The island of Luzon in the Philippines has the greatest concentration of unique animals, say scientists, adding that evolution is not always a question of ‘survival of the fittest’ but sometimes a case of a fortunate animal finding ‘any port in a storm’. Luzon even beats Madagascar as far as the concentration of unique mammals is concerned.
The Conversation explains that islands have frequently been cited as examples of an evolutionary free for all, where new arrivals find themselves in the perfect situation, either because the place has no predators or competitors, or the habitat and resources are ideal for a particular species.
Previously ‘mediocre’ mainland species can become spectacular and wonderful new creations when they arrive at a new island ecosystem.
The largest island of the Philippines – Luzon – has the world’s greatest concentration of unique mammals. These are mammals that exist only on the island, and nowhere else on Earth. (Right) Coloured pencil illustration of cloud rats, some of the mammals found only on Luzon. (Image: fieldmuseum.org. Credit: Velizar Simeonovski)
Many mammal species unique to one island
There are many mammal species today that exist on one island and nowhere else in the world – they are known as island endemics. Madagascar has some lemurs that exist nowhere else on Earth, while the flightless cormorants of the Galapagos Islands can only be found there. In the Isles of Scilly, off the coast of Cornwall, England, there are some weird species exclusive to the area.
Let us not forget the Orkney vole, a common vole found in the Orkney Islands off the northern coast of Scotland. They are larger than voles from other parts of the world and occur nowhere else on the planet.
Unusual adaptations occur on islands
Not only are islands a melting pot for new mammal species, as well as other forms of life, they are also responsible for some unusual adaptations, often allowing species to develop physically in ways that would never have occurred had they remained on the mainland.
This is perhaps best demonstrated by the island rule which, when all complicated bits are taken away, means that all large species become small and vice versa – all small ones become big.
Many of Luzon’s larger mammals are unique to the island and have evolved differently from their counterparts in other regions of the world. (Image: fieldmuseum.org)
The island rule is a hypothesis whereby smaller mammals evolve bigger size on islands while large insular mammals shrink. The rule is believed to emanate from the smaller mammals growing bigger to control more resources and enhance metabolic efficiency, while big mammals evolve smaller size to reduce resource requirements and increase reproductive output.
Look at the dwarf humans and dwarf elephants in Indonesia and a long time ago in the Mediterranean respectively. Examples of small creatures that became giants are the tortoises from Ecuador and Madagascar that washed up in the Galapagos and Seychelles respectively, and thrived as the Goliaths of their species.
Many scientists see islands as nature’s evolutionary labs, where natural selection simply goes nuts. However, even between islands, some are more remarkable than others.
A team of scientists from the Field Museum in Chicago has published details of their study and findings in Froniers of Biogeography (citation below), the scientific magazine of the International Biogeography Society, where they looked for the world’s largest concentration of unique animal species.
The largest island in the Philippines – Luzon – it turned out, came top of the list. After fifteen years – that was how long the study lasted – they concluded that out of fifty-six species of mammals on the island, excluding bats, a total of fifty-two were found to be endemic. Ninety-three percent of the island’s non-flying animals are unique to Luzon, you cannot find them anywhere else on Earth – the island is a biological treasure trove.
Project leader, Lawrence Heaney, the Negaunee Curator of Mammals at The Field Museum in Chicago, said:
“We started our study on Luzon in 2000 because we knew at the time that most of the native mammal species on the island were unique to the island, and we wanted to understand why that is the case. We did not expect that we would double the number already known.”
Unless drastic action is taken now, Luzon’s beautiful small mammals, many of which are unique to the island, face a bleak future due to loss of habitat, pollution and hunting. (Image: fieldmuseum.org)
Luzon is big and never touched the mainland
We know that virtually all islands are special for the emergence and development of new species, so what makes Luzon so spectacular? The scientists believe it is due to the island’s size – it is larger than Cuba or Iceland, covering an area of over 40,000 square miles – plus the fact that it has never been connected to the mainland.
With abundant space – in different habitats – and across a very long period, Luzon has given many colonizing animals just the right ingredients to adapt and evolve into new and unique species.
Luzon is much bigger and at least five times older than Hawaii’s oldest island, so it has had time for the few species that arrived from the mainland to evolve and diversify extensively.
For creatures that swam across from other islands, or were swept over on rafts of palm trees or mangroves, it was the ideal opportunity not only to adapt into new species themselves, but then for these novel species to diversify into even more species.
— Mental Floss (@mental_floss) 15 July 2016
Isolated pockets with Luzon itself
There were even isolated pockets within the island itself, what the scientists described as forest-covered mountains that acted as sky islands. These were separate ecosystems which were cut off from the land at lower altitudes, with different evolutionary pressures.
From unusual-looking mice that prey mainly on earthworms, to other rodents with long elegant whiskers which stretch the entire length of their bodies, Luzon is a fantastic example of island evolution.
Co-author, Eric Rickart, who is based at the Natural History Museum of Utah, said:
“All 28 of the species we discovered during the project are members of two branches on the tree of life that are confined to the Philippines. There are individual mountains on Luzon that have five species of mammals that live nowhere else.”
“That’s more unique species on one mountain than live in any country in continental Europe. The concentration of unique biodiversity in the Philippines is really staggering.”
— Lyanne Blu (@LyanneBelleBlu) 17 May 2016
Unfortunately, these ecosystems are extremely fragile – it does not take much for them to deteriorate rapidly and push many creatures to the verge of extinction.
Goats were introduced to Galapagos – these animals compete with the giant tortoises for food, in fact, they are better at it. Snakes, which were accidentally taken to Guam, are destroying the island’s delicate ecosystem. Birds in Guam had never seen a snake before.
Add to this the threat we bring with hunting, pollution, and the ever-growing problems of climate change, and the future for many of these island species looks bleak. If we are serious about preventing hundreds of unique species from going extinct in these beautiful islands across the world, we need to start helping them now.
Co-author Danny Balete, a Research Associate at the Field Museum, who is based in the Philippines, said:
“We also wanted to learn more about the conservation status of these wonderful animals. The Philippines is one of the most heavily deforested countries in the tropics; only about seven percent of the old-growth tropical forest is left. We learned that quite a few of the species are seriously threatened by habitat loss and over-hunting, but none are yet extinct.”
Fifty million humans live on the island of Luzon, including about 23 million in the country’s capital, greater Manila.
“Protecting all of these species from extinction is going to be a big challenge. The good news is that when the native forest is allowed to regenerate, the native mammals move back in, and the pest rats get kicked out.”
Citation: “Doubling diversity: a cautionary tale of previously unsuspected mammalian diversity on a tropical oceanic island,” Heaney, Lawrence Richard, Balete, Danilo S., Duya, Mariano Roy M., Duya, Melizar V., Jansa, Sharon A. and Steppan, Scott J. Frontiers of Biogeography 8.2, e29667. Publication 2016.
Video – Luzon Bleeding Heart Dove
The Luzon Bleeding Heart is a type of dove that can only be found in the island of Luzon. It gets its name from a reddish hue that extends down the body, furthering the illusion of blood having run down its breast.