Multivariate Ratio Analysis Research Articles

And Yet They Differ: Reconsiderations of Diversity within Dactylochelifer latreillii (Arachnida: Pseudoscorpiones)

Morphological stasis is a widespread characteristic of pseudoscorpions, suggesting that much cryptic diversity remains unexplored. Here, we revise the polytypic species Dactylochelifer latreillii in the framework of an integrative taxonomic approach, using DNA barcoding, multivariate ratio analysis, geometric morphometry of the male foretarsus, and genitalic morphology. The pattern of mitochondrial variation suggests three species-level entities in central Europe, which widely overlap in morphospace, but differentiate in the structure of the female genitalia, and by their ecology. Dactylochelifer latreillii (Leach) is a halobiont species, occurring exclusively in coastal habitats and in Pannonian salt steppes, and D. l. septentrionalis Beier syn. nov. is a junior synonym of the nominate species. Dactylochelifer degeerii (C. L. Koch) stat. rev. is the oldest available name for an inland species that has long been mistaken for the nominotypical subspecies of D. latreillii. New habitat information suggests a preference for higher shrub vegetation. Dactylochelifer ninnii (Canestrinii) stat. rev. is a halophilic Mediterranean species that extends to the northern limits of the Pannonian basin. The distinctiveness of the Mediterranean “form” was recognized by early naturalists in the 19th century, but was ignored by later authorities in the field.

Torymus sinensis and its close relatives in Europe: a multilocus phylogeny, detailed morphological analysis, and identification key

The introduction of the biological control agent Torymus sinensis Kamijo (Hymenoptera, Chalcidoidea, Torymidae) to control the populations of the chestnut gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera, Cynipidae) is considered one of the successful programs in biological control. The species was involved in interspecific hybridisation in Japan and the specimens imported into Europe were derived from this hybrid lineage, showing signs of introgression. The discovery of mitochondrial haplotypes or possible Enolase haplotypes from T. beneficus or of specimens with shorter ovipositor does not necessarily imply that T. beneficus is present in Europe, only that the European specimens are of hybrid origin. Of the native European Torymus species associated with D. kuriphilus, the molecular and morphometric results indicate Torymus notatus (Walker) as the closest species to T. sinensis. The two are part of the same species-group (cyaneus group), are nested together in the multivariate ratio analysis and are the closest genetically based on all three nuclear markers: Enolase (1.5% divergence), Wingless (2%) and ITS2 (13%). However, on the mitochondrial marker COI the closest species is Torymus rubi (Schrank) at 9.9% divergence. As such, T. notatus is the most likely candidate for accidental interspecific hybridisation if this is to happen in Europe. We provide an illustrated identification key for the European species of Torymus associated with D. kuriphilus, an important but lacking tool for biological control programs.

Two species? - Limits of the species concepts in the pygmy grasshoppers of the Tetrix bipunctata complex (Orthoptera, Tetrigidae).

Today, integrative taxonomy is often considered the gold standard when it comes to species recognition and delimitation. Using the Tetrix bipunctata complex, we here present a case where even integrative taxonomy may reach its limits. The Tetrix bipunctata complex consists of two morphs, bipunctata and kraussi, which are easily distinguished by a single character, the length of the hind wing. Both morphs are widely distributed in Europe and reported to occur over a large area in sympatry, where they occasionally may live also in syntopy. The pattern has led to disparate classifications, as on the one extreme, the morphs were treated merely as forms or subspecies of a single species, on the other, as separate species. For this paper, we re-visited the morphology by using multivariate ratio analysis (MRA) of 17 distance measurements, checked the distributional data based on verified specimens and examined micro-habitat use. We were able to confirm that hind wing length is, indeed, the only morphological difference between bipunctata and kraussi. We were also able to exclude a mere allometric scaling. The morphs are, furthermore, largely sympatrically distributed, with syntopy occurring regularly. However, a microhabitat niche difference can be observed. Ecological measurements in a shared habitat confirm that kraussi prefers a drier and hotter microhabitat, which possibly also explains the generally lower altitudinal distribution. Based on these results, we can exclude classification as subspecies, but the taxonomic classification as species remains unclear. Even with different approaches to classify the Tetrix bipunctata complex, this case is, therefore, not settled. We recommend continuing to record kraussi and bipunctata separately.

Multivariate ratio analysis and DNA markers reveal a new Australian species and three synonymies in eucalypt-gall-associated Megastigmus (Hymenoptera: Megastigmidae).

The genus Megastigmus Dalman, 1820 (Hymenoptera: Megastigmidae) contains potential biocontrol agents of the invasive eucalypt galling chalcid Leptocybe spp. (Hymenoptera: Eulophidae), with several species reported in various parts of the world. Species discrimination is challenging due to intraspecific morphological variation, difficulty in measuring sizes of body parts, and the lack of information regarding the global distribution of parasitic Megastigmus. We used two species commonly associated with Leptocybe in its native range to review taxonomic methods and determine the most reliable morphological characters in species delimitation. We examined size variation of body characters, and conducted species discrimination using multivariate ratio analysis, mitochondrial Cytochrome c oxidase subunit 1 (COI) and nuclear 28S rDNA (28S) sequences. Morphological traits were effective in species delimitation yet revealed high variation in several characters employed in current keys. Knowledge generated on morphology and DNA justified the description of a new species, M. manonae, sp. n., the first record of M. pretorianensis in Australia, and revised diagnostic characters for M. zvimendeli. Based on these diagnostic characters and molecular data, we synonymize three species (M. judikingae, syn. n., from Australia, M. sichuanensis, syn. n., from China and M. icipeensis, syn. n., from Kenya) with M. zvimendeli. Our findings highlight the importance of molecular markers in assisting taxonomic decision-making and the need for coordinated work in identifying Megastigmus associated with Leptocybe spp.

Data–rich description of a new genus of praying mantid egg parasitoids, Lasallegrion gen. n. (Hymenoptera: Torymidae: Podagrionini), with a re-examination of Podagrion species of Australia and New Caledonia

ABSTRACT The genus Lasallegrion gen. n. is described, and three species, Lasallegrion koebelei (Crawford 1912), comb. n., Lasallegrion virescens (Strand 1911), comb. n., and Lasallegrion washingtoni (Girault 1915), comb. n., are redescribed and transferred to it. Podagrion holbeini Girault 1923, syn. n., and Podagrion metatarsum Girault 1929, syn. n., are synonymised here with Lasallegrion koebelei. Further, 14 species from Australia and New Caledonia are confirmed as belonging to Podagrion Spinola, 1811. The classic morphological approaches are combined with multivariate ratio analysis and molecular and additional morphological methods for (re-)descriptions. A comprehensive set of morphometric data, COI barcode sequences, a fully sequenced transcriptome and detailed µCT data are provided. An updated key to the Australasian genera of Podagrionini and to the Lasallegrion species is given. Additionally, we present some discussion on the collisions of the concepts of modern taxonomy, and the restrictions caused by poorly conditioned old type material.

Adding the West-African riverine component: Revision of the Recent freshwater snails belonging to Pseudocleopatra Thiele, 1928 (Caenogastropoda, Cerithioidea, Paludomidae).

While Africa's lacustrine gastropod fauna, in particular of Lake Tanganyika, has received much attention, the continent's riverine malacofauna has long been neglected. Pseudocleopatra is a relatively poorly known paludomid gastropod genus with species found throughout the lower reaches of the West African Volta and Congo rivers. In the course of ongoing systematic revisions of African paludomids, we present here a morphometric analysis and revision of the recent species assigned to the genus, i.e., P. togoensis, P. voltana, P. dartevellei and P. bennikei, to improve taxonomic acuity for this group. We use available museum material for geometric morphometrics, multivariate ratio analysis and comparisons of radular and opercular characters. Our results demonstrate that the four recent species of Pseudocleopatra are clearly distinguishable on the basis of ratios of shell measurements as well as radular and opercular characters. Pseudocleopatra has generic-level synapomorphies including: concentric opercula with relatively large paucispiral nuclei, and rachidian radular teeth with usually 13-20 cusps. On the basis of this characterisation, the nominal species Cleopatra broecki is transferred to Pseudocleopatra. Additionally, the nominal taxon P. bennikei is synonymized with P. broecki n. comb. The phylogenetic relationships of Pseudocleopatra are currently unknown, but the observed tendency of some fossil taxa assigned to Pseudocleopatra towards thalassoidism, i.e., the resemblance to marine gastropods, has led to the hypothesis that some of the thalassoid endemics in Lake Tanganyika may have originated from or be related to Pseudocleopatra. Should this hypothesis be correct, which is in need of testing by molecular genetic methods when suitable samples become available, Pseudocleopatra may play a crucial role in understanding of the evolution of thalassoidism in African Paludomidae.

Ophelimus mediterraneus sp. n. (Hymenoptera, Eulophidae): a new Eucalyptus gall wasp in the Mediterranean region.

We report here for the first time the presence of Ophelimus mediterraneus sp. n. in Mediterranean Europe. This species appears to be closely related to Ophelimus maskelli, a well-known invasive pest of Eucalyptus. Based on molecular (cytochrome oxidase I, 28S), morphological (multivariate ratio analysis) and bio-ecological investigations, our study gives unambiguous relevant criteria that allow the discrimination between these two species. A full description of O. mediterraneus sp. n. is also provided. The geographic distribution of O. mediterraneus sp. n. as well as its impact on Eucalyptus species needs to be more widely assessed since its presence may have been confused with O. maskelli in their sympatric introduced areas. Further investigations of potential parasitoids in the native area may thus be welcomed to evaluate classical biological control achievability.

Description of four new species of Eadya (Hymenoptera, Braconidae), parasitoids of the Eucalyptus Tortoise Beetle (Paropsis charybdis) and other Eucalyptus defoliating leaf beetles

EucalyptusL’Héritier, 1789 (Myrtales: Myrtaceae) plantations are a global economic resource with a wide array of uses. As this forestry crop grows in popularity around the world, the exotic introduction of pests such as the leaf beetles belonging to the generaParopsisOliver, 1807 andParopsisternaMotschulsky, 1860 increases in frequency. These pest introductions have spurred a need to understand the natural enemies of these pests for use in classical biological control programs. One such enemy,EadyaparopsidisHuddleston & Short, 1978 (Hymenoptera: Braconidae), has shown potential as a biological control agent againstParopsischarybdis, an exotic pest of New ZealandEucalyptusplantations. However, observations made by biocontrol researchers have raised concerns thatE.paropsidisis a complex of cryptic species. A comprehensive large-scale phylogenetic study utilizing both host and molecular data (Peixoto et al. 2018), as well as a morphological multivariate ratio analysis, was utilized to ensure accurate delimitation of the species ofEadya. Here we formally describe the three new species (EadyaannleckieaeRidenbaugh, 2018,sp. n.,EadyadaenerysRidenbaugh, 2018,sp. n.,EadyaspitzerRidenbaugh, 2018,sp. n.), and one additional new species discovered in the Australian National Insect Collection (EadyaduncanRidenbaugh, 2018,sp. n.). All distributions and host associations forEadyaare listed as well as a redescription of the originally describedE.paropsidisandE.falcata. An illustrated key to all known species is included to assist biological control researchers. The value of citizen science observations is discussed, along with the need for a further understanding of mainlandEadyapopulations given the recent spread of paropsine pests. Finally, we discuss the subfamilial placement ofEadya, and suggest it belongs within Euphorinae based on morphological characters.

Formal nomenclature and description of cryptic species of the Encyrtus sasakii complex (Hymenoptera: Encyrtidae).

With the recent development of molecular approaches to species delimitation, a growing number of cryptic species have been discovered in what had previously been thought to be single morpho-species. Molecular methods, such as DNA barcoding, have greatly enhanced our knowledge of taxonomy, but taxonomy remains incomplete and needs a formal species nomenclature and description to facilitate its use in other scientific fields. A previous study using DNA barcoding, geometric morphometrics and mating tests revealed at least two cryptic species in the Encyrtus sasakii complex. (Hymenoptera: Encyrtidae). To describe these two new species formally (Encyrtus eulecaniumiae sp. nov. and Encyrtus rhodococcusiae sp. nov.), a detailed morphometric study of Encyrtus spp. was performed in addition to the molecular analysis and evaluation of biological data. Morphometric analyses, a multivariate ratio analysis (MRA) and a geometric morphometric analysis (GMA) revealed a great number of differences between the species, but reliable characteristics were not observed for diagnosing the cryptic species. We thus diagnosed these three Encyrtus species on the basis of the characteristics that resulted from genetic markers (mitochondrial cytochrome c oxidase subunit I and nuclear 28S rRNA) and biological data. A formal nomenclature and description of cryptic species was provided on the basis of an integrated taxonomy.

From a lost world: an integrative phylogenetic analysis of Ansonia Stoliczka, 1870 (Lissamphibia: Anura: Bufonidae), with the description of a new species

While the island of Borneo is considered a global biodiversity hotspot, the species richness in many groups remains unknown and appears underestimated. During herpetological surveys carried out in the interior of Sarawak, East Malaysia, several individuals of a small species of the genus Ansonia Stoliczka 1870 were collected on the Usun Apau plateau and in the Gunung Hose mountain range (Ansonia sp. Usun Apau). An integrative taxonomic approach comprising phylogenetic (2.4 kb mitochondrial rDNA fragment, Bayesian Inference and Maximum Likelihood, >5.1 % to its closest relative) and morphometric analyses (25 measurements, multivariate ratio analysis and linear discriminant analysis), as well as morphological comparisons support the status of this operational taxonomic unit as a separate taxon at species level. The obtained phylogenetic hypothesis corroborates the two major clades within Ansonia found in previous studies. Within Clade One Ansonia sp. Usun Apau and the enigmatic Ansonia torrentis are part of a monophyletic group of the Bornean species Ansonia hanitschi, Ansonia minuta, Ansonia platysoma, Ansonia spinulifer, Ansonia vidua, and two additional undescribed taxa. This subclade must be considered as the result of an on-island radiation in the complex evolution of Ansonia. The new species is formally described including the identification of diagnostic morphometric traits. Ansonia sp. Usun Apau is endemic to two isolated mountain ridges in central Sarawak and must be considered as a new element of the unique diversity of the Bornean amphibian fauna that is potentially threatened by habitat loss at least in parts of its range.

A revision of the Encarsia pergandiella species complex (Hymenoptera: Aphelinidae) shows cryptic diversity in parasitoids of whitefly pests

AbstractEncarsia pergandiella Howard, described from North America (USA), and Encarsia tabacivora Viggiani, described from South America (Brazil) (Hymenoptera: Aphelinidae), are two formally recognized taxonomic entities, that have been treated by several authors as synonyms due to lack of strong diagnostic characters. Taxonomy of these species is further complicated because several populations, geographically separated and differing in their biology, have been included under the concept of E. pergandiella. Among these, a population originally collected in Brazil and introduced to North America reproduces by thelytokous parthenogenesis and is infected by the symbiont Cardinium, while a morphologically indistinguishable population, naturally occurring in Texas, is biparental and infected by a related strain of Cardinium that induces cytoplasmic incompatibility. A third population known from California and introduced to the Old World is biparental and uninfected by intracellular symbionts. While adult females of the first two populations have entirely light yellow bodies and pupate face up (light form), those of the third population have largely brown bodies and pupate face down (dark form). Other dark form populations are known from Texas, Florida and New York. Because these parasitoids are economically important biological control agents of cosmopolitan whitefly pests, it is critical to characterize them correctly. In this study, we integrated molecular and morphometric analyses to substantiate observed differences in biological traits, and resolve the complicated taxonomy of this species complex. We sequenced the mitochondrial cytochrome c oxidase subunit I gene and the D2 region of the ribosomal 28S gene for individuals of both light form (from Texas and Brazil) and dark form (from California, Texas, Italy and Canary Islands) originating from laboratory cultures or collected in the field. Phylogenetic analysis unambiguously distinguished three well‐supported groups corresponding to the Texas light form, the Brazil light form and the dark form. Individuals of these three groups, in combination with all available type material (E. pergandiella, its synonym Encarsia versicolor Girault and E. tabacivora) and additional museum specimens of the dark form from New York and Italy, were subjected to multivariate morphometric analyses using Burnaby principal component analysis followed by a linear discriminant analysis, and multivariate ratio analysis. Overall, the analyses showed that: (i) E. pergandiella and E. tabacivora are two distinct species; (ii) the thelytokous Brazil light form corresponds to E. tabacivora; (iii) the biparental Texas light form is a new species formally described here as Encarsia suzannae sp.n.; (iv) two new biparental species can be referred to the dark form, one described as Encarsia gennaroi sp.n. including the populations sampled in California, Texas, Italy and Canary Islands, and the other corresponding to the population from New York described as Encarsia marthae sp.n. A dichotomous key for both sexes of the species of the E. pergandiella complex is provided for identification.This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:278475A0‐C2C4‐4400‐A042‐A5716457829D.

Toward Objective, Morphology-Based Taxonomy: A Case Study on the Malagasy Nesomyrmex sikorai Species Group (Hymenoptera: Formicidae).

Madagascar is one of the world’s greatest biodiversity hotspots, meriting special attention from biodiversity scientists. It is an excellent testing ground for novel techniques in taxonomy that aim to increase classification objectivity and yield greater taxonomic resolving power. Here we reveal the diversity of a unique and largely unexplored fragment of the Malagasy ant fauna using an advanced combination of exploratory analyses on quantitative morphological data allowing for increased objectivity in taxonomic workflow. The diversity of the Nesomyrmex sikorai species-group was assessed via hypothesis-free nest-centroid-clustering combined with recursive partitioning to estimate the number of morphological clusters and determine the most probable boundaries between them. This combination of methods provides a highly automated and objective species delineation protocol based on continuous morphometric data. Delimitations of clusters recognized by these exploratory analyses were tested via confirmatory Linear Discriminant Analysis (LDA) and Multivariate Ratio Analysis (MRA). The final species hypotheses are corroborated by many qualitative characters, and the recognized species exhibit different spatial distributions and occupy different ecological regions. We describe and redescribe eight morphologically distinct species including six new species: Nesomyrmex excelsior sp. n., N. modestus sp. n., N. reticulatus sp. n., N. retusispinosus (Forel, 1892), N. rugosus sp. n., N. sikorai (Emery, 1896), N. striatus sp. n., and N. tamatavensis sp. n. An identification key for their worker castes using morphometric data is provided.

Morphometric analysis and taxonomic revision of Anisopteromalus Ruschka (Hymenoptera: Chalcidoidea: Pteromalidae)-an integrative approach.

We use an integrative taxonomic approach to revise the genus Anisopteromalus. In particular, we apply multivariate ratio analysis (MRA), a rather new statistical method based on principal component analysis (PCA) and linear discriminant analysis (LDA), to numerous body measurements and combine the data with those from our molecular analysis of Cytb and ITS2 genetic markers (on a subset of species) and all available published data on morphology, karyology, behaviour, host associations and geographic distribution. We demonstrate that the analysis of quantitative characters using MRA plays a major role for the integration of name-bearing types and thus for the association of taxa with names. Six species are recognized, of which two are new: A. cornis Baur sp.n. and A. quinarius Gokhman & Baur sp.n. For Anisopteromalus calandrae (Howard), a well-known, cosmopolitan parasitoid of stored-product pests, we have selected a neotype to foster continuity and stability in the application of this important name. The species was sometimes confused with the related A. quinarius sp.n., another cosmopolitan species that is frequently encountered in similar environments. We also show that several species originally described or later put under Anisopteromalus actually belong to different genera: Cyrtoptyx camerunus (Risbec) comb.n.; Meraporus glaber (Szelényi) comb.n.; Dinarmus schwenkei (Roomi, Khan & Khan) comb.n. Neocatolaccus indicus Ayyar & Mani is confirmed as a junior synonym of Oxysychus sphenopterae (Ferrière) syn.n. and Anisopteromalus calandrae brasiliensis (Domenichini) stat.rev. must be considered as a valid but doubtful taxon.This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:BDFE96D3-D0F4-4012-90F5-9A087F7F5864.

A new species of the paper wasp genus Polistes (Hymenoptera, Vespidae, Polistinae) in Europe revealed by morphometrics and molecular analyses.

We combine multivariate ratio analysis (MRA) of body measurements and analyses of mitochondrial and nuclear data to examine the status of several species of European paper wasps (Polistes Latreille, 1802) closely related to P. gallicus. Our analyses unambiguously reveal the presence of a cryptic species in Europe, as two distinct species can be recognized in what has hitherto been considered Polistes bischoffi Weyrauch, 1937. One species is almost as light coloured as P. gallicus, and is mainly recorded from Southern Europe and Western Asia. The other species is darker and has a more northern distribution in Central Europe. Both species occur syntopically in Switzerland. Given that the lost lectotype of P. bischoffi originated from Sardinia, we selected a female of the southern species as a neotype. The northern species is described as P. helveticus sp. n. here. We also provide a redescription of P. bischoffi rev. stat. and an identification key including three more closely related species, P. biglumis, P. gallicus and P. hellenicus.

Diversity versus disparity and the role of ecological opportunity in a continental bird radiation

AbstractAimThe Neotropical parrots (Arini) are an unusually diverse group which colonized South America in the Oligocene. The newly invaded Neotropics may have functioned as an underused adaptive zone and provided novel ecological opportunities that facilitated diversification. Alternatively, diversification may have been driven by ecological changes caused by Andean uplift and/or climate change from the Miocene onwards. Our aim was to find out whether Arini diversified in a classical adaptive radiation after their colonization of South America, or whether their diversification occurred later and was influenced by more recent environmental change.LocationNeotropics.MethodsWe generated a time‐calibrated phylogeny of more than 80% of all Arini species in order to analyse lineage diversification. This chronogram was also used as the basis for the reconstruction of morphological evolution within Arini using a multivariate ratio analysis of three size measurements.ResultsWe found a concentration of size evolution and partitioning of size niches in the early history of Arini consistent with the process of adaptive radiation, but there were no signs of an early burst of speciation or a decrease in speciation rates through time. Although we detected no overall temporal shifts in diversification rates, we discovered two young, unexpectedly species‐rich clades.Main conclusionsArini show signs of an early adaptive radiation, but we found no evidence of the slowdown in speciation rate generally considered a feature of island or lake radiations. Historical processes and environmental change from the Miocene onwards may have kept diversification rates roughly constant ever since the colonization of the Neotropics. Thus, Arini may not yet have reached equilibrium diversity. The lack of diversity‐dependent speciation might be a general feature of adaptive radiations on a continental scale, and diversification processes on continents might therefore not be as ecologically limited as in isolated lakes or on oceanic islands.

Multivariate ratio analysis reveals Trigonoderus pedicellarisThomson (Hymenoptera, Chalcidoidea, Pteromalidae) as a valid species

AbstractWe demonstrate by multivariate ratio analysis (MRA) the validity of two female colour morphs as separate species in what was previously regarded as a single species, Trigonoderus cyanescens (Förster, 1841) (Hymenoptera: Pteromalidae). As a result, T. pedicellaris Thomson, 1878 stat.r., is resurrected from synonymy under T. cyanescens and T. filatus binubilatus Erdős, 1960 syn.n. is synonymized with T. cyanescens. More than 20 characters were measured as part of two MRA dataset analyses. The first analysis excluded all measurements related to the gaster, whereas the second included gaster length, gaster breadth and seventh gaster tergite breadth. The first analysis revealed that the best separating morphometric ratios for the two species are head breadth:metatibia length and OOL:parastigma length, whereas the second analysis revealed OOL:gaster length as the second best separating ratio. The measurement error of all characters was below the admissible level of 30%. Gaster length proved to be a good character for separating the two groups, showed the lowest measurement error, and its percentage coefficient of variation was not greater than for other characters. This indicates that gaster length should not be discarded out‐of‐hand as a morphometric character in Pteromalidae. The variables that gave the best separating ratios included different body parts; therefore we suggest that the body of a specimen should be taken as a whole for use in MRA analyses, where each distance measurement can interact freely with any other. A key, figures and re‐descriptions of T. cyanescens and T. pedicellaris are provided.

Impact of season, habitat and research techniques on diet composition of roe deer (Capreolus capreolus): a review

AbstractWe summarize the information on the diet of roe deer Capreolus capreolus found in 33 European studies. After giving a short overview of the differences between the existing studies, we compare the information for each season. We submit the information, summarized in a matrix of 83 cases on 10 food groups, to a detrended correspondence analysis (DCA) and a two‐way indicator species analysis (TWINSPAN). We calculate weighted averages grouping the information by season, habitat, research method and their cross‐products. The weighted averages are also used as input for a multivariate ratio analysis. Since the available food items dictate the possible diet composition we further investigate the influence of the habitat on the reported food selection. The influence of season on the diet composition is compared with the effect of the habitat, and other factors such as research method and geographical location of the study site. The review shows that there is relatively little seasonal variation in the diet composition, which is more closely correlated to the habitat than to the season.

A computer program for multivariate ratio analysis (MISCAT)

Analysts must deal frequently with missing data in multivariate analysis. In such cases, estimating the covariance maxtrix V of the dependent variables usually involves initial estimation and iterative adjustment of imputed missing data values, and/or smoothing of an estimate V̌ which is not necessarily positive semi-definite. This paper presents an alternative procedure for computing estimates of relevant multivariate parameters in situations where missing data occur at random and with small probability. MISCAT is a computer program which computes multivariate ratio estimates of the means and a corresponding positive semi-definite estimate of the covariance matrix. It is an extension of GENCAT, which is a program for the generalized least squares analysis of categorical data. Thus, one advantage of dealing with missing data in this manner is that variation among the ratio estimates may be conveniently analyzed within MISCAT using asymptotic regression methodology, provided that sample sizes are sufficiently large. An example is given to illustrate such analysis for longitudinal data from a multicenter clinical trial.