Land masses and oceanic currents drive population structure of Heritiera littoralis, a widespread mangrove in the Indo‐West Pacific

Abstract

Phylogeographic forces driving evolution of sea‐dispersed plants are often influenced by regional and species characteristics, although not yet deciphered at a large spatial scale for many taxa like the mangrove species Heritiera littoralis . This study aimed to assess geographic distribution of genetic variation of this widespread mangrove in the Indo‐West Pacific region and identify the phylogeographic factors influencing its present‐day distribution. Analysis of five chloroplast DNA fragments’ sequences from 37 populations revealed low genetic diversity at the population level and strong genetic structure of H. littoralis in this region. The estimated divergence times between the major genetic lineages indicated that glacial level changes during the Pleistocene epoch induced strong genetic differentiation across the Indian and Pacific Oceans. In comparison to the strong genetic break imposed by the Sunda Shelf toward splitting the lineages of the Indian and Pacific Oceans, the genetic differentiation between Indo‐Malesia and Australasia was not so prominent. Long‐distance dispersal ability of H. littoralis propagules helped the species to attain transoceanic distribution not only across South East Asia and Australia, but also across the Indian Ocean to East Africa. However, oceanic circulation pattern in the South China Sea was found to act as a barrier creating further intraoceanic genetic differentiation. Overall, phylogeographic analysis in this study revealed that glacial vicariance had profound influence on population differentiation in H. littoralis and caused low genetic diversity except for the refugia populations near the equator which might have persisted through glacial maxima. With increasing loss of suitable habitats due to anthropogenic activities, these findings therefore emphasize the urgent need for conservation actions for all populations throughout the distribution range of H. littoralis .

Population subdivision promoted by a sea‐level‐change‐driven bottleneck: A glimpse from the evolutionary history of the mangrove plant Aegiceras corniculatum

“…As mentioned before, the substantial genetic break between "s-SCS" and "n-SCS" has also been observed in E. agallocha and H. littoralis (Banerjee et al, 2020), which may also be attributed to the mechanism we described above. However, the mismatch distribution analyses presented in the original papers provided no support for a sudden expansion model (Banerjee et al, 2020;. Notably, obvious differentiation has been observed between the populations sampled from…”

“…This water barrier appears less dominant that populations of several species are not isolated, e.g. Acanthus ilicifolus (Guo et al, 2020), H. littoralis (Banerjee et al, 2020), Scaevola taccada (Banerjee et al, 2021), and X. mucronata . The difference in the ability to disperse across the sea currents may underlie the different population structures, even in congeneric species like X. granatum and X. mucronata .…”

Contrasting Phylogeographic Patterns in Lumnitzera Mangroves Across the Indo-West Pacific

“…The haplotype similarity between the populations of the South East Asia and northern Australia could be traced back to the Late Miocene when the Australian plate was nearer to the Sundaland margin ( Hall, 2009 ), thereby facilitating genetic exchange between these two regions. Present day, LDD-assisted gene flow appears to be unlikely given the presence of Sahul Shelf as the land barrier ( Lohman et al, 2011 ), the cryptic barrier generated due to the Indonesia ThroughFlow ( Banerjee et al, 2020 ), and the restricted LDD ability of the L. racemosa propagules ( Clarke et al, 2001 ). Genetic differentiation across the Indo-Australian Archipelago in many mangrove taxa has been found to be caused by these factors ( Urashi et al, 2013 ; Duke, 2017 ).…”

Congruence between ocean‐dispersal modelling and phylogeography explains recent evolutionary history of Cycas species with buoyant seeds

“…This mode of transport is particularly relevant for littoral plants that tend to be widely distributed and often are equipped with buoyant seeds, fruits, or vegetative propagules. Although the role of transoceanic LDD as the driving mechanism for shaping phylogeography of these taxa is well-recognized (Miryeganeh et al, 2014;Gallaher et al, 2017;Guo et al, 2018;Banerjee et al, 2020;Wee et al, 2020), only a few previous studies (e.g. Wee et al, 2014) have integrated comprehensive phylogenetic and ocean-circulation modelling into explanations of the evolutionary history of littoral plants.…”