Boechera botulifructa D.P. Morin, 2018

Morin, David P., Alexander, Patrick J., Beck, James B., Windham, Michael D. & Bailey, C. Donovan, 2018, Deciphering the sexual diploid members of the Boechera suffrutescens complex (Brassicaceae, Boechereae), PhytoKeys 98, pp. 15-50 : 27-29

Boechera botulifructa D.P. Morin sp. nov. Figures 3 , 5

Type.

U.S.A. California. Lassen County: 1.75 mi SSE of Coulthurst Flat on E road cut berm of Champs Flat Road. 1.35 air mi SSW of Cleghorn Reservoir, 26 Jun 2012, C.D. Bailey & D.P. Morin 24 (holotype: NMC!; isotypes: DUKE!, MO!) .

Diagnosis.

As a member of the B. suffrutescens complex, B. botulifructa can be distinguished from most other species of Boechera by pendent relatively wide siliques (2-6 mm). Within the complex, the species is one of just five that produces narrowly ellipsoid symmetrically tricolpate pollen (Suppl. material 1: fig. 1A) indicative of diploid sexual reproduction. Boechera botulifructa is distinguishable from four other sexual diploid B. suffrutescens complex species by the presence of small petals (4-6 mm long), abruptly tapered silique distal apices and a geographic distribution along the Cascade Province in California and Oregon.

Description.

Plants long-lived perennials, with woody caudices raised above ground level 1-5 cm, lacking crowded, persistent leaf bases; herbage without an obvious bluish cast. Fertile stems 1(-3) per caudex branch, each arising from a basal rosette, lower parts pubescent to densely pubescent with short-stalked, 2-3(4) rayed trichomes 0.1-0.3 mm. Leaves: at stem bases oblanceolate, 1.7-5.8 mm wide, entire, ciliate with 2-3(-4) rayed trichomes to 0.07-0.40 mm; cauline leaves (4-)6-12, occasionally concealing stem proximally, the uppermost glabrous, with auricles (0)0.3-1.4 mm. Inflorescences mostly unbranched, 6-12 flowered; mature fruiting pedicels 9-17 mm, reflexed, distinctly geniculate proximally, but straight distally, glabrous. Flowers pendent at anthesis; sepals glabrous; petals 4.5-6.0 long × 2.0-2.5 mm wide, pale lavender or whitish with rose apices; anthers with mostly well formed, narrowly ellipsoid, symmetrically tricolpate pollen; ovules 20-30 per fruit. Fruits 3-7(-10) cm long × 2.0-2.5 mm wide, pendent, straight to somewhat curved, with undulate edges; apical angle of fruit valve 30-38° (measured from base of style to 5 mm proximate); style persistent 0.2-1.2 mm long. Silique apex mostly rounded apically. Seeds uniseriate, 2.5-5.5 × 1.8-3.5 mm; wing continuous, 0.8-1.5 mm wide.

Distribution, habitat and phenology.

As currently known, the species occupies three distinct regions in the Cascade Province: western Deschutes County, Oregon, near Medicine Lake, Siskiyou County, California and the area west of Eagle Lake in Lassen County, California. It favours rocky slopes and gravelly felsic soils in association with Artemisia tridentata , Purshia tridentata , Pinus jeffreyi , Pinus contorta and Juniperus at elevations of 1300-2100 m; flowering from May to July.

Comments.

Morphologically, B. botulifructa is most similar to B. duriuscula and these two taxa are parapatric along the southern distribution of B. botulifructa . The species is distinguished from close relatives primarily by the abrupt tapering of the apex of the fruit, resulting in a sausage-like profile to which the specific epithet refers. Like most other members of the B. suffrutescens complex, it has a suffrutescent habit and wide (>3 mm), reflexed, often secund, fruits. Molecular data suggest that the specimens from the southernmost population in Lassen County, California, have diverged from the northern populations and may have a history of gene flow with B. constancei from the vicinity of its type locality. The latter B. botulifructa individuals, from Lassen County, also have reduced cauline leaf auricles relative to other non-serpentinicolous members of the complex.

Though the species spans a large geographic range, we have only identified nine populations systems thus far, suggesting a need for future investigation of conservation status. Within the populations we visited, individuals were sparsely dispersed across broad areas. The species occurs on public lands with noted impacts from grazing activity and potential impacts from logging of local native forests.

The holotype for Arabis dianthifolia Greene was collected at Crater Lake, Oregon, but our access to this type was limited to high resolution images. Although Crater Lake lies within the overall range of B. botulifructa , the specimen observed lacked the diagnostic fruit apex character. Furthermore, preliminary microsatellite analyses of specimens collected near the type locality indicate that A. dianthifolia is probably A2X (Windham, unpubl. data).

Specimens examined.

California. Lassen County: Pine Creek near Bogard Ranger Station , 23 Jun 1960, S.K. Harris 21448 A, B (GH); USFS 22N02. 1.25 road mi N of highway 44, 26 Jun 2012, D.P. Morin 22 A - I (NMC); 1.75 mi SSE of Coulthurst Flat on E road cut of Champs Flat Road. 1.35 air mi SSW of Cleghorn Reservoir, 26 Jun 2012, D.P. Morin 24 A, B, C (NMC), D, E, F, (DUKE), G, H, I (MO); Coulthurst Flat area (T34N, R10E, S27, SW), 29 Jun 1983, G.D. Schoolcraft 1038 (NY). Siskiyou County : Medicine Lake , 28 Jul 1921, A. Eastwood 10885 A, B, C (GH). Oregon. Deschutes County : Along Elk Lake , 13 Jun 1925, C.H. Peck 14337 (WILLU); Take unnamed dirt road E 0.4 mi from Jones Well Rd. 7 air mi SSW of Paulina Lake, 26 Jun 2012, D.P. Morin 17 A, B, C, D - J (NMC); Deschutes NF, Ann’s Butte, ca. 3.5 mi W of Sunriver on Rd. 40, 26 Jun 1992, D.W. Taylor 12889 A, B (NMC); Paulina Lake, 29 Jul 1894, J.B. Leiberg 584 A, B, (OSC) .

Figures

Figure 3. Geographic distribution of B. suffrutescens (CP-su, SNP-su, and TL-su) and B. rollei (TL-ro) lineages inferred from Analysis 2. A map of Plumas Co., California with distributions of the B. constancei clusters is presented in Fig. 4.

Figure 5. Boechera botulifructa, Morin 24 (MO).