Croton stanneus Baill.

Croton stanneus Baill. in Bull. Mens. Soc. Linn. Paris 2: 850. 1890 [as stanneum] (Fig. 1B, 2A, 4 C-D, 5).

Typus: MADAGASCAR: “Central Madagascar”, rec’d. XI.1885, Baron 3382 (holo-: K [K001040368]!, iso-: P [P00133580]!).

= Croton perrieri Leandri in Bull. Mus. Natl. Hist. Nat., sér. 2, 3: 369. 1931. Lectotypus (designated here): MADAGASCAR. Prov. Mahajanga: L e Berizoka [Le Beritsoka], X.1897, Perrier de la Bâthie 353 (P [P00404485]!; isolecto-: K [K001040360]!, P [P00404484, P00404486, P00404487]!), syn. nov.

= Croton baldauffii Leandri in Ann. Mus. Colon. Marseille, sér. 5, 7: 55. 1939 [as baldauffi]. Lectotypus (designated here): MADAGASCAR. Prov. Toliara: Forêt de Besomaty, entre le Fiherenana et l’Isahena (Mangoky), 750-800 m, X.1933, Humbert 11249 (P [P00301487]!; isolecto-: P [P00127468]!), syn. nov.

= Croton ikopae Leandri in Ann. Mus. Colon. Marseille, sér. 5, 7: 83. 1939. Lectotypus (designated here): M ADAGASCAR. Prov. Antananarivo: Analamanga Reg., vallée de l’Ikopa, au NW d’Ankazobe, 15.III.1930, Decary 7554 (P [P00154394]!; isolecto-: K [K001040362]!, P [P00154395, P00154396, P00154397]!), syn. nov.

= Croton crocodilorum var. platyaster Radcl.-Sm., Gen. Croton Madag. Comoro 113. 2016. Typus: MADAGASCAR. Prov. Toliara: Forêt du Zombitsy, près de Sakaraha, III.1960, Keraudren 510 (holo-: P [P00154485]!), syn. nov.

= Croton parvifructus Radcl.-Sm., Gen. Croton Madag. Comoro 122. 2016. Typus: MADAGASCAR. Prov. Toliara: Forêt de Zombitsy, au NE de Sakaraha (150 km NE Tuléar), 600-800 m, 2.XI.1960, Leandri & Ratoto 3605 (holo-: P [P00132992]!), syn. nov.

= Croton stanneus var. hirsutus Radcl.-Sm., Gen. Croton Madag. Comoro 64. 2016. Typus: MADAGASCAR. Prov. Fianarantsoa: Ivohibe Distr., Antambohobe, Lomanosiny, Andranovola, 13.VIII.1967, Service Forestier 26381 (holo:- P [P00133592]!), syn. nov.

Shrubs or small trees 3-7(-10) m tall, dichotomously branching, internodes sometimes so short as to give the appearance of whorled branches. Young stems yellowishgray or occasionally rusty-brown, flattened and ridged, later becoming terete, somewhat broadened below the nodes. Stems, petioles, rachis, and flower buds yellowish to rusty-colored, with lepidote to stellate trichomes. Stipules 4-15 × 2-5 mm, lanceolate to narrowly falcate, caducous or semipersistent. Leaves opposite or ternate, sometimes subopposite, semideciduous. Petioles 2-5 cm long, adaxially canaliculate, stellate, with 2 shortly stipitate to subsessile discoid, concave, acropetiolar glands (c. 0.5 mm diam). Leaf blades firmly membranaceous, entire to minutely crenate, broadly ovate, 4-8(-14) × (2-)3-5(-9) cm, apex acuminate, base rounded to truncate or shallowly cordate, adaxial surface green and minutely stellate with impressed veins, abaxial surface gray to silvery or yellowgreen, with a dense indument (sometimes hirsute) of lepidote to stellate-lepidote trichomes and an underlaying of stellate to stellate-lepidote trichomes each with a porrect central radius; venation 3-5 palminerved at the base then penninerved with the more distal lateral nerves in 4-7 pairs, veins prominent below, usually with stipitate cylindrical glands with a discoid head at the junction of the secondary veins with the midvein (Fig. 1B), rarely also at the junction of secondary and tertiary veins. Inflorescences terminal thyrses 3-10(-18) cm long, the flowers densely grouped in cymules that are irregularly packed along the rachis, sometimes with bare sections of the rachis in between (Fig. 5A, B), most cymules staminate, but bisexual cymules often present at the base (Fig. 5H, I), bracts inconspicuous, 1-2 mm long. Staminate flowers in dense cymules with densely lepidote, depressed-globose, pale yellowbrown buds 2-3 mm diam., pedicels 0.5-1 mm long in bud, to 1.5 mm at anthesis; sepals 5, broadly triangular-ovate, c. 2 × 1.5 mm, lepidote to stellate-lepidote abaxially; petals 5, spathulate, c. 2 × 1 mm, ciliate, yellowish-white; disc-glands 5, minute, triangular; stamens 15-20, filaments 2-2.5 mm long, distally glabrous, pubescent in lower half, anthers broadly ovate, c. 0.7 × 0.5 mm; receptacle densely pubescent. Pistillate flowers few to many in basal portion of rachis, either solitary or in mixed cymules with staminate flowers, pedicels 1-3.5 mm long, stouter than in the staminate flowers; sepals 5, firm, triangular, sulcate, c. 2 × 1 mm, lepidote to stellate-lepidote abaxially, adaxially glabrous and yellow to green when fresh, persistent, not accrescent; petals 0; ovary depressed-globose, c. 2 mm diam., densely lepidote to stellate-lepidote, light golden and often specked with darker or rusty trichomes (Fig. 5G, I); styles 3, 1- 2 mm long, suberect, bifid, the 6 arms abaxially stellate-lepidote, adaxially glabrous, semi-persistent in fruit. Capsules, depressed-globose, 4.5-6.5 × 5-7(-8) mm, lepidote to stellate-lepidote (Fig. 4C); columella 3.5-4 mm long, capitate. Seeds broadly ovoid, 4-4.5 × 3-3.6 × 2.4-2.5 mm (Fig. 4D), finely pitted or sometimes ventrally obliquely 2-3-grooved on each facet, dorsally with 2-3 somewhat irregular oblique ribs per facet, slightly shiny, dark brown to blackish on the ridges, paler brown in the grooves; caruncle obcordate, bilobate, c. 0.5 × 1 mm, whitish.

Phenology. – This is a species that usually loses most of its leaves towards the end of the dry season (generally September to November). Plants often retain inflorescences with floral buds throughout the year, but flowering occurs during rainy periods, which varies across the wide range of the species.

Distribution, habitat and ecology. – This is a widespread species and one of just six species of Croton that have been found in all six provinces of Madagascar (Fig. 2A). It occurs in dry to moist forests on sandy, lateritic- or volcanic soils, as well as on inselbergs, at c. 300-1500 m elevation. Croton stanneus is found from Montagne d’Ambre in the north to Andohahela in the southeast, with its range centered in the phytogeographical Central Domain of HUMBERT (1955). It may be locally common and sometimes grows in hedgerows, and it is reported to have a spicy odor when crushed or boiled.

Conservation assessment. – Given the very widespread distribution of this species in all provinces of Madagascar, it should be assigned as “Least Concern” [LC] according the IUCN Red List Categories and Criteria (IUCN, 2012).

Vernacular names. – “Andriambolafotsy” (Cours 5215), “Karimbola” (Andriamihajarivo et al. 879), “Molanga” (Lehavana & Rasolofonirina 391), “Mongy” (Service Forestier 26381).

Notes. – The species epithet stanneus refers the tin-colored undersides of the leaves.

Croton stanneus has been confused with members of the Adenophorus Group due to its opposite leaves with stipitate glands on the lower surface. However, analyses of nrDNA data indicate that it is not closely related to this group, but rather is part of a clade with C. trichotomus Geisel. and C. salviformis Baill. Croton stanneus can best be distinguished by its long-petiolate, ovatecordate, bicolored leaves often with large, falcate stipules and terminal, dense, spike-like inflorescences with depressed-globose buds in irregularly spaced clusters. Unlike most members of the Adenophorus Group, which have laminar glands in the axis of both secondary and tertiary veins, those of C. stanneus are usually limited to the junctions of the secondary veins with the midvein, and only rarely at the junctions of the secondaries and tertiaries (see Fig. 1B). Although the stems, buds, and emerging leaves are generally covered in lepidote scales, the fully expanded leaves may have stellate-lepidote or stellate trichomes (in both cases often with an ± elongated, porrect, central radius) that are initially covered by the lepidote scales. The extent to which the central radius protrudes varies (even in the Anja population), with the more hirsute type represented by Decary 7554 (type of C. ikopae), van Ee et al. 804 and 2038 (see Fig. 5H and I). In these specimens a long protruding central radius is present in most trichomes, even in the lepidote trichomes on the shoots and buds. In comparison, the type of C. stanneus var. hirsutus is not particularly hirsute. Besides C. stanneus var. hirsutus, RADCLIFFE-SMITH (2016) also described C. crocodilorum var. platyaster and C. parvifructus, both typified by specimens from Zombitsy, in Toliara Province, and he furthermore considered them part of the Adenophorus Group (as opposed to C. stanneus and C. ikopae, which he placed in his Stanneus and Tiliifolius Groups, respectively).The type of C. baldauffii approaches the type of C. ikopae in its dense, stiff indument, and has relatively small leaves and short inflorescences, but it conforms well to the characterization of C. stanneus given above, including the presence of laminar glands along the midrib. The type of C. perrieri has only young leaves (with laminar glands), but these, and the inflorescences, match well those of the type of C. stanneus.

LEANDRI (1939) placed Croton stanneus in his Stanneus Group, which was characterized by the silvery lepidote undersides of the leaf blades (which separated it from the Adenophorus Group), staminate flowers with more than 12 stamens, no petals in the pistillate flowers, and the leaf blades at least half as wide as long. It was distinguished from the other three species recognized in the group by having glands at the insertion of the secondary veins on the leaf undersides, whereas the others lack them.

Additional specimens examined. – MADAGASCAR. Prov. Antananarivo: Analamanga Reg., Ankazobe Distr., Talata-Angavo, Manontanitsiloza, Ankafobe forest, 18°07’09”S 47°11’36”E, 1455 m, 31.VII.2005, Lehavana & Rasolofonirina 391 (MO, P, TAN); Sur le Manambolo, affluent de la Betsiboka, 900 m, XI.1925, Perrier de la Bâthie 17401 (P); Angavokely, 8.VI.1971, Schmitt 374 (P); Carion [Nandihizana], 28.VI.1971, Schmitt 487 (P). Prov. Antsiranana: Diana Reg., Ambanja Distr., Tsaratanana, Camp III (piste vers Camp II), 16.II.1966, Debray H362D (P); SAVA Reg., Vohemar Distr., Daraina, Bobanora forest, 13°13’13”S 49°46’19”E, 410 m, 3.III.2003, Gautier 4204 (G); ibid.loc., Antsahabe forest, 13°12’36”S 49°33’25”E, 550 m, 11.I.2004, Nusbaumer 906 (G, MICH, MO); Montagne d’Ambre, 12°34’56”S 49°07’44”E, 1106 m, 4.I.2002, Nusbaumer 3379 (G); Antsahabe forest, 13°12’36”S 49°33’41”E, 420 m, 6.XI.2005, Razafitsalama et al. 786 (CNARP, G, MO, P, TAN); Montagne d’Ambre, 12°34’56”S 49°07’45”E, 1020 m, 7.I.2008, Razanajatovo et al.26 (G). Prov. Fianarantsoa: Amoron’i Mania Reg., Ambatofinandrahana, P.K. 2 route de Fenoarivo, Centre Ouest, IX.1956, Bosser 9862 (MO, P); Ihorombe Reg., Ambia, cton et poste Iakora, bord de l’Ianaivo, 570 m, 16.V.1957, Cours 5200 (P); Anketsihetsy, cton Begogo, poste Iakora, 600 m, 18.VII.1957, Cours 5202 (P); Atsimo-Atsinanana Reg., Antamboara, cton de Ranotsara Sud, distr. Midongy du Sud, massif de l’Ivakoany, montagne Analanavelo, s.d., Cours 5215 (P); Haute Matsiatra Reg., Anja Community Reserve, E of RN 7, c. 9.5 km W of Ambalavao, 21°51’04”S 46°50’37”E, 970 m, 29.XI.2012, Gillespie 10802 (CAN, MICH, MO, TAN); Ambatofinandrahana, X.1963, Morat 122 (P); Haie autour d’un village près du Mt Ambohimalaza (Bassin du Mahatriaka), 1500 m, VI.1912, Perrier de la Bâthie 9661 (P); Route Nationale 7, c. 15 km S of Fianarantsoa, c. 30 km N of Ambalavao [village of Anjamana], 21°34’51”S 47°01’12”E, 1170 m, 7.II.2009, van Ee et al. 804 (MICH); ibid. loc., 1148 m, 23.VII.2015, van Ee et al. 2038 (MICH, TAN); Anja Park, 21°51’09”S 46°50’44”E, 940- 971 m, 6.VIII.2015, van Ee et al. 2157 (MICH, TAN); ibid. loc., van Ee et al. 2158 (MICH, TAN); ibid.loc., 21°51’09”S 46°50’46”E, 941-970 m, 6.VIII.2015, van Ee et al. 2159 (MICH, TAN); ibid.loc., 21°51’07”S 46°50’43”E, 941-970 m, 6.VIII.2015, van Ee et al. 2160 (MICH, TAN). Prov. Mahajanga: Betsiboka Reg., Maevatanana Distr., Antsiafabositra, Bemanevika, 17°13’28”S 46°59’37”E, 350 m, 7.V.2005, Andrianjafy et al. 1000 (MO; P, TAN); Sofia Reg., env. de Mandritsara, IV.1974, Morat 4467 (MO, P); Soalala, 12.VII.1977, Rakotozafy 1920C (MO, TAN); Borziny Distr., Tsiningia, Amberoverobe, 15°34’13”S 47°21’55”E, 60 m, 23.XI.2004, Razakamalala et al. 1877 (MO, P, TEF); au lieu dit Analankeboka, à l’W de Bealanana, 20.XI.1966, Service Forestier 27103 (G, K, MO, P). Prov.Toamasina: Alaotra-Mangoro Reg., Amparafaravola Distr., Petites forêts à l’W d’Analamanatrika, cton d’Ambohijanahary, 1200 m, 5.I.1945, Cours 2167 (MO, P); avant la chute de Maningory, 850 m, 15.XII.1944, Homolle 1966 (P). Prov. Toliara: Atsimo-Andrefana Reg., Sakaraha Distr., Zombitsy National Park, 22°53’06’’S 44°41’47’’E, 800 m, 16.I.2006, Anderberg et al. 120 (MO, S); ibid. loc., 22°46’21’’S 44°40’25’’E, 540 m, 8.IV.2006, Andriamihajarivo et al. 879 (MO, P); Sakaraha Distr., Mahaboboka, Marotsiraka, Analavelona forest, 22°39’08’’S 44°11’19’’E, 1055 m, 21.II.2009, Andriamihajarivo et al. 1670 (MO; P, TAN); Zombitsy, XII.1959, Bosser 13873 (P); ibid.loc., XII.1960, Bosser 13995 (P); 20 km de Sakaraha, route d’Ankazoabo, 21.II.1970, Bosser 19969 (P); Vallée du Fiherenana, 300-500 m, 1-2.VIII.1928, Humbert & Swingle 5067 (P); Anosy Reg., Bassin supérieur du Mandrare (SE): col et sommet de Marosoui, 1000-1400 m, 14-15.XI.1928, Humbert 6592 (MO, P); Ivakoany Massif de l’Ivakoany (centre S), pentes occidentales, 1000-1200 m, 17.XII.1928, Humbert 7029 (P); Haute vallée de la Manambolo, affluent de l’Ionaivo, 900- 1100 m, XI.1933, Humbert 12144 (P); forêt d’Analamarina, vallée de l’Hazoroa (affluent de la Taheza, bassin de l’Onilahy) au Sud de Sakaraha, c. 300 m, 6-9. XII.1946, Humbert 19647 (MO); Zombitsy, III.1960, Keraudren 482 (P); ibid. loc., 600-800 m, 1.XI.1960, Leandri 3544 (P); ibid. loc., 600-800 m, 1.XI.1960, Leandri 3570 (P); ibid. loc., 600-800 m, 2.XI.1960, Leandri 3611 (P); forêt d’Analavolona, entre le Fiherenana et la Manombo, 1000 m, V.1933, Perrier de la Bâthie 19190 (P); Sakaraha, Mahaboboka, Marotsiraka Betsileo, Analavelona forest, 22°39’36’’S 44°11’51’’E, 923 m, 13.XI.2010, Rakotoarivelo et al. 407 (MO, P, TAN); Andohahela, 24°31’S 46°38’E, 600-1700 m, 5-22.VII.1993, Randriamampionona 522 (K, MICH, MO); Zombitsy, 22°53’S 44°38’E, 700-800 m, 23.IV.1998, Randrianaivo et al. 192 (MO, P); ibid. loc., 22°49’14’’S 44°42’26’’E, 817 m, 22.V.2004, Rogers 599 (MO); Androy Reg., Ampandrandava, 1000 m, 1943, Seyrig 53 [= Herb. Jard. Bot. Tana 5733] (P); Zombitsy, 22°53’09”S 44°41’32”E, 810 m, 24.VII.2015, van Ee et al. 2039 (MICH, TAN). Sine loc.: 1952-1963, Dequaire E39 (P).