Sagittanthera Mart., 2013

Martínez-Azorín, Mario, Crespo, Manuel B., Dold, Anthony P., Wetschnig, Wolfgang, Pinter, Michael, Pfosser, Martin & Jaarsveld, Ernst Van, 2013, Sagittanthera (Hyacinthaceae, Urgineoideae), a new buzz pollinated genus from the Eastern Cape Province of South Africa, Phytotaxa 98 (2), pp. 43-54 : 46-47

Sagittanthera Mart. -Azorín, M.B.Crespo, A.P.Dold & Van Jaarsv., gen. nov. ( Figs. 1–4 )

Herbae bulbosae; squamae bulbi crassae, carnosae, claviformes vel obovatae laxe dispositae, partim epigaeae. Folia hysterantha, longa, linearia, subplana vel teretiuscula. Inflorescentia laxa, longe racemosa, floribus numerosis, pedicellatis, subpatentis vel nutantis; bracteis acutis, triangular-subhastatis, basalibus longe calcaratis; bracteola minuta, solitaria, in parte basali pedicelo affixa. Tepala 6, biseriata, subaequalia, usque ad basin libera, oblonga vel oblongo-lanceolata, per anthesin stellato-patentia, albicantia, fascia notata centrali instructa, ad margines subrevoluta. Filamenta staminum vix manifesta, quam antherae multo breviora vel subaequantia, libera vel connata, recta erectaque. Antherae connatae stylo cingentes, sursum gradatim angustatae, per poros apicales minutos dehiscentes. Stylum gracile, erectum, longum, rectum, post anthesim antheras subaequante vel paulo superante; stigma subcapitatum. Fructus trilocularis, loculicidalis; semina numerosa, oblonga, subplana, nigrescens. Genus distinctissimum Rhadamantho et Tenicroa affine , sed ab utraque maxime differt floribus bracteolatis et antheris connatis per apicales minutos poros dehiscentibus.

Typus generis: — Sagittanthera cyanelloides (Baker) Mart. -Azorín, M.B. Crespo, A.P. Dold & Van Jaarsv. (holotype).

Bulbous plant. Bulb partially epigeal, with thickened, fleshy, shortly stalked, loose scales, easily proliferating when detached. Roots thickened and branched. Leaves hysteranthous, up to 50 cm long, linear, subflattened and keeled to subterete. Inflorescence a long, lax, many-flowered raceme, with pedicellate and subpatent or nodding flowers. Bracts acute, triangular-subsagittate, the lowermost with a long basal spur; prophylls present, small, solitary at the base of pedicels. Tepals 6, biseriate, free from the base, subequal, oblong to oblong-lanceolate with subrevolute margins, stellate-patent at the anthesis, white with a darker longitudinal narrow central band. Filaments of stamen much shorter or subequal to the anthers, free or connate, straight and erect. Anthers sagittate, dehiscing by minute apical pores, connate to form a conical structure that surrounds the style. Ovary ovoid-tapering, 6 grooved, sometimes shortly stipitate. Style narrow, erect, long, straight, included in the cone-like structure formed by the anthers at the beginning of the anthesis, elongating to overtop the anthers after their dehiscence. Stigma punctiform to subcapitate. Capsule triloculate, loculicide. Seeds numerous, oblong, subflattened, black ( Fig. 1−4 ).

Etymology:— Sagittanthera (sagitta, -ae = lat., arrow head; - anthera, -ae = lat., anther). Named after the characteristic arrow-head morphology of both the anthers and the androecium outline. A second allegorical meaning can arise from the Latin verb sagitto (to shoot with a bow), regarding the release of pollen grains through the apical pores of the connate anthers due to the vibrations produced by large hymenoptera, the socalled “buzz pollination” ( Fig. 2 ).

Ecology and biogeography:—Rocky grasslands and crevices of vertical shale cliffs, usually southfacing, in thicket vegetation patches, associated with the Eastern Valley Bushveld and Bhisho Thornveld ( Mucina & Rutherford 2006), in regions with mostly summer rainfall and few rains in winter (total yearly precipitation ca. 500−1000 mm), and infrequent frosts. Remarkable biogeographic differences exist between Sagittanthera and Rhadamanthus / Tenicroa , the latter occurring both mainly in winter rainfall regions of southwestern South Africa and southern Namibia, with only a single species, Tenicroa exuviata ( Jacquin 1793 -94: 18) Speta (1980: 195), reaching East as far as Grahamstown.

Distribution:—Eastern parts of the Eastern Cape Province of South Africa ( Fig. 5 ), from SW of Komgha (one site) and Kei River (two sites along its gorge) to NW of Port St. Johns (three sites along the Mzimvubu River gorge), over 200 km apart. It is expected that further populations will be found in the neighbouring areas of the former Transkei region, a still botanically poorly sampled area.

Figures

FIGURE 1. Main diagnostic characters of Sagittanthera Mart.-Azorín, M.B.Crespo, A.P.Dold & Van Jaarsv. (S. cyanelloides (Baker) Mart.-Azorín, M.B.Crespo, A.P.Dold & Van Jaarsv. from Libode district, confluence of the Tina and Tsitsa rivers, A.P.Dold s.n., GRA). Arrow-heads indicate the connate anthers forming a conical structure dehiscing by minute apical pores, and the presence of bracteoles.

FIGURE 2. Flowers and pollen release by vibration in Sagittanthera cyanelloides (Baker) Mart.-Azorín, M.B.Crespo, A.P.Dold & Van Jaarsv. (from Libode district, confluence of the Tina and Tsitsa rivers, A.P.Dold s.n., GRA). a. Pedicellate flower with spurred bract and connate anthers, and hidden style; b. Detail of the connate anthers dehiscing by minute apical pores, with style protruding subsequent to pollen release; c−d. Release of pollen grains when a tuning fork is applied to the flower.

FIGURE 3. Sagittanthera cyanelloides (Baker) Mart.-Azorín, M.B.Crespo, A.P.Dold & Van Jaarsv. (Libode district, confluence of the Tina and Tsitsa rivers, A.P.Dold s.n., GRA). a. Plant; b. Flower dissection; c. Bract and bracteole; d. Inflorescence with atypical flowers in the upper part with 4−5 tepals; e. Leaves; f. Bulb scales. Scale bars: 1 cm.

FIGURE 4. Sagittanthera cyanelloides (Baker) Mart.-Azorín, M.B.Crespo, A.P.Dold & Van Jaarsv. (Libode district, confluence of the Tina and Tsitsa rivers, A.P.Dold s.n., GRA). a−b. Transversal sections of leaves; c−d. Bulb with leaves. Scale bars: a = 5 mm; c = 1 cm.

FIGURE 5. Known distribution of Sagittanthera Mart.-Azorín, M.B.Crespo, A.P.Dold, & Van Jaarsv. in the Eastern Cape Province of South Africa. Green circles: S. cyanelloides; Red triangle: S. mzimvubuensis.