Mimulus peregrinus Vallejo-Marin, 2012

Vallejo-Marin, Mario, 2012, Mimulus peregrinus (Phrymaceae): A new British allopolyploid species, PhytoKeys 14, pp. 1-14 : 4-5

Mimulus peregrinus Vallejo-Marin sp. nov. Figure 1

Mimulus Section Simiolus Green (= Erythranthe Section Simiola (Green) Nesom & Fraga)

Type.

United Kingdom. Scotland: Grown from seed collected in South Lanarkshire near Leadhills, on the banks of Shortcleuch Water. Vice county 77, Ordinance Survey grid reference: NS 9029 1578. WGS84 coordinates: 55.4237°N, 3.7349°W; altitude: 360 m. 27 Aug 2011. M. Vallejo-Marín 11-LED-seed; vouchered as M. Vallejo-Marín 11-LED-seed-2-14 (holotype: E; isotypes: BM, K).

Species nova Mimulus x robertsii Silverside similis. Herba perennis, pollen et semen fertile, corollae, flavae, lobo centrali cum macula parva rubro. Folia ovata ad oblonga, dentata, regulariter ad irregulariter triangulo-dentata. Calyx interne cum capillis simplicibus instructis.

Description.

Perennial herb 5-30 cm (-1 m) high, freely rooting at the nodes. Stem erect or prostrate, glabrous below and glandular pubescent above. Leaves variable, mostly ovate-oblong 3-14 × 1.5-4 cm, with regular to irregularly dentate margins; basal leaves oval to spatulate, with petioles up to three-quarters as long as the blades; upper leaves ovate with much shorter petioles or sessile. Inflorescence racemose, many-flowered; pedicels 2.5-5 cm long, normally equalling or slightly longer than the corolla, but shorter in later flowers. Calyx 1.5-2.5 cm long, with 5 triangular teeth, the upper tooth distinctly longer; pubescent outside covered with glandular hairs throughout, and with short, simple hairs in the base of the calyx extending along the ridges; calyx becoming inflated in fruit, with the lower two calyx-teeth curving upwards and enclosing the fruit. Corolla ovate in frontal view, 4-5 cm wide, 3-5 cm tall, and 4-5 cm long (deep); the lobes almost truncate, particularly the two lateral ones; yellow, with a single faint-red, vertically-elongated 2 × 5 mm spot located approximately half-way on the central lower lobe; throat hairy, spotted with red, more or less open; lobes subequal, the central lower lobe slightly longer ( Fig. 2 ). Style glabrous, ending in a bi-lobed, thigmotropic stigma. Fruit a broadly oblong capsule; seeds striate, very small (<0.02 mg; ~0.1 mm2). Anthers yielding abundant quantities of viable pollen (percent of viable pollen: 86.39 ± 4.01%, range: 73.24 - 96.40%, N = 6 individuals); pollen diameter from 53.43 ± 1.22 μm (mean ± SE; N =5 individuals, 100 pollen grains per individual; Hoyer’s medium) to 48.78 ± 0.97μm (mean ± SE; N =6 individuals, 100 pollen grains per individual; 70% ethanol) depending on mounting medium. Sets abundant seed following artificial self-pollination. Germination rates of self-fertilized seed 80% ± 4.2% (N =6 families, 50 seeds per family). Stomata length 35.44 μm ± 0.99 (N = 7 individuals, 20 stomata per individual). Chromosome number 2n = 92 (J. Bailey).

Distribution.

Currently known only from the banks of Shortcleuch Waters, Leadhills, South Lanarkshire, Scotland, UK (v.c. 77).

Ecology.

Occurring on the banks of a stream on a substrate of sand and shingle. Mimulus peregrinus is found alongside Mimulus x robertsii , whichis locally common. Flowering of Mimulus in this region starts in early June. Seeds of Mimulus peregrinus were collected in August.

Etymology.

The name is taken from the Latin peregrinus - foreigner, traveller.

Preliminary conservation status.

Currently known only from a single collection outside of a protected area, Mimulus peregrinus is provisionally assessed as Critically Endangered (CR D; population size estimated to number less than 50 mature individuals) ( IUCN 2011).

Specimens examined.

United Kingdom. Scotland: Grown from seed collected at South Lanarkshire near Leadhills, on the banks of Shortcleuch Water. 55.4237°N, 3.7349°W; altitude: 360m. 27 Aug 2011. M. Vallejo-Marín, seed voucher: 11-LED-seed. All Mimulus peregrinus specimens examined here were derived from open-pollinated seed collected at the type locality and grown in a controlled environment. Some of these first generation seed-grown individuals (11-LED-seed-1 to 11-LED-seed-7) were then used produce a second generation via self-fertilization (e.g. 11-LED-seed-2-14).

Figures

Figure 1. Holotype of Mimulus peregrinus Vallejo-Marin [11 - LED-seed- 2 - 14; barcode E 00570050].

Figure 2. Flowers of Mimulus peregrinus and closely related taxa. A Mimulus guttatus B Mimulus x smithii (Mimulus luteus luteus x Mimulus luteus variegatus) C Mimulus x robertsii (Mimulus guttatus x Mimulus luteus), and D Mimulus peregrinus. Each taxon is represented by flowers from two individuals from a single locality to illustrate within-population variability: Mimulus guttatus = Dunblane, Perthshire; Mimulus x smithii = Coldstream, Scottish Borders; Mimulus x robertsii = Nenthall, Cumbria; Mimulus peregrinus = Leadhills, South Lanarkshire. Scale bar = 1 cm.