Molecular ecology of Bottlenose (Tursiops sp.) and common (Delphinus sp.) Dolphins

Bottlenose (Tursiops sp.) and common dolphins (Delphinus sp.) are amongst the most common small cetaceans. They both have a world-wide distribution from warm temperate to tropical waters inhabiting pelagic and coastal waters, and they both show high morphological variability throughout their range, leaving the taxonomic issues in both species unresolved. This thesis provides a comparative assessment of these two species, by molecular analysis, especially in the context of comparing coastal and pelagic populations of each species. The aim is to better understand the evolutionary processes and the factors involved in shaping the population structure in small delphinids. The strategy 1 followed was: 1) Analyse the population structure of the bottlenose and common dolphins on a worldwide scale and compare large scale patterns in the context of known similarities and differences with respect to life history. 2) Analyse populations on a smaller geographic scale (Mediterranean Sea and South Africa) to further understand the relationship between habitat and population generic structure. On a worldwide scale, bottlenose dolphins showed high genetic diversity and strong population structure, both between different and similar morphotypes, suggesting limited gene flow. Two populations, of the same morphotype, have diverged considerably to the extent that they should be considered different species. Common dolphins showed lower genetic diversity and weak population structure even over a large geographic range, suggesting higher level of gene flow. However, this species also has similar morphotypes that were genetically differentiated from one another. On a smaller geographic scale, we found a similar pattern of population structure, with the bottlenose dolphin showing higher population divergence than common dolphins. However, both species provided evidence supporting the role of habitat in defining population structure in these species. These findings should facilitate the development of effective conservation and management strategies for these species, especially for the specific case studies for populations in the Mediterranean Sea and off the Natal coast of South Africa

Marine Mammals of the Emirates: Whales, Dolphins, Porpoises and Dugongs

Marine mammals have always captured the imagination of the people they share their environment with, but few people know that various species populate the waters of the United Arab Emirates (UAE). The world’s second largest population of dugongs reside in the Abu Dhabi Emirate, while two species of dolphins (Indian Ocean humpback and Indo-Pacific bottlenose dolphin) and the elusive finless porpoises inhabit Abu Dhabi and Dubai waters. Facing both the Sea of Oman and the Arabian Gulf, the UAE hosts a total of 18 species of marine mammals. These include the biggest animal on Earth, the blue whale, Bryde’s, humpback whales and killer whales, to name a few. However, ecological information about these species is still scarce. With the exponential increase of anthropogenic pressure and effects of climate change on the UAE marine environment, they are facing the risk of disappearing unnoticed. It is imperative to gain a better understanding of their ecology and main threats that affect them to support the implementation of effective conservation measures. Here we review the evolutionary history and adaptation to the water environment of these charismatic group of animals and provide the most up-to-date information on their status in UAE

Citizen science data of cetaceans in the Arabian/Persian Gulf: Occurrence and habitat preferences of the three most reported species

Citizen science data are becoming increasingly relevant in wildlife studies, especially when obtaining data requires costly logistics. In the Arabian/Persian Gulf, baseline information about cetaceans is scarce despite their regular presence. From 2012 to 2019, a citizen science campaign conducted in the United Arab Emirates (UAE) obtained information on 1,292 cetacean sightings. These were methodically validated by experts, resulting in 1,103 records where species was confidently assigned. From the 12 species reported, we analyzed the spatial patterns of occurrence and drivers of habitat preference for the three most reported species: Tursiops aduncus (Ta 53%), Sousa plumbea (Sp 45%), and Neophocaena phocaenoides (Np 2%). Ecological niche modelling, considering seven environmental variables (physicochemical: temperature, silicate, calcite, pH; physiographic: distance from coast, bathymetry; biological: chlorophyll) showed subtle niche partitioning among the three species. Our results suggest different diets and energy requirements for Np, with Ta and Sp, segregating mostly by different patterns of space use. Specifically, Sp prefers close proximity to shore, particularly areas with complex networks of inland canals. This information provides an estimate of habitat preferences, that can be used in formulating effective conservation measures. Sp shows the narrowest area of suitable habitat and is at particular risk from habitat degradation

Low genetic diversity after a bottleneck in a population of a critically endangered migratory marine turtle species

Hawksbill turtles (Eretmochelys imbricata), which are distributed throughout the world's oceans, have undergone drastic declines across their range, largely due to anthropogenic factors. Assessing sizes, genetic variability and structure of their populations at global and regional levels is critical to the development of conservation management strategies. Here, nuclear and mitochondrial markers were used to analyse patterns of parentage and population structure in hawksbill turtles in United Arab Emirates (UAE) waters, utilizing samples from two life stages (hatchlings and juveniles), and to compare the UAE population with neighboring populations. Weak genetic differentiation was detected between juveniles and hatchlings and between the nesting sites of Dubai and Sir Bu Nair. Parentage analysis suggested that only 53 females and 74–80 males contributed to the hatchlings from 67 nests across three nesting sites in UAE (Dubai, Sir Bu Nair, Abu Dhabi). No females were identified as nesting in more than one location. In Dubai and Abu Dhabi, single paternity was the norm (75%), whereas on Sir Bu Nair, multiple paternity was detected in the majority of nests (67%). Polygyny was also frequently detected on Sir Bu Nair (15% of the overall number of males), but not in the other nesting sites. Comparison of the UAE population with published data from other populations suggests that population structure exists both within the Gulf and between the Gulf and Indian Ocean populations, and that the UAE population has lower genetic variability than the Seychelles population. Finally, the data suggest that the UAE population, and the Gulf population overall, experienced a bottleneck/founder event. The observed overall low genetic variability, evidence of population structure in the Gulf, and strong differentiation between the Gulf and the Indian Ocean populations, raises concerns about the sustainability of this species in this near-enclosed basin. These results highlight the need for regional collaboration in the development of management measures for the long-term conservation of this Critically Endangered specie

Phylogenomics of the genus Tursiops and closely related Delphininae reveals extensive reticulation among lineages and provides inference about eco-evolutionary drivers

Phylogeographic inference has provided extensive insight into the relative roles of geographical isolation and ecological processes during evolutionary radiations. However, the importance of cross-lineage admixture in facilitating adaptive radiations is increasingly being recognised, and suggested as a main cause of phylogenetic uncertainty. In this study, we used a double digest RADseq protocol to provide a high resolution (∼ 4 Million bp) nuclear phylogeny of the Delphininae. Phylogenetic resolution of this group has been especially intractable, likely because it has experienced a recent species radiation. We carried out cross-lineage reticulation analyses, and tested for several sources of potential bias in determining phylogenies from genome sampling data. We assessed the divergence time and historical demography of T. truncatus and T. aduncus by sequencing the T. aduncus genome and comparing it with the T. truncatus reference genome. Our results suggest monophyly for the genus Tursiops, with the recently proposed T. australis species falling within the T. aduncus lineage. We also show the presence of extensive cross-lineage gene flow between pelagic and European coastal ecotypes of T. truncatus, as well as in the early stages of diversification between spotted (Stenella frontalis; Stenella attenuata), spinner (Stenella longirostris), striped (Stenella coeruleoalba), common (Delphinus delphis), and Fraser’s (Lagenodelphis hosei) dolphins. Our study suggests that cross-lineage gene flow in this group has been more extensive and complex than previously thought. In the context of biogeography and local habitat dependence, these results improve our understanding of the evolutionary processes determining the history of this lineage

The Emirates at 2050: Balancing Development and Environmental Stewardship

The United Arab Emirates (UAE) faces the challenge of balancing rapid economic development with environmental preservation and conservation in the Anthropocene era. The nation’s unique ecosystems, characterized by arid desert, rugged mountains, and diverse marine habitats, are vulnerable to disturbances such as urbanization, habitat degradation, groundwater extraction and climate change. To chart a more sustainable course for the Emirates by 2050, the paper proposes policy recommendations such as adopting a national strategy for sustainable development, strengthening environmental policies, investing in urban planning and design, promoting sustainable water management, encouraging use of nature-based solutions, addressing climate change, fostering environmental education, supporting research in environmental sciences, encouraging national and regional cooperation, promoting sustainable business practices in the private sector, and monitoring the progress of environmental policies. By embracing a vision of development that respects the natural environment and safeguards its plant and animal life, the UAE can demonstrate its commitment and serve as a model for other nations to follow, becoming a shining example of responsible development by 2050

Correction to: Cluster identification, selection, and description in Cluster randomized crossover trials: the PREP-IT trials

An amendment to this paper has been published and can be accessed via the original article