An experimental study of phytoplankton feeding in three tilapiine cichlids

Three species of tilapia ( Oreochromis lidole, O. karongae and O. niloticus ) were fed on four planktonic algal diets in the laboratory. The algal concentrations were measured over a 24-h period and the ingestion rates calculated. In monocultures of large algae (average filament length=477 μm) O. niloticus had the highest ingestion rate, but on small algae (particle size <8 μm) O. lidole was the fastest, while O. karongae enhanced nanoplankton production. With algae of mixed sizes, O. niloticus was able to remove small algae quicker than the other fish species. Thus, the presence of larger algae can influence the impact of a planktivorous species on nanoplankton. O. lidole is likely to have the greatest impact on plankton communities heavily dominated by smaller algae.     

Reproductive isolation and the nest sites of Lake Malawi chambo, Oveochvomis (Nyasalapia) spp.

The nest sites of chambo, Oreochromis (Nyusalupia) spp. were surveyed in the vicinity of Cape Maclear, Lake Malawi. O. karongae (Trewavas) nested at depths of 0.5 to 28 m, while O. lidole bred at depths greater than 17 m. Nesting areas overlapped between these two species. O. lidole (Trewavas) nests were generally larger than those of O. karongae . Both species bred from September to March. Contrary to previous suggestions, the two chambo species were not reproductively isolated by breeding depth, season, or beach type.     

Evolutionary relationships of the Lake Malawi Oreochromis species: evidence from allozymes

Three tilapiine species belonging to the endemic Lake Malawi species flock known as' chambo' Oreochromis ( Nyasalapia ) karongae , O. (N.) lidole and O. (N.) squamipinnis and the species Oreochromis (Oreochromis) shiranus were collected from the wild. These four species were analysed at 43 enzyme loci using starch gel electrophoresis. No significant deviations from Hardy-Weinberg equilibrium were observed after correcting for multiple simultaneous testing. The expected heterozygosity ( H _e) was lowest in O. (O.) shiranus ( H _e=0.082). The three chambo species had higher levels: H _e=0.103 to H _e=0.116. The three chambo species as a whole were polymorphic (99%) at 16 different loci sharing 10 of these in common. No fixed differences between the three chambo species were observed but highly significant allele frequency differences existed between all the chambo species. The F _ST calculated for the three chambo species was 0051, closer to intra-specific than to inter-specific levels. O. (O.) shiranus could be clearly separated from all chambo species at five fixed loci. Comparison of the allozyme data from these species with five species from the same sub genera support the hypothesis that the chambo form a monophyletic group and that O. (N.) macrochir or a related species represents the sister taxon.     

The diet of Oreochromis lidole (Trewavas) and other chambo species in Lakes Malaŵi and Malombe

Oreochromis lidole (Trewavas) is a member of a flock of tilapünes endemic to the Lake Mala% catchment area, of which it is considered to be the most pelagic and planktivorous species. Analysis of the stomach contents of adults from the South East Arm of Lake Malaŵ, from fish caught by both the offshore trawl fishery, and the inshore gillnet fishery, indicates a very narrow dietary breadth, dominated by the filamentous diatom Melosira . The presence of quantities of sand in the stomach indicates that at least some of the food is obtained from sediment feeding. During the breeding season, in November, brooding female O. lidole caught in shallow water exhibited a much broader diet, resembling the more inshore species O. squarnipinnis (Gunther) and O. karongae (Trewavas), with a higher proportion of filamentous chlorophytes and a large amount of sand. Juvenile chambo initially feed mainly on epilithic and epiphytic algae, turning more to plankton and sediment at larger sizes. In general, the different Oreochromiv spp. Caught in the same place at the same time have very similar diets, suggesting that any avoidance of competition for food resources results from habitat partitioning.     

牛科(哺乳纲:偶蹄目)动物与生境利用有关的适应形态模式

对广义牛科动物颅后骨骼的多元变量分析揭示了牛科生境利用和体型之间的骨学特征。利用逐步分辨分析方法和一个基于机器学习的决策树方法鉴别了每种生境中牛科动物颅后解剖结构的形态特征。从110个广义牛科动物测量了43个指标进行了这项分析。利用所有主要肢骨测量值和以单根肢骨测量为主的测量值获得的分辨函数和决策树可以完美地区分适应开阔生境、森林和山地的牛科动物(在所有分析中得到了100 %正确的再分类)。由于调整的函数仅涉及到很小的颅后骨骼测量集,这些函数可以应用于研究考古学和古生物学发掘物中保存的不完整标本。这些表征生境利用的生态适应函数与那些用颅齿部性状建立、用于推测牛科动物食物选择的函数结合,具有刻画已灭绝的分类类群的古个体生态学和重建古环境的潜力。我们还分析了多元回归是否较单一因子回归表现出较高的预测能力,并提出了从每一种单根主要肢骨测量的颅后形态变量得到的最好代数函数     

A preliminary classification of running-water sites in Great Britain based on macro-invertebrate species and the prediction of community type using environmental data

SUMMARY. 1. Macro-invertebrate species lists were obtained for 268 sites on forty-one river systems throughout Great Britain by qualitative sampling in spring, summer and autumn. Information on twenty-eight environmental variables was also collated for each site. The sites were ordinated on the basis of their species content using detrended correspondence analysis (DCA) and classified by two-way indicator species analysis (TWINSPAN). Correlation coefficients between ordination scores and single environmental variables indicated that Axis 1 distinguished between types of rivers and Axis 2 reflected variation along the length of rivers. A preliminary classification of sites into sixteen groups has been proposed, together with a key which allows new sites to be classified. Information on the species and environmental features which characterize each group is also presented.
2. Multiple discriminant analysis (MDA) was employed to predict the group membership of the 268 sites using the twenty-eight environmental variables. 76.1% of sites were classified correctly. An independent assessment of predictive ability using forty test sites yielded a 50% success rate. Predictive ability was higher for the classification presented in this paper than in fifteen additional classifications produced using data from single seasons and/or different taxonomic treatments.
3. TWINSPAN and MDA were found to be useful approaches to the classification of running-water sites by their macro-invertebrate fauna and the prediction of community type (as indicated by the occurrence of species in the sites comprising the group) using environmental variables. Extension of the scope of the classification, coupled with the use of additional environmental variables to increase predictive ability, is now in progress.     

(鼲)属(啮齿目,仓鼠科)同域分布物种形态学鉴别特征组的筛选

现有的分类系统尚缺乏可用于减少䶄属物种种间鉴定不确定性的形态学鉴别特征。鉴于此,本研究旨在筛选出能够对同域分布的棕背䶄（Myodes rufocanus）, 红背䶄（M. rutilus）和堤岸䶄（M. glareolus）进行可靠鉴定的头骨形态指标和方法。为了达到以上目的,本文一方面筛选出能够用于种间鉴别的头骨和齿列形态特征,另一方面提出可用于鉴别以上三个物种的计算公式。对不同研究者提出来用于鉴别以上三个同域分布物种的35个特征进行筛选。头骨形态测量数据的获取需要花费较长的时间,而且结果变异很大。在本研究中,在分析中剔除15个形态特征,20个相对保守的特征被选择用于分析（包括来自头盖骨、牙齿和头骨其它部位的特征）。在20个特征中,有8个特征被选择出来,并使用Statistica 10 计算出判别公式。这些特征使准确鉴定不同个体各自所属种类成为可能。     

An assessment of sex using the skull of black South Africans by discriminant function analysis

The derivation of discriminant function equations for skeletal elements of South African populations continues to be an area of interest to both forensic anthropologists and skeletal biologists alike. The skull of black South Africans has previously been subjected to discriminant function analysis, using four measurements and two indices; however, no equations were derived to address the issue of sex determination. Recently Franklin, Freedman and Milne [2005. Sexual dimorphism and discriminant function sexing in indigenous South African crania. HOMO J. Comp. Hum. Biol. 55, 213-228] used the crania of black South Africans, in a three-dimensional approach, with eight linear measurements to investigate sex determination. This study, although valuable, requires the use of highly technical and expensive morphometric equipment that renders it less feasible in South Africa. In response to this, our study uses traditional anthropometric measurements and equipment to address the question of sex determination from the crania and mandible of blacks. One hundred and twenty non-pathological skulls were randomly selected from the Raymond Dart Collection of Human Skeletons, equally distributed by sex and belonging to individuals whose age at death ranges between 25 and 70 years. Fourteen cranial and six mandibular measurements were subjected to discriminant function analyses and discriminant function equations were derived for sex determination. Average accuracies ranged between 80% and 85% and were on par with that obtained in previous studies. Our study shows that traditional methods provide average accuracies that are comparable to those obtained using more complex techniques.     

Morphological variability of potato cyst nematodes (Globodera spp.) in the Canary Islands

Thirty populations of potato cyst nematode (Globodera spp.) from the Island of Tenerife and two populations from the UK were assessed for several morphometric and non-morphometric characters thought to discriminate between the species G. rostochiensis and G. pallida. Also 200 cysts from each population were analysed by isoelectric focusing of soluble proteins. Correlation analysis, analysis of variance and principal component analysis were used to investigate relationships between the morphometric characters, how the relationships varied between species and between populations, and which characters were most useful for discriminating between species. The two species differed significantly for each of the four morphometric characters: stylet length, fenestra length, anus-fenestra distance and the number of ridges. The stylet length and fenestra length also showed differences between populations of G. rostochiensis while stylet length and number of ridges showed differences between populations of C. pallida. In general, populations of G. pallida showed greater variation than populations of C. rostochiensis. Principal component analysis of the population means indicated that over 73% of the variation in the characters could be explained by the contrast of stylet and fenestra lengths against the anus-fenestra distance and number of ridges. A plot of the first two principal components separated the two species. Stepwise discriminant analysis provided a linear combination of these four variables which discriminated between the species. Stylet length was found to be the most useful characteristic for distinguishing the species whilst anus-fenestra distance was the least useful.     

基于形态特征判定五种鹬类性别的可靠性

快速准确地鉴定两性同型鸟类个体性别在鸟类生态学研究中具有重要意义。本文选择2008年春季迁徙期在崇明东滩停歇的大滨鹬(Calidris tenuirostris)、红腹滨鹬(C.canutus)、红颈滨鹬(C.ruficollis)、尖尾滨鹬(C.acuminata)及翘嘴鹬(Xenus cinereus)5种两性同型的鹬类,用分子生物学方法进行性别鉴定,并基于个体的形态特征(体重、翅长、喙长、头喙长及跗跖长)采用判别分析方法对性别进行判定。结果表明,尖尾滨鹬雄性各形态特征均显著大于雌性,其他4种鹬类则相反。5种鹬类形态特征的性别差异指数在0.5%~25.3%之间,重叠度在29.4%~98.6%之间。5种鹬类判别分析判定性别的准确率在(0.69±0.06)~(0.96±0.01)之间,其中,尖尾滨鹬判别准确率(0.96)最高,翘嘴鹬判别准确率(0.69)最低。形态特征在两性间的差异程度影响性别的判别准确率。另外,两性性比对性别判别的准确率也有影响:性比偏雄性鸟类的雄性判别准确率高于雌性,而性比偏雌性鸟类的雌性判别准确率高于雄性。采用判别分析估测的性比与分子生物学鉴定结果相似,表明判别分析在判定种群的性比方面具有较高的可靠性。     

The relationships among three habitat scales and stream benthic invertebrate community structure

1. The relationships between three habitat scales and lotic invertebrate species composition were investigated for the 15 540 km² Yakima River basin in south-central Washington, U.S.A.
2. The three spatial scales were sample (the sampled riffle), reach (a length of ten–twenty stream widths) and segment (a length of stream of nearly uniform slope and valley form having no change in stream order).
3. Physical variables were highly correlated between scales and expressed a relationship between altitude, basin form and small-scale physical structure.
4. Multiple discriminant function analyses indicated that segment- and reach-scale variables discriminated among species-defined groups better than sample-scale variables.
5. Species composition varied along a complex altitudinal gradient of changing basin form and resultant land use.
6. There was no clear relationship between species richness and altitude on a site basis. However, when viewed at the basin scale, maximum richness was observed at the transition between montane and valley sites.     

Morphometric analysis of nonadult characters of common species of American gordiids (Nematomorpha: Gordioidea)

The nonadult stages, egg strings, eggs, larvae, and cysts of Gordius robustus, Paragordius varius, and Chordodes morgani are described morphometrically. The goal was to document the differences between species and to evaluate the usefulness of morphometrics in species identification. In concert, multivariate analysis of variance (MANOVA) and univariate analysis of variance (ANOVA, a posteriori contrasts) statistical tests demonstrated that each species is morphometrically distinguishable from all others. Additionally, discriminant function analysis indicated that postseptum length, pseudointestine length, and stylet width were the most important variables in the discrimination of species based on larval characters. Finally, differences in oviposition behaviors among these 3 species were found. It is suggested that ovipositioning differences may place larvae into distinct niches and may ultimately lead to the use of different paratenic hosts by different gordiid species.     

Identification and sex determination of Bicknell's Thrushes using morphometric data

ABSTRACT The similar plumage of Bicknell's (Catharus bicknelli) and Gray‐cheeked (C. minimus) Thrushes have hindered attempts to better understand the nonbreeding biology of these species. We used morphometric data, specifically primary formulae, from Bicknell's Thrushes of known sex and age throughout their breeding range in the United States and Canada to examine possible differences between sex and age classes. We compared these data with similar data from Gray‐cheeked Thrushes in Alaska, United States and Newfoundland, Canada to examine mensural characters for distinguishing the two species. We performed a discriminant function analysis (DFA) for each age class to examine morphometric differences between male and female Bicknell's Thrushes. For second‐year (SY) and after‐second‐year (ASY) birds, wing chord was the strongest differentiator, in conjunction with tarsus length. Wing chord and tail length were used to create a discriminant function to differentiate between the two Catharus species. The discriminant functions for both age classes did not permit unambiguous separation of male and female Bicknell's Thrushes nor did the DFA enable unequivocal species identity, but most individuals were correctly classified. Significant differences in the p8–p1 measurement of Bicknell's and Gray‐cheeked Thrushes and of male and female Bicknell's Thrushes suggest that this character may be useful to augment published wing chord criteria for species identification and sex determination. Our results indicate that wing chord, in combination with tail length, is the most useful measurement for distinguishing Bicknell's from Gray‐cheeked Thrushes and, when augmented with tarsus length, to differentiate between male and female Bicknell's Thrushes outside the breeding season.     

ACOUSTIC IDENTIFICATION OF NINE DELPHINID SPECIES IN THE EASTERN TROPICAL PACIFIC OCEAN

Acoustic methods may improve the ability to identify cetacean species during shipboard surveys. Whistles were recorded from nine odontocete species in the eastern tropical Pacific to determine how reliably these vocalizations can be classified to species based on simple spectrographic measurements. Twelve variables were measured from each whistle ( n = 908). Parametric multivariate discriminant function analysis (DFA) correctly classified 41.1% of whistles to species. Non-parametric classification and regression tree (CART) analysis resulted in 51.4% correct classification. Striped dolphin whistles were most difficult to classify. Whistles of bottlenose dolphins, false killer whales, and pilot whales were most distinctive. Correct classification scores may be improved by adding prior probabilities that reflect species distribution to classification models, by measuring alternative whistle variables, using alternative classification techniques, and by localizing vocalizing dolphins when collecting data for classification models.     

Multivariate discrimination between East African cape hares (Lepus capensis) and savanna hares (L. victoriae) based on occipital bone shape

In East Africa, cape hares (Lepus capensis) and savanna hares (L. victoriae) look much alike where their ranges overlap. Earlier studies suggested discrimination between the two species by several skull traits, but did not present morphometric statisitics. Our present discriminant analysis based on seven metric variables of the occipital bone related to skull length (condylobasal length) resulted in a high (95.1%) overall probability of correct separation of the two species. While all cape hares were classified correctly, correct classification was a bit lower in savanna hares (88.2%). A principal components analysis of the same variables confirmed the shape difference for the two species. Both region and sex-specific variation in the shape of the studied occipital bone complex was found in savanna hares but not in cape hares. The somewhat reduced level of correct identification of savanna hares might be due to a tendency for higher shape variation. Application of our discriminant analysis to other regions in East Africa is discussed.     

Sexual dimorphism in human skulls. A comparison of sexual dimorphism in different populations

Application and comparison of sex discriminant functions in different populations led to the conclusion that a certain combination and weighting of a few sex dimorphism variables (in this study we only used craniometric variables) can give a good discrimination between male and female individuals, independent of the racial group to which this function is applied. In our study, the sex-discriminatory power of five discriminant functions which were based on different ordination and selection procedures (e.g. professional knowledge, stepwise discriminant analysis, literature) of the cranial variables is compared. These discriminant functions were applied to three different data sets, the first being skull measurements from an Amsterdam series (Europids), the second skull measurements of a Zulu series (Negrids) and the third skull measurements of a Japan series (Mongolids). Our decision as to whether a function is a good or less good sex-discriminating function is determined by the Dt values (these values give an idea about the discriminatory value of the discriminant function when applied to a new test sample), the number of variables necessary to obtain this Dt and the location of the sectioning point (i.e. comparison between the estimation of the sectioning point and the ”real” sectioning point). These discriminant functions were compared withGiles Elliot's (1962, 1963) “race-independent” sex function.     

Sex determination of Antarctic Petrels Thalassoica antarctica by discriminant analysis of morphometric characters

We present data on sexual dimorphism in some morphological measurements (wing length, head length, bill depth and bill length) in the Antarctic Petrel Thalassoica antarctica. Males were on average larger than females for all measurements. Sexual dimorphism was on average largest for bill depths whereas wing lengths discriminated least between the sexes. A discriminant function including bill depth, head length and wing length correctly sexed 92% of the sample. Due to between-measurer variation it is recommended that morphometric measurements obtained by others on sexed birds are compared with ours before proceeding with the use of the discriminant function on unsexed individuals.Publication No. 116 of the Norwegian Antarctic Research Expeditions (1991/92)     

Automated classification of bird and amphibian calls using machine learning: A comparison of methods

We compared the ability of three machine learning algorithms (linear discriminant analysis, decision tree, and support vector machines) to automate the classification of calls of nine frogs and three bird species. In addition, we tested two ways of characterizing each call to train/test the system. Calls were characterized with four standard call variables (minimum and maximum frequencies, call duration and maximum power) or eleven variables that included three standard call variables (minimum and maximum frequencies, call duration) and a coarse representation of call structure (frequency of maximum power in eight segments of the call). A total of 10,061 isolated calls were used to train/test the system. The average true positive rates for the three methods were: 94.95% for support vector machine (0.94% average false positive rate), 89.20% for decision tree (1.25% average false positive rate) and 71.45% for linear discriminant analysis (1.98% average false positive rate). There was no statistical difference in classification accuracy based on 4 or 11 call variables, but this efficient data reduction technique in conjunction with the high classification accuracy of the SVM is a promising combination for automated species identification by sound. By combining automated digital recording systems with our automated classification technique, we can greatly increase the temporal and spatial coverage of biodiversity data collection.     

Stepwise and Canonical Discriminant Analysis of Longidorus Species (Nematoda: Longidoridae) from Arkansas

During a 1998-to-2001 survey from Arkansas, nine distinct species of Longidorus were found including five new species. Morphometrics of these nine species were used in a stepwise and canonical discrimination to select a subset of characteristics that best identified each species. Student''s t test was applied to compare Longidorus breviannulatus Norton &Hoffman, 1975; L. crassus Thorne, 1974; L. diadecturus Eveleigh &Allen, 1982; L. fragilis Thorne, 1974; L. biformis Ye &Robbins, 2004; L. glycines Ye &Robbins, 2004; L. grandis Ye &Robbins, 2003; L. paralongicaudatus Ye &Robbins, 2003; and L. paravineacola Ye &Robbins, 2003 to examine interspecies variation and test for the most useful morphometric characters in species discrimination. Most of the morphometric characters were useful to differentiate species, but species identification could not be based on a single character because the morphometric character ranges often overlap. Stepwise discriminant analysis indicated that the guide ring position, head width, tail length, body length, odontostyle length, and anal body width were the most important variables. These were used to generate canonical variables in discriminating the species. The first three canonical variables accounted for 95% of the total variance. The scatterplots by the first three canonical variables grouped and separated the Longidorus species from Arkansas. Stepwise and canonical discriminant analyses were useful for examining the groupings and morphometric relationships of the nine Longidorus species.