Genetic evidence for a single founding population of the Lakshadweep Islands.

Lakshadweep is an archipelago of 36 islands located in the Southeastern Arabian Sea. In the absence of a detailed archaeological record, the human settlement timing of this island is vague. Previous genetic studies on haploid DNA makers suggested sex-biased ancestry linked to North and South Indian populations. Maternal ancestry suggested a closer link with the Southern Indian, while paternal ancestry advocated the Northern Indian genetic affinity. Since the haploid markers are more sensitive to genetic drift, which is evident for the Island populations, we have used the biparental high-resolution single-nucleotide polymorphic markers to reconstruct the population history of Lakshadweep Islands.  Using the fine-scaled analyses, we specifically focused on (A) the ancestry components of Lakshadweep Islands populations; (B) their relation with East, West Eurasia and South Asia; (C) the number of founding lineages and (D) the putative migration from Northern India as the paternal ancestry was closer to the North Indian populations. Our analysis of ancestry components confirmed relatively higher North Indian ancestry among the Lakshadweep population. These populations are closely related to the South Asian populations. We identified mainly a single founding population for these Islands, geographically divided into two sub-clusters. By examining the population's genetic composition and analysing the gene flow from different source populations, this study contributes to our understanding of Lakshadweep Island's evolutionary history and population dynamics. These findings shed light on the complex interactions between ethnic groups and their genetic contributions in making the Lakshadweep population.

Biofilm-forming bacteria associated with corals secrete melanin with UV-absorption properties.

Corals are colonized by a plethora of microorganisms, and their diversity plays a significant role in the health and resilience of corals when they face oxidative stress leading to bleaching. In the current study, we examined 238 bacteria isolated from five different coral species (Acropora hyacinthus, Pocillopora damicornis, Podabacea crustacea, Porites lobata, and Pavona venosa) collected from the coral reef ecosystems of Kavaratti, Lakshadweep Islands, India. We found that bacteria such as Psychrobacter sp., Halomonas sp., Kushneria sp., Staphylococcus sp., Bacillus sp., Brachybacterium sp., Citrobacter sp., and Salinicola sp. were commonly present in the corals. On the other hand, Qipengyuania sp., Faucicola sp., Marihabitans sp., Azomonas sp., Atlantibacter sp., Cedecea sp., Krasalinikoviella sp., and Aidingimonas sp. were not previously reported from the corals. Among the bacterial isolates, a significant number showed high levels of biofilm formation (118), UV absorption (119), and melanin production (127). Considering these properties, we have identified a combination of seven bacteria from the genera Halomonas sp., Psychrobacter sp., Krasalinikoviella sp., and Micrococcus sp. as a potential probiotic consortium for protecting corals from oxidative stress. Overall, this study provides valuable insights into the coral microbiome and opens up possibilities for microbiome-based interventions to protect these crucial ecosystems in the face of global environmental challenges.

The maternal ancestry of the Kavaratti islanders and the last glacial maximum aftermath.

The prehistoric human settlement of the Lakshadweep islands remains a mystery for various reasons. Uncertainty about the existence of indigenous tribes in these islands and the lack of folklore records present major obstacles to the reconstruction of Lakshadweep ancestry. However, with extant population data, we seek to understand the maternal ancestry of the Kavaratti islanders. Mitochondrial control region variation analysis of 80 individuals from this island shows maternal links with the populations in the northwestern region of the South Asian mainland. The founder clade R30b2, observed in the Kavaratti islanders, is so far present only in the Scheduled Castes from the Punjab region, Jat Sikhs and Nairs. All other mainland populations carry basal R30 or R30a subclades. The presence of a specific Uralic U4 lineage in our samples, in addition to the Indo-European affinity observed in the phylogeny tree, substantiates a northwestern maternal ancestry of the Kavaratti islanders and implies an ancestral admixture with early humans in the Near East at the time of the last glacial maximum (LGM). Based on our Bayesian analysis, we furthermore propose that a group bearing mostly R30b2 during the LGM recovery, moved eastward and southward, where they received Indian-specific M haplogroups. Hence, the maternal ancestry of the Kavaratti islanders is evidently a consequence of the demographic changes in the northwestern region of the Indian subcontinent caused by the Last Glacial Maximum. The haplogroup distribution pattern and nucleotide sequence data produced in this study will enrich the forensic database of the Lakshadweep islands.

The peopling of Lakshadweep Archipelago.

The archipelago of Lakshadweep is considered as a stopover to the maritime route since ancient time. It is not very clear when the human first occupied these islands, however in the long history of the islands, the local legends suggest that Lakshadweep has been ruled by different kingdoms. To have a better understanding of peopling of Lakshadweep, we have analysed 557 individuals from eight major islands for mitochondrial DNA and 166 individuals for Y chromosome markers. We found a strong founder effect for both paternal and maternal lineages. Moreover, we report a close genetic link of Lakshadweep islanders with the Maldives, Sri Lanka and India. Most of the Lakshadweep islands share the haplogroups specific to South Asia and West Eurasia, except Minicoy Island that also shares haplogroups of East Eurasia. The paternal and maternal ancestries of the majority of island populations suggest their arrival from distinct sources. We found that the maternal ancestry was closer to South Indian populations, whereas the paternal ancestry was overwhelmed with the haplogroups, more common in the Maldives and North of India. In conclusion, our first genetic data suggest that the majority of human ancestry in Lakshadweep is largely derived from South Asia with minor influences from East and West Eurasia.