Hennig and Rosa and Croizat

[John Grehan]

I cannot add much on Rosa regarding the comments by Thomas Schlemmermeyer as I
cannot read French or Italian - the languages of Rosa's principal publication.
However, I can refer to an English translation by Giuseppe Sermonti of a
brief article by


Rosa published in Rivista di Biologia Biology Forum 81 (4)  613-615.

I reproduce a portion below:

This is a theory of evolution by internal causes, closely linked to that of
Naegeli. Its basic
statements are verbatim in the following:

1. The evolution of the specific idioplasm, apparent in the phylogenetic
evolution of the organisms, stems from both internal and external factors,
not necessarily requiring the variation of the latter, since it takes place
even if they are stable.

2. Also the direction of evolution is independent of variations in the
external factors.

3. The phylogenetic evolution is not however, rectilinear, but
(dichotomically) branched through differentiating divisions occurring in
the specific idioplasm as a result of a structure successively achieved in
the course of its evolution.

4. To these three statements an additional fourth should be added: in each
dichotomy (bifurcation) one of the produced phyletic line bears, in respect
to the other, the traits of a precocious line (linea precoce), the other
those of a tardy line(linea tardiva).

The above quotes are too limited for anyone to judge Rosa's entire work,
but may help give some insight into his theory. Rosa's mechanisms of
internal causes  may conform to that of orthogenesis - the concept of
evolution taking place without requiring differential reproduction.
Orthogenesis has been incorrectly circumscribed by Simpson, Mayr, Gould and
others as representing purposeful evolution or linear evolution. Neither
characterizations  are representative of the basic concept as developed by
most of its practitioners, and the concept may be related to that of
concerted evolution in molecular genetics. Croizat supported orthogenesis,
and in this respect  may have held a position related to that of Rosa.
Croizat also proposed widespread ancestors  for vicariant taxa, but may
have recognized a greater level of re-distribution than Rosa. Croizat
disagreed with Rosa and Hennig on speciation being primarily dichotomous .

Regarding the comment by Thomas that Croizat  contrasted with Hennig in
dealing primarily with distributions and not with organisms themselves, it
is true that Croizat's foundation was spatial biogeography, but he also
examined questions  of phylogeny, and organic evolution. Hennig also worked
on biogeography.