162
J. HESLOP-HARRISON
continued up to the present (Clausen, 1951; Clausen et al., 1940, 1948;
Faegri, 1937; Gregor, 1939, 1944, 1946a, b, 1956; Gregor and Watson,
1954, 1961; Langlet, 1959, 1963; Sinskaia, 19311, and the immediately
succeeding paragraphs survey some of the background.
C. ECOTYPES OR ECOCLINES?
For reference to graded variation within populations or population
systems of organisms the useful word cline is available, introduced by
Huxley ( 1938) as.an “auxiliary taxonomic concept”. “Cline” unqualified
implies simply the existence of a variational gradient; the prefix ecoindicates that the gradient can be correlated with an environmental
variable.
The well known researches of Gregor and his associates on Plantago
maritima (Gregor et at., 1936, 1950; Gregor, 1938, 1939) revealed several
types of graded inter-population variation, including some which was
evidently ecologically correlated. I n the discussion of his paper of 1938
and in his review of 1944, Gregor considered various genetical, ecological
and taxonomical aspects of such variation, and subsequent work has
confirmed the general validity of most of his conclusions. The cline concept is extensively used by Gregor in the recording of graded variation.
Geographical clines (which may have an ecological basis where the variation is correlated with regional changes of climate) he refers to as
topoclines; where the variation can be associated with the stages of an
ecological sequence (which may never appear as an actual physical range
of habitats to be encountered in a transect between two geographical
points), it is referred to as an ecocline. Gregor emphasizes the need
always to consider ecological variation in relation to the habitat range of
species viewed as a continuum rather than as a complex of discrete nonoverlapping environments ; this leads him to the view that the ecotype
must be imagined subjectively “as a certain range of variation on a
genotypic gradient selectively developed in response to a climatic,
edaphic, biotic, or for that matter any environmental gradient we may
choose to examine”. The Plantago data contain examples of quantitative
characteristics - growth habit, scape length, spike density - which
follow the environmental gradient waterlogged-mud drained “saltings”.
For reference purposes Gregor divided the populations into three ranges:
predominantly decumbent, ascending, and erect, which he referred to as
ecotypes. This treatment illustrates his attitude towards the use of the
term ecotype : that it should be employed in a subjective sense to refer
to “certain populations belonging to an ecocline”. The definitions of
certain terms concerned with infraspecific variation advocated by
Gregor in 1939 were:
J. HESLOP-HARRISON
continued up to the present (Clausen, 1951; Clausen et al., 1940, 1948;
Faegri, 1937; Gregor, 1939, 1944, 1946a, b, 1956; Gregor and Watson,
1954, 1961; Langlet, 1959, 1963; Sinskaia, 19311, and the immediately
succeeding paragraphs survey some of the background.
C. ECOTYPES OR ECOCLINES?
For reference to graded variation within populations or population
systems of organisms the useful word cline is available, introduced by
Huxley ( 1938) as.an “auxiliary taxonomic concept”. “Cline” unqualified
implies simply the existence of a variational gradient; the prefix ecoindicates that the gradient can be correlated with an environmental
variable.
The well known researches of Gregor and his associates on Plantago
maritima (Gregor et at., 1936, 1950; Gregor, 1938, 1939) revealed several
types of graded inter-population variation, including some which was
evidently ecologically correlated. I n the discussion of his paper of 1938
and in his review of 1944, Gregor considered various genetical, ecological
and taxonomical aspects of such variation, and subsequent work has
confirmed the general validity of most of his conclusions. The cline concept is extensively used by Gregor in the recording of graded variation.
Geographical clines (which may have an ecological basis where the variation is correlated with regional changes of climate) he refers to as
topoclines; where the variation can be associated with the stages of an
ecological sequence (which may never appear as an actual physical range
of habitats to be encountered in a transect between two geographical
points), it is referred to as an ecocline. Gregor emphasizes the need
always to consider ecological variation in relation to the habitat range of
species viewed as a continuum rather than as a complex of discrete nonoverlapping environments ; this leads him to the view that the ecotype
must be imagined subjectively “as a certain range of variation on a
genotypic gradient selectively developed in response to a climatic,
edaphic, biotic, or for that matter any environmental gradient we may
choose to examine”. The Plantago data contain examples of quantitative
characteristics - growth habit, scape length, spike density - which
follow the environmental gradient waterlogged-mud drained “saltings”.
For reference purposes Gregor divided the populations into three ranges:
predominantly decumbent, ascending, and erect, which he referred to as
ecotypes. This treatment illustrates his attitude towards the use of the
term ecotype : that it should be employed in a subjective sense to refer
to “certain populations belonging to an ecocline”. The definitions of
certain terms concerned with infraspecific variation advocated by
Gregor in 1939 were: