Reassessing Those Rattlers | Research Frontiers.One of the indispensable dogmas of creationism in its desperate attempt to fool people into thinking the Theory of Evolution is fatally flawed is that 'microevolution' and 'macroevolution' are different things needing different processes to explain them. 'Microevolution' is supposedly the evolution of variation, varieties, races, subspecies etc, while 'macroevolution' is supposedly the evolution of a new species.
Until quite recently, creationists were required to believe that evolution simply didn't happen, full stop. A magic man supposedly created everything exactly as it is today just a few thousand years ago, so evolution never happened.
Unfortunately, because that dogma was based on a literal interpretation of the Bible, the brighter creationists began to realise they also had to allow for the legend about everything being drowned in a global flood about 4000 years ago, apart from a pair of each species which survived on a boat; everything alive today coming from those few survivors.
Of course, this was easier when Earth was small and the few animals all lived within a few days walk of Noah's house. If you're not familiar with the Abrahamic religions, Christianity, Judaism and Islam, perhaps I should explain that this is the sort of childish thing they have to believe. I kid you not!
We are able to see that these different subspecies, which have different habits, live in different areas and have other different characteristics, have heads that have been shaped differently over evolutionary time.
Anyway, the frauds who keep them supplied with the disinformation they crave for about what the science actually is and what it shows, had to come up with something to 'explain' to their scientifically illiterate dupes how so many different varieties of each species could have arised from just one pair of each species in such a short time. Pretending they had all been on the boat was becoming untenable, even to creationists.Mark A. Davis, Author. (quoted in ScienceDaily)
The daft notion they have recently come up with is that evolution, which they used to say was impossible, is now possible at massively higher rates than science shows it to occur. Each species, almost immediately it got off the boat, and with nothing to eat on a sterile planet, started evolving at warp speed to produce lots of different regional varieties, subspecies, etc. Apparently too, this all happened before anyone noticed it and recorded it, because creationists still insist no-one has ever seen evolution happening.
To explain all this, they have had to invent the infantile parody of evolution where a new species would require the 'impossible' type of evolution, 'macroevolution'; the one which occurred at warp speed when no-one was looking, 'microevolution', was well capable of producing all the subspecies, varieties, races, etc.
So, pieces of research like that done by a team from the University of Kansas, USA, led by Michael Douglas, is a little bit of a shock to them. It shows there is no difference at all in the mechanism which leads to new subspecies and that which leads to new species. Actually, the distinction is often so blurred and indistinct it requires very detailed genetic analysis to decide whether two variations are different species or merely different subspecies.
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Operational Taxonomic Units in the Western Rattlesnake Complex. The Western Rattlesnake, historically composed of 9 subspecies (sensu Klauber), displays a level of phenotypic variability that is concomitant with its vast geographic range in North America. This variability is captured in the following images, identified to subspecies and location, and published with permission of the photographer (as indicated). Subspecies are as follows (from left to right, top to bottom): Crotalus cerberus (Pinal County AZ: Martin Feldner); C. oreganus (San Luis Obispo County CA: Martin Feldner); C. o. helleri (Los Angeles County CA: Martin Feldner); C. o. caliginis (San Coronado Island, Baja California: Rob Olivier); C. o. concolor (Coconino County AZ: Martin Feldner); C. o. lutosus (Mohave County AZ: Martin Feldner); C. o. abyssus (Coconino County AZ: Martin Feldner); C. viridis viridis (Harding County SD: Mark Davis); C. v. nuntius (Coconino County AZ: William Wells).* |
Abstract
Morphological data are a conduit for the recognition and description of species, and their acquisition has recently been broadened by geometric morphometric (GM) approaches that co-join the collection of digital data with exploratory ‘big data’ analytics. We employed this approach to dissect the Western Rattlesnake (Crotalus viridis) species-complex in North America, currently partitioned by mitochondrial (mt)DNA analyses into eastern and western lineages (two and seven subspecies, respectively). The GM data (i.e., 33 dorsal and 50 lateral head landmarks) were gleaned from 2,824 individuals located in 10 museum collections. We also downloaded and concatenated sequences for six mtDNA genes from the NCBI GenBank database. GM analyses revealed significant head shape differences attributable to size and subspecies-designation (but not their interactions). Pairwise shape distances among subspecies were significantly greater than those derived from ancestral character states via squared-change parsimony, with the greatest differences separating those most closely related. This, in turn, suggests the potential for historic character displacement as a diversifying force in the complex. All subspecies, save one, were significantly differentiated in a Bayesian discriminant function analysis (DFA), regardless of whether our priors were uniform or informative (i.e., mtDNA data). Finally, shape differences among sister-clades were significantly greater than expected by chance alone under a Brownian model of evolution, promoting the hypothesis that selection rather than drift was the driving force in the evolution of the complex. Lastly, we combine head shape and mtDNA data so as to derived an integrative taxonomy that produced robust boundaries for six OTUs (operational taxonomic units) of the C. viridis complex. We suggest these boundaries are concomitant with species-status and subsequently provide a relevant nomenclature for its recognition and representation.*
The woolliness of the definition of 'species' is alluded to in the introduction to this paper:
Discussion
Evolutionary history of the Western Rattlesnake
Despite two centuries of accumulating evidence, a comprehensive and formal reevaluation of Western Rattlesnake taxonomy has been slow to emerge. This reticence has been driven largely by three distinct, interrelated factors: (1) a long-standing disagreement over species concepts; (2) the convoluted history of this particular complex; and (3) an “essential tension” separating taxonomy and systematics. The first two are most relevant to our discussion and are parsed below.
By consensus, ‘species concepts’ represent the assumptions necessary for the recognition of morphological and genetic gaps among species. While these concepts do not delineate the gaps themselves, they provide a framework to interpret observed patterns, with the underlying premise that most, but not all, represent our attempts to explain or decipher how species came to be. This situation has been a source of confusion in that it conflates pattern with process. Our tact herein is to delineate gaps that correctly identify species rather than ponder mechanisms underlying the diversification.
The convoluted taxonomic history of the Western Rattlesnake complex is epitomized by the fact that no fewer than seven junior synonyms, 11 synonymizations, and 11 subspecific epithets have been applied to encompass its diversity. Fossil evidence for the complex is first recorded from the Late Pliocene and extends through Late Pleistocene. Molecular genetic data suggested a mid-Cenozoic origin, concomitant with the Neogene uplift of the North American Cordillera presumably promoting the separation of eastern and western lineages, followed by constrictions and isolations within refugia during Pleistocene that drove additional differentiation within each. Shallow genetic divergence and relatively low diversity were manifested in subsequent radiations, resulting in species boundaries being obscured by incomplete lineage sorting and ancestral polymorphism. Both are artifacts prevalent in geologically recent and rapid diversifications, and they promote incongruent phylogenies and misinterpreted diversities when molecular data are used to derive taxonomic hypotheses. [citations omitted for clarity]*
So from this, is should be clear that, whatever infantile parody of the science creationist frauds are using to mislead their dupes with, the decision taxonomists use to determine whether different forms of a genus are different species, different subspecies, different varieties, etc, has nothing whatever to do with there being entirely different mechanisms; one possible and able to progress at several new species per generation, or an impossible one, prohibited in some way by the laws of physics and chemistry.
In fact, all that taxonomists are concerned about is whether naturally-isolated gene pools exists and whether these differ substantially from one another so as to inhibit interbreeding when populations come into contact. The latter would, of course, mean there is not a naturally-isolated genepool.
*© 2016 Davis et al. Reprinted under the terms of the Creative Commons Attribution License, (CC-BY 4.0)
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