For my PhD research at California Botanic Garden, I studied the genus Malacothamnus (Malvaceae), commonly known as the bushmallows, which has several conflicting taxonomic treatments and many rare taxa. I used a combination of morphometric analyses, Restriction site Associated DNA Sequencing (RAD-Seq), comparative phenology, and extensive field evaluations to clarify taxon boundaries within the genus and evaluate the conservation status of each taxon. This work will hopefully be published by the end of 2023.
For a summary of this research, you can watch my 2020 presentation for the Southern California Botanists Symposium here and/or my 2022 PhD dissertation defense here. The 2020 presentation may be a better starting place if you don’t know much about Malacothamnus but the 2022 presentation has more up to date information.
Treatments and Identification:
As mentioned above, there are several conflicting treatments. They are all problematic one way or another, mostly due to taxonomic lumping and splitting as well as a lot of overlapping morphological characters. Treatments follow below. Calphotos and iNaturalist are useful to check IDs, but some photo IDs could be questionable.
I recommend following the Kearney treatment until my treatment is published. Kearney was more of a splitter, but this treatment still actually lumped several taxa from earlier treatments. This treatment aligns with the current evidence the most closely and includes rare taxa lumped by other treatments. The keys aren’t perfect, but better than nothing. The Munz treatment mostly follows Kearney and is a bit simplified, so this is another good option. These treatments are missing both Malacothamnus lucianus and Malacothamnus enigmaticus. The Munz treatment is also missing taxa from Mexico.
Do not use the Flora of North America or Jepson treatments. The 1993 Jepson Manual and Flora of North America treatments by David Bates are pretty much identical to each other. The taxa in these treatments were way over-lumped making them very problematic in relation to rare taxa. To the author’s credit, he does say that the Kearney treatment is as justifiable as his own. Likewise, the current Jepson Manual treatment is best avoided. Author Tracey Slotta made some good progress in splitting back out some lumped taxa based on morphological analyses, but her key is problematic in various ways.
Draft regional keys and guides:
Key to the Malacothamnus of the Channel Islands, CA – Updated Mar. 17, 2023
Key to the Malacothamnus of Kern, Los Angeles, San Bernardino, and Ventura Counties, CA – Updated Mar. 9, 2023
Key to the Malacothamnus of Monterey, San Benito, San Luis Obispo, and western Fresno counties, CA – Updated Mar. 17, 2023
Key to the Malacothamnus of San Diego, Orange, and Riverside Counties, CA and Baja CA, Mexico – Updated Mar. 9, 2023
Key to the Malacothamnus of the San Francisco Bay Area, CA – Updated Mar. 17, 2023
Key to the Malacothamnus of the Sierra Nevada Range, CA – Updated Mar. 17, 2023
Illustrated guide and key to the Malacothamnus of San Diego, Orange, and Riverside Counties, CA (varieties not included)
Illustrated guide to distinguishing Malacothamnus from Sphaeralcea
A morphological assessment of the Malacothamnus palmeri complex (Malvaceae) – Jan. 2021
Malacothamnus enigmaticus (Malvaceae), a new rare species from the desert edge of the Peninsular Range in San Diego County, CA – Oct. 2019