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Biological systems occurring in ecologically heterogeneous and spatially discontinuous habitats provide an ideal opportunity to investigate the relative roles of neutral and selective factors in driving lineage diversification. The grey mangroves (Avicennia marina) of Arabia occur at the northern edge of the species' range and are subject to variable, often extreme, environmental conditions, as well as historic large fluctuations in habitat availability and connectivity resulting from Quaternary glacial cycles. Here, we analyse fully sequenced genomes sampled from 19 locations across the Red Sea, the Arabian Sea and the Persian/Arabian Gulf (PAG) to reconstruct the evolutionary history of the species in the region and to identify adaptive mechanisms of lineage diversification. Population structure and phylogenetic analyses revealed marked genetic structure correlating with geographic distance and highly supported clades among and within the seas surrounding the Arabian Peninsula. Demographic modelling showed times of divergence consistent with recent periods of geographic isolation and low marine connectivity during glaciations, suggesting the presence of (cryptic) glacial refugia in the Red Sea and the PAG. Significant migration was detected within the Red Sea and the PAG, and across the Strait of Hormuz to the Arabian Sea, suggesting gene flow upon secondary contact among populations. Genetic‐environment association analyses revealed high levels of adaptive divergence and detected signs of multi‐loci local adaptation driven by temperature extremes and hypersalinity. These results support a process of rapid diversification resulting from the combined effects of historical factors and ecological selection and reveal mangrove peripheral environments as relevant drivers of lineage diversity. [ABSTRACT FROM AUTHOR]

Mangrove forests occur throughout the coastlines of Arabia, one of the most environmentally extreme regions of their global distribution. The gray mangrove [ Avicennia marina (Forsk.) Vierh.] is the only widespread tree species in this region, providing a unique evergreen habitat that supports high mangrove-associated biodiversity and many ecosystem services of socio-economic importance. This study provides the first literature-based analysis of the status and historical development of mangrove science in Arabia. The goal was to identify trends and gaps in regional mangrove research, providing information essential to guiding future science and conservation programs. The analyses incorporated 400 publications from over six decades since the first article in 1955, each classified into 11 major research topics and including studies from each of the regional seas (Red Sea, Arabian Sea, Sea of Oman, and the Persian/Arabian Gulf). The results demonstrate that there has been exponential growth in research on regional mangroves in recent decades (particularly around human impacts and ecology). The study further reveals knowledge gaps in important research topics and geographical areas that could be exploited to provide insights into broader biogeographic issues. These results provide a comprehensive assessment of the growing body of knowledge on regional mangroves, and provide direction for future research that can guide conservation, management and scientific knowledge of these critical ecosystem engineers. Image 1 • First literature-based analysis of Avicennia marina research in the Arabian region. • Exponential growth in publications, with 400 since the first in 1955. • Research growth mainly supported by local authors. • Research output varies geographically across region, as does focal research topics. • Understudied research topics: evolutionary biology, physiology and molecular biology. [ABSTRACT FROM AUTHOR]