Residency, movement patterns, behavior and demographics of reef manta rays in Komodo National Park

Comparative population genomics of manta rays has global implications for management

Understanding population connectivity and genetic diversity is of fundamental importance to conservation. However, in globally threatened marine megafauna, challenges remain due to their elusive nature and wide-ranging distributions. As overexploitation continues to threaten biodiversity across the globe, such knowledge gaps compromise both the suitability and effectiveness of management actions. Here, we use a comparative framework to investigate genetic differentiation and diversity of manta rays, one of the most iconic yet vulnerable groups of elasmobranchs on the planet. Despite their recent divergence, we show how oceanic manta rays (Mobula birostris) display significantly higher heterozygosity than reef manta rays (Mobula alfredi) and that M. birostris populations display higher connectivity worldwide. Through inferring modes of colonization, we reveal how both contemporary and historical forces have likely influenced these patterns, with important implications for population management. Our findings highlight the potential for fisheries to disrupt population dynamics at both local and global scales and therefore have direct relevance for international conservation of marine species.

Utilising tourist-generated citizen science data in response to environmental challenges: A systematic literature review

There has been a proliferation of studies that have examined the impacts of public participation in Citizen Science (CS) that respond to environmental challenges and the recovery of ecosystems, endangered species or other important natural assets. However, comparatively few studies have explored how tourists may play a critical role in the generation of CS data and thus it has been posited that many potential opportunities remain unrealised. By systematically analysing studies that have utilised tourist-generated data in response to environmental challenges or issues, this paper seeks to establish an appraisal of what has so far been established in extant literature and to identify future possibilities for the inclusion of tourists in CS. Via our literature search, a total of 45 peer-reviewed studies were identified via the PRISMA search protocol. Our findings reveal numerous positive outcomes were reported that highlight the significant, yet largely untapped, potential of tourist integration in CS, with studies also offering a range of recommendations on how tourists could be included more effectively to expand scientific knowledge. Notwithstanding, several limitations were observed, and it is critical that future CS projects that utilise tourists for data collection purposes are acutely aware of the challenges they may encounter.

Genomic evidence indicates small island-resident populations and sex-biased behaviors of Hawaiian reef Manta Rays

BACKGROUND

Reef manta rays (Mobula alfredi) are globally distributed in tropical and subtropical seas. Their life history traits (slow growth, late maturity, low reproductive output) make them vulnerable to perturbations and therefore require informed management strategies. Previous studies have reported wide-spread genetic connectivity along continental shelves suggesting high gene flow along continuous habitats spanning hundreds of kilometers. However, in the Hawaiian Islands, tagging and photo-identification evidence suggest island populations are isolated despite proximity, a hypothesis that has not yet been evaluated with genetic data.

RESULTS

This island-resident hypothesis was tested by analyzing whole mitogenome haplotypes and 2048 nuclear single nucleotide polymorphisms (SNPs) between M. alfredi (n = 38) on Hawai'i Island and Maui Nui (the 4-island complex of Maui, Moloka'i, Lāna'i and Kaho'olawe). Strong divergence in the mitogenome (ΦST = 0.488) relative to nuclear genome-wide SNPs (neutral FST = 0.003; outlier FST = 0.186), and clustering of mitochondrial haplotypes among islands provides robust evidence that female reef manta rays are strongly philopatric and do not migrate between these two island groups. Combined with restricted male-mediated migration, equivalent to a single male moving between islands every 2.2 generations (~ 64 years), we provide evidence these populations are significantly demographically isolated. Estimates of contemporary effective population size (Ne) are 104 (95% CI: 99-110) in Hawai'i Island and 129 (95% CI: 122-136) in Maui Nui.

CONCLUSIONS

Concordant with evidence from photo identification and tagging studies, these genetic results indicate reef manta rays in Hawai'i have small, genetically-isolated resident island populations. We hypothesize that due to the Island Mass Effect, large islands provide sufficient resources to support resident populations, thereby making crossing deep channels separating island groups unnecessary. Small effective population size, low genetic diversity, and k-selected life history traits make these isolated populations vulnerable to region-specific anthropogenic threats, which include entanglement, boat strikes, and habitat degradation. The long-term persistence of reef manta rays in the Hawaiian Islands will require island-specific management strategies.