{"id":4232,"date":"2022-05-26T22:00:00","date_gmt":"2022-05-26T22:00:00","guid":{"rendered":"https:\/\/modernsciences.org\/staging\/4414\/?p=4232"},"modified":"2022-05-12T08:01:52","modified_gmt":"2022-05-12T08:01:52","slug":"a-tug-of-war-between-survival-and-fitness-how-chameleons-become-even-brighter-without-predators-around","status":"publish","type":"post","link":"https:\/\/modernsciences.org\/staging\/4414\/a-tug-of-war-between-survival-and-fitness-how-chameleons-become-even-brighter-without-predators-around\/","title":{"rendered":"A tug of war between survival and fitness: how chameleons become even brighter without predators around"},"content":{"rendered":"\n
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\n \n Martin Whiting<\/span>, Author provided<\/span><\/span>\n <\/figcaption>\n <\/figure>\n\nMartin Whiting<\/a>, Macquarie University<\/a><\/em><\/span>\n\n

Invasive species offer a rare research opportunity, as they often colonise new environments very different to their native habitat. One such species is the Jackson\u2019s three-horned chameleon (Triocerus j. xantholophus<\/em>), which was accidentally introduced to the Hawaiian Islands in the 1970s. <\/p>\n\n

Our study, published today<\/a> in Science Advances, shows Hawaiian chameleons display much brighter social signals than individuals from their native habitat range in East Africa \u2013 and could represent an example of rapid evolution. <\/p>\n\n

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\n A male Jackson\u2019s three-horned chameleon (above) courting a female (below) in Kenya.<\/span>\n Martin Whiting.<\/span><\/span>\n <\/figcaption>\n <\/figure>\n\n

A long way from home<\/h2>\n\n

In 1972, about 36 Jackson\u2019s chameleons made their way from their native Kenya to the Hawaiian island of Oahu, destined for the pet trade.<\/p>\n\n

The chameleons were a little worse for wear by the time they arrived in Hawaii, following a long and taxing journey that would have begun days before they were loaded onto the plane in Nairobi.<\/p>\n\n

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\n Invasive chameleons have made it to the Hawaiian islands \u2013 the world\u2019s most isolated island archipelago.<\/span>\n Wikimedia Commons<\/span><\/span>\n <\/figcaption>\n <\/figure>\n\n

The story goes<\/a> that an Oahu pet shop owner, Robin Ventura, opened the crate in his garden to give them fresh air and an opportunity to recover. Presumably, he underestimated the speed with which chameleons can move (and recover) \u2013 and they quickly dispersed into the surrounding area.<\/p>\n\n

This founding population represented an accidental invasion, and subsequently became an unplanned experiment in evolution. What happens when an animal with colourful social displays \u2013 from a population with lots of bird and snake predators \u2013 is introduced to an island virtually free of predators? <\/p>\n\n\n\n

Evolution in action?<\/h2>\n\n

We predicted Hawaiian chameleons, as a result of being relatively free from predation, would have more elaborate or brighter displays than their Kenyan counterparts. We also predicted they would be more conspicuous when viewed by their East African predators, such as birds and snakes.<\/p>\n\n

In the animal kingdom, bright or colourful displays can attract the attention of sharp-eyed predators. This reduces an individual animal\u2019s likelihood of survival and, by extension, its reproductive fitness (or the number of genes it passes on to future generations). <\/p>\n\n

When survival is threatened, natural selection<\/a> acts as a brake and halts the further elaboration of colour, or shifts bright colours to areas of the body less visible to predators. <\/p>\n\n

For instance, many lizard species have bright colours concealed on their undersides or throats. In South Africa, male Augrabies flat lizards will signal to rival males by raising their underside and exposing the throat, which is puffed out.<\/p>\n\n

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\n Many lizard species, such as this Augrabies flat lizard, have bright colours on body parts that are less visible to predators such as birds.<\/span>\n Martin Whiting<\/span><\/span>\n <\/figcaption>\n <\/figure>\n\n

On the other hand, conspicuous displays may also increase fitness. For example, brighter or more colourful males may gain greater access to females, either by winning contests with rival males, or simply appearing more attractive to females.<\/p>\n\n

This tug of war between survival and fitness is well documented in species with fixed or seasonally dependent colouration. For instance, guppies<\/a> become less colourful when dangerous predators share their streams. However, it\u2019s less understood in animals with dynamic colour change such as chameleons. <\/p>\n\n

Although we have a good understanding of how chameleons change colour<\/a>, we don\u2019t know if they modulate their displays when there are more predators in their environment. It may also be that natural selection prevents them from producing colour signals that are colourful or bright beyond a certain threshold.<\/p>\n\n

To test our predictions, we travelled to Kenya and Hawaii to study colour change in wild chameleons.<\/p>\n\n

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