Abstract
BackgroundMangroves are key components of coastal ecosystems in tropical and subtropical regions worldwide. However, the patterns and mechanisms of modern distribution of mangroves are still not well understood. Historical vicariance and dispersal are two hypothetic biogeographic processes in shaping the patterns of present-day species distributions. Here we investigate evolutionary biogeography of mangroves in the Indo-West Pacific (IWP) and western Atlantic-East Pacific (AEP) regions using a large sample of populations of Rhizophora (the most representative mangrove genus) and a combination of chloroplast and nuclear DNA sequences and genome-wide ISSR markers.ResultsOur comparative analyses of biogeographic patterns amongst Rhizophora taxa worldwide support the hypothesis that ancient dispersals along the Tethys Seaway and subsequent vicariant events that divided the IWP and AEP lineages resulted in the major disjunctions. We dated the deep split between the Old and New World lineages to early Eocene based on fossil calibration and geological and tectonic changes. Our data also provide evidence for other vicariant processes within the Indo-West Pacific region in separating conspecific lineages of SE Asia and Australia-Pacific at the Oligocene-Miocene boundary. Close genetic affinities exist between extant Fijian and American lineages; East African and Australian lineages; and Australian and Pacific lineages; indicating relatively more recent oceanic long-distance dispersal events.ConclusionsOur study demonstrates that neither vicariance nor dispersal alone could explain the observed global occurrences of Rhizophora, but a combination of vicariant events and oceanic long-distance dispersals can account for historical diversification and present-day biogeographic patterns of mangroves.
Highlights
Mangroves are key components of coastal ecosystems in tropical and subtropical regions worldwide
Rhizophora samoensis and R. apiculata showed the highest divergence among all pairs (3.785.18%) whereas R. mucronata and R. stylosa the lowest (0.22-2.22%)
This study presents new evidence of phylogeographic patterns of Rhizophora across its global range
Summary
Mangroves are key components of coastal ecosystems in tropical and subtropical regions worldwide. Historical vicariance and dispersal are two hypothetic biogeographic processes in shaping the patterns of present-day species distributions. We investigate evolutionary biogeography of mangroves in the Indo-West Pacific (IWP) and western Atlantic-East Pacific (AEP) regions using a large sample of populations of Rhizophora (the most representative mangrove genus) and a combination of chloroplast and nuclear DNA sequences and genome-wide ISSR markers. Phylogeographic analysis of one of the most widespread mangrove genera, Rhizophora, integrating genetic relationships, fossil records and geological/tectonic processes, will help to elucidate the role of vicariance and long-distance dispersal in the historical development of contemporary biogeographic patterns of mangroves, and to provide objective evaluation of these different but not mutually exclusive views. The genus is relatively old amongst cosmopolitan mangrove genera, and it has notable disjunct species distributions in both the AEP and IWP. While the reason for these disjunct occurrences might be complex, once created most discontinuities were persistent over millions of years – as evidenced by Wallace’s Line in the IWP region
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