Geographic potential of Argentine ants (Linepithema humile Mayr) in the face of global climate change by Dr N Roura-Pascual, Dr AV Suarez, Dr C Gómez, Dr P Pons, Dr Y Touyama, Dr AL Wild and Dr AT Peterson
We examined the potential worldwide distribution of the Argentine ant (Linepithema humile) based on current climate models and also in the face of projected future climate change. Native to South America, Argentine ants have invaded broad areas around the world. Our results suggest that Argentine ants still have the potential to spread into areas not currently known to be occupied, particularly in regions of Africa and Asia. Higher latitudes appear to become more suitable for the Argentine ant under global climate change scenarios. Because invasion processes have the potential to alter global biodiversity considerably, this improved knowledge of the potential geography of the Argentine ant should be considered in preventive efforts.
Contact: Dr Núria Roura-Pascual, Departament de Ciències Ambientals, Universitat de Girona, Facultat de Ciències, GIRONA, 17071, Spain
Genetic and environmental contributions to pro-social attitudes: a twin study of social responsibility by Dr JP Rushton
A new study surprisingly shows genes, more than home environment, shape social responsibility attitudes. 174 pairs of identical twins and 148 pairs of non-identical twins from the University of London Twin Register rated themselves on 22 social attitudes such as "I am a person people can count on" and "It is important to finish anything you have started." Identical twins were almost twice as similar as non-identical twins. Genes determined 42%; home environment, 23%; and the non-home environment, the remainder of the variance. The ratings predict real life behaviour such as voting and helping others, implying these too have a genetic component.
Contact: Dr John Rushton, Psychology, University of Western Ontario, 1151 Richmond Street, ONTARIO, N6A 5C2, Canada
Distance-dependent costs and benefits of aggressive mimicry in a cleaning symbiosis by Dr I Cote and Dr KL Cheney
We have analysed how teeth form in the trout, an animal with a complex dentition where teeth are not only associated with the jaws but are found at other sites within the mouth. Comparison with detailed knowledge of the mouse remarkably shows that the same genes are deployed in trout at equivalent stages of tooth development. We conclude that the genes needed to build a dentition are conserved from fish to mouse and notably are repetitively used for all generations of teeth, from the mouth margins to rear gill arches. Thus a molecular tool kit for making teeth emerged early in vertebrate evolution.
Contact: Dr Isabelle Cote, School of Biological Sciences, University of East Anglia, Centre for Ecology, Evolution and Conservation, NORWICH, NR4 7TJ
Inbreeding uncovers fundamental differences in the genetic load affecting male and female fertility in a butterfly by Dr IJ Saccheri, Dr HD Lloyd, Dr SJ Heylar and Professor PM Brakefield
The focus of inbreeding depression studies has been on viability, with much less attention being paid to effects of inbreeding on fertility. Experiments with the butterfly Bicyclus anynana show that sterility accounts for 70% of the total inbreeding depression in this species. More remarkable is that the sterility effect is restricted to males, with female fertility being unaffected by inbreeding, suggesting that spermatogenesis is more sensitive to deleterious mutations than oogenesis. This asymmetry in inbreeding depression for functionally equivalent traits raises questions about the generality of the standard evolutionary explanation for differences in sensitivity to inbreeding among traits.
Contact: Dr Ilik Saccheri, Division of Population and evolutionary Biology, School of Biological Sciences, University of Liverpool, Nicholson Building, BROWNLOW STREET, LIVERPOOL, L69 3GS
The effect of energy reserves on social foraging: hungry sparrows scrounge more by Dr AZ Lendvai, Dr Z Barta, Dr A Liker and Dr V Bokony
Search for food or steal your companion's meal? Although this is a widespread dilemma facing almost every social being, from insects to humans, we hardly understand how animals choose between these tactics. In this study we manipulated the esuriency of house sparrows and observed whether they adjust their feeding strategy according to their state. We found that hungry birds scrounged (exploited their flockmates' food findings) more often than their companions. We showed that by scrounging more, hungry birds were able to reduce the variation of their food intake, thereby decreasing the risk of starvation.
Contact: Dr Adam Lendvai, Dept of Ethology, Eotvos University, Pazmany P. s. 1/c BUDAPEST, H-1117, Hungary
Paying for nectar with wingbeats: a new model of honeybee foraging by Dr AD Higginson and Dr FS Gilbert
Honeybees acquire wing damage as they age and older foragers visit lavender inflorescences with fewer flowers. As wing damage increases wingbeat frequency increases. A model was constructed that assumed that bees have a limited total number of wingbeats that the flight motor can perform and that they reduce their choosiness as they acquire wing damage. The optimal relationship between wing damage and the average number of flowers on inflorescences was very close to what we recorded bees doing. This suggests that wing wear strongly affects bee behaviour and bee lifespan is limited by the flight mechanism.
Contact: Dr Andy Higginson, Animal Behaviour and Ecology Research Group, School of Biology, University of Nottingham, NOTTINGHAM, NG7 2RD
Adaptation to the cost of resistance: a model of compensation, recombination, and selection in a haploid organism by Dr PJ Wijngaarden, Dr RF Hoekstra, Dr F Van den Bosch and Professor MJ Jeger
The spread of pesticide resistance increasingly interferes with efforts to control populations of pest organisms. Prior to pesticide use resistant types are often kept at low frequencies because they have a lower fitness than susceptible types. Mutations that compensate for this 'cost of resistance' enable resistant types to remain in the population at appreciable frequencies after pesticide use; this reduces the efficacy of future pesticide applications. We examined a model of compensatory evolution in a haploid organism. A key finding is that reduction of the cost of resistance makes it easier for resistance to become fixed in a population of pest organisms.
Contact: Dr Pieter Wijngaarden, Laboratory of Genetics, Wageningen University, Arboretumlaan 4, WAGENINGEN 6703 BD, Netherlands
Natural selection on mitochondrial DNA in Parus and its relevance for phylogeographic studies by Professor RM Zink
Thousands of studies in the last two decades have compared DNA sequences among populations to elucidate evolutionary relationships, and to reveal historical aspects such as patterns of migration and growth. A critical assumption is that the sequences evolve in a neutral fashion, unaffected by natural selection. Here, mitochondrial DNA sequences from tits of the genus Parus were tested for signatures of natural selection. Although there appears to be some selection on these sequences, it is insufficient to alter conclusions about the relationships of populations and their demographic histories. Although requiring confirmation with other species, these results support the interpretations of many studies that previously only assumed selective neutrality.
Contact: Professor Robert Zink, Bell Museum of Natural History, 1987 Upper Buford Circle, 100 Ecology Building, ST PAUL, MN 55108, USA
Theta oscillations by synaptic excitation in a neocortical circuit model by Dr JML Budd
What is the origin of different types of brain wave activity? Attention, learning, and memory tasks are correlated with 'theta' oscillatory activity (4-8 cycles per second or Hz). Animal experiments on neocortex, the largest part of cerebral cortex, suggest that networks of a particular type of deep-layer neuron may generate theta oscillations. Here, a realistic computer model was constructed to test this hypothesis, as this cannot yet be done experimentally. In support of this hypothesis, the model was able to generate robust theta wave activity implying that these deep-layer neuron networks may be the source of neocortical theta waves.
Contact: Dr Julian Budd, Dept of Informatics, Sussex University, BRIGHTON, BN1 9QH
A parasite reveals cryptic phylogeographic history of its host by Dr CM Nieberding, Dr S Morand, Dr R Libois and Dr JR Michaux
Our study compared the geographic and genetic structures of the woodmouse Apodemus sylvaticus, with those of its specific nematode parasite, Heligmosomoides polygyrus. Our results provided evidence that both species survived similarly to the Quaternary ice ages in Spain, Italy and Sicily, and both species recolonised Western Europe from Spain at the end of the last ice age (10,000 years ago). Moreover, the parasite's rate of DNA evolution is 1.5 fold higher as compared to the one of its host. Therefore, the parasite was used as a biological magnifying glass to highlight previously undetected events in its host's history, like cryptic differentiation and refuge zones.
Contact: Dr Caroline Nieberding, Unité de recherches zoogéographiques, Université de Liège, Institut de Zoologie, LIÈGE, 4020, Belgium
Proceedings of The Royal Society A: Mathematical, Physical and Engineering Sciences
Exact transient full-field analysis of a finite crack subjected to dynamic anti-plane concentrated loadings in anisotropic materials by Dr Y Ing and Professor C-C Ma
In this study, the elastodynamic full-field response of a finite crack in an anisotropic material subjected to a dynamic antiplane concentrated loading with Heaviside-function time dependence is investigated. Exact analytical transient solutions for dynamic shear stresses, displacement and stress intensity factor are obtained in explicitly compact formulations. The solutions have accounted for the contributions of all diffracted waves generated from two crack tips. Numerical results for the time history of shear stresses and stress intensity factors during the transient process are calculated based on analytical solutions and are discussed in detail. The dynamic stress intensity factor will reach a maximum value when the incident wave arrives at the crack tip, and remain constant before the first diffracted wave generated from the other crack tip arrives, and then oscillate near the static value. A simple explicit expression of the dynamic overshoot for stress intensity factors is derived as a function of the location for applied loadings, the crack length and material constants.
Contact: Professor Ma, Mechanical Engineering, National Taiwan University, No 1 Roosevelt Road, Sec 4, Taipei, TAIWAN 10617, REPUBLIC OF CHINA
Wave drag due to lift for transonic airplanes by Professor JD Cole and Dr ND Malmuth
A new method has been developed that provides a systematic approximation to quickly calculate and reduce the drag associated with shock waves generated by wings travelling near the speed of sound. The method uniquely allows us to do the complete design on a small personal computer as contrasted to supercomputers. It gives a very precise recipe of how to shape the wing using a new form of Whitcomb's area rule that dictated coke bottle fuselages for fighters to help them break the sound barrier. This new method will help airplanes achieve higher speed and greater range according to special new mathematical analogue to the old area rule.
Contact: Dr Norman Malmuth, Science Center, Rockwell International Corporation, 1049 Camino des Rios, THOUSAND OAKS, CA 91358, United States