A comparison of numerical taxonomic techniques using measurements on the genera Gammarus and Marinogammarus (Amphipoda)

Numerical taxonomy involves the use of quantitative techniques to assess the similarity between species. In this work a comparative study has been made on seven of these methods. The data consisted of measurements made on thirteen amphipod species belonging to the genera Gammarus and Marinogammarus. A principal coordinate analysis, a canonical variate analysis and several methods of cluster analysis were used. There is also a discussion on the Uniquely derived character concept.
The main conclusion was that the numerical techniques give results which agree generally but certainly differ in detail. The consequences are discussed and certain methods are recommended. On the basis of the seven methods of analysis, a number of well-defined groups were recognized within the animals in the study. The genus Gammarus is reckoned to be distinct from the genus Marinogammarus. G. pulex and G. lacustris are similar to each other but rather different from the other Gammarus species. All the thirteen species are clearly differentiated although the two forms of G. duebeni are quite similar.     

Two new species of the interstitial genus Parvocythere (Crustacea, Ostracoda, Cytheroidea) from Japan: an example of morphological variation

Two new species of the interstitial ostracod genus Parvocythere, Parvocythere gottwaldisp. n. and Parvocythere gracilissp. n., are herein described. Although these two new species are clearly distinguishable by certain morphological differences in elements of the male copulatory organ, and the carapace, they share the following simplified characters of the appendages and male copulatory organ: antennular fourth podomere with no suture; reduced claws on the distal end of antenna; and asymmetric male copulatory organ. The morphological differences among known and new Parvocythere species suggest that the species of this genus can be classified into two groups by the presence/absence of the suture on the antennular fourth podomere. The "Group S" is characterised by the presence of the antennular suture, and all species of this group have a two-clawed antenna and symmetric male copulatory organ, characters which are generally seen in cytheroid ostracods. The species belonging to "Group N" are characterised by the absence of the suture, regarded as a pedomorphic character, show the following characters: two clawed or one clawed antenna, and symmetric or asymmetric male copulatory organ. The morphological variation within Group N includes reductive characters regarded as an adaptation to the narrow spaces of the interstitial environment of a sandy beach. These intrageneric morphological variations of the exclusively interstitial genus Parvocythere suggest the possibilities that Group N might be derived from Group S, and that some adaptive characters to an interstitial environment could have developed after the colonisation of these environments.     

Diversity and distribution of genetic variation in gammarids: Comparing patterns between invasive and non‐invasive species

Biological invasions are worldwide phenomena that have reached alarming levels among aquatic species. There are key challenges to understand the factors behind invasion propensity of non‐native populations in invasion biology. Interestingly, interpretations cannot be expanded to higher taxonomic levels due to the fact that in the same genus, there are species that are notorious invaders and those that never spread outside their native range. Such variation in invasion propensity offers the possibility to explore, at fine‐scale taxonomic level, the existence of specific characteristics that might predict the variability in invasion success. In this work, we explored this possibility from a molecular perspective. The objective was to provide a better understanding of the genetic diversity distribution in the native range of species that exhibit contrasting invasive propensities. For this purpose, we used a total of 784 sequences of the cytochrome c oxidase subunit I of mitochondrial DNA (mtDNA‐COI) collected from seven Gammaroidea, a superfamily of Amphipoda that includes species that are both successful invaders (Gammarus tigrinus, Pontogammarus maeoticus, and Obesogammarus crassus) and strictly restricted to their native regions (Gammarus locusta, Gammarus salinus, Gammarus zaddachi, and Gammarus oceanicus). Despite that genetic diversity did not differ between invasive and non‐invasive species, we observed that populations of non‐invasive species showed a higher degree of genetic differentiation. Furthermore, we found that both geographic and evolutionary distances might explain genetic differentiation in both non‐native and native ranges. This suggests that the lack of population genetic structure may facilitate the distribution of mutations that despite arising in the native range may be beneficial in invasive ranges. The fact that evolutionary distances explained genetic differentiation more often than geographic distances points toward that deep lineage divergence holds an important role in the distribution of neutral genetic diversity.     

SPECIATION AND FEATHER ORNAMENTATION IN BIRDS

The hypothesis that sexual selection promotes speciation has rarely been tested. We identified 70 evolutionarily independent events of feather ornaments in birds. For each focal species we noted the number of ornamented and nonornamented species belonging to its genus and its number of subspecies, as well as its mating system and the extent of its geographic range. For purposes of comparison, we randomly chose a second, nonornamented species for which we obtained information on the number of subspecies, and in cases in which the nonornamented species was in the same genus, we chose a third, nonornamented species in a related genus and obtained the same information. We then noted the number of species in each genus and the difference in numbers of species, or species richness, between paired genera. For the genera of the focal ornamented species, we regressed number of ornamented species on number of nonornamented species and found a positive relationship. As number of species per genus rose, number of ornamented species per genus rose more rapidly, indicating that more speciose genera have a higher proportion of ornamented species than less speciose genera. We then took the deviations from this regression, the residual number of species, and regressed them on the differences in species richness between the paired genera. This relationship was positive indicating that ornamented genera with more than the expected number of ornamented species were more speciose with respect to their paired genera than were genera with fewer than the expected number of ornamented species. Finally, we compared the deviations from this regression, the residual number of ornamented species, with species' mating system and found a greater residual number of ornamented species among species whose mating system is associated with greater skew in male mating success and thus more intense sexual selection. Ornamented species had more subspecies than nonornamented species, even when controlling for geographic range, suggesting an association between subspeciation and ornaments.     

Taxonomic scale-dependence of habitat niche partitioning and biotic neighbourhood on survival of tropical tree seedlings

In order to differentiate between mechanisms of species coexistence, we examined the relative importance of local biotic neighbourhood, abiotic habitat factors and species differences as factors influencing the survival of 2330 spatially mapped tropical tree seedlings of 15 species of Myristicaceae in two separate analyses in which individuals were identified first to species and then to genus. Using likelihood methods, we selected the most parsimonious candidate models as predictors of 3 year seedling survival in both sets of analyses. We found evidence for differential effects of abiotic niche and neighbourhood processes on individual survival between analyses at the genus and species levels. Niche partitioning (defined as an interaction of taxonomic identity and abiotic neighbourhood) was significant in analyses at the genus level, but did not differentiate among species in models of individual seedling survival. By contrast, conspecific and congeneric seedling and adult density were retained in the minimum adequate models of seedling survival at species and genus levels, respectively. We conclude that abiotic niche effects express differences in seedling survival among genera but not among species, and that, within genera, community and/or local variation in adult and seedling abundance drives variation in seedling survival. These data suggest that different mechanisms of coexistence among tropical tree taxa may function at different taxonomic or phylogenetic scales. This perspective helps to reconcile perceived differences of importance in the various non-mutually exclusive mechanisms of species coexistence in hyper-diverse tropical forests.     

A new species of Sabellacheres M. Sars, 1862 (Copepoda: Gastrodelphyidae) from a deep-water benthic polychaete in Antarctic waters, with a key to the species of the genus

Specimens of a deep-living sabellid polychaete of the genus Perkinsiana Knight-Jones dredged in Antarctic waters were found to be parasitised by an undescribed species of the cyclopoid copepod genus Sabellacheres M. Sars, 1862. Specimens of both sexes were studied using light microscopy and SEM, and compared with its congeners. The new species, Sabellacheres antarcticus n. sp., can be distinguished from its congeners by the shape and proportions of the body and brood-pouch, its 4-segmented antennae, the shape and length of the distal process of the second antennular segment, the position of leg 3, and the structure of the male maxilliped. This is only the second record of a species of this genus from the southern hemisphere. The new species was found on a single host species, as is typical for most species of Sabellacheres. A key for the identification of both sexes of the species of Sabellacheres is included.     

Species-typical patterns of infant contact, sleeping site use and social cohesion among nocturnal primates in Africa

This paper provides a checklist and summary of what is currently known of the variation in infant contact, sleeping site preference and aspects of social cohesion in the nocturnal primates of Africa. Genera and species are compared, based on previously unpublished field observations and a review of the literature. There is a clear pattern of similarity between the species within each genus and distinct differences between genera. Species in the same genus tend to be ecologically equivalent and replace each other allopatrically, whereas species in different genera are more likely to be sympatric, with up to 6 species living together. Maximum sympatry within genera is found in Otolemur and Galagoides, where species are ecologically divergent. This may reflect an ancient origin of species within these genera or suggest that further taxonomic revision is required at the generic level. Some data are recorded for the first time for species that have only recently been separated (cryptic species), but some taxa remain very poorly known. It is concluded that field studies are still at an elementary stage and further research with radio tracking is urgently needed in the face of rapidly declining habitats.     

浙江省温岭海区虾类资源调查

于1999－2001年间对温岭海区虾类进行了调查,调查表明,该海区计有虾24种,分属7科16属。其中,对虾科8种12种;樱虾科1属2种;玻璃虾科1属1种;鼓虾科1属3种;长臂虾科2属3种;藻虾科2属2种;龙虾科1属1种。对该海区的虾类资源作了评价,并提出了资源开发保护的建议。     

Diversity of ectomycorrhizal fungi in Britain: a test of the species–area relationship, and the role of host specificity

The host range of ectomycorrhizal (ECM) fungi in Britain was examined by compilation of a data matrix from published literature sources, based primarily on accounts of sporocarp associations with particular host genera. Information was gathered for 577 species of ECM fungi belonging to 51 genera, and 25 genera of host trees, representing the majority of ECM fungal species and host genera recorded in Britain.
Pronounced variation was recorded in the number of ECM fungal species associated with different host genera, with over 200 species recorded with Betula , Fagus , Pinus and Quercus . There was a positive linear relationship ( r ²=0·47, P =0·007) between the number of species of ECM fungi associated with different host genera and the total area occupied by each tree genus in Britain (both values log-transformed). There was also variation in the number of species of ECM fungi which were apparently specific to particular host genera, values ranging from zero (in 15 genera) to >40 in the case of Betula and Fagus . In total, 233 fungal species appeared to be specific to a single host genus (i.e. 40% of those surveyed). Comparison of the ECM mycota associated with different host genera by PCA accounted for 17% of the total variation, with genera belonging to the Fagaceae ( Quercus , Fagus and Castanea ) tending to cluster together, indicating a degree of overlap in their ECM associates. Exotic conifer species, which displayed a lower ECM diversity than would be expected from their distributional areas, were characterized by a high degree of overlap with the ECM associates of Pinus and Betula .
These results indicate that the abundance of different genera of host trees and variation in host specificity could provide a basis for understanding patterns of diversity in ECM fungi within Britain.     

High degree of conservation of nuclear microsatellite loci in the genus Clusia.

In plants, microsatellites and their flanking DNA are rarely conserved across a whole genus, let alone other genera in the same family. Therefore, the possibility of using microsatellite primers developed for a species across a large number of plant species in the same genus is often limited. Remarkably, dinucleotide nuclear microsatellites developed for Clusia minor and for Clusia nemorosa amplified homologous microsatellites in species across the whole genus Clusia. In this present study, we report on the DNA sequence variation across the genus of 3 microsatellite loci with varying levels of variation. Compared over the species, there was a correlation between the lengths of the microsatellite loci. Interrupts occurred multiple times and did not seem to lead to the death of the microsatellite. These highly conserved markers will be useful for studying the variable reproductive systems in the genus Clusia.     

Genus age,provincial area and the taxonomic structure of marine faunas

Species are unevenly distributed among genera within clades and regions, with most genera species-poor and few species-rich. At regional scales, this structure to taxonomic diversity is generated via speciation, extinction and geographical range dynamics. Here, we use a global database of extant marine bivalves to characterize the taxonomic structure of climate zones and provinces. Our analyses reveal a general, Zipf–Mandelbrot form to the distribution of species among genera, with faunas from similar climate zones exhibiting similar taxonomic structure. Provinces that contain older taxa and/or encompass larger areas are expected to be more species-rich. Although both median genus age and provincial area correlate with measures of taxonomic structure, these relationships are interdependent, nonlinear and driven primarily by contrasts between tropical and extra-tropical faunas. Provincial area and taxonomic structure are largely decoupled within climate zones. Counter to the expectation that genus age and species richness should positively covary, diverse and highly structured provincial faunas are dominated by young genera. The marked differences between tropical and temperate faunas suggest strong spatial variation in evolutionary rates and invasion frequencies. Such variation contradicts biogeographic models that scale taxonomic diversity to geographical area.     

Constancy and change of basipodial variation patterns: a comparative study of crested and marbled newts —Triturus cristatus,Triturus marmoratus — and their natural hybrids

To test the concept of stable and lineage-specific developmental constraints the stability of biased limb skeletal variation patterns was examined by the comparative approach: 384 limbs of crested and marbled newts as well as their natural hybrids were cleared and stained for cartilage and bone. The variation in autopodium was recorded and compared between samples. The frequencies of variations were the same for crested and marbled newt samples. In the hybrids digital variation was significantly elevated, but the basipodium was as conservative as in the parental crested and marbled newts. The tarsus had to be excluded from further statistical analysis, since variation in tarsus was too rare to allow rigorous tests. The carpal variation was highly biased; out of twelve geometrically possible fusions of two neighbouring elements only three were found in the 219 forelimbs. The frequency of the fusions was the same in the parental as well as in the hybrid populations. In one sample of the marbled newt from a marginal population, the frequency of one fusion type was elevated, leading to an even more pronounced bias in phenotypic variation. Hence, neither in the hybrids nor in the marginal population could a breakdown of the constraint be observed. Also the pattern of variation was the same in all Triturus-samples examined here. The comparison of our results with within-population variation from other genera showed qualitative differences. The most common variant from our samples was found as a natural variant and even as the typical pattern in some species, but has not been observed in species of other genera. On, the other hand, fusions commonly observed in other genera were not observed in our sample. Even if all populations exhibit a highly bound variation pattern which may restrict the possible directions of morphological evolution, the direction of variation changes from genus to genus. It is suggested that shifts in constrained variation patterns have to be considered as key-events in the evolution of a clade. The cause of these shifts are unknown.     

Evolutionary dynamics of taxonomic structure

The distribution of species among genera and higher taxa has largely untapped potential to reveal among-clade variation in rates of origination and extinction. The probability distribution of the number of species within a genus is modelled with a stochastic, time-homogeneous birth-death model having two parameters: the rate of species extinction, μ, and the rate of genus origination, γ, each scaled as a multiple of the rate of within-genus speciation, λ. The distribution is more sensitive to γ than to μ, although μ affects the size of the largest genera. The species : genus ratio depends strongly on both γ and μ, and so is not a good diagnostic of evolutionary dynamics. The proportion of monotypic genera, however, depends mainly on γ, and so may provide an index of the genus origination rate. Application to living marine molluscs of New Zealand shows that bivalves have a higher relative rate of genus origination than gastropods. This is supported by the analysis of palaeontological data. This concordance suggests that analysis of living taxonomic distributions may allow inference of macroevolutionary dynamics even without a fossil record.     

ADAPTATION IN THE GENUS PHYLLOSCOPUS

The paper describes variation among species of the genus Phylloscopus in weight, relative wing-, tail-, tarsus-, and bill-length, tail/wing ratio and degree of roundness of the wing, wing formula, emargination, and plumage colour. This variation is compared with differences in niche preference within the genus, and relationships between niche, feeding strategies, and morphology are suggested. It is concluded that evolution within the genus has taken place mainly through the development of different feeding strategies, to suit the structural properties of different niches, without altering the range of size of the prey. The genus Sylvia is treated briefly in order to provide comparison, and other genera of Sylviinae are discussed where parallel adaptation seems likely.     

Cytophotometric studies on the DNA content in diploid and polyploid enchytraeidae (Oligochaeta)

The amount of DNA in nerve nuclei was determined by Feulgen cytophotometry in 45 species and cytotypes. The DNA value of spermatids, spermatogonial nuclei and nerve nuclei in newly hatched worms was determined in some species. The total variation in DNA content ranges from a relative value of 0.40 to 4.85. The DNA content in diploid species ranges from 0.40 to 1.12. In two genera (Lumbricillus and Enchytraeus) wide diversification in chromosome numbers at the diploid level is accompanied by wide variation in DNA values, whereas other genera and species groups (Mesenchytraeus, Henlea and Marionina), which are conservative in this respect, are closer in DNA values. In the genus Fridericia constancy in chromosome number is associated with wide variation in DNA values, this may be due to an increase in DNA taking place in old individuals. In 9 out of 10 cases nearly identical ratios are found between chromosome numbers and DNA values in polyploids and related diploids or lower polyploids. Differential polyteny is recorded in two cases.Dedicated to Professor Dr. J. Seiler on the occasion of his eightieth birthday.     

Phylogenetic structure of the genera Flexibacter,Flexithrix, and Microscilla deduced from 16S rRNA sequence analysis

The 16S rDNA sequences of 40 strains of 17 species in the genus Flexibacter, 5 strains of 4 species in the genus Microscilla, and 1 strain of Flexithrix dorotheae, including all type strains of approved and validated species in these genera, were determined to reveal their phylogenetic relationships. The 16S rRNA sequence analysis demonstrated the extreme heterogeneity of the genera Flexibacter and Microscilla. The strains examined diverged into 24 distinct lines of descent (1 group included both flexibacteria and flexithrix, and 1 group included both flexibacteria and microscilla) that were remote from each other at the genus level or higher. Flexibacter strains were scattered across the cytophaga-flavobacteria-bacteroides phylum and divided into 20 phylogenetic groups, and the genus Microscilla was separated into 5 groups. Flexibacter flexilis, the type species of the genus Flexibacter, and Microscilla marina, the type species of the genus Microscilla, were isolated from other organisms in their respective genera. This means that each genus should be restricted to only the type species. Flexithrix dorotheae, the type species of the genus Flexithrix, clustered with Flexibacter aggregans. The heterogeneity was found not only within genera but also within species. Flexibacter aggregans, Flexibacter aurantiacus, Flexibacter flexilis, Flexibacter roseolus, Flexibacter tractuosus, and "Microscilla sericea" each contained phylogenetically distant strains. The taxonomic concept of the genera Flexibacter, Flexithrix, and Microscilla should be reorganized in accordance with the natural relationships revealed in this study.     

Life histories of Clethrionomys and Microtus (Microtinae)

Although there have been numerous life-history reviews of mammals at high taxonomic levels (e.g. among families within orders), there are far fewer studies at lower taxonomic levels (e.g. among species within genera). Data on adult weights, litter size, gestation length, neonate weight, age and weight at weaning, growth rate to weaning, maximum life span, and length of the breeding season were compiled from the literature on five species of Clethrionomys and 33 species of Microtus. Variability in litter size and male body weights was not significantly different when compared between cyclic and non-cyclic populations. Coefficients of variation were also calculated for the three species with the most data (C. gapperi, C. glareolus and M. pennsylvanicus ). These values showed that the amount of intraspecific variation differed among traits as well as among species. Gestation length was the most invariable of all traits and variation in adult weights, neonate weight, gestation length, and litter size had similar values to those reported for Peromyscus maniculatus. Five and eight traits differed among Clethrionomys and Microtus species, respectively. Differences in litter size, adult weights and length of the breeding season were common to both genera. Male weight, gestation length and neonate weight as well as length of the breeding season were different between genera. Very few traits covaried within C. gapperi, C. glareolus or M. pennsylvanicus. Similarly, few traits covaried among all Clethrionomys populations. However, among all Microtus populations and Microtus species, 11 and 12 correlations were significant. Many of the patterns found in Microtus involved positive relationships between female weight and some other trait. These patterns have also been found by broader surveys at higher taxonomic levels. Large species of Microtus had larger offspring, a greater litter size and occurred in short-season environments relative to small species of this genus.     

四棱草属比较形态及其分类系统位置的研究Ⅰ．四棱草属及近缘属叶片毛状体微形态

采用“外类群对比准则”（ＯｕｔｇｒｏｕｐＣｏｍｐａｒｉｓｏｎＣｒｉｔｅｒｉａ,Ｃａｒｃａｒｆｔ１９８３）的性状分析方法,对我国特有植物四棱草属Ｓｏｈｎａｂｅｌｉａ及其近缘属筋骨草属Ａｊｕｇａ,香科科属Ｔｅｕｃｒｉｕｍ（唇形科）和莸属Ｃａｒｙｏｐｔｅｒｉａ大青属Ｃｌｅｒｄｅｎｄｒｏｎ（马鞭草科）等５属６种主要植物比较研究,首次发现在这些植物叶片上,具有一种新的毛状体,其形状呈箭形,故定名为箭形毛（Ａｒｒｏｗ—ｓｈａｐｅｄ—ｈａｉｒ）,在扫描电子显微镜下观察是由头部、柄部和基部组成,在光学显微镜下,确认这类毛状体属于多细胞单列毛,由细胞变形而成形。此外,尚有长柔毛（Ｓｈａｇ－ｈａｉｒ）,盾状毛（Ｐｅｌｔａｔｅ—ｈａｉｒ）和鳞片毛（Ｓｃａｌｅｓ—ｈａｉｒ）等四种类型。从以上毛状体的微形态特征及其演化规律,作者认为四棱草属和近缘属在唇形科与马鞭草科系统演化框架里,可能是处于中间过渡类型。     

Intraspecific variation in nemerteans (Nemertea): synonymization of genera Paroerstedia and Oerstediella with Oerstedia

Intraspecific variation in internal morphological charactcrs is substantial in many nemertean species, mainly due to the tendency for specimens to contract during fixation. It is shown that variation within the type species for the genus Oerstedia, O. dorsalis (Abildgaard, 1806), encompasses all the character states that have been used to erect the two related genera Oerstediella and Paroerstedia. These genera are synonymized with Oerstedia , and the validity of species previously assigned to these genera is discussed.     

A molecular phylogeny of the genus Gammarus (Crustacea: Amphipoda) based on mitochondrial and nuclear gene sequences

A phylogeny of the genus Gammarus Fabricius, 1775 was constructed using DNA sequence data from the mitochondrial genes COI and 16S, and the nuclear genes 18S and 28S. Both parsimony and Bayesian analyses were conducted on separate and combined data partitions. The Bayesian phylogeny from the combined analysis was selected as the preferred phylogenetic hypothesis. The hypothesis supports monophyly of the genus Gammarus, paraphyly of the European-North American Gammarus, and monophyly of the Asian Gammarus. The Asian clade was further split into a southeastern group and a northwestern group. The dramatic climate change following the uplift of the Tibetan Plateau was probably the most important factor in triggering the diversification of southeastern and northwestern groups. The genus Sinogammarus is invalid and should be part of the genus Gammarus.