EvC Forum: Ring Species!!

Hi drpepperandmilk, and welcome to the fray.

Re: How are ring species evidence for upward change?

"Upward change" is a meaningless term in biology. What do you really mean?

What is up?

You can’t substantiate a claim by saying you simply know something happened.

Nor can you rebut it with ignorance of the many examples.

quote:
Successive fossils in the Pelycodus fossil record show the gradual evolution of increased size, which can be recognized as a series of species. The coexistence of two simultaneous size trends indicates a speciation event.

Speciation happens, it has been observed in the fossil record, and it has been observed in the field and in the lab.

Take the Ensatina salamanders in CA. Indeed there was variation from one group to the next in color, size, with the ability to breed with neighboring groups remaining intact, until the end groups lost this tendency and had their opportunities to breed basically cut in half.

Curiously, this does not follow logically from the evidence. The salamanders are fairly dispersed within each area, and the opportunities that each individual has are related to the number of other individuals within mating distance. If every salamander lives with mating distance of 50 other individuals, there would be no difference in mating potential. If there was a difference at the edges of the areas inhabited by the salamanders that reduced this number, then this edge effect would apply to all salamanders along the edges, regardless of whether they were "end" varieties, "middle" varieties, or hybrid varieties.

Additionally, there is some evidence that the hybrid zones are small because interbreeding is less successful than breeding within a varietal population. There could be problems with compatibility and viability reducing the opportunities of these populations. For these individuals, they could be surrounded by 50 individual salamanders, but not all of them would qualify as potential mates or high on the list of choices (resulting in delayed of missed mating opportunities) and non-viable offspring could be a higher proportion than normal, thus resulting in less production from the opportunities that are accepted.

If this (ring species) is an example of how progressive changes occur in biological evolution, how do apparent small steps backward like this add up to big steps forward over time?

What's forward? What's backward? Evolution is change, there is no up\down forward\backward higher\lower.

Evolution is the change in hereditary traits in populations from generation to generation.

Speciation is the division of a parent population into reproductively isolated daughter populations.

The isolation is caused by the build up or different hereditary traits in the daughter populations until they don't interbreed.

Once the interbreeding link is broken -- as it is for ring species in spite of having some continued gene flow possible (subject to several generations and natural selection along the way) from one end to the other, the end species are different enough that breeding does not occur -- once the link is broken by a speciation event (as seen in pelycodus above) there is no constraint on the evolution of the daughter populations to remain similar.

Message 40

I'd like to know how the variation observed in ring species demonstrates the potential of MACRO changes, i.e. new major structures.

They demonstrate the potential for one population of similar organisms to become two populations of similar organisms that are different, one from the other, populations. Like exponential growth, this simple mechanism can produce significant differences in populations over time.

If you want to discuss "MACRO changes, i.e. new major structures" then this is not the thread for it.

Try MACROevolution vs MICROevolution - what is it? or Dogs will be Dogs will be ???

The lack of ability/inclination in the converging groups to breed seems to indicate that significant information from a finite gene pool was lost, not gained.

If you want to discuss "information" gain\loss then try Irreducible Complexity, Information Loss and Barry Hall's experiments

Enjoy.

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