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FORTY YEARS O F GENECOLOGY
“Cline, any gradation in measurable characters.
Topocline, a cline following a geographical gradient.
Ewcline, a cline apparently correlated with an observable ecological
gradient.
Topotype, a population in a geographical region possessing characters
differing from those of another region. A topotype may be extraclinal if it does not fall within a geographical gradient in character
expression, or intraclintll if it has reference to a particular range on
a geographical gradient.
Ecotype, a particular range on an ecocline.”
In Gregor’s usage of this period, then, ecoclines, rather than ecotypes
are to be regarded as representing the significant “ecological subcategories” of plant species.
The genecological work of the Carnegie group (Clausen et al., 1940,
1948, Clausen and Hiesey, 1958a) reveals a notably different outlook
upon infraspecific patterns of ecological differentiation. The study of
variation in Potentilla glandulosa along a transect across central California recorded in the publication of 1940 suggested a comparatively
simple pattern, the populations falling into morphologically distinguishable climatic ecotypes corresponding to the taxonomic subspecies typica,
reJEexa, hanseni and nevadensis. Although these are in a sense ecoclinal in
that their distribution is related to a climatic gradient, they were interpreted by Clausen et al., as population complexes replacing each other
geographically in rather an abrupt manner, not at all comparable with
the “ranges on ecoclines” envisaged by Gregor. An emphasis upon the
distinctness of these major intraspecific groupings is a feature of the
earlier publication; it also appears in that of 1948 devoted to the
Achillea millefolium complex, although here a somewhat different situation is described. The populations sampled across the same California
transect were regarded as belonging to eleven distinct climatic races (“or
ecotypes”), four of the hexaploid A. borealis and the remainder of the
tetraploid A . lanulosa. The races of A. lanulosa from the western slope of
the Sierra Nevada are said to form “a graded altitudinal series that
shows the close interrelationships between the physiological characteristics of the races and their environments”; they thus form an ecocline
in the sense of Gregor. However, while for Gregor the ecotype is no more
than an arbitrary section of an ecocline, the climatic race within
Achillea is considered by Clausen et al. to be a coherent entity, distinct
from others. It is described as follows: “Each climatic race consists of
many local populations possessing in common those characteristics
essential for survival in their particular environmental zone. Similarity
in essential characteristics does not preclude individual variability. No
FORTY YEARS O F GENECOLOGY
“Cline, any gradation in measurable characters.
Topocline, a cline following a geographical gradient.
Ewcline, a cline apparently correlated with an observable ecological
gradient.
Topotype, a population in a geographical region possessing characters
differing from those of another region. A topotype may be extraclinal if it does not fall within a geographical gradient in character
expression, or intraclintll if it has reference to a particular range on
a geographical gradient.
Ecotype, a particular range on an ecocline.”
In Gregor’s usage of this period, then, ecoclines, rather than ecotypes
are to be regarded as representing the significant “ecological subcategories” of plant species.
The genecological work of the Carnegie group (Clausen et al., 1940,
1948, Clausen and Hiesey, 1958a) reveals a notably different outlook
upon infraspecific patterns of ecological differentiation. The study of
variation in Potentilla glandulosa along a transect across central California recorded in the publication of 1940 suggested a comparatively
simple pattern, the populations falling into morphologically distinguishable climatic ecotypes corresponding to the taxonomic subspecies typica,
reJEexa, hanseni and nevadensis. Although these are in a sense ecoclinal in
that their distribution is related to a climatic gradient, they were interpreted by Clausen et al., as population complexes replacing each other
geographically in rather an abrupt manner, not at all comparable with
the “ranges on ecoclines” envisaged by Gregor. An emphasis upon the
distinctness of these major intraspecific groupings is a feature of the
earlier publication; it also appears in that of 1948 devoted to the
Achillea millefolium complex, although here a somewhat different situation is described. The populations sampled across the same California
transect were regarded as belonging to eleven distinct climatic races (“or
ecotypes”), four of the hexaploid A. borealis and the remainder of the
tetraploid A . lanulosa. The races of A. lanulosa from the western slope of
the Sierra Nevada are said to form “a graded altitudinal series that
shows the close interrelationships between the physiological characteristics of the races and their environments”; they thus form an ecocline
in the sense of Gregor. However, while for Gregor the ecotype is no more
than an arbitrary section of an ecocline, the climatic race within
Achillea is considered by Clausen et al. to be a coherent entity, distinct
from others. It is described as follows: “Each climatic race consists of
many local populations possessing in common those characteristics
essential for survival in their particular environmental zone. Similarity
in essential characteristics does not preclude individual variability. No