Deep phylogeographic splits and limited mixing by sea surface currents govern genetic population structure in the mangrove genus Lumnitzera (Combretaceae) across the Indonesian Archipelago

Abstract

The Indonesian Archipelago accommodates the largest mangrove area in Southeast Asia and possesses the world's richest composition of mangrove species. The archipelago comprises areas of the biogeographic regions Sunda and Wallacea, separated by Wallace's line. Here, we used the true mangrove species Lumnitzera littorea and Lumnitzera racemosa as a study case for understanding the effects of phylogeographic history, sea surface currents, and geographical distance on genetic diversity and genetic structure. We sampled 14 populations of L. littorea (N = 106) and 21 populations of L. racemosa (N = 152) from Indonesia and used 3122 and 3048 SNP loci, respectively, genotyped using the ddRADseq approach. We assessed genetic diversity, genetic structure, and effective dispersal of the populations and related them to geographical distance and sea surface currents. Our study revealed low levels of genetic variation at the population level in Lumnitzera. Pronounced genetic differentiation between populations indicated two phylogroups in both species. While in L. littorea the two phylogroups were largely separated by Wallace's line, L. racemosa showed a northwest vs. southeast pattern with strong mixture in Wallacea. Our findings provide novel insights into the phylogeography of the mangrove genus Lumnitzera and the role of sea surface currents in the Indonesian Archipelago.

Challenging Structure Elucidation of Lumnitzeralactone, an Ellagic Acid Derivative from the Mangrove Lumnitzera racemosa

“…The extracts from mangroves from different locations varied significantly in their anti-bacterial activity. Remarkably, only two extracts obtained from locations close to each other (the Maluku islands Ternate and Halmahera) completely inhibited the growth of the Gram-positive bacterium Bacillus subtilis when applied at 500 µg/mL [8,34], which could indicate a connection between the locations of the plants and their anti-bacterial activity. This activity correlated with the occurrence of a signal at m/z 289 [M − H] − (peak 1 in the chromatogram in Figure 1A) in the LC-MS profiles, which could be exclusively observed in the two active extracts.…”

“…Compound 1 was found in only two of the 31 investigated Lumnitzera samples [8,34]. Therefore, it is likely that biosynthesis of the natural product is not (exclusively) dependent on the plant host, which shows low levels of genetic variation at a population level [59].…”

“…Compound 1 was found in only two of the 31 investigated Lumnitzera samples [8,34]. Therefore, it is likely that biosynthesis of the natural product is not (exclusively) dependent on the plant host, which shows low levels of genetic variation at a population level [59]. Instead, biosynthesis is the result of interactions with associated microorganisms that can highly depend on local environmental conditions.…”

“…Since 1 was detected exclusively in the two anti-bacterial crude extracts [8,34], the contribution of 1 to this activity was hypothesized. Thus, the anti-bacterial activity of 1 was checked.…”

Past, present, and future of mountain and island systems

“…Studies on historical biogeography and phylogeography of mountain and island organisms, using genetic, ecological, and trait data, revealed the impact of past global change on natural communities and their organisms (e.g., Muellner et al, 2008; Richardson et al, 2012; Favre et al, 2015, 2016; Matuszak et al, 2016; Ebersbach et al, 2017a, 2017b, 2018; Marx et al, 2017; Antonelli et al, 2018; Hauenschild et al, 2018; Hoorn et al, 2018; Mosbrugger et al, 2018; Zimmer et al, 2018, 2023; Muellner‐Riehl, 2019; Peyre et al, 2020; Rosero et al, 2021; Anthelme et al, 2022; Holzmeyer et al, 2023; Manurung et al, 2023; Cantera et al, 2024; Carruthers et al, 2024). Knowledge about the past will be useful to make predictions about the future and inform conservation measures and policy.…”