New Royal Society journal studies

11/08/04

Biology Letters

Moa were many by Dr NJ Gemmell, Dr K. Schwartz and Dr C. Robertson
Until a few hundred years ago, New Zealand hosted several species of giant flightless birds (similar to emu), collectively known as the moa. Their demise following the arrival of humans to New Zealand has been widely documented, but a long standing controversy is whether moa were already in decline prior to human settlement. Using new genetic analyses on an extinct species for the first time we have been able to shed light on this mystery. We estimate that, as little as 1,000 years ago, the standing population of moa was c. 3ľ12 million. This estimate is much larger than the accepted population estimate (c. 159,000) for moa at the arrival of humans and suggests that moa numbers had already declined prior to human settlement, perhaps as a result of habitat loss through volcanism or disease. If our new estimates of moa numbers are correct then we need to think again about the factors that might have influenced these populations prior to the arrival of humans, perhaps gaining greater insight into modern conservation problems from the lessons of the past.
Contact: Dr Neil Gemmell, School of Biological Sciences, University of Canterbury, PB 4800, CHRISTCHURCH 8008, New Zealand

The social implications of winner and loser effects by Dr LA Dugatkin and Dr M Druen
More and more evidence from the animal world suggests that "winning begets winning" and "losing begets losing." Prior work on such winner and loser effects has focused on pairwise interactions, and not the extent to which winner and loser effects impact hierarchy formation. We examined the impact of winner and loser effects on hierarchy formation in the green swordtail, Xiphophorus helleri. Our results demonstrate that randomly chosen winners in pairwise contests were more likely to emerge as top-ranked individuals in a hierarchy, while randomly chosen losers were more likely to emerge as the lowest ranking individuals. These results strongly suggest that information on such measures as size and "fighting ability" are not sufficient to predict hierarchy formation-instead, these factors must be combined with a knowledge of winner and loser effects to make detailed predictions regarding hierarchy formation.
Contact: Dr Lee Dugatkin, Department of Biology, University of Louisville, LOUISVILLE, KY 40208, United States

Nocturnal colour vision in geckos by Dr LSV Roth and Dr A Kelber
The night-active helmet gecko can discriminate colours under dim light conditions when humans are colour-blind. These geckos are the first known vertebrates with such colour vision ability. We trained and tested helmet geckos on different blue and grey chequered patterns. Both patterns were associated with one cricket each but the cricket together with the grey pattern was salted and distasteful for the geckos. Our results show that the geckos were able to learn and discriminate the blue pattern from the grey one even though the patterns were changed every training day.
Contact: Dr Lina Roth, Department of Cell and Organism Biology, University of Lund, Helgonavńgen 3, LUND, S-223 62, Sweden

Distress calls may honestly signal bird quality to predators by Dr P Laiolo, Dr JL Tella, Dr M Carrete, Dr D Serrano and Dr G Lopez
Predators and prey engage in an arms race in which interactors tend to increase their fitness and survival. As predators tend to attack the most vulnerable prey to reduce energy loss, preys are expected to advertise their escape ability. We recorded the distress calls (those screams emitted in conditions of the utmost danger) of a small passerine, and examined the relationship between call physical properties and caller nutritional and immunological condition. Scream harshness, a feature expressing aggression, was related to caller health, suggesting that these calls might honestly signal prey condition and thus escape ability, on which predators might base their foraging choice.
Contact: Dr JosÚ Tella, Applied Biology, Estacion Biologica de Do˝ana (CSIC), Avda. M¬ Luisa s/n, SEVILLA, 41013, Spain

Queen and worker policing in monogynous and monandrous colonies of a primitively eusocial wasp by Dr T Saigo and Dr K Tsuchida
A queen is, by definition, a sole producer in social insects. Theory paradoxically predicts that workers prefer to produce sons in colonies headed by a once-mated queen. Using behavioural observation and genetic method, we evaluated the fate of eggs by workers in colonies of a paper wasp. Our results showed that the workers produced eggs according to the theory while they also removed nestmate-workers' eggs contradicting the theory. Conflict over reproduction between workers using an unknown mechanism to recognize the origin of eggs is important for the regulation of worker reproduction in primitively eusocial stage rather than self constraint.
Contact: Dr Koji Tsuchida, Laboratory of Entomology, Gifu University, Yanagido 1-1, GIFU, 501 1193, Japan

Proceedings of The Royal Society B: Biological Sciences

Modelling strategies for minimizing the impact of an imported exotic infection by Dr MG Roberts
The global epidemic of severe acute respiratory syndrome (SARS) in 2003 demonstrated the need to determine control strategies for new and emerging infections, but the design of these strategies is hampered by the obvious lack of data. A new model, based on work first published in 1927 is described. The model is parameterized by the progression of the infection in an individual and the initial doubling time of the epidemic, with more detailed structure added by allocating cases to risk groups. The model's use in the design of strategies to minimize the risks of SARS in a previously unexposed community is demonstrated.
Contact: Dr Mick Roberts, Institute of Information and Mathematical Sciences, Massey University, Private Bag 102 904, North Shore Mail Centre, Auckland, New Zealand.

Novel chromatic and structural biomarkers of diet in carotenoid-bearing plumage by Dr R Bleiweiss
Many captive birds change colour in response to dietary intake of carotenoid pigments, which produce vivid yellows, oranges, and reds. However, evidence for the phenomenon in the wild remains controversial. A study of carotenoid-bearing plumages among more than 50 wild tanager species found that carotenoid intake measured as an amount of dietary fruit (a rich source of carotenoids) was associated with reduced plumage reflectance in the ultraviolet, a band of wavelengths visible to birds but not humans. The effect probably arises from increased pigment concentrations and modifications to the structure of feathers. Thus, birds follow a dress code invisible to humans.
Contact: Dr. Robert Bleiweiss, Department of Zoology & Zoological Museum, University of Wisconsin, Madison, WI 53706, USA

Fitness and evolutionary stability in game theoretic models of finite populations by Dr G Wild and Professor PD Taylor
The mathematical theory of games has proven useful to our understanding of the evolution of social behaviour. These so-called "evolutionary games" seek to identify certain "stable strategies," considered to be the end result of evolution. For mathematical convenience, evolutionary games are often played among members of an ideal infinite population. However, populations in nature are never infinite. Unlike much previous work, this study considers a simple two-player game, played among members of a finite population. We establish that different notions of Darwinian fitness and different formal definitions of stability lead to identical conclusions about the outcome of evolution.
Contact: Dr Geoff Wild, Department of Mathematics and Statistics, Queen's University, KINGSTON, ON K7L 3N6, Canada

Conserved deployment of genes during odontogenesis across osteichthyans by Dr GJ Fraser, Dr A Graham and Professor MM Smith
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: Professor Moya Smith, Craniofacial Development, United Dental & Medical Schools, Guys and St. Thomas Hospitals, Floor 27 Guy's Tower, LONDON BRIDGE, SE1 9RT

Proceedings of The Royal Society A: Mathematical, Physical and Engineering Sciences

On an infinite integral arising in the numerical integration of stochastic differential equations by Dr DM Stump and Professor JM Hill
Financial institutions value many of their deals using mathematical equations that describe how the prices of assets change with time. Sometimes these equations can be very difficult to solve and require long computer calculations for an accurate answer. In this study we look at one of the solution methods and work an approximation for what is normally the slowest part of the calculation. This may help improve the speed of these types of solution methods and allow banks to employ more realistic valuation equations.
Contact: Dr David Stump, National Australia Bank, 32/500 Bourke Street, MELBOURNE 3000, Australia

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