In this study, 11 microsatellite primers (MS 2.2.2, MS 2.3, MS 5.10, MS 2.14, MS 3.2, MS 6.45, MS 6.29, MS 5.2, MS 7.1, MS 8.24 and MS 6.47)
(Azuma et al., 2004) were used. However, we failed to analyze the samples using MS 5.2 microsatellite primer. The results of heterozygosity study using each microsatellite primer were presented in Table 3.
Use of different microsatellite primers for detecting heterozygosity and allelic frequency
Microsatellite primer MS 5.10
With this primer, we analyzed a total of 68 samples from seven localities. Among them, all the samples from the locality L4, L46, L27, L67 L50 and L66 were sharing both the loci 98 and 99 while the samples from locality 13 were sharing both the loci 96 and 97 (Table 3). L13 was identified as Indian type of
Oecophylla smaragdina by both mitochondrial and nuclear DNA analysis. However, L34, L46, L67, L50 was determined as SE Asian type and L27 and L66 was characterized as Indian type. So, in this case for the primer MS 5.10, we failed to distinguish identical alleles for Indian and SE Asian types although we found heterozygosity as it showed the two peaks in almost all the samples.
Microsatellite primer MS 2.14
This primer detected several allele positions for Indian and SE Asian types. The samples from L46, L27 shared the loci positions 231 and 234 whereas sample from L34 shared the locus 221, in addition, 1 sample from L50 shared the locus 262 with loci 231 and 234. The samples from locality L13 and L66 showed a quite different pattern of sharing allele frequencies. The samples from L13, shared the loci 245, 247, 262, 270 and 273. The samples from L66 shared the loci 238, 252 and 270 (Table 3). So, no distinguished locus position sharing by Indian and SE Asian types of samples were observed.
Microsatellite primer MS 3.2
For identifying the identical allele, I tested 32 samples from 4 localities. The samples from L27 and L67 shared the locus 81 while the samples from L13 shared the locus 86. The samples from locality 50 shared both locus 81 and locus 86 (Table 3).
Microsatellite primer MS 7.1, MS 6.29 and MS 6.47
Eight samples from each of two localities (L67 and L13) were tested by microsatellite primer MS 7.1, MS 6.29 and MS 6.47. All 08 samples shared the locus 100, locus 128 and locus 172 for MS 7.1, MS 6.47 and MS 6.29, respectively (Table 3). So, no locus was identified that can separate Indian and SE Asian type of
Oecophylla in Bangladesh.
Microsatellite primer MS 2.3 and MS 2.2.2
Sixty samples from seven locaities were tested each for MS 2.3 and MS 2.2.2. All the samples from MS 2.3 shared the locus 144, while two samples from L34 and L46 shared both the loci 100 and 144. In the case of MS 2.2.2, all the samples sharing the locus 103 except the samples from L13 and L66 that were sharing the locus 97. The samples from other locality that were identified as Indian type also shared the locus position 97 along with some samples from L34 which was identified as SE Asian type. So, with these two primers the identical allele position was not possible to distinguish between Indian and SE Asian types (Table 3).
Successful detection of identical allele
The identical allele between Indian and SE Asian types of
O. smaragdina population in Bangladesh were possibly detected with the microsatellite primer MS 6.45 and MS 8.24. For MS 6.45, four samples from the locality L67 were analyzed and all 04 samples shared the locus 238. However, the samples from locality L13 shared the locus 244 and locus 250. As the colony of L13 locality was identified as Indian type and L67 was SE Asian type so, these locus positions was identical. Similarly, the samples with 8.24, among 08 samples, 4 samples from L67 shared the locus 277 while the rest 4 samples from locality L13 shared the locus 262 (Table 3).
There was not too many evidence of such heterozygous condition within the colony of
O. smragdina in India or any other SE Asian country and this is the first report of such mixed colony in Bangladesh as well. Similarly,
Roos et al., (2011) studied tracing the evolution and hybridization of colobine monkey in the Asian continent, found several hybridization patterns by testing the mitochondrial and nuclear DNA which was found to be supported by
Blaimer (2012). The observed phylogenetic incongruences resulted by hybridization among ancestral lineages most likely occured, due to the presence of potential contact zones like today’s Bangladesh, Myanmar and the northeast of India, which is suggested as hybridization area
(Karanth et al., 2008). However, several big mountains and big rivers in the border region of today’s Myanmar, India and China might have been a possible diversification hotspot
(Chakraborty et al., 2007) which leads to develop such hybridization pattern.
Divergence time is also an important factor for many ant genera.
Oecophylla is thought to be a significant factor in such distribution (
Bolton, 1995). Diversification within groups in this continent was recorded from the middle Pliocene to early Pleistocene
(Azuma et al., 2002). After this period, the world has encountered a significant climatic change. It might also affect the distribution of
Oecophylla in different parts of the world. During Last Glacial Maximum (LGM), the tropic region shifted southward and it retained northward after glaciation. This study suggested that the Indian and Southeast Asian clades of
O. smaragdina expanded their distribution northward along suitable regions with high temperature and humidity and then the two clades supposedly encountered and overlapped in central Bangladesh. Similar trends were also observed in the case of study of the origin of Asian elephants
(Vidya et al., 2009). They suggested a contraction-expansion scenario during climatic oscillation leads to geographical overlaps of two mtDNA clades created the allopatric population of Asian elephants in India, Sri Lanka and Myanmar. In the case of weaver ant in Bangladesh, as both the Indian and SE Asian types were dominated in Western and Eastern part of the country, respectively and there was not such a big border of separating those two populations
(Rahman et al., 2017a). The probability of the contact of both the types was considered very usual.
Pusch et al., (2006) reported that ant colony with heterozygous produce hybrid workers. This type of gene introgression may increase the genetic diversity of the hybrid relative to its parental species and can lead to hybrid vigor (
Helms and Keller, 2003). In this case, the
O. smaragdina colony from the locality 11 and 15 in Bangladesh might have the influence of the arising of new evolutionary lineages. This hybridization therefore, can be considered as a process of the evolutionary significance of
O. smaragdina in Bangladesh.