The Lion's Mane

The moment someone mentions a lion, the mind conjures up an image of a magnificent beast whose most prominent mark of identification is it's mane. Charles Darwin theorized that the lion's mane existed to dampen the blows received from attacks by conspecifics. He was also the first to categorize them as a social trait, considering that lions are the only cats with manes and the only social cat. It has remained a status symbol to most people, but for years it was thought to enhance the chances of mating - a sexual trait - a thick mane signifying the male's fighting ability and nutritional status. The thicker and darker the mane, the overall fitness of the male would be advertised well to opponents as well as to potential mates.

If the lion's mane evolved to protect the neck area from injury during fights with opponents, it would be a consistent trait among all populations of lions throughout their range. Lions found in some areas are known to have scanty or thin manes. Studies conducted by the Lion Research Centre, University of Minnesota, have found that there is no evidence to suggest the neck is the prime area of attack, hence evolution would not necessarily have confined a think mane to the neck region, and if it did then there would be a similar adaptation in the case of juveniles and females, as they too are involved in occassional bouts of ill-temper. Of course, their experiments to prove that the mane is a sexual trait were successful. It was found that females did prefer males with darker, thicker manes and the males with such manes had higher levels of testosterone. But it still did not explain the lack of manes in males found in other regions.

The thickness of the mane has one very serious drawback. In warm climates such as in the tropical sanctuary of Gir in India and in the lower elevation habitats for lions in Africa, the males would suffer from heat stress. Evolution then stepped in to take control. Lions in the lower elevation, warmer climes have very scanty manes, similar to those of the males found in India.

An ingenious study conducted on zoo animals throughout the United States showed that the thickness of the lion's mane is directly related to the temperature that it lives in. Colder the temperature, thicker the mane, luckier the male will be with the ladies. The study suggests that the condition of the mane has no relationship with social or sexual factors, or with genetics. Zoo animals in warmer climates lost their manes to avoid overheating their bodies. There is a theory that states that if global temperatures keep inceasing, then the males with luxurious, thick, black manes that one would image a lion as would become a thing of the past.

In a similar study across the African wilderness, it was found that lions developed manes according to the climatic conditions of the area. Lions in equatorial East Africa have varied mane thicknesses depending on the elevation of their habitat. The most beautiful, thick manes occurred in higher elevations and the condition of "manelessness" was found in populations inhabiting the lower elevations such as areas around Tsavo.

But there was a hitch. Paradoxically, some males in the Tsavo population who were not supposed to sport good manes were found to do so. In fact it was reported that the mane variation in this region crossed the entire spectrum, from almost no manes to the most luxurious manes. The latest study shows that the lion's mane continues to develop way after the individual has crossed it's sexual prime. Young lions were found to have lesser manes than the older ones, the mane continued to grow as the individual grew older. Lions in the age group of 3-7 years, the ones in their prime were found to have marginal manes, while the older classes possessed enviable manes. This can be theorized as being related to the temperature again. Young lions require all their potential to mate, they cannot afford any loss of energy through heat stress, hence the lesser manes. But as they grow and cannot compete in the sexual arena, the manes grow.

This topic was first discussed in 1833 by Capt. W. Smee - “On the maneless lion of Gujerat,” Proceedings of the Zoological Society of London; part 1, page 140, 1833.

This is still a debatable issue. On the one hand there is ample evidence that suggests the mane is more a sexual trait, while on the other groundbreaking research suggests a link to age. This cannot be concluded unless the condition of the lion's mane is studied throughout the range, including all subpopulations in Africa as well as in India. Scientists have also tried to link the lack of manes in some males to the baldness gene carried only by the males.

Technorati tags: lion's mane, sexual trait, genetic adaptation, heat stress, manelessness, age related

The Evolutionary Arms Race

We all know that crickets "sing" to enable them to locate their mates, their wings being their "singing" apparatus. Male crickets are provided with minute "teeth", like that in a comb, on the edge of their wings which when rubbed together make the familiar chirps. Each species, of course, has a different chirp, the species-specific song required so that the females of each species of cricket finds its corresponding mate, and not mate with that of another species. The result of this interspecific mating could be an infertile offspring. Evolution does not allow for the progress of a species in that respect, infertile offspring will essentially lead to the demise of the species itself over time.

What is very interesting is that on the island of Kauai, Hawaii, a particular species of field cricket (Teleogryllus oceanicus) has lost the ability to chirp. This is the latest news from the evolutionary front. It has been discovered by a group of scientists from the University of California, Riverside, that this species of cricket underwent a mutation, a heritable change in the genetic structure, only about 20 generations ago, which produced offspring with wings similar to that of the females (flat wings). 20 generations means the change took place approximately a decade ago, or maybe even less, depending on the life span of this species. This mutation occurred to ensure the males are not attacked by the parasitic fly that deposits its egg on the body of the cricket.

The lack of a chirp would mean that the cricket is unable to mate, the females would not be able to locate the males without the chirp, a trait that would essentially be evolutionarily harmful to the reproductive success of the species. But it has been ascertained that this species is mating successfully, suggesting that there is some change in their behavior that allows the females to locate the males, thus ensuring evolutionary success. The males have developed female-like wings and this is the case only on the island of Kauai, elsewhere the males of the same species have normal wings. It has been suggested that the "flatwing" males congregate near the few males that can call and manage to copulate. It is very suprising that a mutation which is evolutionarily harmful has spread so quickly through the population on the island.

But essentially this is how the evolutionary arms race works. One species develops a trait to escape from another and the second finds another to counter it. Given time, the parasitic fly might develop a trait that will help it detect the silent males. And so it will continue. If not the fly population on the island will be extinct, or the maggots would feed on the remaining males and the cricket population would disappear.

Wikipedia defines the evolutionary arms race as "an evolutionary struggle between competing sets of co-evolving genes that develop adaptations and counter-adaptations against each other". The most common examples come the predator-prey relationships, a cycle that tries to outdo one another, the prey trying to outdo the predator and vice-versa. Examples can be cited from the ancient trilobites, extinct segmented arthropods from the Cambrian period. They developed a hard outer exoskeleton when the marine habitats were getting increasingly dangerous and inhospitable. The exoskeleton protected them from the large number of predators that were roaming the seas then. Their cousins who lacked the hard outer shell failed to survive the Cambrian.

From more familiar examples, the story of the cuckoo and the wren is very popular. The cuckoo is a brood parasite, laying its eggs in the nests of other birds, allowing them to nourish the chick. The smaller bird fails to recognize a large food-guzzling chick in their nest as an outsider. But it has been discovered that there is a bird that can do so. A recent development in the "arms race". The superb fairy-wren in New South Wales, Australia, has developed the ability to recognize a cuckoo chick in it's nest and reject it. The cuckoo had developed the ability to mimic the egg of the wren, and the little bird learnt to counter that too. The suspicion starts when the wrens find only one large chick in the nest as it ejects all other natural inhabitants. What clinches the matter is the food call of the larger chick which is slightly different from that of the wrens'. Of course, after mimicking the egg of the cuckoo, the parasitic chick can develop the ability to mimic the begging call of the young wrens.

A lot of nature documentaries on television showcasing rainforest life tell of insects dependent on plants for food and shelter. In most cases, this dependence is harmful to the physical well-being of the plant. So plants that develop a chemical to counter the insect attack is favored by evolution. But this in turn stimulates the insect population to produce defence mechansims against that of the plant's, and the cycle will continue. Marine animals like some molluscs have developed hard shells and spines to protect them from predators such as crabs, but the predators themselves have claws and pincers to get to the flesh.

There will be no end to the evolutionary arms race, there will always be a struggle between species for the upper hand in survival. Survival of the toughest. Even between the members of the same species is there conflict, a tough competition for mates. The arms race comes into play during mate selection, too. The male (and in some cases the female) with the strongest traits will be selected by evolution, the weaker ones are eliminated. So as generations go by only the stronger individuals will survive the competition, the lesser ones will not see the origin of better and harder individuals that may ultimately evolve into a completely new species.

Technorati tags: evolution, evolutionary arms race, crickets, cricket chirps, mating, extinction, mutation, trilobites, brood parasite, plant-insect interaction

The Discovery of New Species

It is a known fact that the tropical ecosystems around the globe are the most diversity rich areas, be it on land or under the sea. Coral reefs and tropical rainforests hide the maximum number of species of plants and animals, most of which are yet to be discovered. Every year sees the discovery of new species from the Neoptropical forests, including primates, bats and insects. In an example cited by Bruce Patterson, the checklist of animals from around the world published in 1992, shows an average of 8 new species being discovered annually, in addition to one new genus per year. [article] If this be the rate of discovery from one ecoregion, then taking all into consideration every other ecoregion around the globe, the rate of discovery will be a phenomenal number.

Since a large number of mammals fall under the category of "megafauna", the media advertises their discovery, especially if they are found in areas that are threatened habitats. Take, for example, the new civet-like animal that was found in the heart of Borneo in December 2005. It received much media coverage considering it was a previously unknown species and that the area where it was first photographed is currently under threat. What goes unnoticed by the public are the discoveries made in small pools, or in rivers, where there are crustaceans waiting to be discovered, species of moths and butterflies in lesser known forests around the world, even fungi and algae in remote corners or in hard to access places. Large number of bacteria are being discovered in places that is inhospitable to most lifeforms. Even the discovery of fossil remains of some ancient species new to science goes unnoticed by the common people. Such discoveries find mention in research papers published by scientific publications, finding no room in popular media.

The significance of each of these discoveries lies in its evolutionary relationship with related species. When the fossil remains of the Archeoptryx was discovered it proved to be a huge leap in evolutionary science, finally was there an evolutionary link between the birds and the reptiles. Darwinism ruled. Earlier this year, the fossil remains of a new species of fish was found in northern Canada that was dubbed a "tetrapod fish", apparently the skeletal remains showed that it had jointed fins, and a ribcage that could support the body while it was being dragged on land, filling a part of the evolutionary gap between fish and land animals. This discovery was popularised in the US, the New York Times and the Washington Post wrote about it.

But coming back to the tropics. The density of diversity of plants and animals is mind-blowing and what is far more interesting than the numbers would be the number of species that are being discovered ever so often. The Tibetan macaque (Macaca thibetana) was discovered in 2003-2004 in Arunachal Pradesh by a team led by Dr. Anindya Sinha. December 2005 saw the discovery of the civet-like animal in Borneo, followed by a the discovery of a new species of honeyeater along with butterflies, frogs, palms and a large rhododendron in Indonesia. [article]

A few days ago, Indonesia was again in the headlines with 50 new species being discovered in an underwater Eden, amongst them is a shark that can "walk" or stand on its fins. [article] This could have a some significance when it comes to evoultion of the tetrapod. Another link between the fishes and land animals. The same day saw another Arunachal discovery, a new bird called Bugun Liocichla, a very colorful little bird, could be some sort of a babbler.

From predictions made through the years, these discoveries may just be the tip of the iceberg. Not only will the tropics call for more attention, but other ecosystems as well will have to be explored - dark abysses below the sea, hot springs and geothermal vents, spores lying dormant under polar ice, and even bacteria lying undiscovered in the stomach of a carcass-feeder. There is no limit to what this blue planet has to offer in terms of new species. Its the taxonomists who seem to have their work cut out for them. With each new discovery comes the task of placing the species in the right taxa or classifying them under new taxa if the need arises. This also means there will always be changes in the taxonomy of existing species. Biology has always been a science of changes and exceptions, and the natural world provides enough and more suprises.

Technorati tags: ecology, evolution, darwinism, new species, discovery, walking shark, Bugun Liocichla, Macaca thibetana

Aurva

I have always wondered about the pioneers of ecological sciences. Till maybe a decade ago this science was almost unheard of, but picked up on the popularity index quite fast with a lot of attention being given to it because of the deterioration to the environment. These pioneers had no academic training in ecology or environmental sciences, the bulk of them were engineers, if not from any other profession. Wildlife was a hobby, and they made a profession out of it. And their contribution to this science is tremendous.

There has been a lot of talk on the changes in human lifestyle, leading to global warming, climate change, illegal logging and destruction of forests and endangered species. But does the common man know enough to be interested in the environment? Considering that there are still a large number of people out there who are interested in wildlife and the ecological sciences as a hobby, but not as a profession, this seems to be a good place to start discussing the natural world. More and more youngsters are thinking out of the box and opting for academic degrees in this science.

Taking into account this surge of interest in wildlife biology and the environment, and equipped with an academic background in ecology, here will be published my take on what is happening in the field of ecology and wildlife. Not specifically for the professionals, but for anyone who remotely might find these issues interesting reading or worth discussing. I start this blog so that the lay person can read and hopefully understand, so that it may capture more people into the the community that wants the rest of the world to realize that its not all about research journals that are not available to the public, but that exclusive news and research too can reach the masses.

'Aurva', meaning related to the Earth!