Posted on 08/23/2004 6:06:04 PM PDT by PatrickHenry
Being kicked out of its coral home may have forced the evolution of a new species of fish, say Australian scientists.
Research published in today's issue of the journal Current Biology provides more support for the idea that geographic isolation is not always needed for new species to develop.
Marine biologist, Dr Philip Munday of James Cook University in Townsville and team studied a new species of coral-dwelling goby fish found in southern Papua New Guinea to try and see how it evolved.
The most established doctrine of how new species form is that a group of organisms becomes separated and geographically isolated from the rest of a population.
But there is another idea that has been around, even since the time of Darwin, that a new species can arise without geographic isolation. This theory of sympatric speciation is controversial, not least because there have been few convincing cases.
The new species of coral-dwelling goby could have evolved according to the common wisdom, as the fish has a larval stage that spends time in the plankton and can easily float far away from the original population.
But there were other clues that suggested sympatric speciation was at work.
First, genetic studies showed the new species was a recent descendant of another species that lived on the same reef. The new species was estimated to have diverged from its ancestor between 200,000 and 700,000 years ago.
Second, the new species of goby inhabited a different species of coral not inhabited by the ancestral goby or any other goby species.
"Even though there are lots of fish that live on coral reefs, these particular gobies have a very intimate association with the corals," Munday told ABC Science Online. "They live among the branches of small coral colonies and they rely on them for shelter and breeding.
"They have to live in these corals to survive and they compete quite strongly for access to these corals."
Munday and team theorised that a group of ancestral gobies could have been essentially kicked out of their normal coral home and sought refuge in another species of coral that wasn't being used at the time.
"If they continued to colonise that coral there would be very little gene flow between the new fish and the ancestor, and the new environment would then select for traits that favoured its survival in the new coral," said Munday.
A third piece of evidence for sympatric speciation was the distribution of the new species, which appeared to be a small 'bullseye' at the centre of the range of the ancestral species.
"If this new species evolved from geographic isolation, you might expect that their ranges wouldn't overlap," said Munday.
Before this case, there had only been a few good examples of sympatric speciation, said Munday. One example involved leaf-eating insects which, like the coral-dwelling gobies, had very precise and close associations with their host.
Munday and team said it was possible that the new goby species arose from geographic isolation, but if it did, more steps would have been required.
First a part of the population of the ancestor would have to become geographically isolated, become established into a new species and changed its coral habitat. After that there would had to have been a shift in the new species' geographic range so it came back to a bullseye distribution at the centre of the range of the ancestor.
"There are other possibilities and we recognise that, this is probably just the simplest explanation," said Munday.
Is a Darwin Award appropriate here?
< |:)~
What is the difference between this goby and its ancestral goby? Future goby experts want to know.
No other fish could pay the rent. HAHAHA
I donno. I'm starting to realize that threads about fish -- even evo threads -- aren't very popular. Next time I'll stick with mammals. Dinosaurs are always good. Birds too. But not fish.
Maybe it's the sympatric speciation. What is that?
Aw...don't give up....Muttly appreciates these articles.
...even if they just make him hungry.
So does "Rades" :-)
The opposite of sympatic speciation is allopatric speciation, where new species form when a species is cut into subpopulations that are not in contact with each other (e.g., by the formation of a mountain range that geographically isolates populations). This is offered as an explanation for the lack of transitional forms in the fossil record: new species form in out-of-the-way, isolated regions; cut off from the main population. Imagine a mountain range forming, and isolating a subpopulation, which is subject to changing conditions and therefore adapts to the new conditions. A new species forms but is still isolated. But suppose conditions change, so a wide area is now hospitable to the new species. It will spread to the new area. This has the effect of making the new species suddenly appear in the fossil record (the relatively few transitional forms are only in a relatively limited geographical area, which may well have not been preserved in the fossil record).
Dinosaurs are so 4004 B.C!
Welcome to the science threads. :-)
So....those folks over at Liberty Post are forming separate species?
More accurately, new species form when their old DNA is changed.
What is in dispute is how, who, or what instigates such genetic reprogramming.
5 Legislative Days Left Until The AWB Expires
i love the part where they provide a half a million year span as a possible time for species deviation.
thats right up there with Kerry being "somewhere near Cambodia"
Thanks for the ping!
Similar but not quite the same as the difference between the Rockies and the Ancestral Rockies.
A new (or even a ring) species of bitter vetch probably wouldn't draw much attention either. (Except from Canadians with their "ers.")
Darwin suggested that, and it's a satisfactory explanation for both the scarcity of transitionals, and their "sudden" appearance. Satisfactory except to the 'noids, for whom only inexplicable explanations will suffice.
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