Erythranthe michiganensis
Phytoneuron 2012-39: 44. 2012.
Perennials, rhizomatous, usually producing numerous leafy stolons from basal nodes, rooting at distal nodes, sometimes forming mats. Stems ascending-erect or basally decumbent, becoming erect in inflorescence, branched, 12–50(–70) cm, glabrous or minutely hirtellous and stipitate-glandular. Leaves cauline, basal not persistent; petiole 1–5(–15) mm, mid stem and distals 0 mm; blade palmately 3–5-veined, broadly ovate to broadly ovate-elliptic or suborbicular, 8–30 mm, relatively even-sized or diminishing in size distally, bracteal reduced, slightly falcate, base truncate to cuneate, margins evenly or unevenly dentate-serrate to dentate, teeth 3–8 per side, apex usually rounded, surfaces glabrous or minutely hirtellous and stipitate-glandular. Flowers herkogamous, 2–14, mostly from distal nodes or medial to distal nodes. Fruiting pedicels 10–25 mm, villous-glandular to minutely villosulous-glandular. Fruiting calyces cylindric-campanulate, inflated, sagittally compressed, 7–10 mm, puberulous to softly hirtellous, mixed with longer, stipitate-glandular hairs, throat not closing, adaxial lobe 2 times longer than others, slightly upcurving. Corollas yellow, sometimes faintly red-spotted, bilaterally symmetric, strongly bilabiate; tube-throat cylindric-campanulate, 10–14 mm, exserted 5–8 mm beyond calyx margin; limb expanded 10–15 mm. Styles glabrous. Anthers included, glabrous. Capsules unknown. 2n = (28)30.
Phenology: Flowering Jun–Aug(–Oct).
Habitat: Cold calcareous springs, seeps, depressions, streams, alkaline shorelines at mouths of small drainages, steep moraine slopes, bluff bases, commonly in northern white cedar swamps.
Elevation: 500–600 m.
Discussion
Based on data from allozyme and RAPD studies, morphology, and crossing studies, A. L. Posto and L. A. Prather (2003) raised Erythranthe [Mimulus] michiganensis to specific rank. The species is endemic to a small area in the Mackinac Straits and Grand Traverse regions of Michigan; it is known to be extant at 15 sites and apparently is extinct at three previously known sites. Plants of all but one of the populations are essentially pollen-sterile and reproduce through rhizomes. However, the didynamous stamens and stigma positioned above the adaxial anther pair, along with the relatively large corollas with broadly expanded limb, are reflective of an allogamous breeding system, which seems unusual in view of its apparent sterility. The narrow geographic distribution of E. michiganensis lies within the wider range of E. geyeri, and the two are known to co-occur at two sites, apparently without hybridization or morphologically intermediate individuals.
Erythranthe michiganensis (as Mimulus michiganensis) is in the Center for Plant Conservation’s National Collection of Endangered Plants.