Posted on 11/08/2007 2:05:43 PM PST by blam
When Animals Evolve On Islands, Size Doesn't Matter
ScienceDaily (Nov. 8, 2007) — A theory explaining the evolution of giant rodents, miniature elephants, and even miniature humans on islands has been called into questions by new research.
The new study refutes the 'island rule' which says that in island environments small mammals such as rodents tend to evolve to be larger, and large mammals such as elephants tend to evolve to be smaller, with the original size of the species being the key determining factor in these changes. (Credit: iStockphoto/Andy Diamond)
The new study refutes the 'island rule' which says that in island environments small mammals such as rodents tend to evolve to be larger, and large mammals such as elephants tend to evolve to be smaller, with the original size of the species being the key determining factor in these changes.
The new research findings suggest that the tendency to either evolve larger or smaller on islands varies from one group of species to another, irrespective of original size. The research team, from Imperial College London, suspect instead that a number of external factors, including the physical environment of the particular island, the availability of prey, the presence of predators and the presence of competing species all play a role in determining the size evolution of island mammals.
Dr Shai Meiri from the NERC Centre for Population Biology at Imperial College London, lead author on the paper, explains: "If the island rule was correct, then most large mammals living on islands would be smaller than their continental relatives, and most small island mammals would be larger those living on continents. Our large dataset of mammal body sizes shows that this isn't the case: there is evidence that most mammal groups show no tendency to consistently either grow larger or smaller, in contradiction to the island rule."
Dr Meiri, who carried out the work with Professor Andy Purvis and Natalie Cooper from the College's Department of Life Sciences, added: "The island rule suggests that the smallest mammals such as mice will exhibit the most evolutionary growth on islands, whilst the largest mammals like elephants will dwarf the most, with all mammals in between on a sliding-scale.
"Our analyses showed this isn't the case, and the relationship between mammal size and evolutionary size change on islands is not that straightforward. Crucially, when we examined size change in light of the evolutionary relationship between different species, there was no connection between an evolution towards large size and greater degree of dwarfism on islands, or between evolution towards small size and island gigantism."
The research team concluded that although there does appear to be a weak correlation between the size of a mammal and how its size then evolves in an island habitat, this reflects some groups' specific tendencies towards gigantism or dwarfism, and not the general course of evolution. "The course of size evolution is dependent on a complex interplay of many other factors, that have led to the evolution of fascinating miniature and giant species of mammals on islands," concludes Dr Meiri.
This research was published November 7, 2007 in the Proceedings of the Royal Society B: Biological Sciences.
Adapted from materials provided by Imperial College London.
5...4...3....
Sadly, the actual count was -1. The Democrats get to play "Keep Away" with our lunches once again.
In theology, this would fall under ‘presuppositional apologetics’.
IANAB (...biologist), but I think it's more a matter of natural selection going weird in a situation of small sample size. That's why New Zealand, to take one example, got the three-eyed lizard, the six-foot earthworm that glows in the dark, and the alpine parrot that has an IQ higher than most politicians.
Sounds like the bar scene in Star Wars. :-)
Beautiful bird. The Kea pictures.
Aren’t pygmies from that island called Africa?
And just how will this knowledge change the world for the better???
The "biggist lie perpetrated [up]on mankind" is the idea that stupid, insane, and dishonest people are as likely to be correct as those who are intelligent, rational, and honest, because "everyone is entitled to their own opinion".
Tachyeres brachypterus is the flightless Steamer Duck...there is a flying Steamer Duck:
http://www.arthurgrosset.com/sabirds/flyingsteamer-duck.html
Tachyeres patachonicus
The Flying Steamer-duck is distributed in southern Chile, the extreme south of Argentina, Tierra del Fuego and the Falkland Islands. It is the only steamer-duck that is found on inland water-bodies as well as at the coast...
I think they’re here.
http://www.damisela.com/zoo/ave/ratities/casuario/casuarius/indexe.htm
The Southern Cassowary (Casuarius casuarius) is natural of the coastal area to the northeast of Queensland, Australia. It is also present on low elevations regions of New Guinea and some of the smaller nearby islands. Usually stays at low elevations. This species is the one with southern most distribution among the three cassowaries, that is why it is called the “Southern Cassowary”.
The Southern Cassowary prefers the thick vegetations, such as the tropical jungles of forests.
Normally stays solitary and hidden inside the vegetation. It is hard to observe this bird in its natural habitat since it remains where the vegetation is abundant. Occasionally it comes out to clearings or the edges of the jungle, but never far into the opening. They have also been seeing crossing rivers swimming, which it can do rather well...
NEAT.
dinosaur footprints...
|
|
|||
Gods |
Thanks Blam. |
||
|
· Mirabilis · Texas AM Anthropology News · Yahoo Anthro & Archaeo · · History or Science & Nature Podcasts · Excerpt, or Link only? · cgk's list of ping lists · |
|||
Another ‘theory’ debunked!
Interesting! Evolution on islands is a great topic. I remember reading about lizards on different islands having the same morphology but different genomes. The explanation was that as the different founder populations spread into new environments they evolved the same set of characteristics in similar environments. Therefore even though all the mountain lizards populations looked alike they were genetically closer to the beach lizards on the same island than the mountain lizards on the next island.
Tell that to the females.
|
|
|||
Gods |
Just updating the GGG info, not sending a general distribution. |
||
|
· Discover · Nat Geographic · Texas AM Anthro News · Yahoo Anthro & Archaeo · Google · · The Archaeology Channel · Excerpt, or Link only? · cgk's list of ping lists · |
|||
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.