Holotypus: Madagascar. Reg. Androy [Prov. Toliara]: env. N de Tsimilofo, Beloha, [24°59′S 45°10′E], 14.XI.1967, fr., Service Forestier 27975 (P [P00518210]!).

Pyrostria costata Klack. & Razafim. differs from all other Malagasy congeners with ribbed fruits by the combination of small leaves clustered on brachyblasts, ribbed pollen presenter, and ± spherical and broadly ellipsoidal and 10-lobed fruits.

Shrub with stout, terete, glabrous branches. Leaves basically opposite but clustered on brachyblasts; petioles 0.5–1 mm long, with hairs around base; blade elliptic, 15–20 × 5–8 mm, cuneate at base, bluntly acute to rounded at apex, glabrous, herbaceous, with flat margin; venation pinnate, arched; midrib and 2–3 pairs of primary nerves visible when dry, only faintly so above, slightly raised on lower surface, flush with leaf surface above; domatia sometimes present as tufts of hairs in axils of main nerves; stipules broadly triangular, 2.2 × 1.8 mm, acuminate at apex, glabrous, soon dehiscent, with hairs present inside seen as small tufts on tip of brachyblasts. Inflorescences axillary on short (< 1 mm long) peduncles, umbel-shaped, c. 5 (male) to 1 (female)-flowered; peduncular bracts 2.5–3 mm long, paired, connate, navicular, acute, hairy inside, glabrous outside; pedicels 2.5–3.5 mm long at anthesis (male) and in fruit, glabrous but hairy around base. Flowers 5-merous, white. Male flowers with calyx glabrous; tube flat; limb tube 0.6 mm long with shallow lobes; corolla glabrous outside; tube ± cylindric to somewhat barrel-shaped, 4.5–5.5 mm long, at mouth filled with 5 dense tufts of moniliform hairs between the stamens; lobes triangular to oblong, 3 – 3.4 × 2 – 2.3 mm, rotate to recurved? with reflexed tip, acute at apex, finely papillate on upper side; stamens attached to corolla tube at mouth; anthers ± sessile, ellipsoidal, 1–1.1 mm long, partly exserted, recurved after dehiscens; style including pollen presenter 6–7 mm long, shortly exserted; pollen presenter 1.2 mm long, ribbed; disc flat, glabrous. Female flowers not seen. Fruit (immature?) ± spherical to broadly ellipsoidal, 3.5–4 × 3.5–4 mm, topped by flat disc and calyx, with wrinkled distinct longitudinal ribs, glabrous, 2-locular.

Etymology. – The epithet costata refers to the ribbed fruits of the species.

Distribution and ecology. – Pyrostria costata is known from the drylands of southern Madagascar (Fig. 2). It has been collected in dry deciduous forest and dry spiny thicket.

Phenology. – Collected in both flower and fruit in November.

Conservation status. – Pyrostria costata has a restricted geographic range in the minimum AOO of 8 km2. It is known from two localities, one of which is situated within the boundary of the Andohahela National Park. Forests within Parcelle II of the National Park are threatened by wild fires and demand of forest goods for the nearby coties (Goodman et al., 2018). Outside of the protected area, the species is threatened by forest clearing for agriculture and wild fire which would result in continuing decline of quality of habitat and number of mature individuals. Pyrostria costata is therefore assigned a preliminary conservation status of “Critically Endangered” [CR B2ab(i,ii,iii,iv,v)] in accordance with IUCN Red List Categories and Criteria (IUCN, 2012).

Notes. – Ribbed fruits are rare in the Malagasy Pyrostria (Leroy, 1972). Pyrostria costata and P. verdcourtii (Cavaco) Razafim. et al. are the only Malagasy Pyrostria species with ribbed, two-locular fruits (as opposed to the other species with ribbed, 5–8 locular fruits). The former species is distinct by its small (2.2 × 1.8 mm), broadly triangular stipules and ± spherical and broadly ellipsoidal and 10-locular fruits, while the latter species differs by its larger (c. 5 mm long), lanceolate stipules and obconical and 8-locular fruits. Furthermore, P. costata is restricted to the drylands of southern Madagascar, whereas P. verdcoutii is confined in the northwest and north of the island.

Additional specimens examined. – Madagascar. Reg. Androy [Prov. Toliara]: env. N de Tsimilofo, Beloha, [24°59′S 45°10′E], 14.XI.1967, fl., Service Forestier 27974 (P [P00518210]); Andohahela RNI, parcelle 2, c. 50 km WNW of Taolagnaro (Fort Dauphin), forest 4.1 km due E of Ihazofotsy, [24°48′58″S 46°35′38″E], 150 m, 30.XI.1997, fr., Davis et al. 1164 (K, BR [BR0000021253812]).

Holotypus: Madagascar. Reg. Androy [Prov. Toliara]: à 20 km env. au S de Beraketa, [24°22′50″S 45°37′300″E], 18.XII.1968, fr., Service Forestier 28513 (P [P00518215]!).

Pyrostria macrocarpa Klack. & Razafim. differs from the other Malagasy Pyrostria congeners by its large, 5–6-locular, obconical, non-ribbed fruits with a rather flat apex.

Shrub with branches often having short internodes, terete, younger parts covered by short erect hairs, glabrescent, with lenticels. Leaves opposite, covered on both sides with erect hairs, more densely so along the nerves below; petioles 1.5–2 mm long, hairy; blade elliptic, 4–5 × 1.5–2.5 cm, drying brown above and light green below, cuneate at base, acute to acuminate at apex, herbaceous, with flat margin; venation pinnate, arched; midrib and 5–7 pairs of primary nerves clearly visible on both sides when dry, ± flush with leaf surface above, raised below; domatia not clearly separated from hairy veins; stipules narrowly ovate to triangular, 3–5.5 × 2–4 mm, acute to acuminate at apex, keeled, hairy, dehiscent. Inflorescences axillary on short (c. 0.5 mm long) peduncles to almost sessile, umbel-shaped, 1 (female) to 5–10 (male)-flowered; peduncular bracts large, 4–5 mm long, paired, navicular, acute, with a tuft of long hairs inside, shortly hairy outside; pedicels 2.5–5 mm long at anthesis (male) and in fruit, ± glabrous (male) to hairy, with longer hairs at the very base. Male flowers with calyx 5-merous, glabrous; tube flat, very short; limb tube c. 0.8 mm long with broadly triangular acute lobes; disc conical, glabrous; corolla, stamens and style not seen. Female flowers not seen. Fruits ± obconical and 5–6-lobed towards a rather flat apex, cuneate to rounded at base, up to 1.5 × 2 cm, glabrous.

Etymology. – The epithet macrocarpa refers to the large fruits of the species.

Distribution and ecology. – Pyrostria macrocarpa is known only from the type locality in the dry spiny thicket of southwestern Madagascar (Fig. 2).

Phenology. – Overblown and fruiting specimens seen in December.

Conservation status. – Pyrostria macrocarpa has a restricted geographic range in the minimum of 4 km2. It is known from a single locality outside of the protected area network. The dry spiny thicket is threatened by clearing for agriculture and wild fires, which would result in continuing decline of quality of habitat and number of mature individuals. The species has further not been observed since 1968. Pyrostria macrocarpa is therefore assigned a preliminary conservation status of “Critically Endangered” [CR B2ab(i,ii,iii,iv,v)] in accordance with IUCN Red List Categories and Criteria (IUCN, 2012).

Notes. – Pyrostria verdcourtii and P. macrocarpa are known to have obconical fruits but those of the former are 2-locular, deeply ribbed as opposed to 5–6-locular, non-ribbed in the latter. Furthermore, P. verdcoutii is confined in the northwest and north of Madagascar, while P. macrocarpa is confined to the south of the island.

Additional specimen examined. – Madagascar. Reg. Androy [Prov. Toliara]: à 20 km env. au S de Beraketa, [24°22′50″S 45°37 ′300″E], 18.XII.1968, old ♂ fl., Services Forestier 28512 (P [P00518214]).

Holotypus: Madagascar. Reg. Atsimo-Andrefana [Prov. Toliara]: au N d'Andranohinaly, PK 45 de la route Tuléar-Sakaraha, [23°15′S 44°01′E], XII.1961, fl., Service Forestier 20754 (P [P00518204]!).

Peponidium leroyi Klack. & Razafim. differs from the other congeners by the combination of hairy leaves with ciliate margins, sparsely pubescent flowers, and ribbed pollen presenters.

Shrub 2–3 m tall; branches somewhat compressed when young becoming terete, youngest branches densely hairy, glabrescent. Leaves at top of branches, opposite, hairy on both sides, more densely so along the nerves below; petioles 1–2 mm long, hairy; blade elliptic to obovate, 2.5–5.5 × 1–2 cm, cuneate at base, bluntly acute to rounded at apex, herbaceous, with flat, ciliate margin; venation pinnate with 7–12 pairs of primary veins ± parallel to slightly arched towards margin; midrib and primary veins clearly visible, distinctly raised on lower side when dry, ± flush with leaf surface above; tertiary nerves reticulate; domatia not seen; stipules first narrowly triangular becoming ovate, 4–5 × 0.5–3 mm, acuminate to subulate at apex, hairy, dehiscent. Inflorescences axillary, hairy; male flowers 5–7 in umbels on 2–4 mm long peduncles, female flowers 1–2 on very short peduncles (up to 2 mm in fruit) or peduncles missing; pedunculate inflorescences with small, free bracteoles; pedicels at anthesis 2–3 mm long (male flowers) or c. 1 mm long (female flowers) to 5 mm long in fruit, hairy. Flowers 5-merous, whitish. Male flowers with calyx glabrous or with few hairs; tube almost lacking crowned with shallow very broadly triangular to rounded lobes, c. 0.1 mm long; corolla hairy outside, at mouth filled with 5 tufts of somewhat moniliform up to 0.5 mm long hairs between the stamens; tube campanulate, c. 1.8 mm long; lobes triangular, bent outwards, acute at apex, c. 1.5 × 1.2 mm; stamens attached to corolla tube at mouth; anthers ± sessile, ellipsoidal, c. 1 mm long, partly exserted; style including pollen presenter c. 2.5 mm long, shortly exserted; pollen presenter c. 0.7 mm long, ribbed; disc annular, glabrous. Female flowers with hypanthium with calyx c. 2.2 mm, glabrous; limb tube 0.2 mm long; lobes insignificant; corolla with some hairs outside; tube ± cylindric, c. 1 mm long, with conspicuous tufts of moniliform hairs between the anthers; lobes, triangular, c. 2.5 × 1.1 mm, acute at apex, erect; stamens attached at mouth of corolla tube; anthers sessile, exserted, ovate in outline, c. 0.9 mm long; style with stigmatic head c. 1.8 mm long; stigmatic head c. 0.6 mm long, ridged; disc annular, short, glabrous; ovary 2-locular. Fruit bilobed, broadly obcordate with truncate base, c. 0.9 × 1 cm, sparsely hairy, topped by a short ring from persisting calyx.

Etymology. – The species is named in honour of Jean-François Leroy, who studied the Malagasy Rubiaceae for many years and identified several new species.

Distribution and ecology. – Peponidium leroyi is known from dry deciduous forest and dry spiny thicket at lower altitudes in southwestern Madagascar, hitherto found only in Fiherenana valley northeast of Toliara (Fig. 2).

Phenology. – Collected in flower during November and December, in fruit known from January. Flowers seem to appear simultanously with leafing.

Conservation status. – Peponidium leroyi has an estimated EOO of 51 km2 and a minimum AOO of 12 km2. It is known from three localities, two of which are within the boundary of the Ranobe PK32 protected area. Changes in forest cover of the dry spiny thicket within the delimitation of the actual protected area between 1996 and 2016 have been as high as 35 % loss (Goodman et al., 2018). Forest lost is associated with uncontrolled slash-and-burn shifting agriculture and human settlements (Goodman et al., 2018). These threats would result in continuing decline of quality of habitat and number of mature individuals. The new species is therefore assigned a preliminary conservation status of “Endangered” [EN B1ab(i,i i,iii,iv,v)+B2ab(i,ii,iii,iv,v)] in accordance with IUCN Red List Categories and Criteria (IUCN, 2012).

Notes. – Many Malagasy Peponidium species (including P. leroyi) have bilobed fruits. However, P. leroyi is distinct by its hairy leaves with ciliate margins, sparsely pubescent flowers, and ribbed pollen presenters.

Additional specimens examined. – Madagascar. Reg. Atsimo-Andrefana [Prov. Toliara]: valley of the Fiherenana, NE of Tulear, near Beantsy, 23°13′S 43°53′E, 50 m, 8.I.1989, fr., Phillipson & Rabesihanaka 3105 (MO, P [P00518203]); sur la route de Manombo, au N du Fiherenana, [23°14′S 43°41′E], 8–12.XI.1967, fl., Service Forestier 27919 (P [P00518207]).

Holotypus: Madagascar. Reg. Melaky [Prov. Mahajanga]: forêt de l'Antsingy vers Ambodiriana, E d'Antsalova, [18°40′S 44°44′E], 100–150 m, 8.XII.1952, fl., Leandri, Capuron &Razafindrakoto 2085 (P [P00518216]!).

Peponidium sessile Klack. & Razafim. differs from the other congeners by the combination of sessile, cordate leaves, glabrous calyx with distinct tuft of hairs at tips of lobes, and vaulted corolla lobes topped by horn-like outgrows.

Shrub 2–3 m high; branches terete, with younger parts hairy but soon bark becoming rough with outer layers peeling off. Leaves opposite along branches, ± sessile, mostly glabrous but basal part of midrib and petiole with erect hairs; petioles up to 0.5 mm long; blade ovate, 3–5.5 × 1.5–3.5 cm, cordate at base, subacute to rounded at apex, herbaceous, with flat margin; venation pinnate with 3–4 pairs of primary nerves, arched, hardly visible towards leaf margin; midrib distinct and raised on both sides when dry; primary nerves ± flush with leaf surface below, slightly raised above when dry; domatia sometimes present as tufts of hairs in axils of larger nerves; stipules towards apex distincly laterally compressed, 1.5–2.5 mm long, hairy mostly along margin, persistent 4–5 base pairs but eventually dehiscent. Inflorescences terminal, sessile (female) or on short < 0.5 mm long (male) peduncles, 1–2-flowered; peduncular bracts several, small and fused at base of inflorescence (male) or missing (female); pedicels 1–3 mm long at anthesis, up to 16 mm in fruit, glabrous to sparsely hairy. Flowers 4-merous, creamish white. Male flowers with calyx 0.5 mm with shallow lobes, glabrous except for a distinct tuft of hairs at tips of lobes; lobes very broadly triangular to rounded, 0.25 × 0.5 mm; corolla glabrous outside; tube 0.7 mm long; lobes standing together vaulted above stamens but towards apex separated from each other like four horns, elliptic, c. 1.6 mm long of which free horn-like tip c. 0.4 mm, c. 0.8 mm broad. Female flowers (mature but still closed flowers seen only) with hypanthium with calyx c. 2.2 mm, glabrous except for tips of calyx lobes; limb tube 0.3–0.35 mm long; lobes shallow, c. 0.3 × 1 mm, with a distinct tuft of hairs at tip; corolla glabrous outside; tube ± cylindric, c. 1.3 mm long, with conspicuous tufts of moniliform hairs between the anthers; lobes standing together vaulted above stamens and stigmatic head but towards apex separated from each other like four horns, narrowly triangular, c. 2.5 mm long of which free horn-like tip c. 1 mm, c. 0.8 mm broad; stamens attached at mouth of corolla tube; anthers sessile, oblong, c. 0.9 mm long, included in lower vaulted portion of corolla lobes; style with stigmatic head c. 1.8 mm long; stigmatic head c. 0.6 mm long, vaguely ridged; disc c. 0.6 mm high, glabrous. Fruit bilobed, broadly obcordate with truncate base, c. 0.8 × 1 cm, almost glabrous or with solitary hairs, reddish green, with calyx remaining on top.

Distribution and ecology. – Peponidium sessile is known from limestone rocks in the Tsingy of Bemaraha in western Madagascar (Fig. 2).

Phenology. – Collected in flower from October to December, and in fruit in October.

Conservation status. – Peponidium sessile has a restricted geographic range in the minimum AOO of 8 km2. It is known from two localities, both of which are known within the boundary of the Tsingy de Bemaraha National Park. Fire density detected in the protected area or outside were among the highest in the country between 2006 and 2016 (Goodman et al., 2018). Forest is also threatened by illicit logging and new agricultural lands (Goodman et al., 2018). These threats would result in continuing decline of quality of habitat and number of mature individuals.The species has further not been observed since 1952. Peponidium sessile is therefore assigned a preliminary conservation status of “Critically Endangered” [CR B2ab(i,ii,iii,iv,v)] in accordance with IUCN Red List Categories and Criteria (IUCN, 2012).

Notes. – This species is characterized by its sessile, cordate leaves, glabrous calyx with distinct tuft of hairs at tips of lobes, vaulted corolla lobes that are topped by horn-like outgrows. The presence of distinct tuft hairs at the tips of lobes has also been reported in Peponidium crassifolium Lantz et al. (Lantz et al., 2007) but this latter has petiolate, obovate, and thick and slightly succulent leaves (vs. sessile, ovate, and non-succulent leaves in P. sessile). Further, P. sessile is known only from the Tsingy of Bemaraha in western Madagascar, while P. crassifolium is endemic to the Marojejy Massif in northeast of the island.

Additional specimens examined. – Reg. Melaky [Prov. Mahajanga]: Tsingy du Bemaraha (9e Réserve), à Tsiandro, [18°43′S 44°55′E], 10.II.1933, Leandri 812 (P [P00524235]), 845 (P [P00518217]).