Observation of the Month: Snapdragons (Plantaginaceae)

Lesser Snapdragon (Sairocarpus pusillus) https://www.inaturalist.org/observations/25653906 by @amarillas
Nuttall’s Snapdragon (Sairocarpus nuttallianus) https://www.inaturalist.org/observations/24905636 by @adrianjana

Taxonomy can be taxing. Just when you think you have learned to identify a plant, you find out that the taxon involved has been split or lumped or otherwise changed. Perhaps the change moves us toward a global taxonomy with less reliance on regional floras as opined by one of the administrators of iNaturalist, but sometimes the change confuses me and other iNaturalist users no matter how beneficial it may be in the long term. Recently, this happened with snapdragons.

For a long time, iNaturalist followed the same taxonomic scheme as The Jepson Manual and the Checklist of the Vascular Plants of San Diego County (5th Ed.) placing the plants commonly called snapdragons in the genus Antirrhinum. Two similar looking purple-flowered plants were Antirrhinum nuttallianum ssp. nuttallianum and A. n. ssp. subsessile, both of which are found from the coast to the mountains of San Diego County, although the distribution of A. n. ssp. subsessile tends to be more coastal than A. n. ssp. nuttallianum. Now, on iNat, these plants have been moved to a new genus and are treated as distinct species: Sairocarpus nuttallianus and S. pusillus.

Perhaps the easiest way to tell the two apart is by the hairs on the stems. Sairocarpus nuttallianus has fine hairs of varying lengths without significant glands on the tips—giving a soft fuzzy look. Sairocarpus pusillus has sparser hairs mostly of one length with big glands on the tips. If the hairs are not clearly visible, separating the two species is more challenging, but keep in mind that S. nuttallianus is often a much larger plant, with generally paler, more lavender flowers, and is more likely the farther inland you are.

Observations which were previously identified on iNat as Antirrhinum nuttallianum without indication of subspecies were automatically switched to Sairocarpus nuttallianus which may not be the correct identification. In some cases, the identification should be changed to S. pusillus and in other cases, if the characteristics are not clear, to genus level.

Posted on June 10, 2019 11:38 PM by milliebasden