Reassessment of the Genus Salacia under IUCN Threatened Categories in Sri Lanka

Salacia comprises of five species in Sri Lanka S. acuminatissima, S. chinensis, S. diandra, S. oblonga and S. reticulata while around two hundred species are distributed in tropical countries worldwide. All five species recorded in Sri Lanka are listed under various threaten categories in the National Red List 2012.The present study was carried out to reassess their conservation status based on IUCN threatened categories using preliminary field observations and data in order to contribute to the national red listing with robust data. The species were evaluated based on the criteria B of the IUCN guidelines 2017.The conservation statuses of two Salacia species S. acuminatissima and S. chinensis have remained same as the previous conservation statuses determined at national level as Endangered (EN) and Near threatened (NT) respectively. However, S. diandra was upgraded to the category of Critically Endangered (CR). The statuses of S. oblonga and S. reticulata were downgraded from Endangered (EN) to Near threatened (NT). Conservation statuses obtained using preliminary data and the upgrading the status of a taxa and downgrading of the statuses of two taxa is of prime importance to prioritize conservation of the members of the Genus Salacia in globally.


INTRODUCTION
The genus Salacia comprises of nearly 200 species of woody lianas, scandent or erect shrubs distributed in tropical parts of India, Burma, Sri Lanka, Malaysia, Solaman islands, Africa and New World (Wadhwa, 1996). This genus is well-known for its medicinal values to cure high blood sugar, rheumatism, gonorrhea and skin diseases (Paarakh et al., 2008;Arunakumara and Subasinghe, 2010;Chawla et al., 2013;andMusini andGiri, 2015 andMedagama, 2015). During the revision of the Flora, Wadhwa (1996) recognized four species of Salacia occurring in Sri Lanka; S. chinensis L., S. diandra Thw., S. oblonga Wall ex Wight & Arn. and S. reticulata Wight. However, during the most recent Red listing in 2012, S. acuminatissima has also been recorded as a new species occurring in the wet zone of Sri Lanka (Kostermans,1992). This species has been considered as a synonym of S. diandra during the revision of the Flora by Wadhwa (1996). S. acuminatissima was first described by Kostermans (1992) based on plants collected from Sinharaja forest reserve. Out of the five species recorded in Sri Lanka, S. acuminatissima, S. diandra, S. oblonga and S. reticulata are categorized as endangered species while S. chinensis is recorded as a near threatened species in the National Red List 2012 of Sri Lanka (MOE, 2012). The evaluations of threatened status of above plants in the Sri Lanka are conducted based on the available literature, herbarium records, field experience and records of experts. Therefore, the conservation status decided are considered as national conservation status rather than global, as the requirements laid down by the IUCN Redlisting criteria such as population size reduction and population reduction, geographic range in the form of extent of occurrence and area of occupancy, small population size and decline and very small or restricted population are not achieved. Among the plant species belongs to the genus Salacia recorded island wide, S. acuminatissima and S. diandra limited to the wet zone and majority of S. chinensis and S. reticulata limited to dry zone while S. oblonga majority found also in to the wet zone. A mature plant members of Salacia, produces large number of seeds per a season (Arunakumara and Subasinghe, 2010). This species is can be regenerated by seed propagation, vegetative propagation using stem cuttings and root cuttings (Arunakumara and Subasinghe, 2010). Although these plant species produce several seeds, germination ability are poor (Arunakumara and Subasinghe, 2010). The genus Salacia includes the well-known medicinal plant 'Kothala-himbutu', S. reticulata. The plant is widely used in the Ayurvedic system to treat diabetes and obesity (Medagama, 2015). In some instances, the other Salacia species, especially S. chinensis and S. oblonga are also supplemented in the drug stores for treating diabetics (personal communications). During the exploitation of these species for medicinal use the mature plants are cut-down to obtain parts of the stem and also mature branches which directly affects the survival and reproduction of the plant. Therefore, recording existing populations in different bioclimatic regions with their abundance has become a timely need to conserve these taxa for sustainable use in the future. A study carried out with field visits covering the entire island provides firsthand information in acquiring the information on the habitats and threats for the existing populations. Further the collected data would contribute can be used to update the information for future Red-listing processes. The National Red List 2012 (MOE, 2012) of Sri Lanka is the current working document which includes the IUCN conservation status of many taxonomic groups, including Angiosperms, Gymnosperms, Pteridophytes, Invertebrates, Amphibians, Reptiles, Birds, Fish and Mammals. The National Red listing document provides baseline information obligatory for the preparation of species profiles of threatened taxa, a basis for prioritizing conservation efforts and data necessary for the compiling and implementation of recovery plans. Further it also provides details of information gaps regarding specific taxa and geographic areas and allows for objective prioritization of funding for conservation-oriented research (MOE, 2012). Further, the conservation status of species has been used globally to guide conservation responses, direct conservation policies and legislation, plan protected area networks and prioritize sites to be protected (Possingham et al., 2002). Therefore, the objective of the study was to conduct an eco-geographical survey to record all Salacia species in Sri Lanka in order to reassess the IUCN threatened categories of genus Salacia.

MATERIAL AND METHODS
The study was conducted from the January 2016 to December 2018 for a period of two years. Salacia species were collected from all possible locations in Sri Lanka ( Figure 1 and Table 1), covering all major climatic zones of the country. This included all the administrative provinces of the country.
The plants were identified using the National Herbarium, Royal Botanic Gardens Peradeniya and literature (Flora of Ceylon, Wadhwa B.M., 1996 and Reinwardtia, Kostermans A.J.G.H). All the locations were recorded using a Global Positioning System (Garmin Etrex 10, USA). Possible causes of threats for each subpopulation were recorded at all locations. A visual estimation of the subpopulation for each location was also recorded. The potential distribution maps for each species were developed by plotting the GPS locations on a map of Sri Lanka using the software ArcGIS 10.4 (ESRI, 2017 ) and the extent of occurrence (EOO); "the area contained within the shortest continuous imaginary boundary which can be drawn to encompass all the known, inferred or projected sites of present occurrence of a taxon, excluding cases of vagrancy" (IUCN 2012and 2017); of each species were determined based on the convex hull (the smallest polygon in which no internal angle exceeds 180 degrees and which contains all the sites of occurrence)and the area of occupancy (AOO); "the area of suitable habitat currently occupied by the taxon"; were calculated using a 2 x 2km 2 grid on the map. The conservation statuses of the five Salacia species were evaluated with the available data strictly adhering to the recommended guidelines of the IUCN (IUCN, 2017).
During the present study, assessing the threaten statuses of Salacia species was carried out based on criteria B, which considers only the current AOO and EOO data together with two of the three given conditions; (a) Severely fragmented OR number of locations and (b) Continuing decline observed, estimated, inferred or projected in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) area, extent and/or quality of habitat; (iv) number of locations or subpopulations; (v) number of mature individuals since data and information for other criteria were not available.
Remaining 13 distinct populations out of 82 have been recorded in Revised Handbook to the Flora of Ceylon and herbarium specimens deposited at the National Herbarium, Royal Botanic Gardens, Peradeniya.   According to the habitats, most of the Salacia species recorded during the present study were recorded from the interior of natural forests. Although majority existed in the natural forests, these species were also recorded in disturbed, urbanized and cultivated areas in fewer numbers (Table 3).
The Table 4 gives the IUCN recommended EOO and AOO values for species categorization (IUCN 2017) while the Figure 2 illustrates the distribution maps with the polygons used for the EOO estimations and Table 5 gives the estimated EOO values and AOO values for the genus Salacia.
Among 82 distinct populations encountered during the study majority of them were not under any specific threat except few populations of S. chinensis, S. oblonga and S. reticulata that were recorded in human inhabited areas, urbanized areas and associate with water reservoirs. The threat that was observed for these three species with high medicinal value is the harvesting of mature branches. However, this cropping does not affect the mature individuals as they always resprout with the rains. The term 'severely fragmented' has been used according to the guidelines given by IUCN 2017. For deciding whether there is a severe fragmentation, number of locations and the distribution of area of occupancy (detailed maps of occupied habitat) have been used. According to the IUCN 2017, a taxon can be considered to be severely fragmented if most (˃ 50%) of it is total area of occupancy is in habitat patches that are separated from other habitat patches by a large distance.
Based on the EOO (B1) and AOO (B2) values of the five Salacia species, S. diandra is the rarest species (EOO = 55.01km 2 and AOO = 7.99km 2 ) which is confined to two populations recorded in Galle and Matara districts. According to Criterion B, based on geographic range, with only 55.01km 2 of the extent of occurrence and 7.99km 2 of area of occupancy, this species qualifies for Critically Endangered (CR) category under the thresholds for both B1 and B2 (for this species polygon was not prepared and EOO and AOO were estimated using standard method due to restriction of two populations). Further, the current population of S. diandra is clearly fragmented into small patches of less than 100 m 2 and it can be projected the declining of population. Thus this species qualifies for Critically Endangered (CR) under the both B1a, B1b and B2a and B2b.
Salacia acuminatissima is also a rare species that is confined to the four populations in wet zone (EOO = 3,649.89km 2 and AOO = 15.99km 2 ). According to Criterion B, based on geographic range, with 3649.89km 2 of the extent of occurrence and 15.99km 2 of area of occupancy, this species qualifies for Endangered (EN) category under the thresholds for both B1 and B2. Further, the current population of S. acuminatissima is very clearly fragmented into a four small patches of less than 100 m 2 and it can be projected the declining of population because of number of individuals in each population is very limited. Thus this species qualifies for Endangered (EN) under the both B1a, B1b and B2a and B2b.
Conservation of S. acuminatissima and S. diandra has become a critically important factor not only because they are EN and CR respectively, but also as these two species are restricted to limited areas of undisturbed forests in the wet zone of the country.
Another Salacia species, S. oblonga has a wider population distribution than S. acuminatissima and S. diandra with a 12,322 km 2 of the extent of occurrence and 119.11 km 2 of area of occupancy. According to the EOO value this species qualifies for vulnerable (VU) category and according to the AOO value qualifies for Endangered (EN) category under the thresholds for both B1 and B2. Further, the populations of S. oblonga are not clearly fragmented into small patches and could not be projected to declining of population. Thus this species qualifies for Near threatened (NT) category under B2 and B2b.
Salacia chinensis is the most common species belonging to the genus Salacia in Sri Lanka and has a wide range of population distribution with 29,703.6km 2 of the extent of occurrence and 85.96 km 2 of area of occupancy. According to the EOO value this species not qualifies for Vulnerable or any above conservation level and according to the AOO value, qualifies for Endangered (EN) category under the thresholds for both B1 and B2. Although populations of S. chinensis are widely distributed, there is a probability for declining of population due to high medicinal demand in the local market. Therefore, this species qualifies for Near threatened (NT) under the B2 and B2b.
Salacia reticulata, commercially the most important species that belongs to the genus Salacia occupies an area of 22,899.5km 2 of the extent of occurrence and 72.33km 2 of area of occupancy according to the criterion B, based on geographic range. This species qualifies for Near Threatened (NT) category under the thresholds for both B1 and qualifies for Endangered (EN) category under the threshold of B2. Salacia reticulata can be projected as declining because people tend to harvest this due to high medicinal value for their economic benefits. According to that this species qualifies for near threatened (NT) under the B2 and B2b. Table 6 indicates the proposed

CONCLUSION
According to the present evaluation of the IUCN Red Data status, out of five Salacia species recorded in Sri Lanka, conservation statuses of two Salacia species namely S. acuminatissima and S. chinensis have remained same as the previous conservation categories determined at national level (National red list 2012 of Sri Lanka) as Endangered (EN) and Near threatened (NT) respectively while S. diandra was upgraded to the category Critically Endangered (CR).The conservation statuses of other two Salacia species S. oblonga and S. reticulata were downgraded from Endangered (EN) to Near threatened (NT). The upgrading and downgrading of category is the result of new information about the geographical distribution of populations. The upgrading of S. diandra conservation status and downgrading of S. oblonga and S. reticulata conservation statuses are important outcome of the present study.