186
J. HESLOP-HARRISON
tions. These differences need not, of course, be related to habitat differences within the eighty sites. To test for genecological differentiation,
Harberd grouped the sites into seven variants of the Agrostis-Festuca
community, in the series flushed -+leached. Differences significant at the
1 yo level between the grouped samples were found in only four species
characteristics. In Carex caryophyllea, leaf length differed significantly
between the groups, and this character showed a relationship with the
position of the site in the series, shorter leaves coming from the more
flushed sites. In P Q ~
trivialis, a trend in flowering time was associated
with the site-group series, flowering being later in the flushed sites. I n
Fatuca rubra and F. ovim, differences were observed which did not
relate satisfactorily to the habitat series. In F . rubra, Harberd considers
the observed difference could have arisen from reduplication of genotypes between the sampling sites; he offers no explanation for the
anomalous result with F . ovina. Flowering time in Cerastium vulgatum
was found to be correlated significantly with the position of the site in
the ecological series, although the character did not reach significance in
the site-group comparison. This investigation provides a convincing
demonstration of the value of extensive sampling methods in genecology,
since the design of the programme permitted a clear distinction to be
made between fortuitous inter-population variation and that which is
likely to be of genecological significance.
Ehrendorfer (1953), in a study on a geographical scale similar to that
of Harberd, detected genecological differentiation within an essentially
continuous population of Galium pumilum. The plant community was
Arrhenatherum meadowland, within which various facies could be
recognized according to aspect, exposure and soil moisture. The ten
sampling sites could be placed in four groups, from warm, dry, open to
cool, moist, shaded. The incidence of hairiness was found to vary
markedly between the groups, the proportion of hairy individuals in the
samples falling progressively from 55 in the driest habitat to 19 in the
dampest. Since hairiness is determined by a single dominant gene, this is
an example of ratio ecocline. Observations made in the field showed that
flowering was earlier on the average in the drier sites. Although the
differences in this feature between the sample sites were likely to have
been determined in part by direct environmental effects, Ehrendorfer
found some association between hairiness and precocity, suggesting that
some of the variation between sites in flowering time was genetically
based.
Although many of the published studies of genecological differentiation in the Californian flora have emphasized the large scale, regional
patterns, there have been examples of investigations on a more local
scale, and some have offered comparative data. Thus Grant’s analysis of
J. HESLOP-HARRISON
tions. These differences need not, of course, be related to habitat differences within the eighty sites. To test for genecological differentiation,
Harberd grouped the sites into seven variants of the Agrostis-Festuca
community, in the series flushed -+leached. Differences significant at the
1 yo level between the grouped samples were found in only four species
characteristics. In Carex caryophyllea, leaf length differed significantly
between the groups, and this character showed a relationship with the
position of the site in the series, shorter leaves coming from the more
flushed sites. In P Q ~
trivialis, a trend in flowering time was associated
with the site-group series, flowering being later in the flushed sites. I n
Fatuca rubra and F. ovim, differences were observed which did not
relate satisfactorily to the habitat series. In F . rubra, Harberd considers
the observed difference could have arisen from reduplication of genotypes between the sampling sites; he offers no explanation for the
anomalous result with F . ovina. Flowering time in Cerastium vulgatum
was found to be correlated significantly with the position of the site in
the ecological series, although the character did not reach significance in
the site-group comparison. This investigation provides a convincing
demonstration of the value of extensive sampling methods in genecology,
since the design of the programme permitted a clear distinction to be
made between fortuitous inter-population variation and that which is
likely to be of genecological significance.
Ehrendorfer (1953), in a study on a geographical scale similar to that
of Harberd, detected genecological differentiation within an essentially
continuous population of Galium pumilum. The plant community was
Arrhenatherum meadowland, within which various facies could be
recognized according to aspect, exposure and soil moisture. The ten
sampling sites could be placed in four groups, from warm, dry, open to
cool, moist, shaded. The incidence of hairiness was found to vary
markedly between the groups, the proportion of hairy individuals in the
samples falling progressively from 55 in the driest habitat to 19 in the
dampest. Since hairiness is determined by a single dominant gene, this is
an example of ratio ecocline. Observations made in the field showed that
flowering was earlier on the average in the drier sites. Although the
differences in this feature between the sample sites were likely to have
been determined in part by direct environmental effects, Ehrendorfer
found some association between hairiness and precocity, suggesting that
some of the variation between sites in flowering time was genetically
based.
Although many of the published studies of genecological differentiation in the Californian flora have emphasized the large scale, regional
patterns, there have been examples of investigations on a more local
scale, and some have offered comparative data. Thus Grant’s analysis of