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1.
The phylogenetic relationships of a number of flightless and volant rails have been investigated using mtDNA sequence data. The third domain of the small ribosomal subunit (12S) has been sequenced for 22 taxa, and part of the 5'' end of the cytochrome-b gene has been sequenced for 12 taxa. Additional sequences were obtained from outgroup taxa, two species of jacana, sarus crane, spur-winged plover and kagu. Extinct rails were investigated using DNA extracted from subfossil bones, and in cases where fresh material could not be obtained from other extant taxa, feathers and museum skins were used as sources of DNA. Phylogenetic trees produced from these data have topologies that are, in general, consistent with data from DNA-DNA hybridization studies and recent interpretations based on morphology. Gallinula chloropus moorhen) groups basally with Fulica (coots), Amaurornis (= Megacrex) ineptus falls within the Gallirallus/Rallus group, and Gallinula (= Porphyrula) martinica is basal to Porphyrio (swamphens) and should probably be placed in that genus. Subspecies of Porphyrio porphyrio are paraphyletic with respect to Porphyrio mantelli (takahe). The Northern Hemisphere Rallus aquaticus is basal to the south-western Pacific Rallus (or Gallirallus) group. The flightless Rallus philippensis dieffenbachii is close to Rallus modestus and distinct from the volant Rallus philippensis, and is evidently a separate species. Porzana (crakes) appears to be more closely associated with Porphyrio than Rallus. Deep relationships among the rails remain poorly resolved. Rhynochetus jubatus (kagu) is closer to the cranes than the rails in this analysis. Genetic distances between flightless rails and their volant counterparts varied considerably with observed 12S sequence distances, ranging from 0.3% (Porphyrio porphyrio melanotus and P. mantelli mantelli) to 7.6% (Rallus modestus and Rallus philippensis). This may be taken as an indication of the rapidity with which flightlessness can evolve, and of the persistence of flightless taxa. Genetic data supported the notion that flightless taxa were independently derived, sometimes from similar colonizing ancestors. The morphology of flightless rails is apparently frequently dominated by evolutionary parallelism although similarity of external appearance is not an indication of the extent of genetic divergence. In some cases taxa that are genetically close are morphologically distinct from one another (e.g. Rallus (philippensis) dieffenbachii and R. modestus), whilst some morphologically similar taxa are evidently independently derived (e.g. Porphyio mantelli hochstetteri and P.m. mantelli).  相似文献   

2.
Species of malaria parasite (phylum Apicomplexa: genus Plasmodium) have traditionally been described using the similarity species concept (based primarily on differences in morphological or life-history characteristics). The biological species concept (reproductive isolation) and phylogenetic species concept (based on monophyly) have not been used before in defining species of Plasmodium. Plasmodium azurophilum, described from Anolis lizards in the eastern Caribbean, is actually a two-species cryptic complex. The parasites were studied from eight islands, from Puerto Rico in the north to Grenada in the south. Morphology of the two species is very similar (differences are indistinguishable to the eye), but one infects only erythrocytes and the other only white blood cells. Molecular data for the cytochrome b gene reveal that the two forms are reproductively isolated; distinct haplotypes are present on each island and are never shared between the erythrocyte-infecting and leucocyte-infecting species. Each forms a monophyletic lineage indicating that they diverged before becoming established in the anoles of the eastern Caribbean. This comparison of the similarity, biological and phylogenetic species concepts for malaria parasites reveals the limited value of using only similarity measures in defining protozoan species.  相似文献   

3.
This study is focused on the growth pattern of agnostids, a group of organisms that were very abundant in the Cambrian. The developmental patterns of six agnostid species are compared. It is shown that, like other trilobites, agnostids have two developmental stages, i.e., meraspid degrees 0 and 1 and the holaspid stage. Meraspid degrees are named according to the number of released thoracic segments. Several molts took place during every meraspid stage resulting in successive instars with a unique set of features. Meraspid degree 0 includes two or three instars, the first and last of which have a distinctive morphology and have been encountered in most of the species studied. During meraspid degree 1, the animal molted from two to four times. The number of molt stages appears to be species-specific. The first and last instars are easily distinguished from other developmental forms. Early holaspids of the majority of agnostid species studied also have certain features in common.  相似文献   

4.
记述了采自马来西亚的蝗科6亚科22属30种,包括一新种Vitalisia bangiensus sp. nov.。 并首次发现和描述了Sedulia perakensis Willemse的雄性及Eucoptacra minima Ramme和Pagdenia rufipes Miller的雌性。还发现Meltripata bolivari Willemse 和Pagdenia rufipes Miller具二型:全翅型和退化翅型。提供了马来西亚已记录属和种的检索表。  相似文献   

5.
The principal vector of malaria in sub-Saharan Africa, Anopheles gambiae is subdivided into two molecular forms M and S. Additionally, several chromosomal forms, characterized by the presence of various inversion polymorphisms, have been described. The molecular forms M and S each contain several chromosomal forms, including the Savanna, Mopti and Forest forms. The M and S molecular forms are now considered to be the reproductive units within A. gambiae and it has recently been argued that a low recombination rate in the centromeric region of the X chromosome has facilitated isolation between these forms. The status of the chromosomal forms remains unclear however. Therefore, we studied genetic differentiation between Savanna S, Forest S, Forest M and Mopti M populations using microsatellites. Genetic differentiation between Savanna S and Forest S populations is very low (F(ST) = 0.0053 +/- 0.0049), even across large distances. In comparison, the Mopti M and Forest M populations show a relatively high degree of genetic differentiation (F(ST) = 0.0406 +/- 0.0054) indicating that the M molecular form may not be a single entity, but could be subdivided into at least two distinct chromosomal forms. Previously it was proposed that inversions have played a role in the origin of species within the A. gambiae complex. We argue that a possible subdivision within the M molecular form could be understood through this process, with the acquisition of inversions leading to the expansion of the M molecular form into new habitat, dividing it into two distinct chromosomal forms.  相似文献   

6.
The resolution of taxonomic classifications for delphinid cetaceans has been problematic, especially for species in the genera Delphinus, Tursiops and Stenella. The frequent lack of correspondence between morphological and genetic differentiation in these species raises questions about the mechanisms responsible for their evolution. In this study we focus on the genus Delphinus, and use molecular markers to address questions about speciation and the evolution of population structure. Delphinus species have a worldwide distribution and show a high degree of morphological variation. Two distinct morphotypes, long-beaked and short-beaked, have been considered different species named D. capensis and D. delphis, respectively. However, genetic differentiation between these two forms has only been demonstrated in the Pacific. We analysed samples from eight different geographical regions, including two morphologically defined long-beaked form populations, and compared these with the eastern North Pacific populations. We found high differentiation among the populations described as long-beaked instead of the expected monophyly, suggesting that these populations may have evolved from independent events converging on the same morphotype. We observed low genetic differentiation among the short-beaked populations across a large geographical scale. We interpret these phylogeographical patterns in the context of life history and population structure in related species.  相似文献   

7.
Three forms of the RNA-dependent DNA polymerase were isolated from highly purified avian sarcoma virus B77 grown in duck embryo fibroblasts, using sequential chromatography on DEAE-cellulose, phosphocellulose, and poly(U)-cellulose. One form, which sedimented with about 5.2 S, contained only one species of polypeptide, with a molecular weight of 63,000; a second sedimented with about 7.8 S and contained only one species of polypeptide with a molecular weight of 81,000; and a third form, which sedimented with about 7.3 S, contained two species of polypeptides with molecular weights of 63,000 and 81,000. The molecular constitution of the three enzyme forms were therefore alpha, beta2, and alphabeta. All three possessed almost the same specific activity with poly(rA)-oligo(dT) as the primer-template. Forms alpha and alphabeta of avian sarcoma virus DNA polymerase have already been described in the literature; form beta2 is a new form. All three forms possessed ribonuclease H activity, the relative specific activities of the alpha, beta2, and alphabeta forms being about 1:4:5. All three enzyme forms were inhibited by antiserum to the alphabeta form, but whereas the alpha and alphabeta forms could be inhibited about 95%, the maximum degree of inhibition of the beta2 form was about 80%. The three enzyme forms also differed with respect to heat stability at 46 degrees, the monomeric alpha form of the enzyme being only about one-half as stable as the two dimeric forms.  相似文献   

8.
《Ibis》1950,92(1):84-94
Notes are based on a collection of 700 skins. Extensions of range include Trachylaemus p. togoensis, Prodotiscus i. flavodorscdis, Campethera n. nivosa, Bleda canicapilla, Phyllastreplms i. icterinus, Pedilorhynchus c. aximensis, Sylvia bnrin, Apalis c. caniceps, Macrosphenus concolor , and Spermophaga h. togoensis recorded from Nigeria and Apus c. strenbelii from West Africa for the first time.
Taxonomic points include reasons for regarding Centropus epomidis as a colour phase of Centropus senegalensis and Sylvietta flavixentris nigeriae as a synonym of Sylvietta flainventris.
Dates of breeding are given for many species, and nests and eggs arc described. Indicator indicator was found in the nest of Hirundo setnirufa.
The chick of Porphyrio alleni is described.  相似文献   

9.
A new genus, a new subgenus, four new species and four previously described species are recorded from the Red Sea. The new genus Anomalorbis has four and a half thoracic segments. Re-discovery of the sinistral variety of Janua (Dexiospira) steueri confirms Sterzinger's observation that this species may coil in either direction. Janua (Fauveldora) anticorrugata sp. nov. is also sinistral and a shallow water species. It therefore appears that the Red Sea may have been the centre of origin for sinistral mutants of the Janua complex. Other of the new forms live in fairly deep water. The assemblage encountered shows closest affinity with the Indo-Pacific, but suggests a high degree of endemism, which may be related to the high temperatures prevailing at all depths in the Red Sea.  相似文献   

10.
The conservation of critically endangered flightless birds in New Zealand   总被引:3,自引:0,他引:3  
M. N. CLOUT  J. L. CRAIG 《Ibis》1995,137(S1):S181-S190
The current status of Kakapo Strigops habroptilus and Takahe Porphyrio mantelli is described along with recent developments in programmes for their conservation. Both species were (at different times) thought to be effectively extinct, and both have been temporarily reprieved by the discovery of new populations. Population declines have continued, with Kakapo now reduced to less than 50 individuals and Takahe to about 150. Kakapo are especially at risk; 87% of the remaining birds are over 14 years old and only 17 females are known. Research on relict populations of both species has identified predation and competition from introduced mammals as major threats. Both species have high rates of egg infertility and low survival of young. Increasingly intensive management of both Kakapo and Takahe over recent years has included translocation to predator-free island refuges, supplementary feeding to encourage breeding, clutch manipulation, captive rearing and predator control. All known Kakapo have now been transferred to three island refuges, where the overall rate of population decline has slowed and supplementary feeding has apparently encouraged more frequent breeding attempts. Takahe conservation has concentrated largely on attempts to increase the population in Fiordland, New Zealand, through clutch manipulation and release of captive-reared young, but birds have also been released on four islands, which now hold 19% of the total population. The relict Fiordland populations of both Kakapo and Takahe were confined to apparently suboptimal habitat. Both species have successfully adapted to novel environments and foods when translocated, and the populations which now exist present improved opportunities for intensive management using a range of conservation techniques to enhance productivity and survival. Recent population trends of Kakapo and Takahe are reconstructed, and the contribution of research to their conservation is reviewed.  相似文献   

11.
The limpet Patella ferruginea is the most endangered marine invertebrate in the western Mediterranean rocky shores, whereas Patella caerulea is the most common Mediterranean limpet. From Pleistocene to historic age, P. ferruginea was distributed around the whole Mediterranean basin, since the shells of this species are a characteristic feature of Palaeolithic and Neolithic deposits in this area. However, its Mediterranean range has progressively contracted to a few restricted areas. The ancient origin of the species (18 Ma) and the present geographical isolation among relic populations could have led to a great genetic difference among populations, taking into account the supposedly low dispersal ability of the species. However, we have observed a few genetic differences among populations and a 'star phylogeny' of COI haplotypes from the 41 individuals of P. ferruginea analysed; a similar pattern has also been observed for the seven individuals of P. caerulea studied. Genetic evidences show a possible bottleneck event on late Pleistocene that affected the two species. The results have an important implication on the future management of this endangered species. Additionally, two different morphological types of P. ferruginea have been described by Payraudeau in 1826 : lamarcki and rouxi forms. Clear morphological differences occur between these two types and some authors pointed out the hypothesis about the existence of two different species. The results of the present study conclude that the two different forms of P. ferruginea are ecotypes, rather than different species or subspecies, and intermediate steps are an ecological range instead of hybridization events among different species.  相似文献   

12.
Following the origin of multicellularity in many groups of primitive organisms there evolved more than one cell type. It has been assumed that this early differentiation is related to size — the larger the organism the more cell types. Here two very different kinds of organisms are considered: the volvocine algae that become multicellular by growth, and the cellular slime moulds that become multicellular by aggregation. In both cases there are species that have only one cell type and others that have two. It has been possible to show that there is a perfect correlation with size: the forms with two cell types are significantly larger than those with one. Also in both groups there are forms of intermediate size that will vary from one to two cell types depending on the size of the individuals, suggesting a form of quorum sensing. These observations reinforce the view that size plays a critical role in influencing the degree of differentiation.  相似文献   

13.
14.
The medicinal leech is the most famous representative of the Hirudinea. It is one of few invertebrates widely used in medicine and as a scientific model object. It has recently been given considerable conservation effort. Despite all attention there is confusion regarding the taxonomic status of different morphological forms, with many different species described in the past, but only two generally accepted at present. The results of the phylogenetic analysis of a nuclear (ITS2+5.8S rRNA) and two mitochondrial gene sequences (12S rRNA, COI) suggest that the genus Hirudo is monophyletic. It consists, apart form the type Hirudo medicinalis and the East Asian Hirudo nipponia, of three other, neglected species. All of them have already been described either as species or morphological variety, and can readily be identified by their coloration pattern. The type species is in weakly supported sister relation with Hirudo sp. n. (described as variety orientalis) from Transcaucasia and Iran. Sister to them stands Hirudo verbana from southeastern Europe and Turkey, which is nowadays predominantly bred in leech farms and used as 'medicinal leech.' The North African Hirudo troctina is the sister taxon to this group of Western Eurasian species, whereas the basal split is between H. nipponia and the Western Palaearctic clade.  相似文献   

15.
Cotyledon anatomy in the Leguminosae   总被引:3,自引:0,他引:3  
Cotyledon anatomy has been investigated in approximately 900 species representing all the major tribes of the Leguminosae. Four main cotyledon forms are recognized on the basis of morphological, anatomical and functional criteria. The two modal forms are a leaf-like photosynthetic cotyledon, usually borne in an endospermic seed and occurring in about 60% of species; and a fleshy, storage cotyledon, borne in a non-endospermic seed and occurring in about 30% of species. Two intermediate forms combine the structural and functional characteristics of the modal forms in varying degree. The leaf-like cotyledon is considered to be the basic form from which the others have been derived. Cotyledon anatomy shows correlations with seed size and with taxonomic grouping at the tribal and generic levels and thus provides a set of minor characters of potential taxonomic or phylogenetic value or for use in seed and seedling classification and identification.  相似文献   

16.
The examination of whole mounts prepared for transmission electron microscopy has resulted in the finding of thirteen taxa of nanoplanktonic coccolithophorids from the Weddell Sea, Antarctica. The material was collected as part of the AMERIEZ programme, March 1986. Cold-water adapted nanoplanktonic coccolithophorids have previously been shown to constitute a recurrent plankton element at subarctic and arctic localities. Three of the Weddell Sea species, Wigwamma annulifera, W. arctica , and Papposphaera sagittifera , are conspecific with northern hemisphere material, while two species, Calciarcus alaskensis and Turrisphaera arctica , are possibly identical with previously described arctidsubarctic material. Six taxa new to science have been described from the Weddell Sea, Wigwamma antarctica, W. triradiata, Trigonaspis melvillea, Pappomonas weddellensis, Papposphaera obpyramidalis , and P. simplicissima . The cooccurrence of identical forms at the two poles, and the fact that the species described are allocated to "arctic" genera, indicate a geologically relatively recent exchange of biological material between the poles.  相似文献   

17.
The distribution of phosphodiesterase forms in somatic and germ cells, and their variations during testicular development and germ cell differentiation have been investigated. Seminiferous tubules from immature mice and Sertoli cells in culture possessed two enzyme activities which were comparable to forms described for different tissues and species: (a) a calcium-calmodulin-dependent enzyme with high affinity for guanosine 3',5'-(cyclic)-monophosphate (cGMP), and (b) a calcium-calmodulin-independent enzyme with high affinity for adenosine 3',5'-(cyclic)-monophosphate (cAMP) the activity of which increased in cultured Sertoli cells after treatment with FSH or dibutyryl cAMP. Seminiferous tubules from adult animals and germ cells at the meiotic and post-meiotic stage of differentiation possessed two enzyme forms that could be distinguished from those present in somatic cells of the seminiferous tubules: (a) a calcium-calmodulin-dependent form with high affinity for both cAMP and cGMP, similar to forms described in other tissues from different species, and (b) a calcium-calmodulin-independent phosphodiesterase with high affinity for cAMP and present only in post-meiotic cells, previously identified also in germ cells of the rat.  相似文献   

18.
Two forms of pollen morphology of Impatiens L. (Balsminaceae) have been described before: 3-colpate and 4-colpate pollen grains. Pollen grains of 13 species of Impatiens on Mt. Omei were examined under SEM for the first time and both forms were observed here, which imply the diversity of species in this region. Of the two forms, 3-colpate one is quite similar to that of the genus Hydrocera Blume (Balsaminaceae) in external morphology. This relation also exists between the 3-colpate pollen group and Hydrocera in habit, habitat, and distribution, etc. It is supposed that the group with 3-colpate pollen type is a natural one, and may have a close relationship with Hydrocera. The pollen morphology is of important significance in classification of the taxa and evaluation of systematic position in the fami-ly balsaminaceae.  相似文献   

19.
Pukeko, Porphyrio porphyrio melanotus breed as pairs or groups and the breeding behaviour of individuals in all units is described and compared. Courtship, including copulation, occurred between all adult members in a territory although male-female copulations were most frequent. Low ranking yearlings were excluded from copulation. Participation in copulation by more than two birds was common, and, along with homosexual behaviour, is believed to help synchronize sexual cycles allowing several females to lay in the same nest at the same time. Only adults incubated, while all birds in a territory assisted with chick care, the degree of participation varying with status. In pair territories, older chicks helped feed younger chicks. Stable kin groups were more coordinated and showed less competitive aggression among members than non-kin groups of unstable membership. The significance of these results is discussed and it is argued that in a situation where an adult group is necessary for the defence of a breeding territory, then it is in the interests of all these individuals to participate in all breeding activities.  相似文献   

20.
In nonpedigreed wild populations, inbreeding depression is often quantified through the use of heterozygosity-fitness correlations (HFCs), based on molecular estimates of relatedness. Although such correlations are typically interpreted as evidence of inbreeding depression, by assuming that the marker heterozygosity is a proxy for genome-wide heterozygosity, theory predicts that these relationships should be difficult to detect. Until now, the vast majority of empirical research in this area has been performed on generally outbred, nonbottlenecked populations, but differences in population genetic processes may limit extrapolation of results to threatened populations. Here, we present an analysis of HFCs, and their implications for the interpretation of inbreeding, in a free-ranging pedigreed population of a bottlenecked species: the endangered takahe (Porphyrio hochstetteri). Pedigree-based inbreeding depression has already been detected in this species. Using 23 microsatellite loci, we observed only weak evidence of the expected relationship between multilocus heterozygosity and fitness at individual life-history stages (such as survival to hatching and fledging), and parameter estimates were imprecise (had high error). Furthermore, our molecular data set could not accurately predict the inbreeding status of individuals (as 'inbred' or 'outbred', determined from pedigrees), nor could we show that the observed HFCs were the result of genome-wide identity disequilibrium. These results may be attributed to high variance in heterozygosity within inbreeding classes. This study is an empirical example from a free-ranging endangered species, suggesting that even relatively large numbers (>20) of microsatellites may give poor precision for estimating individual genome-wide heterozygosity. We argue that pedigree methods remain the most effective method of quantifying inbreeding in wild populations, particularly those that have gone through severe bottlenecks.  相似文献   

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