An ecological "footprint" of climate change by Dr. G.-R. Walther, Dipl.-Biol. S. Berger and Prof. MT. Sykes (rspb.2005.3119)
A field survey in southern Scandinavia and north-eastern Germany revealed new occurrences of holly, the only evergreen broad-leaved lower tree species native to central and western Europe, beyond its former northern range margin. This range expansion is in concert with the gradual increase in winter temperature measured at local stations. The synchrony of measured and modelled increases in winter temperatures and observed shifts in species' distribution suggests that climate change is the responsible driver, and makes this species a good (bio-)indicator for global warming.
Contact: Dr. G.-R. Walther, Institute of Geobotany, University of Hannover, Nienburger Str 17, HANNOVER, D-30167, Germany
Behavioural flexibility and migration in temperate Palearctic birds by Dr s Sol, Dr L Lefebvre and Dr. JD Rodriguez-Teijeiro (rspb.2005.3099)
Faced with seasonal changes in the environment, some birds migrate to less severe regions for the winter, while others remain in the same region during the whole year. Why bird species have adopted such different strategies is all the more intriguing. Now an international team of researchers has shown that this may have to do with differences between species in brain size. Big brains are known to enhance the cognitive skills of birds to behaviorally adapt to changes in the environment, and hence might be critical for individuals to survive in seasonal environments. The international team, which was mostly based at McGill University (Canada), tested this hypothesis with a comparative analysis of all passerines that breed in Western Europe. The bigger the species' brain relative to its body size, the higher was the probability that the species was resident, consistent with the idea that enlarged brains function to face with seasonal changes in the environment. Small-brained species, which do not have the behavioural flexibility necessary to respond to seasonal changes, would consequently be forced to adopt the alternative strategy to migrate to more favorable regions in winter.
Contact: Dr s Sol, Centre de Recerca Ecologica i Aplicacions Forestals, Universitat Autonoma de Barcelona, Edifici Ciencies, BELLATERRA, E-08193, Spain
Organic matter dynamics control plant species coexistence in a tropical peat swamp forest by Dr. T Shimamura and Dr. K Momose (rspb.2005.3095)
We studied the relationships between the coexistence of tree species and the dynamics of organic matter in forests. A tropical peat swamp forest was selected as a model ecosystem, where biological processes create habitat heterogeneity. According to our new model based on our field experiments, the death and growth of some influential tree species affect some important variables of organic matter dynamics and change the conditions on the forest floor. Many tree species respond different to these conditions. Thus, we revealed that the spatial and temporal fluctuations of variables in organic matter dynamics, contribute to the coexistence of plant species.
Contact: Dr. T Shimamura, Laboratry of Forest Hydrology, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, KYOTO-CITY, 606-8502, Japan
Speciation: more likely through a genetic or through a learned habitat preference? By Professor JAJ Metz and Mr JB Beltman (rspb.2005.3104)
Individuals prefer environments specific to their species. This preference can be genetic, whereas in other cases individuals prefer the habitat of their youth. Habitat preferences can assist the formation of two species out of one as it fosters matings between individuals specialised on the same environment. The paper considers a model where initially an unspecialised species equally exploits two different habitats. During the formation of two new species specialised on and preferring different habitats, usually a learned preference evolves instead of a genetic one. Thus, early learning is likely to play an important role in forming new species.
Contact: Professor JAJ Metz, Theoretical Biology, Institute of Biology, Leiden University, van der Klaauw Laboratory, LEIDEN, 2311 GP, Netherlands
Associations between malaria and MHC genes in a migratory songbird by Dr H Westerdahl, PhD J Waldenström, Dr B Hansson, Dr D Hasselquist, Professor T von Schantz and Dr S Bensch (rspb.2005.3113)
Studies on humans have demonstrated that genetic factors play a key role for the outcome of malaria infections. We investigated associations between major histocompatibility complex (MHC) genes (genes that are important in the immune defence) and prevalence of three different avian malaria parasites in our study population of great reed warblers (a song bird). We found that birds with variable MHC genes were more likely to survive a malaria infection than birds with less variable MHC genes. Furthermore, we found that a variant of a specific MHC gene gave the same protection. Hence, genetic factors are important for survival in birds.
Contacts: Dr H Westerdahl, Animal Ecology, Lund University, Ecology Building, LUND, 22362, Sweden
Environmental quality and evolutionary potential: lessons from wild populations by Dr A Charmantier and Dr D Garant (rspb.2005.3117)
Evolution depends on genetic variation: when there is little variation, the pace of evolution will be slower than when there is a lot. In this paper we compiled numerous studies of amphibians, birds, molluscs, fish, mammals and insects that have measured genetic variation for the same character in different natural environments. Our analysis shows that when the environment is more favourable, more genetic variation is expressed. This means that evolution may proceed more rapidly in favourable conditions than in unfavourable conditions. This finding has important implications for our general understanding of how animals adapt to variable environments.
Contact: Dr A Charmantier, Department of Zoology, Edward Grey Insitute of Ornithology, University of Oxford, OXFORD, OX1 3PS
Biology Letters
Why not walk faster? Limitations to walking speed imposed by inverted pendulum mechanics by Dr J. R. Usherwood
A simple model of the mechanics of walking provides an account for why bipeds (humans and birds) can't walk faster. The problem of 'take-off' – when gravity cannot provide the centripetal acceleration required to keep the body arcing around the foot – is greatest at beginning and end of stance; this is when the body is moving fastest, and the component of gravity along the leg is lowest. Thus, bipeds cannot walk at high speeds with long steps. Shorter steps permit faster walking without take-off, but then driving the swing leg fast enough becomes an issue.
Contact: Dr J. R. Usherwood, Structure and Motion Lab., The Royal Veterinary College, VBS,
NORTH MYMMS, AL9 7TA, United Kingdom
Epidemiological implications of the contact network structure for cattle farms and the 20-80 rule by Professor MEJ Woolhouse and Dr DJ Shaw
Moving cattle between farm holdings has the potential to spread infectious diseases. Using data from DEFRA's Cattle Tracing System for 55 Scottish farms we worked out how many farms they sent cattle to and received cattle from during 2002; that is, how well 'connected' each farm was. On average, each holding was connected with 24 other holdings, but there was a lot of variation: most farms were connected with only a few others, but a few were connected with over 100. This variation is important: just 20% of farms contribute over 80% of the potential to spread infectious diseases by cattle movements.
Contact: Dr Professor Woolhouse, Centre for Infectious Diseases, University of Edinburgh, Easter Bush Veterinary Centre, MIDLOTHIAN, EH25 9RG, United Kingdom
Sensitivity to dimethyl sulphide suggests a mechanism for olfactory navigation by seabirds by Dr GA Nevitt and Dr F Bonadonna
Petrels and albatrosses have an excellent sense of smell, and routinely navigate over the world's oceans by unknown mechanisms. These birds travel thousands of kilometres to forage on ephemeral prey patches at variable locations, yet they can quickly and efficiently find their way back to remote islands where they nest. Over the seemingly featureless ocean, local emissions of dimethyl sulphide (DMS) produce and odour landscape that reflects features of the ocean floor. Our study is the first to show that an Antarctic seabird can physiologically detect DMS at environmental levels, and use it for orientation in a novel context.
Contact: Dr GA Nevitt, Department of Neurobiology, Physiology and Behaviour and Animal Behaviour Graduate Group, University of California at Davis, 1 Shields Avenue, Davis, CA 95616, USA
Acute Effects of Hurricane Charley on Fish Chorusing by Mr. JV Locascio and Dr DA Mann
On August 13, 2004 Hurricane Charley passed directly over an underwater acoustic recorder deployed in Charlotte Harbor, Florida to collect data on fish sound production associated with courtship and spawning. The underwater recorder not only survived the storm but documented its sounds as it passed through the harbor. Acoustic data collected over the 14 day deployment (August 4 – 17, 2004) revealed that nightly patterns in sound production by fishes were higher on the three nights following the hurricane than the nine nights preceding it. It is unclear however, if the hurricane acted as a stimulus to increase calling activity in fishes or if this behavior was the result of a longer-term cycle that may have taken place without the occurrence of the hurricane.
Contact: Mr. JV Locascio, College of Marine Science, University of South Florida, 140 Seventh Ave. South, ST. PETERSBURG, FLORIDA, 33701, United States
Genetic Diversity Predicts Pathogen Resistance and Cell-mediated Immunocompetence in House Finches by Ms DM Hawley, Dr. KV Sydenstricker, Dr GV Kollias and Professor AA Dhondt
Scientists have long suspected that genetic diversity influences individual health, but this idea had not been tested in an experimental setting where the playing field is leveled. We investigated whether house finches with less genetic variation become more severely diseased in response to a pathogen challenge. Finches with lower genetic variation showed more severe eye symptoms that are characteristic of infections from this naturally-occurring pathogen. The stronger symptoms may reflect compromised immunity: when we challenged birds with a T-cell stimulant, less genetically variable birds mounted weaker responses. Our study provides direct support that genetic variation impacts individual disease resistance and immunity.
Contact: Ms DM Hawley, Ecology and Evolutionary Biology, Cornell University, Corson Hall, ITHACA, NEW YORK, 14853, United States
No sex difference in yolk steroid concentrations of avian eggs at laying by Dr KM Pilz, Professor E Adkins-Regan and Dr H Schwabl
Bird eggs contain steroids of maternal origin. These maternal steroids affect offspring development, and have been hypothesised to influence offspring sex. However, previous studies of the sex-determination hypothesis have examined steroid levels in incubated eggs, which may not accurately reflect maternal steroid levels. We conducted the first study relating steroid concentrations in unincubated eggs with the embryonic sex of offspring, as determined by genetic sexing. Steroid concentrations of male and female eggs were not different in unincubated eggs, but were different in incubated eggs. Thus, maternal steroids do not appear to play a critical role in avian sex determination.
Contact: Dr KM Pilz, Department of Neurobiology and Behaviour, Cornell University, Ithaca, NY , 4853-2702, USA
The multiple signals assessed by female satin bowerbirds: are they used to narrow down females' choices of mates? by Dr TE Robson, Dr AW Goldizen and Dr. DJ Green
In the satin bowerbird, males display to females at structures that they make called bowers; in this species males provide females with sperm but no help with parental care. We studied how female satin bowerbirds choose which males to mate with. Our results suggest that females' decisions about which males' bowers to inspect closely are based on the males' sizes and the rates at which they display. Whether females actually mate with the males that they inspect is based on the males' sizes and the rates at which they "paint" their bower with chewed up plant material and saliva.
Contact: Dr AW Goldizen, School of Integrative Biology, University of Queensland, BRISBANE, QLD 4072, Australia
Terminal reproductive effort in a marsupial by Ms JL Isaac and Dr CN Johnson
This study used a marsupial to test the prediction that older mothers should put more effort into reproduction than younger females. Older females lost more weight during lactation and as a result their offspring were heavier as one year olds. Females that lost the most weight during lactation had reduced body weight the following year. Older females were also more likely to breed twice in a year. This study provides the clearest evidence yet that older mothers put more effort into reproduction than younger mothers; differences in reproductive strategy between marsupial and placental mammals could explain variation in previous studies.
Contact: Ms JL Isaac, Biological Sciences, James Cook University, Douglas, TOWNSVILLE, 4811, Australia
Differential sex allocation in sand lizards: bright males induce daughter production in a species with heteromorphic sex chromosomes by Dr M Olsson, Dr E Wapstra and Dr T Uller
We show that female sand lizards (Lacerta agilis) in a natural population respond to enhancement of their partner's breeding coloration by investing more energetic resources into their offspring (rendering a female in poorer condition), and by producing more daughters. These results agree with the notion that females invest more when mating with higher quality partners. It also suggests that females bias the sex ratio towards the sex most susceptible to genetic inviabilities (such as colour blindness and muscular dystrophy in humans) only when partners are of particularly high genetic quality, i.e., when the risk of having inviable offspring is reduced.
Contact: Dr M Olsson, School of Biological Sciences, University of Wollongong, NSW 2522, Australia
Journal of the Royal Society Interface
A modelling approach to estimate the sensitivity of pooled faecal samples for isolation of Salmonella in pigs by Dr ME Arnold, Mr AJC Cook and Dr RH Davies
Pooling of pen faecal samples for surveillance of Salmonella in pigs is a key part of the UK action plan to reduce Salmonella prevalence. However, it was not known how effective pooled sampling was at detecting Salmonella. In this study experiments were performed to determine the probability of Salmonella being detected in pooled faecal samples from pigs. Pooling of samples was found to be more efficient than individual sampling at detecting Salmonella. These results will enable enhanced surveillance of Salmonella at potentially reduced cost.
Contact: Dr M Arnold, Department of Epidemiology, VLA New Haw, Addlestone, Surrey KT15 3NB
Journal
Proceedings of the Royal Society of London