164
J. HESLOP-HARRISON
two populations are identical in composition, and they are composed of
individuals scarcely two of which belong to the same biotype. Although
the individuals and the populations vary, the races are statistically and
reactionally distinct.” (Clausen et al., 1948, p. 122.)
The viewpoints of Gregor’s and Clausen’s school represent, in a sense,
the poles of opinion in the period prior to 1950. Before reviewing more
recent work, we w i l l consider some methodological problems concerned
in the analysis and interpretation of infraspecific diversification.
D. GENECOLOGICAL CATEGORIES
Turesson’s view of the nature of infraspecific ecological differentiation
led him eventually to treat the ecotype as a form of classificatory
category, and to appIy a nomenclatural system comparable with that of
orthodox taxonomy. I n this, the ecotypes were named according to their
habitat predilections - oecotypus alpinus, oecotypus arenarius etc.
(Turesson, 1925). There is undoubtedly a strong psychological compulsion to attempt to systematize knowledge of infraspeciflc ecological
variation by this kind of classificatory approach, and the existence of
orthodox taxonomy as a model encourages the direct transfer of
methods. Yet it is now quite apparent that systems based upon the
construction of discrete classes are inadequate to accommodate the
diversity of genecological data, even if the additional flexibility of a.
hierarchical arrangement (“ecotypes within ecotypes”) is permitted.
The view that “ecoclines represent the ecological subcategories” has
been expressed by Gregor (1944). It is obvious that the “subcategory”
envisaged here is different in kind from any orthodox taxonomic unit,
since the basis of definition is not character correlation, within a real or
imagined population, as it is for example with all the categories of
nomenclatural taxonomy, but a selected trend of character variation
viewed in relation to an extrinsic factor, either position on the earth’s
surface or ecological distribution. There is a sense in which an ecocline
can be looked upon as a classificatory unit, when it denotes “a series of
habitat populations showing genotypic gradation related to a particular
environmental gradient” (Gregor, 1944) ; this usage would bring to-.
gether a group of populations because of a particular relationship with
each other in the same way that a group of populations may be classed
together in a regional subspecies. The criteria for the grouping together
are, however, obviously different : with the subspecies similarity is what
is significant among the populations, with the ecocline, a particular
pattern of difference. There are in any event good reasons for not thinking of ecoclines as classificatory units in the “group of populations”
sense, the most compelling being that one and the same local population
may contribute to different ecoclines. The essential fact about an eco-
J. HESLOP-HARRISON
two populations are identical in composition, and they are composed of
individuals scarcely two of which belong to the same biotype. Although
the individuals and the populations vary, the races are statistically and
reactionally distinct.” (Clausen et al., 1948, p. 122.)
The viewpoints of Gregor’s and Clausen’s school represent, in a sense,
the poles of opinion in the period prior to 1950. Before reviewing more
recent work, we w i l l consider some methodological problems concerned
in the analysis and interpretation of infraspecific diversification.
D. GENECOLOGICAL CATEGORIES
Turesson’s view of the nature of infraspecific ecological differentiation
led him eventually to treat the ecotype as a form of classificatory
category, and to appIy a nomenclatural system comparable with that of
orthodox taxonomy. I n this, the ecotypes were named according to their
habitat predilections - oecotypus alpinus, oecotypus arenarius etc.
(Turesson, 1925). There is undoubtedly a strong psychological compulsion to attempt to systematize knowledge of infraspeciflc ecological
variation by this kind of classificatory approach, and the existence of
orthodox taxonomy as a model encourages the direct transfer of
methods. Yet it is now quite apparent that systems based upon the
construction of discrete classes are inadequate to accommodate the
diversity of genecological data, even if the additional flexibility of a.
hierarchical arrangement (“ecotypes within ecotypes”) is permitted.
The view that “ecoclines represent the ecological subcategories” has
been expressed by Gregor (1944). It is obvious that the “subcategory”
envisaged here is different in kind from any orthodox taxonomic unit,
since the basis of definition is not character correlation, within a real or
imagined population, as it is for example with all the categories of
nomenclatural taxonomy, but a selected trend of character variation
viewed in relation to an extrinsic factor, either position on the earth’s
surface or ecological distribution. There is a sense in which an ecocline
can be looked upon as a classificatory unit, when it denotes “a series of
habitat populations showing genotypic gradation related to a particular
environmental gradient” (Gregor, 1944) ; this usage would bring to-.
gether a group of populations because of a particular relationship with
each other in the same way that a group of populations may be classed
together in a regional subspecies. The criteria for the grouping together
are, however, obviously different : with the subspecies similarity is what
is significant among the populations, with the ecocline, a particular
pattern of difference. There are in any event good reasons for not thinking of ecoclines as classificatory units in the “group of populations”
sense, the most compelling being that one and the same local population
may contribute to different ecoclines. The essential fact about an eco-