Work in Progress
I was not able to complete these investigations in time to include them in the dissertation. They are all intended for eventual publication.
- Eschscholzia californica ssp. californica has been thought to consist of both annual and perennial races (Cook, 1962; Hoover, 1970). Nevertheless, all the populations I have studied are able to perennate in the greenhouse, even though the plants may function as facultative annuals in the field. I have found no clear-cut dichotomy between annual and perennial growth, but rather a continuum from long-lived perennials to functional annuals which are short-lived even when perennating under greenhouse culture. Perhaps there are populations which are obligately annual in the greenhouse, but I have not yet found these.
Cook (1962) found a correlation between low stamen number and annual growth, but my observations do not substantiate this. Long-lived perennials of the Monterey Co. coast may have stamen numbers within the range of Cook's annuals, and the obligate annual ssp. mexicana sometimes has stamen numbers approaching the range of the perennials.
- "Four closely related species of Eschscholzia are restricted to the deserts of southwestern North America. E. parishii (n=6), E. covillei (n=12), and E. minutiflora (n=18) seem to constitute a polyploid series, although differences in gross morphology and seed coat microsculpturing suggest that E. parishii may differ somewhat from the original diploid ancestor. With increased chromosome number there is decreased flower size and greater adaptation for autogamy. E. glyptosperma (n=7) hybridizes experimentally with E. parishii and no other Eschscholzia. Meiotic analysis suggests that E. glyptosperma arose by a chromosome duplication; it may also differ from E. parishii by one or more translocations. E. glyptosperma seeds possess at maturity a dry, air-filled multiple epidermis which provides buoyancy and is clearly an adaptation for dispersal by runoff water. All three derivative species inhabit harsher climates than E. parishii, and E. glyptosperma and E. minutiflora are widespread (Clark, 1978)."
- Eschscholzia lemmonii and E. hypecoides were considered by Ernst (1964) to be closely related; in fact, plants of E. hypecoides have often been misidentified as E. lemmonii. The two species share nodding pubescent buds, more or less pubescent foliage, and distributions in the south Coast Ranges. The resemblances are more than superficial, however. I have hybridized the species in the greenhouse; the F1's have 20-70% pollen fertility. Meiosis in the hybrids is most often regular, with reduced pollen fertility most likely the result of low pairing frequency in many cells. In some cases bridges at I anaphase suggest that the species differ by an inversion.
Eschscholzia hypecoides is conspicuously restricted to open sites in the oak-digger pine woodland and related vegetation types, whereas E. lemmonii is common in grasslands and in drier and warmer sites in general. The two may represent sibling species which have diverged primarily through genetic changes to adapt to different environments.
- Eschscholzia caespitosa ssp. kernensis appears to be an only slightly aberrant E. lemmonii with erect and glabrous buds, but matching in all other features, including the seed coat microsculpturing, which is virtually identical to that of E. lemmonii and quite different from that of E. caespitosa. I did not see plants of the subspecies in the spring of 1978, but when they are found, experimental hybridization will likely confirm the relationship to E. lemmonii.
Potential Problems in the Genus
- The island endemics, E. ramosa, E. elegans, and E. palmeri, are poorly known. Eschscholzia palmeri is a very distinctive perennial subshrub with corky periderm. It seems quite distinct from the other two, or from any other Eschscholzia, but its tuberculate seeds resemble those reported for E. elegans (Greene, 1905; Part III). The following chromosome numbers have been reported: E. palmeri, n=11; E. ramosa, n=12; E. elegans, n=17 or 18 (Ernst, 1958; Raven, 1963). Eschscholzia ramosa and E. elegans seem to be closely related, and yet their seeds are quite different. It is also possible that first-year flowering individuals of the perennial species have been collected and described as annuals. Extensive study of living plants in the field and greenhouse is warranted if these species are to be understood.
- Eschscholzia caespitosa is a species perhaps as variable as E. californica, but much less well-known. Once again, study of living plants should provide meaningful data. The plants grow in widespread and often less accessible areas, so that an intensive study could prove somewhat difficult.
- Some populations of E. californica, in the driest part of its range, appear only in years of heavy rainfall. It would be interesting to determine what happens to them in the intervening years; seed longevity must be an important factor. Even more intriguing is my observation that in the good rainfall (and grass) year of 1978, populations of E. lemmonii which were present in the previous drought year were not to be found, their locations being covered with a meter-high "forest" of Avena and Bromus. Is there a mechanism for seed dormancy in wet years, or did the seeds germinate, only to be outcompeted by the grasses?
Clark, Curtis. 1978. Evolution of the desert species of Eschscholzia. (Abstract of presented paper.) Bot. Soc. of America, Misc. Ser., Publ. 156:12.
Cook, S.A. 1962. Genetic system, variation, and adaptation in Eschscholzia californica. Evolution 16:278-299.
Ernst, W.R. 1958. Chromosome numbers of some western Papaveraceae. Contr. Dudley Herb. 5:109-115.
__________. 1964. The genus Eschscholzia in the south Coast Ranges of California. Madroño 17:281-294.
Greene, E.L. 1905. Revision of Eschscholtzia. Pittonia 5:205-308.
Hoover, R.F. 1970. The vascular plants of San Luis Obispo County, California. Univ. California Press, Berkeley.
Raven, P.H. 1963. A flora of San Clemente Island. Aliso 5:289-347.