Kalanchoe darainensis (Crassulaceae), a new species from northeastern Madagascar

Abstract Klein, D.-P., R. Shtein, L. Nusbaumer & M.W. Callmander (2021). Kalanchoe darainensis (Crassulaceae), a new species from northeastern Madagascar. Candollea 76: 117–123. In English, English and French abstracts. A new species of small, rosulate and upright-flowered Kalanchoe Adans. (Crassulaceae) from northeastern Madagascar is described and illustrated: Kalanchoe darainensis D.-P. Klein & Callm. Morphologically, Kalanchoe darainensis is most similar to Kalanchoe blossfeldiana Poelln. and Kalanchoe globulifera H. Perrier which are known from the northwestern Tsaratanana Massif, c. 100 km southwest of Daraina. Detailed notes on the habitat and ecology of Kalanchoe darainensis are provided, as well as a short taxonomical overview of allied species of the Kalanchoe subg. Kalanchoe from Madagascar, including an identification key to those species. Despite its restricted distribution in the protected Antsahabe massif, the new species is preliminary assessed as “Least concern” [LC] using the IUCN Red List Criteria.


Introduction
The genus Kalanchoe Adans. (Crassulaceae, Kalanchooideae) comprises more than 150 species known to date and occurs in Madagascar, Africa, Arabia and tropical Asia. Currently 80 species and nothospecies are recognized in Madagascar, all but one of which are endemic to the Great Island (Madagascar Catalogue, 2021). The genus of Kalanchoe consists of three subgenera: the autonymic Kalanchoe subg. Kalanchoe which is known from Madagascar, Africa, Arabia and Asia, as well as Kalanchoe subg. Bryophyllum (Salisb.) Koorders and Kalanchoe subg. Kitchingia (Baker) Gideon F. Sm. & Figueiredo, both endemic to Madagascar (Smith & Figueiredo, 2018).
Kalanchoe subg. Kalanchoe includes species that share the following characters: plants annual or perennial, herbaceous or woody-arborescent, calyx unfused for most of its length with a short to indistinct tube, sepal segments often free, usually adpressed to the corolla tube, filaments inserted ± above the middle of the corolla tube, rarely below, flowers typically erect, rarely omni-directional or pendent, leaves and inflorescences never bulbiliferous, carpels convergent, usually much longer than the styles, scales elongated to linear, with a length/width ratio usually > 3, anthers included in corolla-tube or very slightly exserted, often dressed with a ± spherical connective gland on the anthers (Boiteau & Allorge-Boiteau, 1995;Descoings, 2003;Smith & Figueiredo, 2018).
Excluding Kalanchoe aromatica and K. bouvetii, that have omni directional, zygomorphic flowers and distinct corolla tubes, we consider the species of both informal groups, "Occidentales" and "Globuliferae", to form a common species group. These are small statured shrubs to medium sized herbs, usually at least partially covered with a glandular indumentum, that have erect, actinomorphic flowers, highly reduced to indistinct calyx tubes, long, deltoid to narrowly lanceolate sepals, apically acute to acuminate and linear to filiform nectary scales. Two further recently described species, K. antennifera Desc. and K. pareikiana Desc. & Lavranos can also be placed in this species group, based on their morphology. Kalanchoe antennifera originates from the vicinity of Antsalova in the Tsingy de Bemahara in western Madagascar (Mangelsdorff, pers. comm.). The precise type locality was unknown to Descoings (2004) who stated "Africa" in the protologue. Moreover, despite its occurrence in Arabia, virtually across continental Africa, and in Madagascar, the exact natural geographical distribution range of K. lanceolata remains open to conjecture. Kalanchoe lanceolata rather shares character expressions with species of Kalanchoe subg. Kalanchoe from beyond Madagascar and accordingly we refrain from placing it in this otherwise Malagasy group.
Distribution, ecology and phenology. -Kalanchoe darainensis is known only from the Antsahabe forest in the Loky-Manambato region (Daraina) in northeastern Madagascar (Fig. 1). Being situated between the Eastern humid and the Western dry phytogeographical domains, with elevation levels partially resembling those of the Central domain, this area comprises particularly diverse vegetation types (Ranirison et al., 2018). Only four individuals of the new species were found among all the localities visited during a vegetation study, which included more than 54,000 records of plant occurrences in the 10 main forest areas of that region (Nusbaumer, 2011). These individuals were observed at elevations between 390 and 900 m where the annual mean precipitation reaches 1400 -1450 mm and annual mean temperatures vary from 17.5 -21° C, depending on the elevation level (Nusbaumer, 2011). Kalanchoe darainensis grows on the lower slopes of rocky outcrops on raw mineral soils (lithic erosion soils on leucocratic granite or skeletal soils on cristalin domes) in rupicolous vegetation mainly surrounded by primary mesophilous and ombrophilous forest (Ranirison et al., 2018), but also by matrix habitats on a ridge covered with sparse vegetation with a low canopy. The rupicolous vegetation reaches heights of 1 m with occasionally emerging treelets up to 4 -5(-8)  Kalanchoe darainensis was collected in flowers between April and October.
Conservation status. -While Kalanchoe darainensis is known only from four collections representing four locations (sensu IUCN, 2012), it is situated within a large block of forest in the Loky-Manambato protected area. No future decline is expected in terms of Area of Occupancy (AOO), Extent of Occurrence (EOO), or quality of habitat. We therefore assign a preliminary risk of extinction status of "Least concern" [LC] using the IUCN Red List Categories and Criteria (IUCN, 2012).
Notes. -Kalanchoe darainensis is morphologically most similar to K. blossfeldiana and K. globulifera (Table 1). The two latter species are restricted to the high-altitude humid forests of the Tsaratanana mountain range, c. 100 km south-west from Daraina. Like K. darainensis, these species are perennial, small-sized, soboliferous, rosulate plants with simple leaves and a subcylindrical corolla-throat. Kalanchoe blossfeldiana and K. darainensis share the same flower characters, i.e. the scarlet red flower color and the petals being ovate-obovate, with an obtuse, mucronate apex. Kalanchoe globulifera and K. darainensis both produce few-to many-flowered dichasial cymes, are at least partially glandular pilose and are dressed with connective glands on the anthers. Among the northern representatives of Kalanchoe subg. Kalanchoe in Madagascar, a scarlet red flower color is unique to K. blossfeldiana and K. darainensis.