MACROEVOLUTIONARY ACCESSIBILITY IN TAXONOMIC AND PHENOTYPIC SPACES

The accessibility structure of phenotype spaces in macroevolution is best envisioned as being determined by a variety of causal mappings onto phenotype space, which complement standard genetic mappings. Such mappings may call for causes at different scales and hierarchical levels, be they intrinsic or extrinsic, nomothetic or contingent, at the level of characters and organisms or at the level of species and clades. Within species, genealogical continuity depends on heritability stricto sensu, and relates directly to the genotype-phenotype map and its structure. At and above the species level, genealogical continuity, as well as phenomenological identity, depend on heritability lato sensu. This means that the causal structure of the genotype-phenotype map is necessary but not sufficient to explain the full range of macroevolutionary phenomena.