Chironomid microdistribution in gravel of an English chalk river

1. The study aimed to determine the relative importance of certain environmental variables to the distribution of instars of chironomid species in mid-stream gravels of the River Pang. 2. Core samples of gravel substrata were collected over 1 year. Water depth, current, particle size distribution, substratum porosity and detritus were recorded for each sample. The four principal components from a linear ordination of the environmental variables were used to constrain the ordination of chironomid data using the program CANOCO. 3. Microdistribution was principally related to a temporal gradient of water depth, current and substratum heterogeneity. There was significant spatial separation of instars along a gradient of fine detritus, silt and substratum porosity. The distributions of early instars of three taxa were also significantly related to particle size. There was a significant relationship between the size distribution of larvae and the spatial distribution of fine sediments and detritus. This relationship was strengthened when restricted to larvae classified as scrapers.     

Social Signals and Behaviors of Adult Alligators and Crocodiles

We compare and contrast the signalling systems and social behaviorsof Alligator mississippiensis, Crocodylus aculus, and Crocodylusmloticus. Our qualitative analysis focuses primarily on thebehaviors of adults during three phases of reproduction: I.Defense of Territory and Courtship, II. Nesting and Incubation,and III. Hatching and Post Hatching. Signals and signal elementsare very similar among the three species. For example, all havevocal, non-vocal acoustic, and visual signals, some transmittedthrough air or water and others through both media. In addition,each species' repertoire is composed of discrete, graded andcomplex signals. A few signals are unique to each species. However,their signalling systems differ in the temporal organizationof the behaviors, and in the relative frequency in which certainfunctional groups of signals occuror in which signals occurin a particular sensory mode. Apparently, the signalling systemsof C. acutus and C. niloticus are more similar to each otherthan either is to the signalling system of A. mississippiensis.The signalling systems of the crocodile species appear to beadapted to open water habitats in which visual signals are advantageousand to high density breeding groups and post-copulatory intersexualcontact. In contrast, the Alligatorsignalling system appearsadapted to a marsh habitat in which vocal signals are likelyfavored and to low density breeding groups.     

Denaturing gradient gel electrophoresis (DGGE) screening of clones prior to sequencing

Whilst cloning and sequencing techniques are used ubiquitously for the identification of novel DNA sequences, the necessity to determine a consensus sequence means that this can be both labour‐intensive and costly. Here we describe a rapid and cost effective method of using denaturing gradient gel electrophoresis (DGGE) for the analysis of large numbers of clones prior to sequencing. This procedure allows for the selection of specific clones, eliminates the need to sequence multiple copies of the same clone, and reduces the likelihood of sequencing recombinant PCR product.     

Differentiation of large arionid slugs (Mollusca, Pulmonata) using ligula morphology

A study of the ligula (a holdfast/stimulatory device associated with the distal genitalia) in the species aggregates Arion ater and A. lusitanicus, common in NW Europe, suggests that examination of this organ may permit rapid and reliable differentiation to the sub-specific level. This study describes the ligula and its taxon-specific characteristics, illustrated by three-dimensional stereo photographs, which clearly reveal its structure and can be readily compared with dissected material. The bizarre and intricate variations some taxa exhibit in the form of this organ are interpreted in terms of mating behaviour.     

The relationship between body size and time of breeding in Icelandic Redshanks Tringa t. robusta

The average wing-lengths of male and female Redshanks differ, allowing one to estimate the probabilities of males being larger in pairs whose measurements are known. Using these probabilities in a large number of simulations we showed that larger 'female' Icelandic Redshanks nested earlier than smaller ones. The results support Hale's suggestion that size selection in Redshanks operates on the breeding grounds. There was no evidence of assortative mating.     

Some Remarkable Inflorescences in the Ericales and thier Taxonomic Significance

Certain Epacridaceae have flattened bract-like structures (‘falsebracts’) bearing abortive buds, associated with the flowers.Comparative morphological and anatomical studies show that theseare best interpreted as the modified tips of inflorescence axes.False bracts are limited to three genera where flowers are solitaryin the leaf axils. Taxonomic interest in their distributionlies in the fact that it supports the maintenance of Cyathodes,Styphelia, and other long-standing genera which are sometimesreduced to synonymy.     

Seasonal patterns of occurrence of Palaearctic migrants in southern Africa using atlas data

A statistical method, using presence/absence data from monthly fieldcards, to describe the phenology of migration is developed. The method uses the generalized linear model to fit a Fourier series to binomial-type data giving the proportion of fieldcards reporting a species. A method for estimating mid-arrival and mid-departure dates, and residency period is also developed. The methodology is applied to data collected during the 'Southern African Bird Atlas Project' for the following species: Willow Warbler Phulloscopus trochilus, Red-backed Shrike Lanius collurio, European Swallow Hirundo rustica, White Stork Ciconia ciconia, Steppe Buzzard Buteo buteo and European Bee-eater Merops apiaster.