Temperature and prey capture: opposite relationships in two predator taxa

Abstract 1. All other things equal, predator capture rates are expected to depend on encounter rate with prey, prey escape capability (including prey defences), and on predator agility. Ectotherm predators and their prey both respond to increasing temperature by increased activity, i.e. predators increase their search area and prey may enhance their escape capability. This means that, as temperature changes, the ability of a predator to catch prey will decrease, increase, or remain unchanged depending on the relative effect of temperature on predator and prey. Their responses may further be differentially moulded by light conditions depending on whether the predator is diurnally or nocturnally active. It was hypothesised that flying Diptera are vulnerable to carabid beetles only at low temperatures and over the full temperature range for spiders because carabids, in contrast to spiders, are not built to catch swiftly moving prey. 2. The first experiment examined the spontaneous locomotor activity of the predators and of fruit flies at different temperatures (5, 10, 15, 20, 25, and 30 °C) and light conditions (light, dark). A second experiment examined the effect of temperature and light on the predation rate of two carabid beetles (Pterostichus versicolor and Calathus fuscipes) and two spiders (Clubiona phragmitis and Pardosa prativaga) using fruit flies (Drosophila melanogaster) as prey. 3. All four predators and the fruit fly increased their locomotory activity at higher temperatures. Activity of the carabid beetles peaked at intermediate temperatures; spiders and fruit flies were most active at the highest temperatures. Predation rate of the spiders increased with temperature whereas the beetles caught flies only at low temperatures (5 and 10 °C). 4. Diurnal variation in temperature may bring different prey groups within the set of potential prey at different times of the day or at different seasons. The ability of many carabid beetles to forage at low temperatures may have nutritional benefits and increases the diversity of interactions in terrestrial food webs.     

Effects of Off-Highway Vehicle Use on the American Marten

Abstract Motorized recreation in North American wildlands is increasing, and technological developments in the power and range of vehicles has increased access to high-elevation habitats. The American marten (Martes americana) is vulnerable to this disturbance because martens, like other residents of high-elevation forests, are associated with remote wilderness conditions where the presence of motorized vehicles is a recent phenomenon. We evaluated the effects of vehicles at 2 study sites in California, USA, by comparing marten occupancy rates and probabilities of detection in areas where recreational vehicle use is legal and encouraged (use areas) with wilderness areas where vehicles are prohibited (non-use areas). We sampled vehicle occurrence in nearby use and non-use areas using sound level meters and determined marten occurrence using track and camera stations. We also included 2 secondary measures of potential effects of vehicles on martens: sex ratio and circadian pattern of activity. Martens were ubiquitous in use and non-use areas in both study sites, and there was no effect of vehicle use on marten occupancy or probability of detection. We predicted that females might be less common and martens more nocturnal in use than in non-use areas, but neither occurred. Martens were exposed to low levels of disturbance in our study sites. We estimated that a marten might be exposed to 0.5 vehicle passes/hour and that this exposure had the greatest effect on <20% of a typical home range area. Furthermore, vehicle use usually occurred when martens were inactive. We did not measure behavioral, physiological, or demographic responses, so it is possible that vehicles may have effects, alone or in concert with other threats (e.g., timber harvest), that we did not quantify. We encourage additional studies to determine whether other montane species that are year-round residents demonstrate the same response to motorized vehicles.     

Taphonomic pathways and comparative biofacies and taphofacies in a Recent intertidal/shallow shelf environment

The development of taphonomic approaches to facies analysis requires a foundation in facies-based actualistic studies. Modern intertidal and shallow shelf environments at Provincetown Harbor. northern Cape Cod, Massachusetts (USA) provide an opportunity to compare pattcrns and controlling factors in molluscan biofacies and taphofacies distributions. Variation in faunal composition, ecologic variables, and taphonomic attributes of molluscan death assemblages produce distinct patterns of environmental zonation: (1) Faunal composition (biofacies) primarily tracks variation in substrate type among environments (sand, rock, peat, and Zostera marina beds). (2) Ecologic variables (equitability, infauna: epifauna ratio, gastropod:bivalve ratio, and predation on M. mercenaria) appear to reflect tidal exposure time. (3) Taphononic attributes (fragmentation, abrasionm, corrosion, bioerosion, and encrustation) of the common bivalve M. mercenaria track environmental energy, in particular its effects on the stability and reworking of hardparts at the sediment surface. Shells in different environments proceed along different taphonomic pathways - the order of acquisition of taphonomic features by hardparts. An encrustation/bioerosion-dominated pathway characterizes low energy environments; the upper intertidal and deeper subtidal. An abrasion-dominated pathway characterizes the high energy lower intertidal and shallow subtidal. Contrasting pathways produce distinct proportions of taphonomic attributes in time-averaged samples; proportions that delineate taphofacies. Integrated taxonomic, ecologic and taphonomic data provide a more complete picture of environmental processes than any approach alone. Taphonomic data not only furnish information not readily provided by other approaches, but free paleoecology from the constraints of taxonomic uniformitarianism. □Taphonomy, comparative taphonomy, taphofacies, biofacies, cluster analysis, multidimensional scaling, taphonomic pathways, Recent, actualism, intertidal, molluses.     

Patterns of feeding behaviour in adult male riodinid butterflies and their relationship to morphology and ecology

Adult butterflies are known to visit a wide variety of food substrates, but, with the exception of flower visitation, little is known about what substances are being sought or what determines substrate choice. This is especially true for the Riodinidae, a large family [c. 1300 spp.) of almost exclusively Neotropical butterflies. We present adult male feeding records for 124 species in 41 genera of Riodinidae (out of a total of 441 species in 85 genera collected in the study), based on ten months sampling in Ecuador. Records of food substrates visited in this study include flowers, damp sand or mud (‘puddling’) and rotting carrion. Rotting carrion placed in traps was the most frequently recorded food source in terms of numbers of individuals and taxa, attracting 89 species from 32 genera. A correlation is found between food substrate choice and morphology, specifically wing area to thoracic volume ratio (WA: TV ratio). Our data suggest the possible existence of two adaptive syndromes whose species have significantly different mean WA:TV ratios and differing suites of accompanying ecological traits, with lower ratios being significantiy correlated with species that were recorded feeding. Among species recorded feeding, carrion feeders and puddlers have significantly lower mean WA:TV ratios than flower nectarers, and carrion feeders have a lower mean WA:TV ratio than species not recorded on this food source, a correlation that is significant across all tribes and within some tribes (Riodinini and Saratoni). We reanalyse previously published data on flight and morphology for species in other butterfly and moth families and show mat the ratio of wing area to thoracic mass is significantly negatively correlated with flight speed and oxygen consumption (a direct indicator of metabolic rate). We suggest that adult male riodinids may puddle and feed at rotting carrion to supplement nutrient stores from larval feeding, not only to increase reproductive success, but also to provide the necessary nutrients to maintain high metabolic rates during rapid flight.     

Digestion rate in relation to alternative feeding in three species of polyphagous predators

Abstract. 1. Disappearance of different amounts of aphid ingested by three species of polyphagous predators, the carabids Bembidion lampros (Herbst) and Nebria brevicollis (F.) and the staphylinid Philonthus cognatus Stephens, was monitored by a quantitative enzyme-linked immunosorbent assay (ELISA). The effect on the rate of inactivation of prey antigens by the ingestion of subsequent, non-aphid food was also studied.
2. Antigen inactivation was significantly more rapid in the staphyilinid than in the carabids.
3. No statistically significant differences were found in the rate of antigen inactivation between beetles which consumed only aphids and those which were given a different type of food after feeding on aphids; the detection period was longer in the former groups. A higher proportion of beetles with low levels of aphid antigen were found earlier in the latter group.
4. The results did not unequivocally support the prediction derived from optimal digestion theory that beetles without continuous access to food would retain an initial meal longer than beetles with unlimited access.     

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.