Two Levels of Information in DNA: Relationship of Romanes' “Intrinsic” Variability of the Reproductive System, and Bateson's “Residue” to the Species-Dependent Component of the Base Composition, (C+G)%

The B in ‘BDM.’ William Bateson did not advocate a genic speciation theory

“…As these studies support the non-genic view that William Bateson expounded in the early decades of the twentieth century (Forsdyke, 1999(Forsdyke, , 2001(Forsdyke, , 2006, your readers may find it strange that Bateson's name is linked to the genic viewpoint of Dobzhansky and Muller. It is true that theirs is a model of interaction between genes, and that Bateson introduced the term 'epistasis' to describe such interactions.…”

Differences in (G+C) Content between Species: a Commentary on Forsdyke's “Chromosomal Viewpoint” of Speciation

“…(The reader should also note that the two components of an allopolyploid genome do not necessarily form tetravalents during meiosis.) Forsdyke (1999) states &&in the light of the present work it seems possible that the di!erences in (C#G)% would themselves be responsible for the isolation''; in fairness, he does not otherwise promote this cause-ande!ect relationship. Such an argument does not seem parsimonious when contrasted with a simpler model, whereby two genomes di!ering in chromosomal architecture, and coincidentally compositionally distinct, maintain compositional identities because insu$cient time has passed for organism-speci"c compositional biases to homogenize them toward the same compositional equilibrium.…”

“…Here, we challenge Forsdyke's suggestion that work on viruses, plants and yeasts supports the G#C model. Forsdyke (1999) discusses an article by Yin & Hu (1997) on retroviruses, writing, &&In certain virus species, however, signs of the initial isolation process may still exist. This, indeed, may be the case with two virus species whose members have the potential to coexist in the same host cell (Yin & Hu, 1997); here they would exert a selection pressure on each other to sustain and expand any di!erences which might prevent recombination (otherwise they would recombine and destroy each other as individual species)''.…”

“…&&Haldane's (1922) rule'' is the observation that when hybrids of one sex show a greater reduction in "tness than the other (either by reduced viability or reduced fertility), the less-"t sex is generally the heterogametic sex. Citing Coyne (1992), Forsdyke (1999) argues that convincing genic explanations for Haldane's rule have &&eluded everyone'', and that existing genic explanations must cope with &&adaptive valleys' and other problems''. This view, however, requires that one ignores work from the past 7 years that has led to broad agreement on two major genic explanations contributing to Haldane's rule.…”

“…Several lines of evidence have led researchers to believe that genic di!erences play a greater role in the initiation of the isolation process that leads to species formation (Coyne & Orr, 1998). In recent papers, Forsdyke (1996Forsdyke ( , 1999 argues that di!erences in genomic base composition (G#C content) can explain the initiation of new species formation. He further argues that alleged shortcomings in the genic model (that post-zygotic reproductive isolation between species re#ects genetic incompatibilities in the hybrid o!spring) can be addressed by incorporating the e!ect of G#C content into the &&chromosomal'' model.…”