Embed Size (px)
Citation preview
Duncan's critique of Matsuda'
ROY DOUGLAS PEARSON Science and Medicine Library, Universilj, of Toronto, 7 King's College Circsle, Toronto, Ont., Canada MSS IAS
Received September 1 2, 1985
PEARSON, R. D. 1985. Duncan's critique of Matsuda. Can. J . Zool. 63: 2982-2983. Although Duncan (K. W. Duncan. 1985. Can. J . Zool. 63: 2230-2232) holds, "there can be little point in taking Matsuda's
thesis seriously," this author argues that some of the ideas found in Matsuda's paper (R. Matsuda. 1982. Can. J. Zool. 60: 733-749) are actually a refinement of Waddington's notion of "genetic assimilation" by means of "canalization." The latter term implies not only the rigidity of the genotype but also its flexibility; it was this quality, plasticity, that Matsuda laboured to examine but that Duncan failed to appreciate.
PEARSON, R. D. 1985. Duncan's critique of Matsuda. Can. J . Zool. 63: 2982-2983. Bien que Duncan (K. W. Duncan. 1985. Can. J . Zool. 63: 2230-2232) soutienne qu'il n'y ait pas de raison de prendre
au serieux la thkse de Matsuda, il reconnait tout de m&me que certaines des idees avancees par Matsuda (R. Matsuda. 1982. Can. J . Zool. 60: 733-749) sont en fait le prolongement de la theorie de "l'assimilation genetique par canalisation" proposee par Waddington. Le terme de canalisation souligne non seulement la rigidid du genotype, mais aussi sa flexibilite; c'est justement cette caractkristique, la plasticite, que Matsuda a voulu mettre a I'epreuve, mais Duncan n'a pas SO l'apprkcier.
[Traduit par le journal]
A lifetime spent studying abnormal metamorphoses, life his- tories, comparative physiology, and endocrinology of arthro- pods has brought Matsuda to the view that changing environ- mental factors act upon known physiological processes of organisms, creating new regulatory genetic changes. In his 1982 review article, he posits that a changing environment alters endocrine processes, preadapting future generations with new developmental strategies. In this, Matsuda's work is a continuation of pioneering ideas of others such as Baldwin, Gause, Schmalhausen, and Waddington.
In Duncan's recent critique (1985) of Matsuda, his analysis suffers from some inaccuracy and occasionally misunder- standing. I would like to address a few of the more egregious errors.
For instance, I can find no denial by Matsuda of the possi- bility that terrestrial talitrids could have evolved directly from littoral or estuarine habitats. On the contrary, Duncan himself quotes a passage from the 1982 review in which Matsuda makes an allusion to this very possibility.
Duncan faults Matsuda for theorizing that terrestrial species have undergone a diminution in ecdysis frequency, an idea which has never been conclusively demonstrated. Wildish ( 1972) supports the same idea (p. 273):
'The markedly slow growth of 0. remyi rojfensis is caused by a decrease in moulting frequency rather than a reduction in length increment at each moult.
Duncan references a later article by Wildish (1979) in which the latter states (p. 18):
Life span estimates for the supralittoral species are all within 12- 18 moults, and show that slower growing species must expe- rience fewer moults per life span, and that they become sexually mature at a much earlier growth stage.
'K . W. Duncan. 1985. A critique of the concept of genetic assim- ilation as a mechanism in the evolution of the terrestrial talitrids (Amphipoda). Can. J . Zool. 63: 2230- 2232.
Duncan is clearly incorrect in his understanding of Matsuda's meaning when he paraphrases Matsuda's hypothesis that diminishing light "diminishes" (quoted from Duncan) the amount of androgenic hormone. Rather, Matsuda clearly states (p. 735):
The titer of androgenic hormone in the terrestrial talitrids would then become significantly higher than that in eulittoral and supra- littoral species . . .
As for the reason why the Collembola have many more moults than do their more advanced relatives, one must con- sider these insects ametabolous, i.e., undergoing no definitive metamorphosis as they continue to moult throughout their life- times. Thus, evolutionarily, they stand apart from the hemi- and holo-metabolous orders.
Reading Duncan's critique, I could not help but feel that his main incentive for writing was to defend Neo-Darwinian pan-selectionism. He even implies that "there can be little point in taking Matsuda's thesis seriously . . ." because it does not fit "traditional evolutionary theory." In a recent discussion with Matsuda, I pointed out that since characteristics produced by environmental-endocrinologic canalization (or "pan- environmentalism," Matsuda's term) are not acquired but preadaptive, his theory must transcend both Neo-Darwinism and Neo-Lamarckism. If this is so, it is wrong to measure Matsuda's theory using any traditional yardstick.
All of the life sciences depend on evolution for their foun- dation. Evolutionary theory, until quite recently, has largely been the domain of paleontologists, paleobiologists, popu- lation geneticists, and ecologists. Specialists from these disci- plines have recently shown a renewed interest in canalization, but have mostly focussed on constraints on development. To date, physiologists have had little impact on the evolutionary sciences. But it may well be physiologists who contribute the next significant chapters in the provisional synthesis of evolu- tionary theory by outlining the actual mechanisms of plasticity. If this is true, Matsuda will have prefaced an exciting era.
Can
. J. Z
ool.
Dow
nloa
ded
from
ww
w.n
rcre
sear
chpr
ess.
com
by
Dep
osito
ry S
ervi
ces
Prog
ram
on
11/1
2/14
For
pers
onal
use
onl
y.
COMMENT 2983
IUNCAN, K . W. 1985. A critique of the concept of genetic assimi- WILDISH, D. J . 1972. Post-embryonic growth and age in some lit- lation as a mechanism in the evolution of the terrestrial talitrids toral Orr-hestin (Amphipoda, Talitridae). Crustaceana Suppl. 3: ( Amphipoda). Can. J . Zool. 63: 2230-2232. 267 -274.
MATSUDA, R. 1983. 'The evolutionary process in talitrid amphipods --- 1979. Reproductive consequences of the terrestrial habitat and salamanders in changing environments, with a discussion of in Orc.he.stia. Int. J . Invertebr. Rep. 1: 9-20. "genetic assimilation" and some other evolutionary concepts. Can. J . Zool. 60: 733-749.
Can
. J. Z
ool.
Dow
nloa
ded
from
ww
w.n
rcre
sear
chpr
ess.
com
by
Dep
osito
ry S
ervi
ces
Prog
ram
on
11/1
2/14
For
pers
onal
use
onl
y.
