Forensic and genetic characterizations of diverse southern Thai populations based on 15 autosomal STRs

Abstract

Southern Thailand is home to various populations; the Moklen, Moken and Urak Lawoi' sea nomads and Maniq negrito are the minority, while the southern Thai groups (Buddhist and Muslim) are the majority. Although previous studies have generated forensic STR dataset for major groups, such data of the southern Thai minority have not been included; here we generated a regional forensic database of southern Thailand. We newly genotyped common 15 autosomal STRs in 184 unrelated southern Thais, including all minorities and majorities. When combined with previously published data of major southern Thais, this provides a total of 334 southern Thai samples. The forensic parameter results show appropriate values for personal identification and paternity testing; the probability of excluding paternity is 0.99999622, and the combined discrimination power is 0.999999999999999. Probably driven by genetic drift and/or isolation with small census size, we found genetic distinction of the Maniq and sea nomads from the major groups, which were closer to the Malay and central Thais than the other Thai groups. The allelic frequency results can strength the regional forensic database in southern Thailand and also provide useful information for anthropological perspective.

Figure 1

Heat plot of R_st values between total 17 populations. The “ = ” symbol indicates non-significance of R_st values (p > 0.05).

Figure 2

The three-dimensional MDS plots for 17 populations (A–C) (stress = 0.0030) and the heat plot of standardized values of MDS with five dimensions (D). See population abbreviation in Table 1. Red, purple, green, blue and black indicate populations from southern Thailand, northern Thailand, northeastern Thailand, central Thailand and Malaysia, respectively. Circle, square and triangle indicate Austronesian, Tai-Kadai, Austroasiatic families, respectively.

Figure 3

STRUCTURE result at K = 2–8 (A). Each individual is represented by a single column that is divided into segments whose size and color correspond to the relative proportion of a particular cluster. Populations are separated by black lines and population codes are listed in Table 1. Number of populations with the highest posterior probability expressed as the Delta K (B).

Figure 4

Neighbor-joining (NJ) tree. The NJ tree based on F_st computation from allele frequency of 15 STR loci from 29 populations, including southern Thai populations (indicated by dots) and other comparative Thai and Asian populations.

Figure 5

Map of the sampling locations of the 17 populations in analyses of genetic diversity and genetic structure, color-coded according to geographic region/country: red, purple, blue, green, and black indicating populations from southern Thailand, northern Thailand, northeastern Thailand, central Thailand and Malaysia, respectively while symbol-coded according to language family: Circle, square and triangle representing Austronesian, Tai-Kadai, Austroasiatic families, respectively. (Adob e Illustrat or CS4 14.0.0. http://www.adobe.com/sea/).