ERNST MAYR SPECIATION AND MACROEVOLUTION March 15, 1982
Kinds of Speciation: The term speciation has been used ambiguously throughout much of the history of evolutionary biology. For evolutionists in the vertical tradition, it meant phyletic speciation ( primary speciation), that is the transformation of one species into another one. For those in the horizontal tradition, it meant the multiplication of species ( allopatric, or secondary speciation), that is the establishment of separate populations that are incipient species.
Much of the current conflict about the validity of punctuated equilibria is actually the subconscious perpetuation of the old ambiguity as to what speciation really is. Some of those who support phyletic gradualism are still thinking in terms of phyletic speciation. There is now little doubt that, at least as far as animals are concerned, the prevailing mode of speciation is allopatric. I defined this in 1942 as follows: "A new species develops if a population which has become geographically isolated from its parental species acquires during this period of isolation characters which promote or guarantee reproductive isolation when the external barriers break down."
My comment: Mayr goes on to mention various kinds of speciation, namely: a) Sympatric speciation. b) Stasipatric speciation. c) Parapatric speciation. d) Peripatric speciation
When in a superspecies or species group there is a highly divergent population or taxon, it is invariably found in a peripherally isolated location. In many cases, when I traced a series of closely related allopatric species,
I found that the most distant, the most peripheral, species, was so distinct that ornithologists had described it as a separate genus or at least had not recognized at all its true relationship. In genus after genus I found the most peripheral species to be the most distinct. It is on this strictly the empirical, strictly observational basis that I proposed in 1954 my theory of peripatric speciation. My conclusion was that any drastic re-organization of the gene pool is far more easily accomplished in a small founder population than in any other kind of population. Indeed I was unable to find any evidence whatsoever of the occurrence of a drastic evolutionary acceleration and genetic reconstruction in widespread, populous species. When a drastic change occurs, it occurs in a relatively small and isolated population.
Genetically unbalanced populations may be ideally suited to shift into new niches such as will be available under the changed environmental conditions of the location of the founder population. 5. The genetic reorganization might be sufficiently drastic to have weakened genetic homeostasis sufficiently to facilitate the acquisition of morphological innovations. . The drastically different physical as well as the biotic environment of the founder population will exert greatly increased selection pressures. Since the early generations will be rather small, stochastic processes will play an important role in genetic reorganization. I concluded that the combination of
all these different factors might result in agenetic turnover that was by several orders of magnitude larger than that occurring in a normal deme that is part of a populous widespread species. I referred to such a drastic reorganization as a genetic revolution. My concept of the genetic revolution was based on the idea. of the genetic milieu of each gene. Since my ideas have often been misunderstood or misrepresented let me quote exactly from my 1954 paper: "Isolating a few individuals from a variable population . . . will produce a sudden change of the genetic environment of most loci. This change, in fact, is the most drastic genetic change . . .that may occur in a natural population, since it may affect all loci at once. Indeed, it may have the character of a veritable 'genetic revolution.' Furthermore, this 'genetic revolution,' released by the isolation of the founder population, may well have the character of a chain reaction. Changes in any locus will, in turn, affect the selective values at many other loci, until finally, the system has reached a new state of equilibrium."
My systematic studies of literally thousands of peripherally isolated populations during the preceding 25 years had shown me that such a drastic change occurs only very occasionally.
Those of us who for a long time have been on the road toward the explanation of speciation and evolution and who thought that we were nearing the goal now feel suddenly like the player in a parlor game who is told to go back to position zero. Indeed as far as our understanding of the genetics of speciation is concerned we are almost at position zero.
Since in eukaryotes virtually all the genetic material is located on the chromosomes, no one will question that the chromosomes are important in speciation, the only question being, in what way? Carson's Hawaiian
Drosophila shows that chromosomal reorganization is not a necessary condition for speciation. For 15 or more years various authors have speculated on the importance of speciation of regulatory genes (in analogy to the findings in prokaryotes) and there seems to be indeed a great deal of evidence for the role of such regulatory mechanisms.
My remark: This is a remarkable admission for a 1982 paper. Back then, already, it was known that the gene regulatory network has a decisive role in speciation, and not the genetic information "per sé". This was confirmed by Davidson many years later.
It erroneously assumes that change in protein-coding sequence is the basic cause of change in the developmental program, and it erroneously assumes that evolutionary change in body plan morphology occurs by a continuous process. All of these assumptions are basically counterfactual.
In 1997, evolutionary biologist Keith Stewart Thomson wrote: “A matter of unfinished business for biologists is the identification of evolution’s smoking gun,” and “the smoking gun of evolution is speciation, not local adaptation and differentiation of populations.”
Secondary speciation does not solve Darwin’s problem. Only primary speciation — the splitting of one species into two by natural selection — would be capable of producing the branching-tree pattern of Darwinian evolution. But no one has ever observed primary speciation. Evolution’s smoking gun has never been found. 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.”
There are observed instances of secondary speciation -- which is not what Darwinism needs -- but no observed instances of primary speciation, not even in bacteria.
The splitting of one species into two, usually resulting from natural selection favoring different gene complexes in geographically isolated populations.
the fusion through hybridization of two species that were formerly geographically isolated, followed by the establishment of a new adaptive norm ...
Secondary speciation in the genus level is possible, but at the family level and beyond is not. Organisms can evolve only up to different genera, but not different families.
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
PRIMARY AND SECONDARY TRANSITION ZONES IN SPECIATION AND POPULATION DIFFERENTIATION: A PHYLOGENETIC ANALYSIS OF RANGE EXPANSION
Phylogeography of speciation: Allopatric divergence and secondary contact between outcrossing and selfing Clarkia
There is a distinction between allopatric divergence (followed by secondary contact) versus primary intergradation (parapatric speciation) as alternative divergence histories.
Evolution and Diversification of Land Plants page 296
We have lots of evidence of secondary speciation. We have good reason to believe, for example, that all cats belong to the same created kind. A house cat can't breed with a lion, but it can breed with other small cat species, which can breed with other cat species, which could eventually breed with a lion. We can link all of the cat species (except the clouded leopard) together through a network of known hybrids. Not all of the known hybrids survived very long and many are infertile, but the fact that they can produce offspring shows a fundamental compatibility of the genomes and indicates that they came from a common ancestral stock. They belong to the same created kind. So if the 36 species of cats came from a common ancestral kind, then secondary speciation has occurred and done so multiple times. Something similar is true for the 7 species of equids (horses and donkeys), the 8 species of bears, and many other animal families.
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 and the high probability that simple isolating mechanisms characterize pteridophytes, it seems unlikely that they speciate sympatrically at the diploid level.
Theoretically, reproductive barriers arise when geographically separated populations diverge genetically. But Coyne describes five “cases of real-time speciation” that involve a different mechanism: chromosome doubling, or “polyploidy.” This usually follows hybridization between two existing plant species. Most hybrids are sterile because their mismatched chromosomes can’t separate properly to produce fertile pollen and ovaries; occasionally, however, the chromosomes in a hybrid spontaneously double, producing two perfectly matched sets and making reproduction possible. The result is a fertile plant that is reproductively isolated from the two parents — a new species, according to the BSC. But speciation by polyploidy (“secondary speciation”) has been observed only in plants. It does not provide evidence for Darwin’s theory that species originate through natural selection, nor for the neo-Darwinian theory of speciation by geographic separation and genetic divergence. Indeed, according to evolutionary biologist Douglas J. Futuyma, polyploidy “does not confer major new morphological characteristics… [and] does not cause the evolution of new genera” or higher levels in the biological hierarchy.
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 , 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.
5. Lindsay Marks Harold
First degree of speciation - Macro - Evolutionary claims are pseudo scientific
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