Tuesday, November 22, 2011

albino phenotype in Sequoia sempervirens

albinistic mutations are often recorded in Redwood (Sequoia sempervirens).  Popular literature indicates these mutations are 'very rare' in S. sempervirens: Discover Magazine has “25 of these trees are known to exist around the world, eight of which are at Henry Cowell State Park in California”, while “Field Notes by Barry Evans”, The Journal, Humboldt County “Only about 50 are known to exist”.  Exactly how frequent these mutations occur is uncertain.  

Insofar as I find in literature, there is no certainty as to the type of mutation that results in albinsitic crown sprouts in S. sempervirens.  In general, the albino phenotype in vascular plants results from mutations in either nuclear genes that code precursors for plastid biogenesis, or in chloroplast genes, and at least in grasses, plants with nuclear mutations often have plastids with only carotenoid pigments present, producing a faint yellow in the affected leaves.   The color of the mutant S. sempervirens below suggests no mature carotenoid pigments form, as there is no hint of yellow pigment.

This albino S. sempervirens occurs near Nisene Marks State Park, Santa Cruz, County.  This particular clump has been essentially this size, about 2 meters tall, for nearly 2 decades now, although individual stem axes die and are replaced.    The principal factor seemingly associated with the state of this particular clump is that it gets ‘smothered’ by litterfall, which has broken or bent down individual stem axes over the years. 

The albino phenotype of S. sempervirens was reported upon by George J. Peirce in Proceedings California Academy of Sciences, Third Series, Botany, Volume 2, p. 83-107 (1900-1904), and reading his article it seems these albino trees were known from throughout the Bay Area early on.  Peirce termed them  “not an especially rare peculiarity” and “I have entirely failed to detect even rudiments of plastids” on plants from near La Honda, while albino mutants from near Redwood Retreat (vicinity of Gilroy) he states “contained chromatophores which ranged in size from those about half as large as the average chloroplastids in the normal green leaves down to indistinguishable rudiments.”  His observations might therefore suggest that these albino forms can result from a mutations either in nuclear or chloroplast genes.  

Friday, November 18, 2011

Ramet ‘germination’ in Poa sierrae

My dormant ramets of Poa sierrae, collected at the type station on 1 August 2011, were potted up soon thereafter and were kept well watered throughout the late summer.  Not until daylength began to shorten about Halloween, and the wet season returned, did they begin new growth, however.  In this view, the ramet piece shown in the middle photo of the 18 September 2011 post on Poa sierrae has grown out, and a secondary ramet has formed.  Ramet reproduction thus seems to be a strong tendency under gene (vs. allelic) control in this member of Madropoa.    In some respects, the strength of ramet reproduction contradicts the narrow geographic range of this Sierra Nevada dioecious endemic: it seems odd, because on the surface the ease of vegetative  reproduction would otherwise be characteristic of a vagile or even invasive species of grass.  Go figure.

Saturday, November 12, 2011

Hooveria, a new genus liberated from Chlorogalum

Chlorogalum as treated traditionally is a genus of 8 taxa endemic to the California Floristic province, extending in the north from its northern limit near Myrtle Creek, Josephine County, Oregon southward to far northern Baja California.   Four of the 8 taxa are rare
The genus clearly consists of two distinct elements: three pale to deep purple flowered, diurnal taxa
n = 30    Chlorogalum purpureum Brandegee var. purpureum
n = ???   Chlorogalum purpureum var. reductum Hoover
n = 30    Chlorogalum parviflorum S. Watson
and 5 white flowered, verpertine taxa
n = 17       Chlorogalum angustifolium Kellogg
n = ??       Chlorogalum grandiflorum Hoover
n = 18      Chlorogalum pomeridianum (DC) Kunth var. divaricatum (Lindley) Hoover
n = 18      Chlorogalum pomeridianum var. minus Hoover
n = 15, 17 Chlorogalum pomeridianum var. pomeridianum

In 1940, Hoover (1) did not know of the tetrapolid nature of the two n=30 species, C. parvifolium and C. purpureum; he did remark on the floral differences.  Cave (2) then documented chromosome numbers in the genus, postulating they represented a distinct clade and noted their karyotpyic links with Hastingsia alba.   Now, Halpin (3) has shown that the diurnal-flowered plants are not monophylletic within Chlorogalum.  

In my estimation, Chlorogalum purpureum and C. parviflorum ought to be segregated within a new genus.  The name Hooveria is available for these plants, and would be a fitting tribute for Robert Francis Hoover, one of California’s most able field botanists.

1.  Hoover, RF 1940  Madrono 5:137-147
2.  Cave, MS 1970 Univ. Calif. Pubs. Bot. 57:1-51
3.  Halpin, KM. 2011.  Thesis, Oklahoma State Univ. 103 pp.

Friday, November 11, 2011

How many species of Santa Cruz Cypress are there?

Botanists have not agreed upon use of categories to classify hierarchical variation pattern.  As I see it, trinomials are a type of botanical hedge-fund.  We name a taxon (‘we buy it’), then we purchase a derivative against its being ‘lumped’ as a hedge by treating it as an infrataxon.  Moreover, there are no regulatory mechanisms governing the choice of category in the hierarchy.  Sound familiarly like a financial meltdown?  Some authors publish boatloads of new combinations because it is their habit to use solely a single category of infrataxon.  Literature pollution?

The utility of recognizing infrataxa is not well codified in modern usage.  Hamilton & Reichard (1) document the fact that most taxonomists employ only a single hierarchical category below the rank of species, and that two schools of thought are evident: those whom use the category “subspecies” or those that use “variety”. but few botanists use both.  As Fosberg (2) notes there is no specific prohibition against the practice, perhaps due to an instinctive aversion to quadranomials.  The vast majority of authors fail to provide a rationale for their choice of infraspecific category, or for their viewpoint upon the question of parsing variation into a hierarchical topology. 

Recently, the question arises in the case of the Santa Cruz Cypress. and endangered tree: Silba (3) named 5 subspecies.  Adams & Bartel (4), eventually after some hemming, treat 2.  One might choose to treat the Silba infrataxa as varieties within subspecies; others would want to make them formae (although the nature of forma seem to lack consensus in the literature: mostly forma are taken to be sporadic, rare phenotypes that may not have a genetic basis, that is, the condition may be developmental; or, their genetic basis is viewed as a mutation, albinism in flower color is an example.    There is arboricultural utility in considering the Silba infrataxa as cultivars would be o.k. as “C.V.” would eliminate confusion, but unfortunately horticultural nomenclature in practice is in my experience inaccurate.

Fernald (5) would probably have treated H. abramsiana ssp. abramsiana and within it H. abramsiana var. locatellii, H. abramsiana var. neolomondensis and H. abramsiana var. opleri, and H. abramsiana ssp. butanoensis. 

I could question the decision as to how to parse variation within H. abramsiana by noting that for some individuals of ‘neolomondensis’ their chemical profile was as distinct as is ssp. butanoensis, and ‘opleri’ was about as removed in the ISSR ordination but it also differed in mean cone width, length and number of scales.  Faced with practical necessity, the Adams and Bartel treatment is useful, but one could also craft an alternative classification just as readily. 

The pattern of relationships Adams & Bartel find are suggestive of genetic drift following upon segmentation of a variable, ancestral panmictic population: in some respects, one answer is there are either no subspecies of Santa Cruz cypress, but there are five groves.

I will also make reference to the choice between treating these plants in Cupressus as has been traditionally done: Little (6) made out our cypresses to be polyphylletic  within Cupressus.  By aversion to lumping them into Juniperus (6) out Hesperocyparis was cleaved.  There is also evidence that all cupressus are a single clade (7)  I like the latter approach because by their very nature genera are small (8) and in this instance the Hesperocyparis-Cupressus division is a deep one. 

1. Hamilton, C. and S. Reichard.  1992.  Taxon 41:485-498
2. Fosberg, F. 1942.  Rhodora 44:153-157
3.  Silba, J.  2003 Intern. Conifer Pres. Society 10:1-49
4.  Adams, R and J Bartel. 2009 Phytologia 91(2):287-299
5.  Fernald. M. 1941.  Rhodora 43:156-167.
6. Little, D. 2006 Syst. Bot. 31:461-480.
7. Mao, K. et al. 2010.  New Phytologist 188: 254–272
8.  Cronk, Q.C.B. 1989.  Taxon 38(3):357-370.