The Government has announced that the teaching of evolution will be a legal requirement in science teaching at primary schools from September 2011, although it will be left to schools to decide how it is done.

The new curriculum is to include a requirement “to investigate and explain how plants and animals are ‘interdependent’ and are diverse and adapted to their environment by natural selection”.

The move is particularly notable as it comes despite a drive to slim down the national curriculum for primary schools and leave teachers greater discretion over what to teach. The consultation on proposals to loosen the number of formal topics was however seen as an opportunity by scientific campaigners, and lead to a popular and successful e-petition to Downing Street calling for evolution to be included on the national curriculum.

The BBC today highlights an interesting new theory to explain why trees in Europe tend to produce yellow leaves in autumn, whilst those in America and eastern Asia produce red leaves.

Various theories for why leaves change colour have been proposed over the last decade, although the evidence for many has been inconclusive. One suggestion is that different coloured leaves serve to deter insect predators. Red leaves may signal to potential predators that the leaves contain higher concentrations of toxins, or that they are about to die. Indeed, one review of 262 tree species showed that those with red colours had a long evolutionary history with aphids, which try to lay their eggs on the trees in autumn.

This does not however explain why Europe has more trees with yellow leaves, but a review of leaf colour and its causes by two botanists suggests that the series of ice ages which began in the Tertiary Period may form part of the answer. They suggest that all temperate forests initially had the ability to produce red leaves, having evolved from tropical trees which frequently produce such a colour. However, from about 35 million years ago, the series of ice ages which covered much of Europe and North America meant that plants could often only survive in southern refuges. Whereas North America and East Asia have mountain ridges that run north to south, allowing red-leafed trees to migrate south into refugia where they survived, in Europe, the mountain ranges run east to west. This meant that any red-leafed trees north of the mountains were trapped, and went extinct. Moreover, the selective agents of herbivory that caused red leaves went extinct too, resulting in lower selection for red pigments amongst the trees which recolonised Europe.

Further support for this hypothesis comes from the fact that dwarf shrubs with red leaves, rather than trees, dominate the northern parts of Scandinavia. Such low-lying shrubs may have been able to better survive the cold conditions than the trees above them.

For further information please see:
Lev-Yadun, S., & Holopainen, J.K., ‘Why red-dominated autumn leaves in America and yellow-dominated autumn leaves in Northern Europe?’

The biggest ever exhibition on the life and work of Charles Darwin has today opened at the Natural History Museum in London.

Highlights of the exhibition, which is on until 19 April 2009, include rare specimens of Galapagos mockingbirds, never before displayed, which were instrumental in the development of Darwin’s thinking on the theory of evolution whilst on the HMS Beagle. Other exhibits include live specimens and a recreation of Darwin’s study at Down House in Kent.

2009 marks the 200th anniversary of Darwin’s birth and the 150th anniversary of the publication of ‘On the Origin of Species’, and this is the first of a number of events which will run over the course of the next year marking these important milestones. Find out more about these at the ‘Darwin 200′ website.

Dishonesty in ecology, as a policy for deterring potential rivals, has not been thought of as a common strategy across the animal kingdom until recently.

Dishonesty has been a long-standing conundrum in evolutionary ecology. Previously, well-respected researchers such as Harper & Maynard Smith (2003) and Zahavi (1975) have conceded that cheating is unlikely to evolve as an effective strategy because of the costs of producing dishonest signals. However, new research published in the British Ecological Society’s Functional Ecology journal sheds light on how animals can feign their fighting prowess.

Research focusing on fiddler crabs Uca mjoebergi – so-called because when waving their oversized claw to a female they appear to be playing a fiddle – suggests dishonesty could be much more widespread than previously thought. The research is all the more exciting because, by definition dishonesty is notoriously hard to detect.

There are around 100 species of fiddler crabs world wide, and they tend to live in mangrove swamps and mudflats.

Fiddler crabs provide a good model species to resolve the question of whether armaments, such as claws, are capable of being dishonest. This is because they possess an overtly enlarged claw, not only used in battle to defend territories but to assess fighting ability prior to an encounter, in order to prevent a costly fight. The claw is also used by females to identify high quality partners, so there is a two-fold advantage to possessing an oversized claw in terms of signalling.

The lead author of the research Simon Lailvaux from the Australian National University said: “By studying exactly how animals fight, and what physiological and performance capacities enable males to win fights, we’re getting closer to identifying which traits are likely to be generally important for male combat. Honest signalling is important for several reasons, primarily because it’s important that fights don’t always escalate into bloody violence.”

If male fiddler crabs lose a claw in battle, they are able to regenerate a new claw. The potential for cheating lies in their ability to produce a new claw that is similar in size and impressiveness to the previous claw, but lacking in equivalent strength and effectiveness when fighting.

The researchers pitted males caught from the wild against each other under controlled laboratory conditions, to determine the effectiveness of original vs. regenerated claws in signalling (deterring a rival male from fighting) and fighting (defeating a rival male). Losers of encounters between rival males left the territory, making it easy to identify the victor.

The researchers found that, although size was generally correlated with strength and fighting ability, weaker regenerated claws did not perform as well as original claws in fights.

Lailvaux said: “Males with regenerated claws can ‘bluff’ their fighting ability, like bluffing in a poker game. They’re not good fighters, but the deceptive appearance of their claw allows them to convince other males that it’s not worth picking a fight with them. “

This research also exposes the cost associated with bearing a dishonest signal. Generally, males tend to challenge other males of similar claw size. When males are forced to defend intruders possessing a strong original claw from burrows , the bluff is exposed and they tend to lose. There is also possibly an evolutionary pressure to keep cheating to a minimum, as has been documented in yeast (Greig and Travisano 2004). Since dishonest males are in the overwhelming minority (~7% of the study population), there is clearly sufficient scope for them to get away with it.

Source: Simon P Lailvaux, Leeann T Reaney and Patricia R Y Backwell (2008).
Dishonesty signalling of fighting ability and multiple performance
traits in the fiddler crab Uca mjoebergi. Functional Ecology, doi:
10.1111/j.1365-2435.2008.01501.x, is published online on 12 November 2008.

References:

Greig D., andTravisano, M., 2007, The Prisoner’s Dilemma and polymorphism in yeast SUC genes, Proceedings of the Royal Society B, Vol 271, pp 25-26

Harper, D. & Maynard Smith, J. (2003) Animal Signals. Oxford University
Press, Oxford.

Zahavi, A. (1975) Mate selection: a selection for a handicap. Journal of
Theoretical Biology, 53, 205–214.