[Summary and Contents]
...Placental mammals have experienced unusually rapid evolution at both the chromosomal level and the organismal level, though not at the structural gene level. Hence, gene rearrangement may have a major role in organismal evolution, as Goldschmidt  suggested 35 years ago. Although the mechanism involved is not known, one possibility is that gene rearrangement provides new phenotypes by altering the patterns of gene expression during embryonic development. [Italics mine.]
As noted in the text, I do not doubt that the correlation between chromosomal evolution and phyletic evolution is real; but Dobzhansky (1941) and Mayr (1942), among others, quite rightfully buried Goldschmidt's monster as a plausible explanation for this correlation, and the monster should stay buried--at least until there is quite solid evidence from developmental biologists that any random major chromosomal rearrangement can lead with any significant probability to a selectively advantageous change in development. Certainly there is no evidence to date that this is so. We must therefore seek the causal basis for the relationship between evolution and chromosomal differentiation in the aspects of the genetic system which regulate a species phylogeny rather than its ontogeny.
Larsen and Tanner (1975) would remove 7 species from the small-scaled radiation to form the genus Lysoptychus, which would be primitive to the remaining Sceloporus but probably derived to most of the other sceloporines. Although I retain an open mind on the validity of this grouping, I will continue to follow Smith's (1939) dichotomy in the remaining discussion here. Larsen and Tanner (1974, 1-75) also present new phylogenetic interpretations for the remaining, non-Lysoptychus Sceloporus which are based on Larsen's (1973) multivariate statistical analyses of variation in Sceloporus. The approach offers useful insights, but I believe some of the phylogenetic interpretations to be fundamentally unsound:
My reasoning for these objections may be found in Hall (1973) and will be developed more fully in later papers which will deal in detail with the evolution of Sceloporus.
On two different trips I searched both the Carneros, Coahuila, and the Charcas, San Luis Potosi, localities for goldmani during good weather conditions, and I was unable to find it. At both localities, because of extreme overgrazing, there is no sign of more than a thin stubble of annual grass showing between the exposed stones. Certainly no bunch grass now exists anywhere near these localities that is accessible by road. Based on several attempts to find bunch-grass habitats anywhere in the region determined by the three known localities (in some cases quite far from any reasonably passable road), I fear that this species may now be extinct. The last confirmed specimen was collected in 1962 (Thomas and Dixon, 1976). In any event, given the ever increasing habitat destruction resulting from cattle and goat grazing, if it still does survive in some isolated montane pocket, extermination is still probably a foregone conclusion.
Cole (1970) suggests that the mutation may have been a tandem duplication.
The cytological quality of some of this material is poor and it is sometimes difficult to identify which metacentric is present in a mostly fissioned karyotype. The 4 FM2 individuals suspected to be heterozygous carriers of the metacentric 1 were all collected in or on the edge of the hybrid zone with S, and could easily be backcrosses. Except for these 4 individuals, all samples, especially those closest to FM1 populations were homozygous for the fission of pair 1.
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