between communities can be expressed numerically and similar communities will cluster. If the control station clusters with the stations receiving heated waste water this indicates that no significant biological changes were caused by the waste heat.

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Zusammenfassung Um festzustellen ob die Lebensgemeinschaften des Potomacflusses irgendwie beeinflut oder durch thermischer höhte Abwassern vom PEPCO Dickerson Power Station geändert wurde, wurden mehrere limnologische Untersuchungen (1956–1965) im Flu durchgeführt.Proben wurden 10 Male von 3 Stationen entnommen (4 Male-Hochwasser, 6 Male-Niedrigwasser). Verschiedene Jaccard Coefficient Cluster Analyses wurden geprüft in Beziehung auf 50 Ansammlungen von 370 Arten von Insecten.Ansammlungen innerhalb einzelnen Untersuchungen waren ähnlicher als diejenigen zwischen verschiedenen Untersuchungen. Das zeigt starke Beeinflüsung von Umweltfaktoren in einzelnen Jahren oder in einzelnen Strom-Orten.Ansammlung-Klumpen von den mitteljährigen Untersuchungen älnelt sich mehr als die Früh-oder Spätjährigen. Das könnte auf Umweltsänderungen (alle Stationen) hinweisen. Die letzte Untersuchung war ganz verschieden; wohl ein Zeichen von biotischer Änderung. Die Ursache dafür könnte sich wohl als eine Folge der stromaufwärts des Untersuchungsgebietes neuzeitlichen Verstädterung. Keine von den festgestellten biotischen Änderungen sind auf den thermisch-erhöhten Abwässern des PEPCO elektrizitätswerk zurückzuführen.Diese Klump-Methode wird eine Beihilfe sein um Ähnichkeiten und Verschiedenheiten zwischen Lebensgemeinschaften mathematisch auszudrücken. Ähnlichen Gemeinschaften werden klumpen.Wenn die Kontrolle Biota und die Abwasser Biota klumpen, können wir vermuten da es sich um keinen bedeutsamen biotischen Veränderungen handelt; ferner, da die erhöhte Abwasser-Temperature keine bedeustame Wirkung auf die Biota veranstaltete.

     

北部湾雷州近海春、夏季鱼类群落结构初探

根据2005年4月、7月和8月在北部湾雷州近海进行的渔业资源刺网和底拖网调查,对该海域春、夏季鱼类群落结构进行了初步研究.结果表明,银鲳(Stromateoides argenteus)是当地绝对的优势种,其它鱼类优势种随区域和季节有着较大的差异.分别计算了北部湾雷州近海春、夏季鱼类生物多样性指数的种类丰度指数(R)、多样性指数(H')、均匀度指数(J').聚类分析表明该水域鱼类群落结构存在一定程度的时空异质性,但空间异质性不如时间异质性明显.此外,不同群落中的鱼类呈现出不同的生态型特征.同时部分结果表明,在不同网具的调查下,有的结果会出现较大变化.     

Multivariate pattern analysis of wetland invertebrate communities and environmental variables in Western Australia

Abstract Macro-invertebrates, zooplankton and water quality variables were sampled at 33 wetlands near Perth, Western Australia, in January-February 1989. Wetlands were classified and ordinated using the invertebrate data. Correlations of environmental variables with the ordination were calculated and the importance of seasonality and geomorphology of the wetlands were investigated. The wetlands were also classified and ordinated using the chemical data. Analysis of variance was used to compare species richness, abundances of all invertebrates, macro-invertebrates, copepods and total phosphorus levels among groups. Six groups of wetlands were identified from the invertebrate data, two of which were outliers on the basis of very low pH and high salinity, respectively. The majority of the wetlands grouped on the basis of their degree of nutrient enrichment and colour. The analyses of chemical data gave similar groups. The coloured wetlands and least nutrient enriched non-coloured wetlands were identified as being closest to the probable state of wetlands prior to European settlement. The greatest numbers of rare species were found in wetlands from these two groups. Species richness was significantly higher in the moderately enriched wetlands than in any other group but decreased in the most enriched wetlands where abundances of invertebrates were highest. Changes in community composition among the groups of wetlands are discussed. The most highly nutrient enriched wetlands were dominated by cosmopolitan species with high abundances, whereas less enriched and coloured wetlands had species with more restricted distributions and lower abundances.     

Identifying hotspots for biodiversity management using rank abundance distributions

Aim Identification of biodiversity hotspots has typically relied on species richness. We extend this approach to include prediction to regional scales of other attributes of biodiversity based on the prediction of Rank Abundance Distributions (RADs). This allows us to identify areas that have high numbers of rare species and areas that have a rare assemblage structure. Location Continental slope and shelf of south‐western Australia, between 20.5 and 30° S and depths of 100–1500 m. Methods We use a recently developed method to analyse RADs from biological surveys and predict attributes of RADs to regional scales from spatially abundant physical data for demersal fish and invertebrates. Predictions were made for total abundance (N), species richness (S) and relative evenness at 147,996 unsampled locations using data from two spatially limited surveys. The predictions for S and relative evenness were then independently split into categories, creating a bivariate distribution. The RAD categories are mapped spatially between 20.5 and 30° S to depths of 1500 m to allow identification of areas with rare species and assemblage structure across this region. Results Rank abundance distributions for demersal fish vary with large scale oceanographic patterns. Peaks in abundance and unevenness are found on the shelf break. The bivariate distributions for richness and evenness for both fish and invertebrates show that all assemblage structures are not equally likely. The RAD categories identify regions that have high numbers of rare species and areas with unique assemblage structure. Main conclusions Predicted RADs over large regions can be used to identify biodiversity hotspots in more detail than richness alone. Areas of rare species and rare assemblage structure identified from fish and invertebrates largely overlap, despite the underlying data coming from two different data sets with two different collection methods. This approach allows us to target conservation management at species that would otherwise be missed.     

Biogenic habitat structure and characteristics of temperate reef fish assemblages

Assemblages of non-cryptic, substrate-oriented species of fish were compared on a series of reefs in Southern California, USA. Reefs were grouped according to algal cover: dense beds of giant kelp (Macrocystis pyrifera) with turf understorey; sparse beds of giant kelp with foliose algae understorey: foliose algae < 1 m in height; and open barrens. Despite affinities to particular algal substrates by many individual species, we detected no differences in fish species richness and only weak differences in species composition among reefs of different habitat types. Planktivores and species that consume macro-invertebrates were less likely to occur on reefs that supported giant kelp; the frequencies of occurrence of three other trophic groups (piscivores, herbivores and micro-carnivores) were unaffected by giant kelp. Algal composition on reefs in Southern California is temporally highly dynamic. Changes in macro-algal composition of reefs influenced population dynamics of two fish species (black surfperch and striped surfperch) examined. Overall, the weak spatial variation in fish assemblages on reefs in Southern California appears to result from relatively unspecialized ecological requirements of many species combined with temporal changes in algal structure on reefs that are rapid relative to generation times of the fish. We hypothesize that the degree of spatial differentiation in assemblages of substrate-associated species of fish may be inversely related to the temporal constancy of biogenic reef structure.     

Studies on the ichthyo-fauna in Plover Cove Reservoir, Hong Kong: I. Sequence of fish population changes

Gill-net surveys were made weekly from May 1971 to April 1974 in Plover Cove Reservoir, Hong Kong and the results analysed to determine the fish species composition in the reservoir, the seasonal fluctuation of catches and the length frequency distribution of some major species.
Over 20 species were represented in the fish fauna including almost all the naturally occurring species as well as the stocked species. Of the twenty species, some were collected regularly in gill-net samples while others occurred rarely. Sarotherodon (Tilapia) mossam-bicus (Peters) was the dominant species and contributed the main bulk of the catch. This species also showed distinct age groups in the reservoir and modal changes occurred seasonally. Thus, among the fish species studied only S. mossambicus showed a steady and progressive increase in abundance in the reservoir and the full development of this fish population with its wide range of feeding habits should be beneficial.     

广西北海西村港互花米草对红树林湿地大型底栖动物群落的影响

为了解互花米草(Spartina alterniflora)入侵红树林的生态影响, 作者对位于北海市西村港的红树林湿地以及周边互花米草盐沼的大型底栖动物群落多样性和群落结构进行了研究。2012年10月至2013年9月连续4次取样, 按照取样时间研究大型底栖动物的种类、物种组成、生物量和生物多样性等群落特征的差异, 探讨互花米草入侵红树林湿地对大型底栖动物的影响。本研究共采集底栖动物16种, 隶属于5门7纲15科, 其中互花米草群落10种, 红树林湿地12种。研究发现互花米草入侵后中国绿螂(Glauconome chinensis)个体数量剧增, 导致不同采样时间互花米草盐沼的大型底栖动物生物量均显著高于红树林湿地; 除个别月份外, 红树林湿地大型底栖动物的Margalef丰富度指数、Shannon-Wiener多样性指数、Simpson多样性指数和Pielou均匀度指数均显著高于互花米草群落。基于生境-采样时间的双因素方差分析结果表明, Shannon-Wiener多样性指数和Simpson指数在两种生境间差异显著; 两种生境的Margalef丰富度和Pielou均匀度指数在不同采样时间差异显著; 大型底栖动物生物量和物种数量在两种生境间和不同采样时间差异均显著。基于多元回归分析的研究结果表明, 互花米草密度是影响大型底栖动物生物量的关键因子, 而互花米草株高可以解释物种个体数量、Shannon-Wiener多样性指数和Simpson指数在两种生境的变化。对不同采样时间大型底栖动物群落结构的非度量多维度(non-metric multidimensional scaling, NMDS)分析结果表明, 红树林与互花米草群落的大型底栖动物群落相似性很低。总而言之, 在西村港地区, 互花米草入侵虽然增加了大型底栖动物的生物量, 但由于优势物种的凸显, 显著降低了大型底栖动物群落的多样性, 且种类组成与群落结构与红树林群落相比已有差异。由此可见, 互花米草入侵红树林对当地的大型底栖动物群落多样性造成影响。     

Diversity and composition of estuarine and lagoonal fish assemblages of Socotra Island,Yemen

Estuarine and lagoonal surveys of Socotra Island and selected sites on the Hadhramout coast of Yemen were conducted with the objective of documenting and analysing fish diversity and assemblage structure. A total of 74 species in 35 families were recorded, among which 65 species in 32 families were from Socotra and 20 species in 17 families were from mainland Yemen. Twenty‐one species represent new faunal records for Socotra. Including historic records re‐examined in this study, the total fish species richness of estuaries and lagoons of Socotra Island reaches 76, which is relatively high compared to species inventories of well‐researched coastal estuaries in southern Africa. Five species dominate the occurrence and abundance frequencies: Terapon jarbua, Hyporhamphus sindensis, Aphanius dispar, Ambassis gymnocephala and Chelon macrolepis. Rarefaction and extrapolation analyses suggest that the actual number of fish species inhabiting some of those estuaries might be higher than the one observed. Thus, additional sampling at specific sites should be conducted to record other less conspicuous species. Ordination and multivariate analyses identified four main distinct assemblage clusters. Two groups are geographically well structured and represent northern Socotra and mainland Yemen, respectively. The other two assemblage groups tend to be determined to a greater extent by the synchrony between physical (e.g. estuary opening periods) and biological (e.g. spawning and recruitment periods) variables than by geographical location. Finally, the single intertidal lagoon of Socotra represents by itself a specific fish assemblage. The high proportion of economically important fish species (38) recorded underscores the paramount importance of these coastal water bodies as nursery sites, and for sustaining vital provisioning ecosystem services.     

澜沧江西双版纳段鱼类组成和物种多样性

根据2018-2020年澜沧江西双版纳段5次鱼类资源调查数据,结合相关文献资料,对该流域鱼类组成及物种多样性进行了分析。结果显示：澜沧江西双版纳段此次共调查到鱼类119种,隶属于11目28科79属,而历史记录鱼类共179种,隶属于12目34科106属。随着调查的不断深入,土著鱼类种数逐渐增多,但占比却逐渐下降,外来鱼类种数逐渐增多,占比也逐渐升高;本次调查到土著鱼类92种,占鱼类种数的77.31%,占比进一步下降;外来鱼类27种,占鱼类种数的22.69%,占比进一步升高。该区域鱼类优势种为云南吻孔鲃Poropuntius huangchuchieni和少鳞舟齿鱼Scaphiodonichthys acanthopterus,常见种为长臀鲃Mystacoleucus marginatus和宽额鳢Channa gachua。有《国家重点保护野生动物名录》（2021年）鱼类5种,《中国生物多样性红色名录脊椎动物卷》（2015年）受威胁鱼类8种。相对于我国其他江河,澜沧江西双版纳段有极高水平的鱼类物种多样性,其中澜沧江干流鱼类物种多样性相对于左、右岸支流较低,左岸支流鱼类多样性高于右岸,罗梭江鱼类多样性高于其他一级支流。虽然澜沧江西双版纳段鱼类物种多样性维持在较高水平,但土著鱼类占比下降趋势明显,仍面临着严重威胁,本文分析了受威胁因素,并提出了保护建议。     

New ecological information onScytalina cerdale (Pisces: Scytalinidae) from a central California rocky intertidal zone

Synopsis New information regarding the ecology ofScytalina cerdale was obtained over a four year period as a consequence of a long-term marine ecological study at the Diablo Canyon Power Plant (DCPP), San Luis Obispo County, California. Twenty intertidal fish surveys were conducted at approximately quarterly intervals, between March 1979 and June 1983, at three separate rocky shore locations (stations). During each survey, a total of 108 square meters (36 m² per station) was searched for fish during periods of low tide. A total of 280S. cerdale were collected, identified, measured, and released back into the same 4 m² area, from the same intertidal station (Diablo Cove), throughout the study period. This limited intertidal occurrence most likely reflectsS. cerdale microhabitat requirements; a combination of intertidal elevation (mean = +0.3 MLLW), substratum specificity (loose gravel, 5–10mm size range, overlying a base of sand and shell fragments), and degree of wave exposure (semi-protected). Throughout the study,S. cerdale was seasonally more abundant during summer months (June through August) and less abundant during winter months (November through February). The only exception to this abundance trend followed the 1982 winter storms, which coincided with an El Niño event, whenS. cerdale abundance uncharacteristically dropped during the subsequent 1983 spring and summer surveys. Mean total lengths did not vary greatly, reflecting the absence of early juvenile fishes, and relatively high mean fish densities (3.5 fish per m² for 20 surveys) were recorded. Qualitative comparisons betweenS. cerdale abundance and seasonal changes in water temperature indicated an inverse relationship. Gravid females, demersal egg masses, and early juvenile individuals were never observed during the four years of the study. This suggests that unlike most other intertidal fishes, particularly other blennioids,S. cerdale may not utilize the intertidal zone for reproductive and recruitment purposes; Diablo Canyon is the most southerly reported distribution for this intertidal species, and therefore, may not entirely represent the species' biology as a whole.     

Determining fish avoidance of polluted water

A critical evaluation is given of material and methods to be used for the study of behavioral responses of fish towards polluted water. Experiments with Fathead minnows in a steep gradient of hypochlorite are described and discussed. Methods leading towards standarization of fish avoidance reactions are advocated.This research was supported by the American Electric Power Service Corporation, Canton, Ohio USA     

东海大陆架鱼类群落的空间结构

根据1997～2000年东海大陆架水深30～200米海域4个航次的底拖网调查资料,运用多元分析(聚类分析和非度量多维标度(NMDS))、SIMPER以及BIO-ENV方法分析了东海鱼类群落的空间格局以及与非生物环境因子之间的关系。结果表明,东海大陆架海域鱼类群落在空间上可分为3个群落类型,分别为东海近海群落、东海大陆架外缘群落以及这两个群落之间的东海大陆架混合群落。东海大陆架鱼类群落的种类组成沿着水深梯度的变化明显,每种鱼类均有一定的水深范围。不同的流系具有不同的温盐特征,影响了鱼类的分布及其洄游,从而控制了不同鱼类群落类型的种类组成。东海大陆架鱼类群落类型中,大陆架外缘群落类型各调查季节在空间分布和种类组成上相对稳定,而东海近海群落类型和东海大陆架混合群落类型在夏季融合在一起,其它季节保持各自的空间结构。同时东海陆架区只在一种群落类型中出现的鱼类相对较少,多数鱼类同时出现在两个群落类型中或3个群落类型中,但是它们相对较集中的区域明显不同,在不同群落类型中的生物量和出现频率有很大的差异,这些鱼类在其不同的生长发育阶段由于对海洋环境的不同需求,它们根据繁殖或摄食需求而在东海陆架区范围内洄游以寻找最适的海洋环境,因此对3个群落类型定义是相对的,很难严格确定一个永久的鱼类群落地理区域,以形成相互隔离的鱼类群落,而且鱼类群落之间的边界随着季节不同发生变化。     

How many demersal fish species in the deep sea? A test of a method to extrapolate from local to global diversity

Grassle and Maciolek (1992) estimated that there were of the order of 107 species of benthic macro-invertebrates in the world's deep sea soft sediments. Their estimate was extrapolated from the 798 species they sampled and the pattern of species diversity observed along a 176km transect on the continental slope of the northeast Atlantic Ocean. Relative to the deep sea invertebrate fauna, the deep sea fish fauna has been better sampled, at least in the upper 1500m. To test the validity of the Grassle and Maciolek method of extrapolation, we applied it to data from a survey of fishes along the continental slope off western Australia, a diverse and previously unsurveyed region. The resulting global estimate for the deep sea demersal fishes – 60000 species – was then compared with the number described to date, about 2650 species, and an estimate of total extant species. Our estimate, which considers the proportion of new species found in little-explored regions of the world ocean, such as off western Australia, and the number of new species expected in future taxonomic revisions, is a total of 3000–4000 species. The Grassle and Maciolek method appears invalid as a means to extrapolate global biodiversity from local surveys.     

Trichodinid ectoparasites (Ciliophora: Peritrichida) of freshwater fishes of the Zambesi River System,with a reappraisal of host specificity

Over a period of five years parasitological surveys were carried out on the freshwater fish fauna in the eastern Caprivi which included the upper Zambesi River, a section of the Chobe and Kwando Rivers, and vast swampy areas. This area is well known for its wide variety of indigenous fish and has so far not been influenced in any way by introduced alien fish species. In these surveys 45 different fish species of 12 families were examined. This paper reports on the parasites of the generaTrichodina andHemitrichodina of the eastern Caprivi. A total of 15 species of parasites were recorded of which nine are new species described here-in. The list of host records of known species are expanded and an evaluation of host specificity based on information recorded in this survey as well as previously published data from southern Africa is provided.     

Cascading effects of predatory fish on the composition of benthic algae in high‐altitude streams

Cascading effects of predators can affect ecosystem properties by changing plant biomass, distribution and assemblage composition. Using data from field surveys and whole‐stream experiments we tested the hypothesis that predatory trout change assemblage composition of benthic algae in high‐elevation streams mediated by grazer behavior. Field surveys revealed that the taxonomic composition of algal assemblages differed significantly between streams that contained trout and those that were fishless; but comparisons of palatable versus unpalatable algal taxa between fish and fishless streams were equivocal because of high natural variability. Therefore, we tested for a behavioral (non‐consumptive) trophic cascade experimentally by adding brook trout chemical cues to six naturally fishless streams for 25 days and compared responses of grazers and algae to six reference streams without fish cues added. Algal response variables included rates of change in the abundance of three physiognomic categories, from most palatable (attached erect and prostrate diatoms) to least palatable (non‐diatoms), as determined from food selectivity analyses of the most common grazers (mayflies and caddisflies). Fish cues did not affect the mean densities or changes in densities of total grazers or any individual grazer species. However, in streams where fish cues were added, rates of accrual of attached erect diatoms, which was the preferred algal type for the grazer most vulnerable to trout predation (Baetis), were higher and their densities increased significantly faster with increasing densities of this grazer species than in reference streams. Results of his experiment support the hypothesis that predator induced suppression of grazer foraging behavior, rather than cascading effects of top predators on grazer density, may contribute to variation in the composition of algal assemblages among streams by allowing proliferation of most palatable algal species.     

阳江核电站邻近水域浮游植物群落结构及其季节变化

报道了2009—2010年阳江核电站Ⅱ期工程邻近水域的浮游植物群落结构与季节动态,估算了温排水的影响范围,并探讨了温排水对浮游植物群落的影响和预测。结果表明:78份样品鉴定浮游植物6门50属125种,季节平均丰度为(111.8±120.6)(103cells·L-1;硅藻主导型群落,占所有物种的75.4%,其次为甲藻,占19.8%;着色鞭毛藻(棕囊藻)在11月增殖,其丰度的数量级尚未达到发生赤潮的程度;主要优势种为丹麦细柱藻(Leptocylindrus danicus)、斯氏几内亚藻(Guinaridia striata)、中肋骨条藻(Skeletonema costatum)、尖刺伪菱形藻(Pseudonitzchia pungens)、念珠直链藻(Melosira moniliformis)、球形棕囊藻(Phaeocystis globosa)、叉分角藻(Ceratium furca)、密联角毛藻(Chaetoceros densus)等;种类组成及丰度分布有明显季节变化,密集中心不同;丰度分布总体呈现东部近岸向西南离岸减低的态势;11月的浮游植物物种多样性指数(H’)和均匀度(J’)均低,棕囊藻优势度极高,细胞丰度的种间分配不均匀,群落结构不稳定,4、8月反之;温排水的扩散范围估算为10km,浮游植物种类的季节更替反映了物种对温度的生态适应性,棕囊藻高丰度的发生需引起重视;阳江核电站Ⅱ期的温排水效应对浮游植物群落结构的作用并不明显。     

Novel Relationships Among Ten Fish Model Species Revealed Based on a Phylogenomic Analysis Using ESTs

The power of comparative phylogenomic analyses also depends on the amount of data that are included in such studies. We used expressed sequence tags (ESTs) from fish model species as a proof of principle approach in order to test the reliability of using ESTs for phylogenetic inference. As expected, the robustness increases with the amount of sequences. Although some progress has been made in the elucidation of the phylogeny of teleosts, relationships among the main lineages of the derived fish (Euteleostei) remain poorly defined and are still debated. We performed a phylogenomic analysis of a set of 42 of orthologous genes from 10 available fish model systems from seven different orders (Salmoniformes, Siluriformes, Cypriniformes, Tetraodontiformes, Cyprinodontiformes, Beloniformes, and Perciformes) of euteleostean fish to estimate divergence times and evolutionary relationships among those lineages. All 10 fish species serve as models for developmental, aquaculture, genomic, and comparative genetic studies. The phylogenetic signal and the strength of the contribution of each of the 42 orthologous genes were estimated with randomly chosen data subsets. Our study revealed a molecular phylogeny of higher-level relationships of derived teleosts, which indicates that the use of multiple genes produces robust phylogenies, a finding that is expected to apply to other phylogenetic issues among distantly related taxa. Our phylogenomic analyses confirm that the euteleostean superorders Ostariophysi and Acanthopterygii are monophyletic and the Protacanthopterygii and Ostariophysi are sister clades. In addition, and contrary to the traditional phylogenetic hypothesis, our analyses determine that killifish (Cyprinodontiformes), medaka (Beloniformes), and cichlids (Perciformes) appear to be more closely related to each other than either of them is to pufferfish (Tetraodontiformes). All 10 lineages split before or during the fragmentation of the supercontinent Pangea in the Jurassic. [Reviewing Editor: Dr. Rafael Zardoya]