New species of Uvariopsis (Annonaceae) and Laccosperma (Arecaceae/Palmae) from Monts de Cristal, Gabon

Abstract Monts de Cristal National Park in northwest Gabon is one of the most species rich places in Central Africa. Here, we describe two new species, one in Annonaceae and one in palms. Uvariopsis citrata Couvreur & Niangadouma, sp. nov. is unique in the genus by emitting a strong lemon scent from the crushed leaves and young branches. Laccosperma cristalensis Couvreur & Niangadouma, sp. nov. is a rattan that lacks acanthophylls on the cirrus and has few pinnae. Complete descriptions, photographic illustrations, ecological information and preliminary IUCN conservation status are provided. For both species a data deficient (DD) status is proposed. These new species underline once again that the Monts de Cristal National Park is yet incompletely known botanically.


Introduction
Th e Monts de Cristal National Park, in northwestern Gabon, is located less than 100 km from the capital Libreville. Monts de Cristal is one of the most plant species-rich areas in Central Africa (Sosef et al. 2006). Because of its prime locality, it is often visited by botanists and is one of the most densely botanically collected areas in Gabon (Wieringa and Sosef 2011). However, new species have been regularly described from the national park (e.g. Ječmenica et al. 2016;Stévart et al. 2014), including a new genus of Annonaceae, Sirdavidia (Couvreur et al. 2015) which was recently awarded the top 10 new species of 2016 (International Institute for Species Exploration 2016). Here, we describe two new species collected during a botanical trip to the Monts de Cristal National Park in June 2016, one Annonaceae and one rattan.
Th e genus Uvariopsis (Annonaceae) contains a total of 18 species restricted to Africa (Couvreur and Luke 2010;Gereau and Kenfack 2000;Kenfack et al. 2003). Uvariopsis is unique in African Annonaceae as most of its species have one whorl of 2 sepals and one whorl of 4 petals, in contrast to the typical Annonaceae pattern of 3 sepals, and 2 whorls of 3 petals. Uvariopsis belongs to the Monodoreae tribe and is recovered as sister to the genus Monocyclanthus (Chatrou et al. 2012;Couvreur et al. 2008).
Laccosperma is one of the four rattan genera found in Africa (Sunderland 2007). Laccosperma contains six species and belongs to the subtribe Ancistrophyllinae which also contains two other genera: Oncocalamus and Eremospatha (Sunderland 2007;Sunderland 2012). Laccosperma is distinguished from the latter two by the robust and rounded spines on its leaf sheath and stems coupled with hermaphroditic fl owers (Sunderland 2012). Laccosperma was recently shown to be sister to Eremospatha (Faye et al. 2016).
Preliminary conservation status. Data defi cient. DD. Uvariopsis citrata is only known by two collections and three individuals collected in the same area. Th e type locality is located in a mature forest within the National Park Monts de Cristal, Mbé sector, close to the road that links Kinguélé and Tchimbélé villages. However, the lo- cality does not seem under threat to date and no changes in habitat have been seen in the last few years. However, because it is close to the road and Kinguélé the future of these populations are not certain.
Distribution. Only known to date from Gabon, from one locality in the Monts de Cristal National Park, Mbé sector. 200-300 m in altitude.
Habitat. Th is species grows in mature or old secondary forests near rivers in periodically inundated soils, or on slopes near rivers.
Etymology. Named after the strong lemon scent of the crushed leaves and young branches one of the diagnostic characters for this species.
Paratypes. GABON, Estuaire: Monts de Cristal National Park, Mbé Sector, near fi rst bridge after Kinguélé village, 0°46'66"N, 10°27'81"E, 14 Jun 2016, T.L.P. Couvreur 1126 (WAG!, LBV!, P!) Discussion. Uvariopsis citrata is unique in the genus by the strong lemon smell of its leaves, young branches and young fl owers when crushed. Th is character is rare in African Annonaceae only reported in one other species, also endemic to Gabon, Uvariodendron molundense (Diels) R.E.Fries var. citrata Le Th omas (Le Th omas 1969). Th is latter species grows in the region of Belinga. To date it remains unclear why some species have this character. Other plants around the type locality did not present this same scent. In addition, U. citrata has sessile fl owers, a character it shares with U. sessilifl ora (Kenfack et al. 2003) endemic to Cameroon. All other Uvariopsis species have pedicilate fl owers. However, U. sessilifl ora has smaller leaves (10-15 cm) and globose fl ower buds, while U. citrata has leaves to 50 cm and ovoid-conic ones. Th e total number of species in Uvariopsis is now 19. Diagnosis. Resembles Laccosperma korupensis Sunderland by the lack of acanthophylls on the cirrus. Diff ers from L. korupensis by the fewer pinnae (5-8 vs 10-18) sigmoid in shape (vs lanceolate) lacking spines along the margin (vs with spines) and the short 3-5 mm truncated ocrea (vs 8 cm long and tapering to a point).
Distribution. Only known to date from Gabon, from one locality in the Monts de Cristal National Park, Mbé sector, Tchimbélé.
Habitat. Th is species was found growing in an old secondary forest, on a slope. Preliminary conservation status. Data defi cient. DD. Laccosperma cristalensis is only known by a single collection, thus it is hard to provide an accurate status here. By providing a name to this species, we hope that others will be able to identify potential past collections. Th e type locality is located in an old secondary forest within the National Park Monts de Cristal, Mbé sector, near Tchimbélé. Th is forest is, however, close to the telephone antenna area which is regularly maintained by cutting. Important hunting activity was also seen there, suggesting important human activity.
Etymology. Named after the Monts de Cristal National Park in northwestern Gabon, home to an important number of plant species and endemics.
Discussion. Laccosperma cristalensis closely resembles L. korupensis by the absence (or near absence) of acanthophylls on the cirrus (extension of the leaf rachis). Th ese are the only two species of African rattans (subtribe Ancistrophyllinae) to share this character. However, L. cristalensis is easily distinguished from L. korupensis by having fewer pinnae (5-8 versus 10-18) which are sigmoid versus lanceolate, lacking spines along the margin versus presence of spines along the margin and an ocrea that is 3-5 mm long and truncated versus 7-10 cm long and tapering to a point (Sunderland 2012). To date none of these species have been collected fl owering or fruiting, however, the vegetative characters alone suffi ce to clearly distinguish them. Th e total number of species in Laccosperma is now 7, although new species are yet to be described from West Africa (Faye et al. 2016).