It’s a wet and stormy day locally, so instead of thoughts of the desert like the previous photo I shared, I am thinking of my 2013 trip to Haida Gwaii. The story of how I encountered these plants was discussed in a previous entry on Carex macrocephala. Senecio pseudoarnica even makes an appearance in one of the photos for that entry, but today I’m sharing a picture of one of the few in flower I encountered .
The other photograph illustrates the sandy beach habitat that this species prefers throughout its range. And, it also shows where a botanist-photographer has been trampling around, ruining his eventual photograph (but you may notice the steps were carefully made, avoiding everything but the commonplace big-headed sedge). As explained in the Carex macrocephala entry, my caution was due to being aware of the two rare plants in this locality: the blue-listed Senecio pseudoarnica and the red-listed Lathyrus littoralis (obscured in the upper right of the second photo).
Senecio pseudoarnica, or beach groundsel, has an intriguing distribution. Like Carex macrocephala, it is amphiberingian, occurring oceanside in British Columbia, Alaska and parts of Pacific Asia. However, it also occurs along the coasts of Quebec, Maine, Atlantic Canada and St. Pierre and Miquelon. A quick search revealed no instances of any speculation as to whether this distribution is due to: a) a once-contiguous distribution across the Arctic during a period of warmer climates; b) long-distance disperal by (presumably) migratory birds and subsequent colonization; c) whether the disjunct distributions indeed represent one species or two morphologically similar ones; or d) something I can’t imagine at the moment. Perhaps it is due to long-distance dispersal, as an overall conclusion from this 2015 dissertation by Martha Kandziora on the worldwide distribution of Senecio, Evolution und historische Biogeographie von Senecio L. mit Fokus auf die Alte Welt (PDF) asserted:
Despite its young age and almost cosmopolitan distribution, Senecio is one of the most species-rich genera of plants. Accordingly, diversification rates are high compared to the tribe and similar to other recent or continental radiations. The success of Senecio is probably related to their preference for open or disturbed habitats, facilitating establishment, in combination with their excellent dispersability.