Begoniaceae, section Petermannia), a new species from

Begonia bangsamoro , a new Philippine Begonia species from the section Petermannia is described and illustrated. The new species was discovered in the fragmented riparian forest of Lanao del Sur, along the Ginapukan river in Wao, Mindanao island, Philippines. The previous collections also revealed that it occurs in the nearby province of Bukidnon. Begonia bangsamoro is distinguished from other Philippine Begonia by its lacerate leaf margins, terminal inflorescences, 4-tepaled staminate flowers, and sparsely hirsute ovaries. The new species is compared with the phenetically similar B. quercifolia. Based on IUCN Red List criteria, B. bangsamoro is designated as Endangered (EN).


Introduction
Established by Plumier in 1700 with six species (Dryander 1791;Doorenbos et al. 1998), Begonia Linnaeus (1753: 1056) is now a remarkable genus comprised of 2,001 species making it the sixth-largest genus amongst angiosperms (Moonlight et al. 2018;Hughes et al. 2015).This number, however, is expected to increase as hundreds of possibly undescribed species are likely to be discovered particularly in Southeast Asia-the centre of Begonia diversity (Moonlight et al. 2018;Thomas et al. 2012;Tian et al. 2018).Begonia section Petermannia (Klotzsch 1854: 194) de Candolle (1859: 128), in particular, has the highest species richness in Asia with more than 200 species (Peng et al. 2017).Yet, the same region is also a hotspot of tropical deforestation driven by the expanding plantation economy (Kenney-Lazar & Ishikawa 2019; Zeng et al. 2018).With approximately 82 billion m 2 of the area being converted into croplands (Zeng et al. 2018) and 500 times faster than the expected extinction rate for plants (Humphreys et al. 2019), documenting and conserving the region's flora is a race against time, especially in the remaining ecologically intact landscapes and other little-known biocultural territories.
The Bangsamoro Region on the island of Mindanao, Philippines is one of the botanically unexplored areas of Southeast Asia.Established in 2019, the Bangsamoro Autonomous Region in Muslim Mindanao (BARMM) is a newly recognised region that gained its autonomy after decades of armed conflict between the government of the Philippines and the Bangsamoro people whose historical assertion of self-governance and statehood date back to the middle of 15 th -century Sultanates (Abubakar 2019;Abuza & Lischin 2020;Lingga 2004).The decades of socio-political conflict, violence, and insurgency hampered all fieldwork in the region and many of its mountain flora (i.e., Mount Ragang and Mount Makaturing in Lanao del Sur, BARMM) remain poorly known.
To fill this gap, the field surveys were carried out within the province of Lanao del Sur in the Bangsamoro region.With the photo-documentation of the local flora in the forest patches of Sitio Trese, Barangay Banga, Wao, Lanao del Sur, BARMM (Figure 1), an unidentified Begonia was hypothesised to be an undescribed species.This was validated and confirmed through morphological comparisons of the herbarium specimens with the protologues, digitally available type specimens, and botanical descriptions from relevant literature.As such, with a window of opportunity to botanically explore the Municipality of Wao in the Bangsamoro region, we are delighted to present the discovery of a new species of Begonia from section Petermannia.
etymology:-The specific epithet is named after the Bangsamoro people which refers to the thirteen ethnolinguistic groups native to the southern Philippines.The Bangsamoro people collectively include the Bajao, Iranun, Jama Mapun, Kalagan, Kalibugan, Maguindanao, Palawanon, Maranaw, Molbog, Sama, Sangil, Tausug, and Yakan.With livelihoods and culture intimately intertwined with nature, the Bangsamoro people living within the traditional territory safeguard a number of Key Biodiversity Areas (i.e., Lake Lanao, Mount Piagayungan, and Tawi-Tawi Island).These designated KBA's in the Bangsamoro region is of global importance to biodiversity conservation of terrestrial, freshwater, and marine ecosystems.
Distribution and ecology:-Begonia bangsamoro thrives within the riparian forest along the Ginapukan river in Sitio Trese, Barangay Banga, Wao, Lanao del Sur, BARMM.The population of this species is sparsely distributed on the forest floor and along the riverbanks with a closed canopy.Some individuals were observed to creep up and shallowly rooting into a wet substrate such as the roots of tree fern for support.This forest fragment, however, is surrounded by agricultural lands, in particular, vegetable and sugarcane plantations.To date, this species is observed in Lanao del Sur, but the full extent of the distribution is not known due to the inaccessibility of the terrain.
Conservation status:-With the expanding plantation of cash crops and continuous clearing of the forests, the population of this species within the fragmented forest is restricted and faces a potential decline in the near future.The entire population of B. bangsamoro composed of about 180 individuals occurs within one km 2 .The nearest B. bangsamoro population is approximately 30 metres away from the forest edge surrounded by the aubergine and coffee plantations.However, the new species has also been documented in the nearby province of Bukidnon, Mindanao based on previous collection and photos.An unidentified collection by Ramos & Edaño (39103) from Tangculan, Bukidnon, which was then determined as B. incisa, appears to be of B. bangsamoro as seen from the degree of laceration of the lamina and the pilose stem.B. bangsamoro also occurs in the Mount Kitanglad Range Natural Park based on photographs by Pelser & Barcelona available at the Co's Digital Flora of the Philippines (Pelser et al. 2011 onwards).The photos, which are labelled as B. contracta Warburg (1904: 54), show lacerate leaves, pilose stem, 4tepaled staminate flower and 5-tepalled pistillate flower, characteristics that best describe B. bangsamoro.As such, following the IUCN Red List Version 14, we provisionally classified B. bangsamoro as endangered due to its severely fragmented geographical range and very small population within the province of Lanao de Sur.
Notes:-Begonia bangsamoro is distinctive in having a 4-tepalled staminate flower, a character which is not commonly seen in section Petermannia since most species in the section are 2-tepalled except for a few species which include B. mindanaensis Warburg (1904: 55), B. longibractea Merrill (1920: 293), andB. affinis Merrill (1912: 308).In gross morphology, B. bangsamoro resembles B. quercifolia De Candolle (1859: 129), a species known from the islands of Samar and Leyte in the Visayas, north of Mindanao (Fig. 5).They are most similar in their erect habit and lacerate leaf margin but B. bangsamoro can be easily distinguished by its pilose (vs.glabrous) stem and ovate (vs.oblong) stipules.B. bangsamoro is also evidently different by its shorter petioles (2-6.5 cm long) as compared to the petioles of B. quercifolia which measure from 7.5 mm to 61 mm long.In the reproductive structures, B. bangsamoro is different by its terminal, cymose inflorescence (vs.axillary, racemose) and shorter peduncles at 16-17 mm (vs.26-32 mm), shorter ovary length at 6-7 mm (vs.14-15.5 mm).Additionally, the type specimens of B. quercifolia (Cuming 1696) show that the bracts of the staminate inflorescence are persistent as opposed to the caducous bracts of B. bangsamoro.The new species, B. bangsamoro, can be also readily distinguished from B. quercifolia by the number of their staminate tepals with 4 for the former and 2 for the latter.Detailed comparison is seen in Table 1.