Theory of Intelligent Design, the best explanation of Origins

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Theory of Intelligent Design, the best explanation of Origins » Theory of evolution » Primary, and secondary speciation

Primary, and secondary speciation

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1 Primary, and secondary speciation on Thu Jul 07, 2016 8:52 pm


Primary, and secondary speciation 1

there are observed instances of secondary speciation -- which is not what Darwinism needs -- but no observed instances of primary speciation, not even in bacteria. British bacteriologist Alan H. Linton looked for confirmed reports of primary speciation and concluded in 2001: "None exists in the literature claiming that one species has been shown to evolve into another. Bacteria, the simplest form of independent life, are ideal for this kind of study, with generation times of twenty to thirty minutes, and populations achieved after eighteen hours. But throughout 150 years of the science of bacteriology, there is no evidence that one species of bacteria has changed into another.

Observed cases of speciation by polyploidy are limited to flowering plants. 2 Furthermore, according to American evolutionary biologist Douglas J. Futuyma, polyploidy — known as “ secondary speciation ” — “ does not confer major new morphological characteristics” and does not cause the evolution of higher levels in the biological hierarchy. Darwinism depends on the splitting of one species into two, which then diverge and split and diverge and split, over and over again — a process known as “primary speciation”—to produce the branching-tree pattern required by Darwin’s theory.

Allopolyploidy, i.e. hybridization followed by chromosome doubling, is a frequent mode of secondary speciation in vascular plants (Leitch and Bennett 1997; Haufler 2008). 3The occurrence of diploids and their derived polyploids in the same area provides an excellent natural experiment to test the unique environmental responses that may exist across ploidy levels.

primary speciation : The splitting of one species into two, usually resulting from natural selection favoring different gene complexes in geographically isolated populations. 4

Evolution and Diversification of Land Plants page 296
Primary Speciation
Primary speciation has been used to encompass the most basic and commonly recognized ways of initiating new species, the divergence of diploid populations to the level of species. Having a clear and well-supported phylogeny for the group of taxa being studied is particularly important in developing hypotheses about primary speciation. Unless sister taxa are compared, erroneous conclusions about the processes involved will be obtained. Within this major mode are more specific categories including allopatric speciation, the divergence of populations to the species level through isolation by geographic separation, parapatric speciation, divergence of popUlations to the species level even though populations maintain contiguous but nonoverlapping geographic distributions, and sympatric speciation, divergence of populations to the species level even though the populations occupy the same geographic region. Given the complex biotic and behavioral interactions that have been associated with sympatric speciation [25] and the high probability that simple isolating mechanisms characterize pteridophytes, it seems unlikely that they speciate sympatrically at the diploid level.

Secondary Speciation
When it can be demonstrated that the speciation under investigation involved genomic-level changes, such as hybridization or polyploidy, a separate mode is proposed. The magnitude of genetic modification in secondary speciation often can be characterized, and it appears to be qualitatively different from that caused by the more incremental changes that are typical of primary speciation. Further, secondary speciation usually involves interactions between distinct and separate lineages that remain intact (autopolyploidy is the exception). These interactions result in the production of a new lineage that is reproductively isolated from its progenitors, shares significant portions of its genome with them, and is usually intermediate in morphology between them. Thus, instead of a single lineage evolving into two new lineages (as in primary speciation), two lineages interact to yield a third lineage, and all three lineages persist. Characterization of a variety of patterns provides circumstantial evidence of different kinds of secondary speciation. When different ploidy levels are detected among individuals that are morphologically uniform, autopolyploidy is suspected. Some summaries of speciation have used autopolyploidy as an example of "sympatric" speciation. However, autopolyploidy involves genome duplication, a mechanism that is quite different from those leading to the origin of diploid lineages. As reviewed by Gastony [34], speciation by chromosome doubling within pteridophyte species has been largely overlooked as a significant mechanism. In some groups, however, especially when accompanied by apomixis, autopolyploidy may occur frequently.


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