Influence of Last Glacial Maximum and Contemporary Isolation: Hierarchical Processes Shape the Phylogeography of a Climbing Palm in the Andaman and Nicobar Archipelago
Sarath Paremmal, S. Mahadevakumar, Modhumita Ghosh Dasgupta, Sreekumar Vadakkethil Balakrishnan, Suma Arun DevABSTRACT
Aim
Spatial genetic patterns of populations are a reflection of the combined influence of historical and contemporary climatic and landscape dynamics. This study investigates the influence of these extrinsic factors on the genetic structuring of a climbing palm in the Andaman and Nicobar (A&N) archipelago. Although the archipelago has experienced dramatic geomorphological transformations and climatic fluctuations during and since the Last Glacial Maximum (LGM), phylogeographic studies examining species responses to these changes remain limited.
Location
Andaman and Nicobar Islands, Bay of Bengal, India.
Taxon
Korthalsia laciniosa , climbing palm.
Methods
Genetic diversity of 13 populations sampled across the archipelago's major geographic barriers was assessed using 17 nuclear and 9 chloroplast microsatellites. The influence of LGM‐associated climatic and geomorphological changes was tested using alternative demographic scenarios based on the island's biogeographic affinities and Ecological Niche Modelling (ENM). A landscape genetic framework was used to assess the contemporary environmental factors that drive genetic divergence.
Results
Genetic data reveal a deep divergence between the Andaman and Nicobar Island groups, consistent with their broader biogeographic affinities. Within the Andaman Islands, ENM and demographic models indicate the presence of a potential southern refugium during LGM, and afterwards demographic expansion. In the contemporary landscape, genetic differentiation is primarily driven by a tangled effect of isolation by distance and resistance.
Main Conclusions
The genetic architecture of K. laciniosa in the A&N archipelago reflects a hierarchical interplay of biogeographical barriers and geographical and climate dynamics during the LGM. The potential habitat reduction during the LGM, followed by post‐LGM expansion, has restructured the phylogeographical patterns. The identification of a potential southern refugium, along with the genetic distinctness of Nicobar and Little Andaman populations, highlights the need for conservation efforts to prioritize the delineation and preservation of evolutionarily significant units in this underexplored tropical archipelago.