In article <2eq30h$dkr at controversy.math.lsa.umich.edu> Doug Eernisse
<Doug_Ee at um.cc.umich.edu> writes:
>> As an off-the-cuff response, you may want to distinguish between
> two concepts: 1) "macromutation" includes many varieties of mutations
> except for the long-known point- or frame-shift ("micro") mutations; and
> 2) "macroevolution" in which one is hypothesizing that species
> are evolving through time in a way that is decoupled from "microevolution,"
> or _any_ change within a single population or species. This gets into
As I understand it, macroevolution simply refers to the evolution of any large
phenotypic change. According to Futuyma, it is a vague term, but usually
refers to a change large enough to classify the lineage as a distinct genus.
The controversy between advocates of punctuated equilibrium and neo-darwinists
is whether macroevolutionary changes can be accounted for by microevolutionary
processes (i.e. by a gradual accumulation of many changes each with relatively
small effect) or if most macroevolutionary change is due to short bursts of
very rapid evolution, possibly incorporating changes of relatively large effect
or occurring by selection above the level of the population. That is, the
processes by which macroevolutionary changes occur are currently the subject of
debate.
> debate about whether or not there are "emergent" properties of species.
> Do we gain anything by distinguishing the organismal level at which
> selection occurs among individuals (microevolution) from the level
> at which selection occurs among species (macroevolution)? As far
> as I know, paleontologists such as Steve Stanley and S. J. Gould have
> been the chief proponents of a macroevolutionary view, but this doesn't
> have much to do with the magnitude of a mutational event.
>> Doug
Another off the cuff remark: In my book (unwritten and unedited), data which
link the evolution of new species or significantly novel phenotypes (e.g. new
organs or new enzyme pathways) to genetic changes within populations clearly is
important to the causes-of-macroevolution debate. This data won't often come
by studying the genetic differences between widely divergent taxa, but rather
will come from more closely related taxa. I'm not familiar with the corn
example that Ackerman requested an opinion on, but if the genetic change in
question makes a large contribution to the difference between zea and teosinte,
then it would seem important to the debate. Since the two lineages are
different genera, it might also fit in with definition found in Futuyma's text.
Of course the amount of difference it takes to make two taxa different genera
depends on the taxonomic group, the biases of the taxonomists, and in some
cases can be based on very little genetic change
--
John Bishop
Department of Botany
University of Washington, Seattle
bishopj at botany.washington.edu
