Santa Rosa Plateau (6 May 08)
Wayne's WordIndexNoteworthy PlantsTriviaLemnaceaeBiology 101BotanySearch
    Brodiaea Index      BTK San Marcos       B. elegans      B. jolonensis      Brodiaea Images      Brodiaea Key      Brodiaea Citations 
    Wildflower Index      San Marcos 2008      B. santarosae      SRP Flowers      SRP Rocks      SRP Lichens      SRP Basalt 
Images Of The Santa Rosa Plateau
© W.P. Armstrong 6 May 2008

Themidaceae: Brodiaea terrestris ssp. kernensis

Themidaceae: Brodiaea santarosae

Themidaceae: Brodiaea terrestris ssp. kernensis x B. santarosae

This small brodiaea population on Mesa de Colorado appears to be sterile hybrids between B. terrestris ssp. kernensis (BTK) and Brodiaea santarosae which grow intermixed in certain areas of the Santa Rosa Plateau. The large, strap-shaped staminodes resemble BTK; however, the slender, apical extensions resemble Brodiaea santarosae. Another possible parent is B. filifolia; however, the staminodes of the later species are threadlike (filiform). The anther sacs of these putative hybrids generally are devoid of pollen, with only cellular debris and some malformed pollen grains. The hybrids undoubtedly represent a clonal population that has reproduced asexually from cormlets. The best hypothesis to explain the pollen sterility is non-homologous parental chromosomes resulting in synaptic failure during microsporogenesis. The most likely parental species (BTK and B. santarosae or B. filifolia) have different chromosome numbers. The dissimilar maternal and paternal chromosome sets in the hybrid fail to pair up properly during synapsis of Meosis I. Numerous flowers in this population were carefully examined during a period of three years, and they were all sterile. The presence of viable pollen in one flower sample from this location is unexplained at this time.

The above anthers are undersized and devoid of mature pollen grains. This is to be expected in hybrids between parents with different chromosome numbers, such as BTK and B. santarosae or B. filifolia. Tentative chromosome counts by this author for coastal BTK in San Marcos are at least 36. Tentative chromosome counts by Dale McNeal of University of the Pacific for coastal BTK on Otay Mesa appear to be greater than 40. Niehaus (1971) gives chromosome counts of 48 for BTK in Kern County. His number of 36 for B. jolonensis on Otay Mesa is undoubtedly from coastal BTK. The diploid number for B. santarosae is not known precisely at this time, but tentative counts by Annette Winner of the San Diego Natural History Museum indicate that it is in the low 20s. My observations of microspore mother cells of B. santarosae indicate a chromosome number much lower than BTK. According to Niehaus (1971), the diploid chromosome numbers of B. filifolia and B. orcuttii are 24. Based on similar floral morphology, the chromosome number for B. santarosae is probably closer to the latter two species. Visible pollen grains on the perianth segments in the above images undoubtedly came from insects, including small beetles and flower bees, or possibly by the wind.

A sterile hybrid Brodiaea in San Marcos between Coastal BTK (B. terrestris ssp. kernensis) and B. filifolia or B. orcuttii has very different staminodes. The staminodes are flat (strap-shaped) or slightly hooded at the apex. They do not have an elongated middle tooth like the Santa Rosa Plateau hybrid. Perhaps one of the parents is B. orcuttii rather than B. filifolia? See the following image:

This appears to be a hybrid between Coastal BTK (Brodiaea terrestris ssp. kernensis) and B. filifolia or B. orcuttii which occur nearby. In fact, both B. filifolia and B. orcuttii appeared in a flower pot with corms of the transplanted hybrid. Note the strap-shaped staminodes that are not hooded as in typical coastal BTK. The flower was completely sterile with no mature pollen grains, giving credibility to the hybrid hypothesis.

  A Sterile Brodiaea Hybrid In San Marcos  
Diploidization & Origin Of Sterile Hybrid

Euphorbiaceae: Chamaesyce albomarginata

Mesa de Burro

Campanulaceae: Downingia bella

What appears to be sparkling blue water in these next three images is actually a dense population of Downingia bella (Campanulaceae) growing in the damp soil of a large, desiccated vernal pool.

Poaceae: Orcuttia californica (California Orcutt Grass)

The light green border surrounding the dense, blue population of Downingia bella is California Orcutt grass (Orcuttia californica). This is a rare annual grass endemic to vernal pool habitats in southern California.

Poaceae: Orcuttia californica and Alopecurus saccatus (Foxtail Grass)

Two native annual grasses at Mesa de Burro. A. California Orcutt grass (Orcuttia california). B. Foxtail grass (Alopecurus saccatus).

Polemoniaceae: Navarretia prostrata

Other Vernal Pool Navarretias:

Navarretia prostrata at Mesa de Colorado
See Navarretia fossalis in San Marcos

Return To WAYNE'S WORD Home Page
Go To Biology GEE WHIZ TRIVIA Page