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Aim: Giant clams are iconic bivalves known to serve numerous ecological roles contributing to the functioning of coral reef ecosystems. In the next decade, giant clams will continue to face critical anthropogenic pressures from over‐exploitation for their meat and shells, the aquarium trade and global warming that threaten the persistence of their species. Here, we assess the relationships between different biodiversity components to inform conservation prioritization and management. Location: Indo‐Pacific marine realm. Methods: We quantified taxonomic, functional and phylogenetic diversity measures throughout 25 marine provinces and assessed their relationships for all 12 giant clam species in the subfamily Tridacninae. These biodiversity measures were used to identify potentially threatened species that contribute disproportionately to trait and evolutionary diversity and to highlight areas for global conservation prioritization of giant clam species. Results: Analyses show positive correlations among species richness (SR), functional diversity (FD) and phylogenetic diversity (PD), with the strongest relationship between FD and PD. However, spatial patterns of higher‐than‐expected FD and PD are incongruent with SR patterns, indicating that SR omits information associated with functional and phylogenetic diversity. Among the giant clam species, Tridacna gigas and Hippopus spp. have the greatest functional and evolutionary diversity contributions within assemblies, respectively. Spatial analyses reveal that the Bay of Bengal, Andaman and numerous parts of the eastern Indo‐Pacific potentially hold higher‐than‐expected FD and PD levels relative to their SR and thus warrant more attention with respect to conserving the diversity of giant clams. Conclusions: Our findings underscore the importance of integrating functional trait contributions and evolutionary diversity into conservation planning to better differentiate giant clam assemblages, as it remains challenging to implement dedicated conservation given the limited resources. This study provides comprehensive biodiversity information for managers to initiate measures that holistically capture species' ecological and evolutionary standings across global reef ecosystems. [ABSTRACT FROM AUTHOR]

Aim: The ecosystem functions and services of coral reefs are critical for coastal communities worldwide. Due to conservation resource limitation, species need to be prioritized to protect desirable properties of biodiversity, such as functional diversity (FD), which has been associated with greater ecosystem functioning but is difficult to quantify directly. Selecting species to maximize phylogenetic diversity (PD) has been shown to indirectly capture FD in certain other taxa but not corals. Here, we test this hypothesis, the "phylogenetic gambit", on corals within global marine protected areas (MPAs). Location: Global coral reefs. Methods: Based on the global distributions of reef corals, a complete species‐level phylogeny and trait data, we compared the FD of coral assemblages within MPAs when selected to maximize PD versus FD for assemblages selected randomly. The relationships between PD and FD were also tested as predictors of surrogacy. We then used coral FD and PD to perform spatial prioritization of reefs for protection and assessed the congruence between the two approaches. Results: Selecting assemblages to maximize PD captured significantly more FD than a random subset of species for 83.1% of all selection scenarios across MPAs and would protect on average 18.7% more FD than random selection. Spatial prioritization analyses showed some mismatches between PD‐ and FD‐optimized planning units, particularly in the Tropical Western Atlantic, but the high degree of overlap between the optimizations for other reef regions lends further credence to the PD‐maximizing strategy in conserving coral FD. Main Conclusions: A PD‐maximizing strategy generally protects greater FD of coral assemblages relative to random selection of species, suggesting that the "phylogenetic gambit" is valid for reef corals. There are risks, however, and the mismatches between PD‐maximized and FD‐maximized MPA networks highlight specific shortcomings of the PD‐maximization approach. Nevertheless, in data‐deficient circumstances, maximizing PD may provide a viable alternative. [ABSTRACT FROM AUTHOR]

Summary: Distributed across both the tropical Atlantic and Pacific oceans, the seagrass Halophilia ovalis stabilizes coastal sediment, thereby preventing shoreline erosion and is also an important food source for megaherbivores such as dugongs. However, seagrass meadows globally are under severe duress due to both climate change and anthropogenic activities. We characterized the mycobiome of Halophilia ovalis at seven sites in the Malay Peninsula using ITS1 rDNA amplicon sequences and investigated differences in fungal community structure. We found that geographic location was a significant factor shaping fungal communities and that marine sediment harboured significantly higher diversity when compared to H. ovalis leaves, roots and rhizomes. Taken together, it is likely that locality rather than specific plant structure determines fungal community structure in H. ovalis. Because the plant mycobiome is known to exert a strong effect on plant health, to maximize the success of future seagrass transplantation and restoration work we propose that these efforts consider the importance of seagrass mycobiomes at all stages. [ABSTRACT FROM AUTHOR]

Information about the distribution of alleles among marine populations is critical for determining patterns of genetic connectivity that are essential in modern conservation planning. To estimate population connectivity in Singapore's urbanized equatorial reef system, we analysed single nucleotide polymorphisms (SNPs) from two species of reef‐building corals with distinct life histories. For Porites sp., a broadcast‐spawning coral, we found cryptic lineages that were differentially distributed at inshore and central‐offshore sites that could be attributed to contemporary surface current regimes. Near panmixia was observed for Pocillopora acuta with differentiation of colonies at the farthest site from mainland Singapore, a possible consequence of the brooding nature and relatively long pelagic larval duration of the species. Furthermore, analysis of recent gene flow showed that 60–80% of colonies in each population were nonmigrants, underscoring self‐recruitment as an important demographic process in this reef system. Apart from helping to enhance the management of Singapore's coral reef ecosystems, findings here pave the way for better understanding of the evolution of marine populations in South‐East Asia. [ABSTRACT FROM AUTHOR]

Marine fungal biodiversity remains vastly understudied, and even less is known of their biogeography and the processes responsible for driving these distributions in marine environments. We investigated the fungal communities associated with the seagrass Enhalus acoroides collected from Singapore and Peninsular Malaysia to test the hypothesis that fungal communities are homogeneous throughout the study area. Seagrass samples were separated into different structures (leaves, roots, and rhizomes), and a sediment sample was collected next to each plant. Amplicon sequencing of the fungal internal transcribed spacer 1 and subsequent analysis revealed significant differences in fungal communities collected from different locations and different structures. We show a significant pattern of distance decay, with samples collected close to each other having more similar fungal communities in comparison with those that are more distant, indicating dispersal limitations and/or differences in habitat type are contributing to the observed biogeographic patterns. These results add to our understanding of the seagrass ecosystem in an understudied region of the world that is also the global epicenter of seagrass diversity. This work has implications for seagrass management and conservation initiatives, and we recommend that fungal community composition be a consideration for any seagrass transplant or restoration programme. [ABSTRACT FROM AUTHOR]

Abstract: Freshwater species often show high levels of endemism and risk of extinction owing to their limited dispersal abilities. This is exemplified by the stenotopic freshwater crab, Johora singaporensis which is one of the world's 100 most threatened species, and currently inhabits less than 0.01 km2 of five low order hill streams within the highly urbanized island city‐state of Singapore. We compared populations of J. singaporensis with that of the non‐threatened, widespread, abundant, and eurytopic freshwater crab, Parathelphusa maculata, and found surprisingly high congruence between their population genomic histories. Based on 2,617 and 2,470 genome‐wide SNPs mined via the double‐digest restriction‐associated DNA sequencing method for ~90 individuals of J. singaporensis and P. maculata, respectively, the populations are strongly isolated (FST = 0.146–0.371), have low genetic diversity for both species (also for COI), and show signatures of recent genetic bottlenecks. The most genetically isolated populations for both species are separated from other populations by one of the oldest roads in Singapore. These results suggest that anthropogenic developments may have impacted stream‐dependent species in a uniform manner, regardless of ubiquity, habitat preference, or dispersal modes of the species. While signs of inbreeding were not detected for the critically endangered species, the genetic distinctiveness and low diversity of the populations call for genetic rescue and connecting corridors between the remaining fragments of the natural habitat. [ABSTRACT FROM AUTHOR]