There are many vanishing cultures that possess a wealth of knowledge on the utilization and conservation of plants. Much of the traditional aboriginal knowledge (TAK) [1–3] concerning new drugs was discovered before the middle of the last century , but has risen again in the last decade . New fields have developed such as the "economics of identity", which bridge the economics of aboriginal and scientific classification . The recent interest in this area of research is partly driven by society's interest in healthy lifestyles, which supports a rapidly growing $230 billion dollar market force in USA alone . The World Health Organization  estimates that 80% of the world's population relies on traditional healing modalities and herbs. Many cultures still maintain traditional medical systems based on TAK and researchers are exploring cultural health and success based on TAK [7, 9–11]. These traditional cultures believe that a healthy lifestyle is founded on a healthy environment and some recent research on local or traditional ecological knowledge (LEK or TEK) has improved natural resource conservation and management policies for modern society [3, 12–16].
India is rich in its ethnic diversity of which many aboriginal cultures have retained traditional knowledge concerning the medicinal utility of the native flora. Southeast Indians have been known to put a great emphasis on traditional knowledge systems and practices, which is supported by their vast intra-ethnic diversity . India has over 537 different aboriginal and other ethnic groups constituting approximately eight percent of the country's population [18, 19]. Traditional knowledge systems including various medicinal plant utilities appear to vary according to local population domain . Documentation of these local knowledge systems concerning medicinal plants may have high impacts from a bioeconomic point of view . Tribal communities living in biodiversity rich areas possess a wealth of knowledge on the local utilization and conservation of food and medicinal plants [18, 21]. This traditional knowledge, which developed over years of observation, trial and error, inference and inheritance, has largely remained with the aboriginal people [22, 23]. However, these cultures and their associated botanical knowledge may be in peril and may even become extinct. Migration from one area to another in search of improved livelihoods is a key feature of human history. Many aboriginals in India migrate to access emerging opportunities and industrialization. This widens the gap between TAK and modern knowledge associated with workplace and social skills of the developed mainstream populations. It is a fact that as traditional healers who value TAK are becoming very old; younger generations exhibit a lack of interest in TAK with a trend toward migration to cities for lucrative jobs. TAK in India is declining [24, 25].
The study of ethnobotanical research is deeply rooted within India. There are many examples of medicinal ethnobotanical surveys conducted in India in the past that have recorded many botanical remedies among many aboriginal groups: Malasars ; Malamalasars ; Malayalis [28–31]; Irulas [22, 23, 32–34]; Gonds ; Koysd, Konda reddis, Valmikis, Koyas, Chenchus, Lambadis, Jatapus, Savaras, Bagatas, Kammaras, Khondas, Nukadoras, Porjas, Jatapus ; Paliyar ; Kanikar ; Todas, Kotas [38, 39]; Kattunayakas ; Apatani ; Chellipale . Although there are many descriptive qualitative surveys of TAK, to our knowledge, there are no ethnobotanical studies within India that consider variation in TAK among informants using a quantitative consensus analysis.
Aboriginal knowledge about plants needs to be reliable and repeatable if it is used as a bridge in scientific inquiry with an application to medicine and society-at-large. Trotter and Logan  presented a quantitative method to evaluate consensus among informants in order to identifying potentially effective medicinal plants. In the last 20 years since Trotter and Logan's  publication there has been limited research from several countries: Peru ; Indonesian Borneo & Timor [45, 46]; Northeastern Brazil [47, 48]; Mexico [5, 9, 49]; Chile, Colombia, Ecuador, Guatemala ; Southern Belize ; Kenya [52, 53]; Mali ; Ethiopia ; Tanzania [56, 57] and the Canadian Arctic . This body of literature suggest that there is considerable variation in consensus factors and how this technique has been implemented. Moerman , Phillips and Gentry  and Heinrich  readapted Trotter and Logan's  factor of informant consensus factor (FIC) in order to quantitatively evaluate the degree of selection of certain plants for a particular utility (e.g., ailment). One of the traditional intentions of FIC is to test the homogeneity among informants' knowledge . In fact some researchers use consensus analysis to test falsifiable hypotheses concerning informant selection and use of plants [53, 44]. Many other researchers have employed consensus analysis as a decision making factor [5, 48] to examine the variation in TAK of cultivars by traditional aboriginal farmers , weighing the relative importance of TAK , identifying discrepancies in ratings , estimating the competence of informants [61, 62, 50] and ethnopharmacolgical surveys [54, 48, 47, 55].
The theoretical importance of our study is to test consensus (reliability/repeatability) of TAK within one ancient culture; the Malasars of the Velliangiri hills in the Western Ghats of Nilgiri Biosphere Reserve, India. We chose to work with the Malasars of India, because 1) there are known to be exceptional healers and keepers of TAK of the flora in the Velliangiri holy hills  and 2) there is limited research on the Malasars TAK . We hypothesize that consensus of TAK of specific plants used for different illness categories are high indicating reliable and repeatable TAK among informants at a local scale (within one localized aboriginal group – Malasars of the Velliangiri hills), because it has been used within their culture without interruption for many generations. Scientific inquiry demands repeatability in order to substantiate claims of medicinal utility within any aboriginal culture. Alternatively, consensus of TAK may be low at local scales  because of i) unreliable TAK, ii) informant bias, iii) local remedies; certain villages may have unique uses for plants, iv) variability in local ethnotaxa; certain communities may have found variants or ecotypes for some plants that result in unique qualities that are of particular use at only a local scale, iv) use of pharmaceutical supplements; the availability of modern pharmaceuticals for a particular ailment may result sporadic use of traditional remedies and v) availability of multiple remedies; there may be groups of plants and therefore several remedies available that are preferentially selected by individual healers for various utility (e.g., healing some ailment), thus indicating the potential biological activity for a group of plants . These groups may represent Linnaean taxa (i.e., genus or family) that share similar biological processes, or aboriginal classifications may group plants (e.g., 'chedi' or 'kodi' etc.) that serve a similar utility [65, 25].