Grindelia in Monterey County, California

Just some notes for now - a place to assemble information on local Grindelia taxonomy. Inspired by observations like this one: https://www.inaturalist.org/observations/117539735 and associated comments by @yerbasanta.

Initially, the emphasis is on separating hirsutula and platyphylla, particularly in light of a tricky population on Fort Ord near Watkins Gate Rd.

Taxonomic history:

• Styermark (1934) wrote the main key that splits Grindelia into perhaps over 100 taxa worldwide - with perhaps more splitting than is now considered warranted. Stother & Wetter writing for FNA Vol. 20 (2006) explictly call Steyermark's granularity into question. Styermark's key is very long, and consequently difficult to follow if one is just interested in a particular geography. For example, it splits G. stricta var. platyphylla into two "forms" that occur in completely different parts of the key.

• Keck (1959) was perhaps (?) the first to distill Styermark down to California - including 12 species. G.stricta var. platyphylla occurs under the name G. latifolia ssp. platyphylla. The split between hirsutula and platyphylla is at the top of Keck's key.
  " A. Tips of phyllaries erect or spreading, some gradually curved but not sharply reflexed. --> hirsutula etc.
  AA. Tips of phyllaries (at least of some middle and outer ones) sharply reflexed or looped). --> stricta etc."

• Lane (1992, 1993) was probably the next author to tackle a Californian key. First Lane published a 1992 paper that combined some Gridelia taxa together to arrive at 6 species. Then Lane authored the TJM1 treatment in 1993, in which the hirstula/platyphylla split also occurred at the top level, but upon different characters to those used by Keck. Thus:
  "1. Pappus awns > 0.3 mm wide at base, minutely serrate, V-shaped in X-section; lvs +- fleshy; coastal. --> stricta var. platyphylla, etc.
  1'. Pappus awns < 0.3 mm wide at base, entire, U-shaped in X-section or flat; lvs gen not fleshy; inland. --> hirustula etc."
  Lane also suggested various platyphylla hybrids e.g. that maritima may have arisen from platyphylla x hirsutula.

• Matthews (1997) includes: hirsutula (vars h. and maritima), latifolia, sticta var. platyphylla, and camporum. The split between hirsutula and platyphylla is made at the first couplet, based on phyllary hairiness (platyphylla glabrous) and shape, leaf fleshiness, and head width. The details are helpful. The part about phyllary hairiness is interesting, because it doesn't seem to show up much in other keys.
• Stother & Wetter (2006, FNA) lumped platyphylla under hirsutula, not as a distinct infra-species taxon, but offered some infra-specific notes on what had to date been called "platyphylla", including reference to Lane's notes on hybrids: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=250066812

• Moore (2012, TJM2) recognizes about 8 species, and several subspecies. The hirsutula/platyphylla split is made near the top, on the basis of habitat and leaf fleshiness:
  " 2. Plants of dunes, salt marshes, coastal bluffs, tidal flats, sloughs; leaves ± fleshy. --> platyphylla etc.
  2' Plants of fields, grassland, woodland, serpentine soils, disturbed areas, or interior wetlands; leaves not fleshy; widespread (absent from Suisun delta). --> hirsutula etc."

• Moore also wrote a dissertation (2010) and two papers (2012, 2014) on Grindelia genetics. These are a great read, but they don't directly inform the question of how to ID a plant that could be hirsutula or stricta var. platyphylla. One or two relevant points from Moore et al.'s results are: (i) hirsutula and stricta var. platyphylla are closely related, (ii) geographic variation is pronounced in the genus, and variation is marked between populations and limited within populations.
• Matthews & Mitchell (2015) generall follow Moore (2012) (i.e. not the original Matthews (1997) edition). They include four taxa: angustifolia, platyphylla, hirsutula, and camporum. There's some good info in their text.
• Yeager & Mitchell (2016) just include platyphylla, but theirs is not intended to be an exhuastive list for the County.
• Styer (2019) suggests most Fort Ord Grindelia are platyphylla, and the presence of hirsutula is uncertain. This make sense when you realize that most Fort Ord Grindelia occur west of Hwy 1 in the most dune-like habitats. But it leaves interior Fort Ord Grindelia in question - the inland plants are on ancient dunes, and in grasslands that are somewhat interior.

Summarizing all this for use on Fort Ord in Monterey County, California, if one were to simultaneously accept Keck (1959), Lane (1993), and Moore (2012), it seems that for a plant to be hirsutula, it should have: phyllaries not sharply reflexed; awns that are narrow, entire, and U-shaped or flat; leaves (gen.) not fleshy and a location that is perhaps more like interior grassland than coastal dune. On the other hand, if one were to dismiss all but the most recent author, a hirsutula would simply need to be interior and non-fleshy-leaved.

Note that POWO currently subsumes platyphylla under hirsutula, but iNat recognizes platyphylla as a distinct taxon. The two are supposed to align, but this is not always the case. In such situations, I think it is best to ID to the taxa available in iNat (i.e. platyphylla or hirsutula, depending on characters), and if a lumping is deciding later in iNat, the IDs can be automatically lumped as well.

Disclaimer: I haven't searched beyond the literature I cited. There may be pertinent literature that I haven't looked at yet.

Maybe some other day I'll dig out the text from a few of the regional floras for Monterey, Santa Cruz, and San Luis Obispo counties...

Posted on June 27, 2023 05:07 PM by fredwatson