Distribution of the eggs of Aedes punctor (Diptera: Culicidae)

ABSTRACT.

• 1 Eggs of the mosquito Aedes punctor Kirby were found to be aggregated in a horizontal band within woodland depressions.
• 2 The height of the peak of egg density above the lowest point in the depression varied from 24 to 39 cm in six transect studies.
• 3 One depression, 2 m in diameter, was analysed in detail and found to contain a total of 9231 eggs with a maximum density of 944 eggs in a 250 cmz area.

     

Contributions to the cytòtaxonomy of the Commelinaceae

Representatives of the Tradescantia geniculata alliance (genus Gibasis Rafin.) in cultivation at Kew display considerable cytological and morphological diversity. Chromosome complements consist of either large or small chromosomeS. Plants with small chromosomes have either 2 n = 16 or 2 n = 32, and all form only bivalents at meiosis and have presumed basic numbers of x – 8 and x = 8 or 16 respectively. The 2 n = 32 accessions are considered to represent T.geniculata in its strict sense; the identity of the 2 n =16 plant is uncertain. Plants with large chromosomes have either 2 n = 16 or 2n = 20 and each forms quadrivalents to the extent that they can be considered as cytological autotetraploidS. Basic numbers are then x = 4 and x =5, the lowest yet recorded for the Commelinaceae. The identity of the x = 4 species is uncertain. The x = 5 plants are readily identified as T.karwinskyana.     

THE BIOLOGY OF THE LOBE-FINNED FISHES

1. Interpretation of structural evolution in a group such as the Sarcopterygii requires consideration of a combination of all possible functions, rather than single functions. 2. The Dipnoi are probably more closely related to the Crossopterygii than to other groups of fishes. The Sarcopterygii are a ‘natural’ group. Certain characters in common between the elasmobranchs and the Dipnoi or Coelacanthini seem to be the result of convergent evolution. 3. Evolution of the skull, in connexion with both respiratory and feeding mechanisms, has resulted in extreme specialization in all Sarcopterygii. The crossopterygian intracranial kinesis has evolved from an earlier mobility between the skull and neck and is adapted for increasing the power of the bite and for enclosing the prey from both above and below, in addition to other factors. Adaptive radiation is seen in the feeding mechanisms of all forms. The evolution of the Amphibia proceeded through elongation of the anterior division of the skull (which is not correlated with any changes in brain morphology) and loss of the kinetic mechanism in this sequence is at least partially associated with improved buccal pumping mechanisms for lung ventilation. 4. Adaptive radiation of the respiratory system in Dipnoi shows a progressive increase in the use of aerial respiration. The aquatic condition seen in Neoceratodus is probably secondary. Comparison of the three living genera shows a striking correlation between respiratory physiology and habit. There is little indication of reduction of the branchial respiratory system in known Rhipidistia, in which respiration was probably primarily aquatic. In Dipnoi and Rhipidistia, evolution of the lung allowed a partial control of the hydrostatic properties of the body. In coelacanths, aerial respiration was abandoned, except in certain secondarily freshwater forms, and the single lung is modified as an organ of hydrostatic balance. These changes are reflected in the over-all body proportions. 5. Locomotion in Sarcopterygii (except the coelacanths Laugia and Piveteauia) is adapted for contact with the substrate in relatively shallow water in most cases. Adaptive radiation of the locomotor apparatus is seen with respect to the relative roles and functions of the paired and unpaired fins, over-all body shape, caudal fin shape, and absolute size. An important function of the pectoral fins in advanced Rhipidistia was in supporting the body in shallow water and thus aiding lung ventilation. 6. Aestivation is an early feature of dipnoan biology, but was not evolved in Rhipidistia. The common faculty of urea production via the ornithine cycle and urea retention in coelacanths and dipnoans are adaptations to conditions in which the body tissues may become dehydrated (salt water and desiccation, respectively). The common pattern of nitrogen metabolism seems to have evolved during a marine phase in sarcopterygian evolution. 7. There is evidence that the earliest members of all sarcopterygian lines included marine forms. However, the subsequent major radiations of Dipnoi and Rhipidistia occurred in fresh waters. The distribution of Sarcopterygii was entirely tropical. The late Palaeozoic distribution of the freshwater forms seems to offer evidence for the occurrence of Continental Drift. Coelacanths were primarily coastal fishes. 8. The evolution of a major group of organisms requires a different pattern of evolutionary change than that by which adaptive radiations are produced. It evolves the structural and temporal correlation of modification in a number of different functional systems rather than the separate modification of each system without reference to other systems. 9. The first tetrapods evolved in a highly seasonal swampy environment on the shores of inland lakes or rivers, in permanently moist conditions.     

Conservation genetics of an arctic species, Saxifraga rivularis L., in Britain

Genetic diversity in British populations of Saxifraga rivularis L. (Saxifragaceae) was assessed using isozymes, RAPDs, inter-SSRs and RFLPs of two non-coding chloroplast DNA regions. Low levels of variation were detected: only five molecular phenotypes were recovered, polymorphic for a single RAPD band and Pgd enzyme phenotype. The problem of drawing conservation recommendations from studies that show low levels of marker variation is discussed, and the importance of recognizing the limits of molecular genetic data in conservation biology is emphasized.     

Molecular systematics of the butterfly tribe Preponini (Nymphalidae: Charaxinae)

The nymphalid butterfly tribe Preponini includes some of the Neotropical region's most spectacular and familiar butterflies, but the taxonomy of the group nevertheless remains unstable. Several recent studies of Nymphalidae phylogeny have suggested that both the tribe itself and several genera might not be monophyletic, but to date taxon sampling has not been sufficiently comprehensive to allow informed revision of the group's systematics. We therefore conducted the first complete species‐level phylogenetic study of the tribe to establish a firm higher classification. We used DNA sequence data from three genes, the two mitochondrial genes cytochrome oxidase subunits I and II (COI and COII), and the nuclear gene elongation factor‐1α (EF‐1α), to reconstruct the phylogeny of the tribe using maximum likelihood (ML), maximum parsimony (MP) and Bayesian inference (BI). We included 48 individuals representing the 22 recognised Preponini species, and an additional 25 out‐group taxa to explore taxonomic limits at different levels. Firstly, we found that Anaeomorpha splendida Rothschild never grouped with remaining Preponini, so that maintaining monophyly of the tribe requires the taxon to be excluded, and we thus reinstate the tribe Anaeomorphini stat.rev. Secondly, we investigated generic limits, in particular the relationship of Noreppa Rydon to Archaeoprepona Fruhstorfer, and that of Agrias Doubleday to Prepona Boisduval. The molecular results coupled with previous morphological studies suggest that Noreppa syn.n should be synonymised with Archaeoprepona, and that Agrias syn.n should be synonymised with Prepona. We found Prepona pheridamas (Cramer) to be sister to all other Prepona, and markedly divergent from them in both morphology and DNA sequences, suggesting the possibility that it should be placed in a separate genus. We also found a number of cases of significant DNA sequence divergence and paraphyly or polyphyly within putative species that require further taxonomic attention, including Prepona claudina (Godart) stat.n. and Prepona narcissus (Staudinger) stat.n., Prepona pylene Hewitson and Prepona deiphile (Godart). Future research should focus on a broader population sampling of widespread, polymorphic Preponini species to thoroughly revise the current species‐level taxonomy, thus creating a solid foundation for studies in ecology and conservation.     

Mechanisms of intracranial kinetics in fossil rhipidistian fishes (Crossopterygii) and their relatives

The fishes of the Order Crossopterygii are characterized by a unique articulation within the braincase, by which the anterior division of the endocranium may be moved dorso-ventrally with respect to the posterior division. The structure of the skull in both groups of crossoptery-gian fishes (the fossil Rhipidistia and the fossil and Recent Coelacanthini) is such that 'normal' operation of the intracranial mechanism involves lateral movements of the cheek region and palate corresponding to the dorso-ventral movements of the ethmoid portion of the braincase. The hyomandibular has a function of prime importance in integrating the movements of the various skull components relative to each other. There are important differences between the characteristic intracranial mechanisms of Rhipidistia and Coelacanthini which may be interpreted in adaptive as well as morphological terms. Analysis of the intracranial kinetics of the Rhipidistia reveals a trend, in certain lines, for the amount of relative movement between the skull components to be decreased and this may be used to explain the loss of the intracranial joint in the Amphibia during their evolution from the Rhipidistia. The functional significance of the intracranial articulation has both a kinetic and a dynamic aspect and while in the Amphibia the kinetic ability of the skull is almost wholly restricted, the dynamic features of the ancestral condition are modified and developed as the basal articulation between the palate and endocranium is retained.