Distinguishing between two sympatric Acanthopagrus species from Dapeng Bay, Taiwan, using morphometric and genetic characters

Morphometric and genetic data were used to compare two sympatric and morphologically similar species, Acanthopagrus berda and Acanthopagrus taiwanensis , in Dapeng Bay, South-western Taiwan. A principle component analysis of morphological data indicated a distinction between the two species, with pectoral fin length and eye diameter accounting for 32·27% of the variation. Interspecific sequence divergence, based on mtDNA cytochrome b (0·118 ± 0·01), was larger than intraspecific divergences between haplotypes (0·007 for A. taiwanensis and 0·003 for A. berda ). Individuals of the two species clustered into different groups in three phylogenetic trees with 100% bootstrap support. The mean observed heterozygosity for eight microsatellite loci was 0·471 ± 0·202 for A. taiwanensis and 0·637 ± 0·145 for A. berda . Nei's unbiased measure of interspecific genetic distance ( D _S) was 1·334. F _ST (0·134) and R _ST (0·404) values indicated significant differentiation between species. An unrooted neighbour-joining tree was constructed by allele-sharing distances and the factorial correspondence analysis split all specimens into two distinct clusters. The results of morphometric, mtDNA and microsatellite analyses indicated the presence of two species, A. taiwanensis and A. berda .     

The biometry of gills of 0-group European flounder

The gill surface area of 0-group, post-metamorphic Pleuronectes flesus L. was examined using digital image analysis software and expressed in relation to body mass according to the equation log Y=loga+c logW ( a =239·02; c =0·723). The components that constitute gill area, total filament length, interlamellar space and unilateral lamellar area were measured. The measurement of the length of every filament on all eight arches showed that commonly used methods of calculation can lead to an under-estimation of up to 24% of total filament length. Direct measurements of unilateral lamellar area with digital image analysis showed that previously reported gill area data for the same species was over-estimated by as much as 58%. In addition, in this species the neglect of gill pouch asymmetry after metamorphosis, can bring about a 14% over-estimation of total gill area.     

Morphometries of the respiratory organs of the Indian green snake-headed fish, Channa punctata

Measurements of the dimensions of the different gills and the suprabranchial chambers have been made and the data analysed with respect to body weight using logarithmic transformations (Y = aW^b). The slope (b) for area of the total gill surface is 0–592 and for the supra-branchial chamber 0–696, and their combined respiratory surface: 0–623. The slope values for the surface areas of the 1st, 2nd, 3rd and the 4th gill arches were 0–595,0–578,0–614 and 0–572 respectively.
The slope for secondary lamellae/mm is –0138 and that for the bilateral surface area of an average-sized lamella 0–304.
These results indicate differences in growth patterns for the dimensions of the different gills. The growth-related decrease in the number of secondary lamellae/mm and size of an average secondary lamella together with evidence from "drowning" experiments and diffusing capacity calculation, suggest that this fish is better adapted for aquatic respiration than Anabas or Saccobranchus. The slopes for the total respiratory surface area and gill area seem to be comparatively low in this species.     

The anatomy of the interspecific abundance–range size relationship for the British avifauna: II. Temporal dynamics

In a companion paper, we started an examination of the anatomy of the interspecific relationship between local abundance and geographical range size in the British avifauna by analysing its spatial dynamics. Here, we use the same data to extend this study to a consideration of the temporal dynamics of the relationship. Most species of British breeding bird show a positive intraspecific abundance–range size relationship through time: i.e. in years when a species is locally more abundant it also occupies a higher proportion of census sites. However, the majority of such relationships are not statistically significant, and other relationships that are statistically significant are negative. Therefore, intraspecific abundance–range size relationships do not simply mirror the relationship across species. Where they do arise, positive relationships are more likely to be associated with positive intraspecific relationships between range size and maximum rather than minimum abundance. The interspecific abundance–range size relationship is remarkably consistent across years, and is always significantly positive. The relationships for woodland and farmland census sites show correlated variation, so that in years when the linear regression slope and coefficient of determination are high across species on farmland plots, they also tend to be high across species on woodland plots. Common species tend to be common on both farmland and woodland plots, and tend to be common in all years. Likewise, rare species tend to be rare in all habitats and years. This concordance means that the positive interspecific abundance–range size relationship can be viewed as occurring largely independently of intraspecific relationships. It follows from the above that developing an understanding of intraspecific abundance–range size relationships may be of only limited value in ascertaining the determinants of positive interspecific abundance–range size relationships. We conclude that for interspecific relationships, it will be important to know why some species are consistently common and others rare, whereas for intraspecific relationships it will be important to understand the dynamic links between local abundances across sites.     

Fecundity of the American eel Anguilla rostrata at 45° N in Maine, U.S.A.

The northern portion of the geographic range of the American eel Anguilla rostrata may contribute a great proportion of the reproductive potential to this panmictic species because of apparent increases in average female size and female percentage with latitude. The regressions of fecundity on body length and on body weight of 63 female eels captured at about 45° N latitude on their spawning migration to the sea were log F= 1·2601 + 2·9642 log L and log F= 4·1646+0·9153 log W , where F is fecundity, L is total length (cm), and W is total weight (g). Length and weight each explained about 90% of the variation in fecundity. Estimates of fecundity from counts of aliquots of eggs ranged from 1·84 million to 19·92 million eggs for eels ranging in length from 45 to 113 cm, nearly the range of sizes of migrating females reported in the literature. Fecundities of the American eel were greater than reported in one study at about 37° N and greater than reported for the European eel, A. anguilla , shortfin eel, A. australis , and longfin eel, A. dieffenbachii . If a geographic cline in fecundity does exist in American eels, it is established anew each generation because the species forms a single panmictic population.     

Pattern and process in the geographical ranges of freshwater fishes

North American freshwater fishes were studied to determine whether they displayed the same relationships between log (geographical range size) and log (body size) and the same pattern of range shape as found among North American birds and mammals. The forces that produce these patterns were also investigated. The log (geographical range size) : log (body size) relationship was analysed for 121 North American freshwater fish species. Thirty‐two imperilled species were compared with 89 non‐imperilled species to determine if the overall relationship could result from differential extinction. Range geometries were analysed, within and among habitat guilds, to determine if general patterns could be detected. The log (geographical range size) : log (body size) pattern among freshwater fish species was triangular and qualitatively similar to that found for North American birds and mammals. The results suggest that below a minimum geographical range, the likelihood of extinction increases dramatically for freshwater fishes and that this minimum range size increases with body size. The pattern of fish species’ range shapes differs from that found for other North American vertebrate taxa because, on average, fish possess much smaller ranges than terrestrial species and most fish species’ geographical ranges extend further on a north–south axis than on an east–west axis. The log (geographical range size) : log (body size) pattern reveals that fish species’ geographical ranges are more constrained than those of terrestrial species. The triangular relationship may be caused by differential extinction of species with large bodies and small geographical ranges as well as higher speciation rates of small‐bodied fish. The restricted geographical ranges of freshwater fishes gives them much in common with terrestrial species on oceanic islands. Range shape patterns within habitat guilds reflect guild‐specific historical and current ecological forces. The overall pattern of range shapes emerges from the combination of ecologically different subunits.     

Gross structure of the respiratory organs and dimensions of the gill in the mud–skipper, Periophthalmodon schlosseri (Bleeker)

In Periopkrlialnwdon scldosseri the respiratory organs consist of the gills, the suprabranchial and opercular chambers. The gills are more suited for aerial than aquatic respiration as is shown by the presence of the vascular papillae, blood sinusesand dilated blood vessels in their lamellae. The gill lamellae possess a surface coat of sulphated mucopolysaccharides that prevents water loss during exposure to the air. The filaments of the outer hemibranchs in the first gill arch are reduced to nearly one quarter of those of its posterior hemibranch. The gill area in relation to body weight shows a high slope value ( b =0·93).     

Blood flow distribution and tissue allometry in channel catfish

Blood flow (as percentage of cardiac output) in fasted channel catfish acclimated to 21°C was directed primarily to white muscle (72%) followed by head kidney (5·7%), red muscle (5·5%), trunk kidney (3·1%), liver (2·2%), swim bladder (1·4%) and skin (1·1%). The stomach, intestines, pyloric caeca, gonads, brain, abdominal fat and spleen contained <0·5% of blood flow. There was considerable interfish variation among blood flow distribution to visceral organs with substantial spatial heterogeneity of blood flow to white muscle. The spatial heterogeneity of flow to muscle prevented accurate estimation of total flow to this tissue based on the microsphere deposition of a few sub-samples. Instead, a novel approach, based on the whole animal counting of the eviscerated carcass was used to measure blood flow to white muscle. The scaling relationships for tissue mass in catfish (63–1873 g) followed the allometric equation (aW^b) and tended to exhibit negative allometry, with organ weight decreasing in proportion to body weight. The b values for most tissues ranged between 0·83 and 1·0. The relative mass of the brain showed the greatest decline and with a b value of 0·32. The results, together with previous data on cardiac output, permitted calculation of organ blood flow rates in channel catfish. © 1999 The Fisheries Society of the British Isles     

GENETIC VARIATION AND DIFFERENTIATION IN THE GENUS MABRYA (SCROPHULARIACEAE-ANTIRRHINEAE): SYSTEMATIC AND EVOLUTIONARY INFERENCES

Nine populations of the five species of Mabrya have been examined for allozyme variation at 22 loci using enzyme electrophoresis. The species are homoploid (n = 12), herbaceous perennials and occur in small populations in canyons and barrancas in North American desert scrub and thorn scrub habitats. Although of ancient polyploid origin, the number of isozymes considered typical for diploids is encountered except for a probable duplication at a TPI locus. The average interspecific pairwise comparisons of genetic identities (range 0.434–0.731) are very dissimilar to intraspecific values (range 0.886–0.968). The uniformly low interspecific genetic divergence estimates (average I value of 0.593), large number of unique alleles (average of five per species), pronounced morphological differences, reduced interspecific cross-compatibilities, and (usually) allopatric distributions support recently proposed specific and infrageneric delimitations and hypotheses of a geographical speciation mode, a long period of reproductive isolation, and relictual endemism. Estimates of populational genetic variation are concordant with previous reproductive observations and suggest an outcrossing breeding system for M. geniculata and a mixed mating system for the other species. Because of approximately similar divergence values, phylogenetic relationships in the genus remain unresolved.     

Food resource partitioning and trophic morphology of Brevoortia gunteri and B. patronus

The menhadens Brevoortia gunteri and B. patronus are sympatric and morphologically similar. The two species are planktophagous and exhibited significant ( P < 0·0001) food resource partitioning, with phytoplankton predominating in B. patronus stomachs and zooplankton in B. gunteri. The branchial apparatus of both species is of the typical alosine form. Brevoortia patronus has significantly more branchiospinules per mm (=19·47) and significantly longer gill rakers (=13·35 mm) than B. gunteri (=14·11, =12·01 mm respectively). B. patronus is characterized by a gill raker system forming a fine-meshed filter capable of retaining smaller food items. The results support the hypothesis that food resource partitioning is related to different morphological features of the branchial apparatus.     

Description of Careproctus patagonicus sp. nov. and C. magellanicus sp. nov. (Pisces: Scorpaeniformes) from the lower slope of Drake Passage

Two new species of Liparidae are described from Drake Passage (55°32·8' S, 65°54·3' W). Careproctus patagonicus differs from all other congeneric species in the following combination of characters: C 9 (1+4/4), epural and parhypural unfused to single hypural; gill slit above P base; lower pectoral lobe well developed; pectoral girdle with one ventral radial (0+0+0+1) with a central foramen; da 2·4, aAf 10·2% LS; disk 41·5% HL; some crater-like pits on posterior half of body; head and anterior part of body white. Careproctus magellanicus has the following diagnostic characters: A 46; P 24, well-developed lower pectoral lobe; scattered crater-like spots and some thumb-tack prickles on body; one suprabranchial pore; basal plate of the pectoral girdle with two fenestrae; four radials (3+1), the first with a ventral notch; HL 17·1, preD 18·5% LS. The structure of the endochondral pectoral girdle of both species is commented.     

Genetic relationships among European cattle breeds

Genetic relationships among 37 European cattle breeds were investigated using blood group and serum protein polymorphisms. The 18 859 animals included in the study represented a random sample from pedigree populations in the UK. Within-breed variation was estimated by average heterozygosity and number of alleles observed, and breed relationships were evaluated by genetic distance. Standard errors of the heterozygosity, number of alleles and genetic distance were obtained by bootstrapping. The significance of breed differences was tested using an exact test of differentiation. French, Italian and Channel Island breeds were found to have generally higher heterozygosities and a greater number of alleles than breeds from mainland Britain and North Europe. Genetic distances ranged between 0·011 (±0·005) and 0·309 (±0·071). Two major breed groups were identified; a group of French, Italian and Channel Island breeds together with the Simmental and Gelbvieh, and a second group consisting of the mainland British and North European breeds. The exact test of breed differentiation showed all breeds to be significantly different from one another ( P < 0·0001). Overall relationships among breeds reflected their geographical origin and common ancestry rather than the agricultural use for which the breeds have been selected.     

Analysis of morphometry and mitochondrial DNA sequences from two Trichiurus species in waters of the western North Pacific: taxonomic assessment and population structure

The species status of cutlassfishes ( Trichiurus spp.) in waters of the western North Pacific (five hydrographic areas) was examined using the full-length (consisting of 1141 base pairs) DNA sequence of the mitochondrial cytochrome b gene (mtCyt b ) and truss network-based morphometrics. Two historically confusing Trichiurus morphs are suggested to be two separate species because a decisive difference in the genetic and morphometric data between Trichiurus japonicus and Trichiurus lepturus , using a restricted congener, Trichiurus brevis as the out-group was found. Of all 241 polymorphic sites in mtCyt b at the P _0·95 level, 192 sites fixed within species and variable between species was found. Two-level AMOVA (species and hydrographic areas) results showed significant species differences, while no hydrographic structuring was found within species. Both maximum parsimony and neighbour-joining distance trees supported clear branches for T. japonicus and T. lepturus at 100% bootstrap support. Discriminant function analysis with adjusted body size performed on the morphometric data of T. japonicus and T. lepturus revealed a decisive specific gap of non-overlapping scattering. Combining mtCyt b findings with documented geological events in the western North Pacific, the authors postulate that T. japonicus was evolved peripherally from T. lepturus in middle Miocene, and these two partially sympatric species were achieved secondarily after the Pliocene when intermediate temperatures were located in the subtropical transitions.     

A systematic study of North American Angelica species (Apiaceae) based on nrDNA ITS and cpDNA sequences and fruit morphology

Angelica is a taxonomically complex genus widespread throughout the North Temperate Zone. Previous phylogenetic studies of the genus have focused primarily on its East Asian species. The relationships among its North American members, the monophyly of these species, and the value of fruit morphology in circumscribing its taxa have yet to be examined. This study represents the most comprehensive sampling of Angelica to date (100 species) and includes all 26 species in North America. Relationships are inferred using Bayesian inference, maximum likelihood, and maximum parsimony analyses of ITS sequences and, for multiple accessions of each North American species, cpDNA ndhF-rpl32, rpl32-trnL, and psbM-psbD sequences. The fruit morphological characters examined were those considered phylogenetically important in East Asian Angelica. The results revealed that the North American species fell into three major clades: North American Angelica clade, Archangelica clade, and the Eurasian Angelica clade. Angelica dawsonii has affinities with Lomatium brandegeei. Fourteen species within the North American Angelica clade were strongly supported as monophyletic. Two paraphyletic species resulted in new combinations in A. lineariloba and A. venenosa. Conflict between the ITS-derived and cpDNA-derived phylogenies and the lack of resolution in portions of the trees may be due to chloroplast capture and rapid species radiation. Fruit morphology supported some interspecific relationships based on molecular data, and relationships revealed by ITS and cpDNA data were roughly in accordance with fruit classification type and geographic distribution region, respectively. A diagnostic key based on fruit morphology is provided for the identification of the North American Angelica taxa.     

Discrepancies between otoliths of larvae and juveniles of the American eel: is something fishy happening at metamorphosis?

The use of otoliths to interpret early life history in fishes depends upon the assumptions that otoliths record past events accurately and consistently and that records of events in otoliths are continuous. Both the number of growth microincrements ( I ), and the radii ( R ,μm) of otoliths of American eel Anguilla rostrata , leptocephali increased linearly and highly significantly with leptocephalus body length ( L , mm), as expected on the above assumptions ( I , =2·29 L , − 5·75 and R , =1·05 L , + 12·02, r ²,=0·938 and 0·931, n , =20). In contrast, the number of increments and the radii of the leptocephalus growth zones of otoliths of glass-phase American eels were not related to body length, and they were lower than predicted by the relationships developed for leptocephali. Thus, otoliths of American eels apparently violate one or both assumptions. Possibly, the margin of the otolith is resorbed during metamorphosis from leptocephalus to glass eel, perhaps as part of calcium metabolism as skeletal elements are being formed.     

Morphometry of some structural parameters affecting oxgyen diffusion in body trunk red muscle at different sizes of a tilapia, Oreochromis niloticus

Morphometric measurements were carried out on some of the structural parameters affecting oxygen diffusing capacity in red muscle of 15 specimens of O. niloticus body weight (b.w.) 0.65–812.3 g. Total capillary length and surface area and total morphometric oxygen diffusing capacity in body trunk red muscle had average values of 4792·7 (± 1740.7 s.e.) m, 415·4 (± 157·3 s.e.) cm² and 0·0213 (± 0·0075 s.e.) ml⁻¹ min⁻¹ cm⁻² mmHg respectively. When expressed as functions of b.w. these parameters had scaling values of 1·02, 1·07 and 0·993 respectively. These figures show a slight increase or almost no change in these structural parameters (which affect diffusion of oxygen to mitochondria in red muscle) per unit weight of fish. This should be important as the role of sustained swimming (by red muscle) becomes more important in larger tilapia. Oxygen diffusion distances were short [3·11 (±0·16 s.e.) μm] which facilitates diffusion of oxygen to mitochondria. The scaling value for oxygen diffusion distances of 0·067 (with respect to body weight) shows a slight increase in this parameter with development. This value is significantly different from zero.     

Self-similarity and the relationship between abundance and range size

Patterns in the relationships among the range, abundance, and distribution of species within a biome are of fundamental interest in ecology. A self-similarity condition, imposed at the community level and previously demonstrated to lead to the power-law form of the species-area relationship, is extended to the species level and shown to predict testable power-law relationships between range size and both species abundance and area of census cell across scales of spatial resolution. The predicted slopes of plots of log(range size) versus log(abundance) are shown to be in good agreement with data from British breeding bird and mammal censuses and with data on the distribution of fern species in old-growth forest. The predicted slopes of plots of log(range size) versus log (area of census cell) are consistent with the limited available data for British plant species. Self-similarity provides a testable theoretical framework for a unified understanding of patterns among the range, abundance, and distribution of species.     

Seed size and shape are not related to persistence in soil in Australia in the same way as in Britain

1. Previous studies have shown that among British species, seeds that persist in the soil tend to be small and compact compared with non-persistent seeds. We tested whether or not this pattern is repeated among 101 Australian species, from a range of habitats.
2. Seed mass was plotted against variance of seed dimensions, across all species. Species with persistent seeds were found across the whole range of seed mass (0·217–648·9 mg) and variance (0·0000–0·2497), providing no evidence for a critical mass or variance which separated persistent from transient seeds.
3. We tested whether or not divergence within individual clades between persistent and transient seeds was associated with increased seed mass or seed dimension variance, using phylogenetically independent contrasts (PICs). There was no consistent tendency found.
4. Thus for Australian species, persistent seeds were not smaller or more compact than transient seeds when compared across all species or when compared using PICs. Presumably the natural history of burial and disturbance operates differently in British and Australian habitats.     

Regional differentiation of North American Atlantic salmon at allozyme loci

Allozyme variation was characterised by starch gel electrophoresis at 23 enzyme coding loci and one regulatory locus in Atlantic salmon from 53 rivers in Eastern Canada, encompassing the majority of the species' North American range. Variation among rivers was highly heterogeneous and eight of the 15 polymorphisms showed regionally restricted distributions. Nearest neighbour joining (NJ) analysis and multi‐dimensional scaling suggest six distinct regional groups; Labrador/Ungava, Gulf of Saint Lawrence, Newfoundland (excluding Gulf rivers), the Atlantic shore/Southern Uplands of Nova Scotia, the inner Bay of Fundy, and the outer Bay of Fundy. Approximately 25% of observed genetic variation was distributed among these regions with a weak though significant overall correlation of genetic and geographic distance (Mantel Test, r  = 0·255, P  = 0·005). Collectively, the rivers showed consistent divergence from European populations with strong bootstrap support for the two clusters across loci in the NJ analysis. Mean heterozygosity was 0·061 for both continental groups, but the European population showed more than twice the variation among populations. F _ST values were 0·076 and 0·176 for North America and Europe, respectively, with an overall F _ST of 0·330.