The following Brodiaea species are flowering in a 40 acre vacant field in San Marcos, CA as of 17 May 2012. Although the heavy clay soil is drying up, there are still a lot of plants in bloom, especially B. orcuttii.

With base numbers of 6 and 8 chromosomes, most species of Brodiaea are technically polyploids with multiple sets of chromosomes. For example, B. terrestris ssp. kernensis in Kern County is an octoploid with eight sets of chromosomes, and B. orcuttii is tetraploid with four sets of chromosomes. [B. jolonensis in Monterey County is diploid with two sets of chromosomes.] According to Niehaus (1971), the lack of quadrivalents in meiosis plus the differences in size of individual mitotic chromosomes at different ploidy levels suggests that these are "old polyploids." That is, the tetraploids, hexaploids, and octoploids have been in existence long enough to change by translocations, deletions, and so on. These differences apparently are enough to ensure that during meiosis only bivalents will occur in the higher ploidy levels. In bivalents, only two sets of maternal and paternal chromosomes associate during synapsis of meiosis, in contrast to quadrivalent where four sets of homologous chromosomes associate during meiosis.

If Brodiaea species behave as diploids, then BF and BO each have n = 12 and 2n = 24, and BTK has n = 18 or a higher number. In fact, BTK could be 2n = 36, 38, 40, 42, 44, 46, 48, etc. and still be theoretically fertile with two sets of homologous chromosomes. A hybrid between BF or BO and BTK would be sterile because of the non-homologous pairs of chromosomes that differ in number. Hybridization may occur, but the resulting hybrid offspring grown from seed may by sterile without viable pollen. For example, a cross between BF and BTK could result in a hybrid with 12 BF chromosomes and 18 BTK chromosomes which would not match up during synapsis of prophase I. This hypothesis is a plausible explanation for the sterile hybrids we have observed in San Marcos.

My tentative chromosome count for Coastal BTK in San Marcos was at least 36. Preliminary chomosome counts of Coastal BTK from Otay Mesa by Dale McNeal at University of the Pacific (personal communication, 2006) indicate that the number may be greater than 40. An exact count is difficult because small chromosomes are often obscured by larger ones.

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