Anisotes tablensis T.F. Daniel, 2015

Daniel, Thomas F., 2015, Anisotes tablensis (Acanthaceae), a New Species from Southwestern Madagascar, Proceedings of the California Academy of Sciences 62 (19), pp. 451-455 : 451-454

Anisotes tablensis T.F. Daniel , sp. nov.

TYPE. MADAGASCAR: Toliara: La Table, ca. 20 km N [sic] of Toliara, slope and along ridge, 23°25ʹ26ʺS, 043°46ʹ03ʺE, 50–120 m, 19 May 2004 (flr) , Z. Rogers et al. 483 (holotype: K!; isotype: MO!) . Figures 1 , 3 .

Divaricately branched shrubs to 4.5 dm tall. Young stems hexagonal, evenly and densely pubescent with a whitish, felt-like covering of antrorsely appressed eglandular trichomes to 0.1 mm long, epidermis not visible, trichomes soon ± restricted to troughs of internodes. Leaves sessile to subsessile, petioles (if present) to 2 mm long, coriaceous, blades oblong to oblanceolate, 4–23 mm long, 1.4– 3 mm wide, 2.9–10.5 × longer than wide, gradually attenuate at base, rounded at apex, surfaces pubescent like young stems, margin flat. Inflorescence of axillary or terminal sessile short spikes (usually only 2 fertile bracts per spike) to 9 mm long (excluding corollas), distal bracts fertile, elliptic, 4.5–5 mm long, 3.6–4 mm wide, apex rounded to obtuse-truncate, abaxial surface puberulent with antrorsely appressed eglandular trichomes to 0.1 mm long and erect trichomes <0.05 mm long, margin ± hyaline, proximal bracts sterile and smaller than distal ones. Bracteoles absent. Calyx 5-lobed, 6–7 mm long, lobes oblong-lanceolate, 5–6 mm long, 1–1.2 mm wide, abaxial surface pubescent like bracts (or with antrorsely-appressed eglandular trichomes few or absent). Corolla pinkish red, 27–35 mm long, externally pubescent with erect glandular and flexuose to retrorse eglandular trichomes 0.1–0.2 mm long, tube 12–15 mm long, corolla tube length: corolla length = 0.44–0.49, upper lip 17–21 mm long, lower lip 18–19 mm long with lobes 2.5–3.5 mm long. Stamens 20–23 mm long, filaments pubescent proximally with erect glandular trichomes 0.1–0.2 mm long, glabrous distally, thecae 2–2.3 mm long, glabrous, pollen 3-colporate, 6-pseudocolpate (the two pseudocolpi in one or more mesocolpia sometimes fused near one or both poles), 39–41 µm polar diameter ( P), 26–30 µm equatorial diameter ( E), P: E = 1.37–1.50. Style 28–32 mm long, glabrous, stigma equally 2-lobed, lobes 0.2 mm long. Capsule not seen.

PHENOLOGY.—Flowering: May.

DISTRIBUTION AND HABITAT.—Endemic to southwestern Madagascar (Toliara) where plants occur in the arid thornscrub on soils derived from decomposed coral (sometimes referred to as “coral rag scrub”) at an elevation between 50 and 120 meters ( Fig. 2 ).

CONSERVATION ASSESSMENT.—Because A. tablensis is known from a single, relatively recent collection from a population that was not observed during this study, it is difficult to assess its conservation status according to IUCN (2014) guidelines. Based on IUCN criteria for the threatened categories, A. tablensis likely has both EOO and AOO (criteria B1 and B2) sufficient for Critically Endangered status, but only one (i.e., one known location; i.e., criterion Ba) of two conditions required for assessment in that category. The only known collection does not occur in a locality that is protected. Lacking further data, this apparently rare species must be provisionally assessed as Data Deficient.

Anisotes tablensis is known only from the type collection. It is the third species of the genus known from the dry regions of southwestern Madagascar. The geographic coordinates given on the label of the type are about 2 km southwest of the prominent local mesa-like physiographic feature known as La Table ( Fig. 2 ), from which the epithet is derived. La Table (23°24ʹ32.40ʺS, 43°46ʹ51.73ʺE) is a well-known collecting locale in a region of Tertiary limestone about 12 km southeast of the city of Toliara (Tulear) and home to a large number of Acanthaceae . It is also a popular birdwatching site where several rare birds, including the Red-shouldered Vanga ( Calicalicus rufocarpalis ) and Verreaux's Coua (Coua verreauxi), are often observed. Given its accessibility, it is surprising that undescribed species are still being found on its slopes and ridge. Two other species of Anisotes , A. divaricatus T. F. Daniel, Mbola, Almeda & Phillipson and A. madagascariensis R. Ben. , occur in nearby regions ( Daniel et al. 2007), but neither is known from the vicinity of La Table. These three species can be distinguished by the following key:

1a. Leaves sessile to subsessile, petioles (if present) to 2 mm long, blades 1.4– 3 mm wide, length:width = 2.9–10.5; calyx 6–7 mm long; corolla externally pubescent with glandular and eglandular trichomes throughout, lobes of lower lip 2.5– 3.5 mm long........... A. tablensis

1b. Leaves petiolate, petioles to 12 mm long, blades 4. 5–38 mm wide, length:width = 0.7–2.7; calyx 1.3– 3.5 mm long; corolla externally glabrous or occasionally with a few eglandular trichomes proximally, lobes of lower lip 8–14 mm long.............................. 2

2a. Leaf blades broadly ovate to ovate-elliptic to elliptic to broadly elliptic, 14–45 mm long; margin of calyx lobes ± densely ciliate; corolla with internal surface conspicuously lighter in color than external surface, corolla tube 9–15 mm long, corolla tube:corolla = 0.23–0.38, upper lip 20–35 mm long and distally whitish to pinkish along margin, lower lip spirally coiled, 18–28 mm long, lobes 12–14 mm long; stamens 26–33 mm long; capsule pubescent with flexuose to antrorse eglandular trichomes 0.05– 0.1 mm long.................... A. madagascariensis

2b. Leaf blades broadly obovate to subcircular to obcordate to obdeltate to oblate, 5–14 mm long; margin of calyx lobes eciliate to sparsely ciliate; corolla with internal surface not conspicuously lighter in color than external surface, corolla tube 14–20 mm long, corolla tube:corolla = 0.46–0.56, upper lip (11–) 14–18 mm long and lacking a pale margin distally, lower lip recurved to reflexed (not spirally coiled), 11–19 mm long, lobes 8–12 mm long; stamens 15–18. 5 mm long; capsule ± rugose-granulate but lacking noticeable eglandular trichomes.. A. divaricatus

All three of the species of Anisotes from southern Madagascar lack bracteoles and have coriaceous to subsucculent leaves, bracts lacking reticulate venation (or with venation not evident), and similar 3-aperturate pollen. They would appear to pertain to Baden’s section Spiciflori ( Baden 1981; Daniel et al. 2007). Pollen of A. tablensis ( Fig. 3 ) greatly resembles that of both A. madagascariensis and A. divaricatus from southern Madagascar, except for its somewhat smaller polar diameter (39–41 vs. 62.5–7 µm). The four species from northern Madagascar ( A. hygroscopicus T. F. Daniel, R. Letsara & Martín-Bravo , A. perplexus T. F. Daniel, R. Letsara & Martín-Bravo , A. subcoriaceus T. F. Daniel, R. Letsara & Martín-Bravo , and A. venosus T. F. Daniel, R. Letsara & Martín-Bravo ; Daniel et al. 2013) show greater diversity in pollen shape and sculpturing (varying from 2- to 3-aperturate) and have membranous to subcoriaceous leaves, bracteoles, and bracts with reticulate venation evident. Anisotes tablensis shows greater similarities to those four species than to the other two southern ones in the following characteristics: calyx length, external pubescence of the corolla, and length of lobes of the lower lip.

Figures

FIGURE 1. Anisotes tablensis (Rogers et al. 483). A. Habit. B. Leaf. C. Node with axillary inflorescence bearing a flower. D. Distal portion of stamen with anther. Drawn by Tom Davis.

FIGURE 3. Pollen of Anisotes tablensis (Rogers et al. 483). A. Apertural view. B. Interapertural view.

FIGURE 2. La Table in southwestern Madagascar (looking westward toward Mozambique Channel), habitat of Anisotes tablensis. Photo by the author.