Bidens microcephala W.L. Wagner, J.R. Clark & Lorence, 2014

Wagner, Warren L., Clark, John R. & Lorence, David H., 2014, Revision of endemic Marquesas Islands Bidens (Asteraceae, Coreopsideae), PhytoKeys 38, pp. 37-67 : 48-50

4. Bidens microcephala W.L. Wagner, J.R. Clark & Lorence sp. nov. Figure 5

Type.

Marquesas Islands. Fatu Hiva: Angled rocks above Omoa village (Aiguilles Rocheuses), south-facing, sea cliffs, 524 m [10°31"42.8'S/138°41"17.2'W], 6 September 1995, S. Perlman & K. R. Wood 14946 (holotype: PTBG-066383; isotypes: BISH, K, MO, MPU, NY, P, UC, US).

Description.

Erect, suffrutescent perennial herbs 1-1.3 m tall. Leaves simple, (4-)6-14.5(-20) cm long including petiole, rarely compound, blade lanceolate to lanceolate-elliptic, occasionally lanceolate-linear, (1.5-)3.5-9.5(-14) × (0.9-)1.3-4 cm, glabrous, margins serrate to serrulate, occasionally subentire, apex acuminate. Heads 40-50, in compact cymes, becoming diffuse at maturity, heads often in tight clusters, terminating main stem and lateral branches, main inflorescence axis 6-9 cm, heads 1-2 mm in diameter, peduncles 0.1-1.5 cm long, glabrous; outer involucral bracts 1-2 mm long, well differentiated from inner bracts; ray florets absent; disk florets (1-)5-10, perfect. Achenes gray or black, straight, 3-4 × 0.5 mm, sparsely setose; pappus absent.

Distribution.

Marquesas Islands, endemic to southern and central Fatu Hiva, 10-625 m.

Habitat.

On sea cliffs in mixture of native shrub and trees and alien vegetation, with native species such as Dodonaea viscosa Jacq., Hibiscus tiliaceus , Pisonia grandis R. Br., Celtis pacifica Planch., Psydrax odorata (G. Forst.) A.C. Sm. & S.P. Darwin, Wikstroemia coriacea Seem., and Dinebra xerophila (P.M. Peterson & Judz.) P.M. Peterson & N. Snow, and naturalized species like Casuarina equisetifolia L., Coffea arabica L., Cordyline fruticosa (L.) A. Chev., Psidium guajava L., Miscanthus floridulus (Labill.) Warb., and Morinda citrifolia L.

Etymology.

The specific epithet refers to the extremely small heads, probably the smallest in the genus.

Conservation status.

Proposed IUCN Red List Category Critically Endangered (CR), criteria B1ab, B2a,b (i-iii): B1, total extent of occurrence less than 100 km² (ca. 85 km²), a, severely fragmented and b, continuing habitat decline inferred; B2a, estimated area of occupancy estimated to be less than 10 km²; B2b (i-iii), habitat continuing decline inferred. The estimated area of occupancy for Bidens microcephala on Fatu Hiva (ca. 85 km²) is indicated as an endangered environment, threatened by human activity (deforestation and fire), feral animals, and invasive plant species, thus reducing the extent of the suitable habitat. It is still locally common and regenerating on some cliff areas inaccessible to goats, however, so VU might be an alternative category (Butaud, pers. comm. 2014).

Specimens examined.

Marquesas Islands. Fatu Hiva: Omoa, crete a l’Est du Mt Tefatutea, 625 m, 10°31"S/138°40"W, 25 Jul 1988, Florence & Perlman 9566 (P, PAP); On seacliffs of Aiguilles Rocheuses, S of Omoa village, above Tataaihoa and Tahaoa, 524 m, 6 Sep 1995, Perlman & Wood 14948 (BISH, MPU, P, PAP, PTBG, US) [used in molecular study, Funk et al.]; Tetio, seacliffs between Omoa and Hanavave, Tetio lies S of Matatu Point, about halfway to Omoa, 6-110 m, 15 Sep 1995, Perlman & Wood 14996 (BISH, MO, P, PAP, PTBG, US), cultivated plant from seed from this source, 5 Nov 1996, Lorence 7823 (BISH, PTBG, UBC, US); Hanavave Valley, cliffs below Teani, near Teeavahinenao Pass, up Uiha stream to back wall, 378 m, 16 Sep 1995, Perlman, Wood & Alexi 15009 (BISH, MO, MPU, NY, PAP, PTBG, US); Aiguilles Rocheuses, Tataaihoa side, 533-579 m, 6 Sep 1995, Wood & Perlman 4465 (BISH, K, MO, MPU, NY, P, PTBG, US); Tetio, S of Hanavave, 31-152 m, 15 Sep 1995, Wood & Perlman 4539 (AD, BISH, MO, MPU, NY, P, PAP, PTBG[2], US); About 1 km S of Omoa, 10 m, 31 Oct 1974, Decker 2689 (BISH, BKL, CBG, CHR, K, L, MO, MPU, NSW, NY, P, PAP, PTBG, US); Ridge to south of Omoa village at Angled Rocks (Aguilles Rocheuses), 585 m, 10°31"42.8'S/138°41"17.2'W, 11 Feb 2003, Perlman 18416 (BISH, P, PAP, PTBG, US); Coastline between Hanaui to Hanahoua, north of Omoa, 9 m, 10 Feb 2003, Wood & Price 10103 (BISH, MPU, PTBG, OS, US); Ouia valley, back of valley on south side in forest, 210 m, 10°29"10.3'S/138°37"12.9'W, 14 Feb 2003, Perlman 18444 (BISH, MPU, P, PAP, PTBG, US); Ridge from Omoa to Aiguilles Rocheuses, along ridge crest to Tefatutea Peak, sea cliffs of Needle Rocks above Tahaoa, 594 m, 22 Jul 1988, Perlman 10156 (AD, BISH, MO, MPU, P, PAP, PTBG, US); about 1 km along coast N. of Hanaui, 10 m, 10 Feb 2003, Price & Wood 231 (PAP, PTBG, US) [used in molecular study, Funk et al.]; Chemin d'Omoa à Hanavave, au-dessus de la vallée de Teatapu, 550 m, 18 Sep 1975, Schäfer 5747 (BISH, MPU, P, PAP, PTBG, US).

Discussion.

Bidens microcephala exhibits the most reduced heads of all Marquesan Bidens , generally having 10 or fewer disk florets per head and completely lacking in ray florets. In several specimens (Price & Wood 231, Wood & Perlman 4539, Wood & Price 10103, Perlman & Wood 14996), this reduction is even more extreme; flower heads in these specimens contain consistently fewer than 4 florets each, often only two or even occasionally one. These latter specimens also universally exhibit entire to subentire leaf margins and might represent yet another evolutionary lineage worthy of formal recognition (e.g., in Lorence 7823, specimen from cultivated plant grown from seed from Perlman 14996).

Figures

Figure 5. Bidens microcephala W. L. Wagner, J. R. Clark & Lorence A Distal part of plant B Compound leaf C Head showing bracts and disk florets D Outer Involucral bracts and peduncle E Outer involucral bract showing basal gibosity F Pale G Inner involucral bract H Disk floret I Achene J Inset showing achene surface. Drawn from Perlman 18444 (PTBG) [A, C, D, G and H], Perlman 18416 (unmounted) [B], pickled material of PTBG cult. 950676 (from Perlman & Wood 14996) [E, I and J], and Wood 10103 [F].