Sister Sister: understanding the difference between sister taxa that look the same

One of the most challenging parts of studying this plant is complexity found not only within this species, but at higher levels of taxonomy as well. The genus Linanthus is distributed all across the California Florirstic Province, and while there are some consistent traits that shout out “Here I am!”, the amount of differences between species is astounding. This intuitively makes sense when you start thinking about the complexity of California landscape and differences in rain patterns and temperature, the giant chains of mountains limiting the dispersal to new places, and timescales on the thousands to millions of years.

Basically, this plant looks different depending on where you are. And to add more complications, there are a few other species that look like Eveningsnow (1), but they aren’t: Linanthus maricopensis is a large lobed annual flower found in central and southern Arizona and is identifiable by the glandular trichomes on the calyx and pedicel (there are sticky hairs on the green-maroon base and stem of the flower). Linanthus bigelovii (a sneaky imposter of Linanthus dichotomus) is an annual flower that is mostly found to the East of California, although many observations have been made in the Mojave and Great Basin deserts and even up into the Coastal Ranges of California (think an hour or two south of San Jose). There are two subspecies of in this lineage: ssp johnsonii and ssp bigelovii. Linanthus bigelovii ssp. bigelovii is a small lobed flower that looks an awful lot like L. dichotomus ssp. pattersonii and usually takes additional measures to confirm identification. L. bigelovii ssp. johnsonii look a lot like linanthus dichotomus with large lobes on the corolla but has small glandular trichomes along the calyx and pedicel whereas L. dichotomus is glabrous (or hair and gland free). Last but not least is the benign offender, Linanthus jonesii. This plant has small lobed flowers and glandular trichomes all over the calyx and inside of the upper leaves, so there is no real issues with confusion unless you’re whizzing by at 60mph.

So what’s the difference, you say? How do I see snow? Specifically, there are two. The first, is the insertion of the anthers in the corolla tube. In L. dichotomus, this will be more towards the base and have a hairy nectary at the attachment point of each one (1, pg 67-68). In L. bigelovii, this will be in the middle and will lack hairs and nectaries (1, pg 63).

Too late for flower season? Check out the seeds! In L. dichotomus, the seeds are surrounded by a lattice like white covering, almost like a mini bubble wrap (1, pg 68). This membrane leaves a little space between it and the tiny little brown seed. L. bigelovii, on the other hand, has almost vacuum wrapped this white membrane to the angular seed (1, pg 62), which becomes sticky when wet. Last but not least L. jonesii has cute little brown kidney bean seeds that do not have a membrane, so again, completely different.

Ok ok, yes, you are correct: Tearing apart a corolla to find out what kind of plant it is should be left as an emergency last resort, especially since I am trying to recruit as many participants as follows. Can’t tell if it is Linanthus dichotomus? Make a note to come back and check out the seeds! If you can’t, maybe someone else can! The nice thing about plants is they don’t move, so barring a heavy wildfire or a new mini mall, the stems should still be there a few months later with at least a few seeds still waiting to be dispersed.

(1) Porter, J. M., & Patterson, R. W. (2015). A Fistful of Polemoniaceae: new names and combinations. Aliso, 32(2), 55–88.

Publication can be found online here: https://scholarship.claremont.edu/aliso/vol32/iss2/2/

Posted on March 19, 2019 05:32 PM by enemjee