Showing papers in "Biological Journal of The Linnean Society in 1972"

Convergent and divergent character displacement

Abstract: Consideration of the possibilities and difficulties of detecting character displacement leads to a re-definition of the phenomenon; character displacement is the process by which a morphological character state of a species changes under Natural Selection arising from the presence, in the same environment, of one or more species similar to it ecologically and/or reproductively. This incorporates the principal ideas in the original definition given by Brown & Wilson (1956), but eliminates the restriction of making comparisons of the character states of a species in sympatry and allopatry. The evidence for the ecological (competitive) aspect of character displacement is assessed by analyzing in detail the best documented and well publicized examples in the literature. Some of the examples either do not exhibit displaced characters or, if they do, the “displacement” can be interpreted in other and perhaps simpler ways; this applies to the so-called classical case of character displacement, Sitta tephronota and S. neumayer in Iran. Other examples, involving lizards and birds, constitute better evidence for character displacement, but in no single study is it entirely satisfactory. It is concluded that the evidence for the ecological aspect of character displacement is weak.

Phenology of a tropical rain forest in Malaya.

Abstract: During 1960-69, observations were made of flowering, fruiting and foliar activity of 61 canopy trees (representing 45 species) in a largely undisturbed tract of Hill Dipterocarp Forest. Rainfall was measured by an accumulating gauge and, at a nearby station, the number of rainy days recorded. Annually recurrent floral cycles were displayed by only ten species. In these and in 11 additional species, foliar cycles were also circannual. Gregarious flowering, apparently in response to drought, occurred in many species in 1963 and 1968. In other years, interspecific differences in periodicity maintained a minimal incidence of flowering at 44%, and fruiting at 27% of species in the sample. Despite specific variations in phenology, the community as a whole exhibited regular seasonality, with single annual peaks of flowering and fruiting and a double peak of leaf production.

A numerical revision of the earthworm genus Pheretima auct. (Megascolecidae: Oligochaeta) with the recognition of new genera and an appendix on the earthworms collected by the Royal Society North Borneo Expedition

Abstract: The widely distributed earthworm genus Pheretima auct. containing 746 nominal species and subspecies was last reviewed in 1900 when 167 species were listed. In an attempt to increase our understanding of this group of earthworms numerical methods were used to investigate the affinities of 114 species assigned to the genus with the view to dividing it into smaller, more manageable units. A similarity matrix was obtained from a consideration of 56 characters, it was examined by the method of principal co-ordinates analysis firstly to which a minimum spanning tree was applied, then secondly by using a five nearest neighbours' procedure. From the arrangement of the species, assemblages were detected which permitted the recognition of eight genera (one being divided into subgenera): Archipheretima, Pithemera gen. nov., Ephemitra gen. nov., Metapheretima, Planapheretima, Amynthas, Metapbhe nom. nov., Pheretima (Pheretima) and Pheretima (Parapheretima). Following research into the literature, most known species were assigned to genera and to nominal species-groups within the genera, only a few being listed as species incertae sedis. Keys are provided to the genera and to the species and nominal species-groups. Four Appendices are included, one contains details of a small collection of earthworms from Mount Kinabalu, Sabah, made by the Royal Society Expedition to North Borneo, with the descriptions of a new species and a subspecies. Another concerns the identity of Metaphire fordi (Michaelsen, 1934).

A new calcichordate from the Ordovician of Bohemia and its anatomy, adaptations and relationships

Abstract: The paper describes a new member of a group of Lower Palaeozoic marine fossils which partly bridge the gap between echinoderms and chordates. Evidence suggests that this group included the ancestors of the vertebrates. Its members are traditionally regarded as primitive echinoderms, but are better seen as primitive chordates with echinoderm affinities. They form a basal subphylum of chordates-the Calcichordata Jefferies 1967. The Calcichordata, in accordance with an early suggestion by Gislen, are probably ancestral to all living chordates. The new calcichordate is named Reticulocarpos hanusi gen et sp. nov. It comes from the Lower Ordovician Sarka Formation (Llanvirn) of Sarka near Prague, Czechoslovakia and is placed in the family Amygdalothecidae Ubaghs 1970. It is important because of its position in the Calcichordata. This group is divided into two very different orders–the Cornuta and the Mitrata. The Cornuta are the more primitive order and gave rise to the Mitrata, which had the structure of giant, calcite-plated tunicate tadpoles. Many features show that the new species is a very advanced cornute, closely related to the stock that gave rise to the mitrates. For this reason it is important in the general history of the chordates, since some primitive mitrate was probably the latest common ancestor of the living chordate subphyla i.e. of tunicates, of amphioxus and its allies and of the vertebrates. Being a mitrate-like cornute, the new species allows the cornutes and mitrates to be compared more confidently than before. Four results are especially important. Firstly it is likely that the stem (=tail) of mitrates is equivalent only to the anterior part of the stem of cornutes. This is significant, because traditional views as to which was the upper surface in mitrates have been based on stem homologies now seen as false. Secondly Reticulocarpos hanusi is adapted to stay up on very soft mud, using only the strength of the mud for support. The mitrates, on the other hand, supported themselves on soft mud by a much more reliable method resembling buoyancy. Thirdly, the new form had paired transpharyngeal eyes which are otherwise known only in mitrates, and which are the earliest type of paired eyes in chordates. Fourthly, it becomes possible to homologize the thecal plates of cornutes with those of mitrates. Reticulocarpos hanusi represents an important phase in chordate evolution dominated by the necessity of staying up on mud by a very precarious method. During this phase many pre-adaptations for swimming were acquired. Primitive mitrates, descended from a very similar form, were probably the first chordates that could swim.

A multivariate statistical study of skull measurements of five taxa of gazelles

Abstract: A multivariate analysis using canonical variates and the D2 test show that five taxa of Palaearctic gazelles examined are distinct. Several forms of gazelles of dubious taxonomic position were also compared on the canonical axes, with conclusions not dissimilar to those of recent workers on the Arabian gazelles, viz. that there are three distinct species in the Arabian peninsula; Gazella dorcas saudiya, Gazella gazella arabica and Gazella subgutturosa marica. Gazella dorcas populations in Somalia have a local form in G. dorcas pelzelni distinct in horns but not in skull measurements from Gazella spekei in the nearby highlands.

A preliminary survey of chromosomes in populations of the Chilean burrowing octodont rodent Spalacopus cyanus Molina (Caviomorpha, Octodontidae)

Abstract: Chromosomes obtained from bone-marrow, spleen and testes were studied in samples from five populations of Spalacopus cyanus of Central Chile. Animals of four low-land coastal localities and animals of a high Andean valley showed a karyotype of 2n = 58 chromosomes, with almost no variation, either in number or in structure, both within each population or among the various populations. This karyotype was found to be very similar to that of Octodon degus, but very different to those in species of Ctenomys. The evolutionary and systematic significance of these results is discussed. The lack of karyotypic variation found in Spalacopus is correlated with its taxonomic uniformity, and both could be the result of the high vagility of the populations of this rodent, suggested by previous studies. This high capacity of dispersal is supposed to have enhanced gene flow, and therewith chromosome uniformity and low taxonomic diversification. The occurrence of a case of dimorphism for the presence of a secondary constriction in one of the autosome pairs is reported and discussed.

The scientific names in the german edition of parkinson's plants of use for food, medicine etc., in otaheite

Abstract: Sydney Parkinson, aged 18, was Sir Joseph Banks' private assistant and artist on Captain Cook's first voyage around the world. Parkinson died on the voyage. Among his effects delivered to his brother Stanfield were drawings and notes which the latter published as a journal. Included in it is a chapter on the economic plants of Tahiti, and most of them are given scientific names, some of which were new. In 1941 Fosberg adopted two of them to form names which were new combinations under Artocarpus, and Inocarpus. The writer now indicates that Parkinson's names of 1773 were mononomials, hence invalid, but that in the German edition of 1774, edited by Herr “Z”, the names are valid binomials. For the two plants mentioned, the authorship of the combinations is revised.

A multivariate analysis of measurements on the Scottish Middle Old Red Sandstone antiarch fish genus Pterichthyodes Bleeker

Abstract: A multivariate statistical analysis, using both discriminatory procedures on canonical axes and factor analysis was used to determine if there was any separation into different morphological types corresponding to the ostensible species of the Scottish antiarch Pterichthyodes. These analyses indicated that, although there were two definite types of pectoral appendage, those differences which were apparent in body shape, were part of a continuous variation exhibited by the whole population, and were but extreme forms of a continuum. The distinction in pectoral appendage types is attributed to sexual dimorphism.