FORTY YEARS OF GENECOLOGY
176
where it occurs Clausen and Hiesey interpret it as evidence of hybridization.
Another example of a Californian species with vicarious, ecologically
specialized subspecies is that of Gilia capitata. G . capitata is a polytypic
species with a natural range extending from central California to
British Columbia. Following an intensive study of population samples
from various parts of the range, both as acquired in the wild and in
comparative cultivation, Grant (1950, 1952, 1954) has concluded that
eight recognizable entities worthy of taxonomic recognition as subspecies
are present. Except for subsp. abrotanifolia and pedemontana which have
overlapping ranges, these subspecies replace each other geographically
in a pattern related to both the north-south climatic gradient of the
Pacific coast and the east-west gradient from the coast towards the
interior. Grant recognizes two basic types within the complex, subsp.
capitata, a plant of rocky hillsides, and the two subspecies chamissonis
and staminea, plants of sand dunes or sand plains. These may have had a
common parentage in subsp. abrotanifolia. With subsp. tomentosa,
subsp. capitata forms a pair of ecotypic vicariads, tomentosa maritime
and capitata inland; similarly subsp. chamissonis and staminea can be
looked upon as a pair of ecotypes, one coastal, the other inland. The
remaining races may have arisen through introgressive hybridization
between the primary subspecies. Their success, according to Grant, has
resulted because “ecological opportunities” were available to hybrid
types. Their populations are thus also ecologically differentiated. As
with Potentilla glanddosa, the overall pattern outlined by Grant for
Cilia capitata is one of comparatively stable ecological races extending
over very considerable areas. Within the subspecies, however, he describes several examples of “inter-colonial” variation, in some cases extending to such characters as seed germination and flowering time. The
possibility of clinal variation in the character of glandulosity in subsp.
capitata is also considered. Grant does not attribute ecological significance to this local variation, but it is possible that more intensive study
might show its adaptive character.
In the shrubby California genus Ceanothus, Nobs (1963) describes
“species equivalent to ecotypes” in the section Cerastes. They are accepted as taxonomic species because of their morphological distinctness,
and “the genetic basis of their differentiation and subsequent stabilization . . . revolves primarily on the coherence of the genotypes balanced
against the selective pressures of the natural environments”. All are
completely interfertile in experimental crossings. I n the area north of
San Francisco Bay, where eleven of these “species” occur, the majority
“are geographically separated, and coincide in distribution with changes
in ecological habitats, especially with soil type”. In general, where the
176
where it occurs Clausen and Hiesey interpret it as evidence of hybridization.
Another example of a Californian species with vicarious, ecologically
specialized subspecies is that of Gilia capitata. G . capitata is a polytypic
species with a natural range extending from central California to
British Columbia. Following an intensive study of population samples
from various parts of the range, both as acquired in the wild and in
comparative cultivation, Grant (1950, 1952, 1954) has concluded that
eight recognizable entities worthy of taxonomic recognition as subspecies
are present. Except for subsp. abrotanifolia and pedemontana which have
overlapping ranges, these subspecies replace each other geographically
in a pattern related to both the north-south climatic gradient of the
Pacific coast and the east-west gradient from the coast towards the
interior. Grant recognizes two basic types within the complex, subsp.
capitata, a plant of rocky hillsides, and the two subspecies chamissonis
and staminea, plants of sand dunes or sand plains. These may have had a
common parentage in subsp. abrotanifolia. With subsp. tomentosa,
subsp. capitata forms a pair of ecotypic vicariads, tomentosa maritime
and capitata inland; similarly subsp. chamissonis and staminea can be
looked upon as a pair of ecotypes, one coastal, the other inland. The
remaining races may have arisen through introgressive hybridization
between the primary subspecies. Their success, according to Grant, has
resulted because “ecological opportunities” were available to hybrid
types. Their populations are thus also ecologically differentiated. As
with Potentilla glanddosa, the overall pattern outlined by Grant for
Cilia capitata is one of comparatively stable ecological races extending
over very considerable areas. Within the subspecies, however, he describes several examples of “inter-colonial” variation, in some cases extending to such characters as seed germination and flowering time. The
possibility of clinal variation in the character of glandulosity in subsp.
capitata is also considered. Grant does not attribute ecological significance to this local variation, but it is possible that more intensive study
might show its adaptive character.
In the shrubby California genus Ceanothus, Nobs (1963) describes
“species equivalent to ecotypes” in the section Cerastes. They are accepted as taxonomic species because of their morphological distinctness,
and “the genetic basis of their differentiation and subsequent stabilization . . . revolves primarily on the coherence of the genotypes balanced
against the selective pressures of the natural environments”. All are
completely interfertile in experimental crossings. I n the area north of
San Francisco Bay, where eleven of these “species” occur, the majority
“are geographically separated, and coincide in distribution with changes
in ecological habitats, especially with soil type”. In general, where the