Aiphanes argos R. Bernal, Borchs. & Hoyos-Gómez, 2017

Aiphanes argos R. Bernal, Borchs. & Hoyos-Gómez View in CoL , sp. nov.

Type:— COLOMBIA. Antioquia, Municipio de San Carlos, río Samaná Norte , 385 m elev., 6° 3’ 20.47” N, 74° 53’ 30.19” W, 19 July 2016, Bernal et al. 5005 (holotype COL GoogleMaps ; isotype FMB GoogleMaps ). Figs. 1–2 View FIGURE 1 View FIGURE 2 .

Diagnosis: —Rheophytic, with stems 0.9–4 m long, 3 cm diam; leaves with 15–17 pinnae per side. Differs from other members of the Aiphanes parvifolia complex in the solitary habit (caespitose or solitary in A. parvifolia ), flexuous and variously bent stems (vs. rigid and erect), linear to lanceolate pinnae (vs. cuneate) that are 8–21 times as long as wide (vs.1–4.5 times), with broad, pyramidal inflorescences (mostly narrow to cylindrical in A. parvifolia ) and basal rachillae longer and more loosely arranged vs. short and densely arranged), not appressed to rachis, with an up to 8 cm long, sterile portion at base (vs. rachillae with flowers from base in some members), and the staminate flowers with petals yellowish outside (vs. purple).

Solitary. Stem 0.9–4 m long, 3 cm diam., variously arched and bent, sparsely armed with black spines to 3 cm long, the internodes green near apex. Leaves 6–10; sheath 11.5–13.5 cm long, glabrous, green, armed with brown to black, to 3 cm long spines; petiole 10–11 cm, unarmed or with black, to 3 cm long spines, with sparse ferruginous indumentum near base, otherwise almost glabrous; rachis 24–37 cm, unarmed and mostly glabrous; pinnae 15–17 per side, regularly arranged, or those of the proximal ½ in groups of 2–5 but arranged in one plane, linear to narrowly lanceolate, 8–21 times as long as wide, the apex obliquely or lobulately praemorse or unequally bifid, with a 2–4 cm long projection on the distal margin, pinnae concolorous, glabrous, both margins lined on the distal ½ with a row of ca. 2 mm long, black spinules, midrib lacking spines; basal pinnae 8–10.5 × 0.5–0.8 cm; middle pinnae 15–20 × 1–1.5 cm; apical pinnae 1–2 ribbed, 17–19 × 1.2–1.4 cm, as broad as the remaining. Inflorescence erect or arching, projecting beyond leaves, branched to one order; prophyll 18–21 × 0.8–0.9 cm, unarmed or with a few 3 mm long spines near base; peduncle 39–46 cm long, 3–4 mm diam. at junction with rachis, densely covered with minute, brownish spinules, with scattered, to 3 cm long, soft spines; rachis 33–39 cm, minutely spinulose; rachillae 32–40, slender, densely covered with less than 0.5 mm long, yellowish brown spinules; basal rachillae 17–22 cm long, not appressed to rachis, with a basal, 3–8 cm long sterile part, with triads (a central pistillate and two lateral staminate flowers) for 2/3 of the flower-bearing portion, the remaining part with staminate flowers arranged in dyads; middle rachillae 6–10 cm long, with triads along the basal ½–2/3; distal rachillae 1.7–2 cm long, staminate; triads slightly sunken into the rachis, each subtended by a 1–2 mm long bract overarching the pistillate flower before anthesis; dyads superficial, each subtended by a similar, smaller bract. Staminate flower yellowish outside, white inside, wider than long, 1 mm long, 1.5–2 mm wide; sepals free, imbricate, membranaceous, orbicular, cucullate, keeled, 1 mm long; petals connate for ca. 1/3 their length, valvate, thick, ovoid, obtuse, 1 mm long, 1–1.5 mm wide; anthers slightly broader than long, 0.2 mm wide; pistillode trifid, fused with receptacle and base of filaments into a rounded, dark structure 1 mm diam. Pistillate flowers ca. 2 mm long; sepals free, broadly ovoid, membranaceous, enclosing petals for 4/5, 2 mm long; petals connate for ½ their length, 2.5 mm long, the free portion recurved, obtuse; staminodial cup 2 mm high, remotely dentate; pistil ovoid, 3 mm long, 1.5 mm wide, glabrous. Fruits globose, turning from yellow to purple, and finally red when ripe, ca. 8 mm diam.

Etymology:—The epithet argos is a noun used in apposition. The new species is named after Grupo Argos, a Colombian conglomerate that plans to build a dam 140 m high on the Samaná Norte River canyon, flooding the area where virtually all of the individuals of Aiphanes argos grow. This dam would not only drown the palm and at least 34 other species of rheophytic plants growing along the river, but would also destroy one of Colombia’s most beautiful places. In naming this handsome and extraordinary palm after Grupo Argos, we hope that the Group will be remembered as the one who saved the species by abandoning a dam project and helping to preserve the canyon, rather than the one who led its namesake palm to extinction.

Habitat:— Aiphanes argos is known from a restricted area in the eastern slopes of the Central Cordillera in Antioquia, Colombia. It grows along the rocky banks of the Samaná Norte River canyon and its tributary creeks, between 200 and 800 m elevation, but is particularly abundant between 220 and 370 m. The Samaná Norte River canyon is a depression 60 km long and up to 750 m deep, which cuts through granitoid rocks of the Antioquian batholith, schists, gneisses and marbles of the Cajamarca complex, and shales and quartzites of the Samaná sediments. Soil development in the marble unit is nil, since all weathering products are washed by water runoff; weathering in these rocks is limited to the dissolution of carbonates occurring on the surface and along the joints and fault zones by the effect of acidic waters associated with the lush vegetation of the area (F. Hoyos, pers. comm.).

Aiphanes argos grows side by side with Geonoma interrupta subsp. rivalis (Kalbreyer ex Burret) A.J. Hend. (2011a) . The crowns of both species are subject to the action of the river currents during high water level, and they are, therefore, true rheophytes. Only 18 species, out of the ca. 2600 members of the palm family, are known to have a rheophytic habit ( Dransfield 1978, 1984, 1992, Galeano-Garcés & Skov 1989, Hodel 1992, Beentje 1993, Barrow 1994, Dransfield & Beentje 1995, Baker 1997, Dowe & Ferrero 2000, Dransfield et al. 2008, Galeano & Bernal 2010, Heatubun 2011, Henderson 2011a) ( Table 1 View TABLE 1 ). As in other rheophytes, the pinnae of Aiphanes argos have a high length/ width ratio ( van Steenis 1987) and a thin and flexible stem ( Fig. 1 View FIGURE 1 ). This contrasts strongly with the same characters in other members of the Aiphanes parvifolia complex that grow far from streams.

Additional specimens:— COLOMBIA. Antioquia, Mun.de San Carlos, Alto Samaná, road Jardín-Miraflores, quebrada La Miranda , 700–800 m elev., 24 October 1989, Callejas 8535 ( COL, HUA) ; Mun. de San Luis, vereda Palacio, right margin of the Samaná Norte River , 388 m elev. 6° 00’51” N 74° 55’58” W, 14 February 2015, Hoyos-Gómez et al. 2932 ( JAUM) GoogleMaps .

Conservation status:— Aiphanes argos is known only from the middle basin of the Samaná Norte River, and quebrada La Miranda, one of its tributaries, along a stretch of ca. 30 km. The palm occupies only a narrow fringe along the river margins, no more than 15 m from the lowest water level, and thus its overall area of occupancy is only ca. 0.9 km 2. We estimate the total number of adult individuals to be around 600. The species has not been found in other rivers in the region, where the co-occurring Geonoma interrupta subsp. rivalis has been found.

A strong process of human occupancy along the less steep slopes of the Samaná Norte river canyon is taking place as war recedes in Colombia, and recent deforestation was evident during our visits to the area in July and December 2016. Although the river margins themselves usually are not strongly affected, they do suffer from human activities associated to colonization, such as artisanal mining along the river margins. However, the highest risk for the species is, by far, the planned hydroelectric plant Porvenir II, which the Argos Group intends to build along the river. With a planned dam 140 m high, virtually all of the individuals of Aiphanes argos would be drowned under a water table ca. 125 m deep. Because of this, the new species must be considered Critically Endangered under the categories of the IUCN (2012), according to criteria B2ab(iii): area of occupancy less than 10 km 2 [B2], known from a single location [a], and continuous decrease in habitat extension, area and/or quality [b(iii)].