DNA-metabarcoding supports trophic flexibility and reveals new prey species for the Galapagos sea lion

Photo by Andrés Moreira-Mendieta.

Tropical ecosystems are challenging for pinnipeds due to fluctuating food availability. According to previous research, the Galapagos sea lion (GSL, Zalophus wollebaeki) adopts trophic flexibility to face such conditions. However, this hypothesis comes from studies using traditional methods (hard-parts analysis of scat and isotopic analysis from tissue). We studied the diet of five rookeries in the southeastern Galapagos bioregion (which harbors the highest GSL density), via DNA-metabarcoding of scat samples. The DNA-metabarcoding approach may identify consumed prey with a higher taxonomic resolution than isotopic analysis, while not depending on hard-parts remaining through digestion. Our study included five different rookeries to look for evidence of trophic flexibility at the bioregional level. We detected 98 prey OTUs (124 scats), mostly assigned to bony-fish taxa; we identified novel prey items, including a shark, rays, and several deep-sea fish. Our data supported the trophic flexibility of GSL throughout the studied bioregion since different individuals from the same rookery consumed prey coming from different habitats and trophic levels. Significant diet differentiations were found among rookeries, particularly between Punta Pitt and Santa Fe. Punta Pitt rookery, with a more pronounced bathymetry and lower productivity, was distinguished by a high trophic level and consumption of a high proportion of deep-sea prey; meanwhile, Santa Fe, located in more productive, shallow waters over the shelf, consumed a high proportion of epipelagic planktivorous fish. Geographic location and heterogeneous bathymetry of El Malecon, Española, and Floreana rookeries would allow the animals therein to access both, epipelagic prey over the shelf, and deep-sea prey out of the shelf; this would lead to a higher prey richness and diet variability there. These findings provide evidence of GSL adopting a trophic flexibility to tune their diets to different ecological contexts. This strategy would be crucial for this endangered species to overcome the challenges faced in a habitat with fluctuating foraging conditions.

Read the article in the link: https://doi.org/10.1002/ece3.10921

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In 2022, the Galapagos Science Center (GSC) and the broader UNC & USFQ Galapagos Initiative will celebrate its 10th Anniversary. We are proud to announce the World Summit on Island Sustainability scheduled to be held on June 26–30, 2022 at the Galapagos Science Center and the Community Convention Center on San Cristobal Island.

The content of the World Summit will be distributed globally through social media and results documented through papers published in a book written as part of the Galapagos Book Series by Springer Nature and edited by Steve Walsh (UNC) & Carlos Mena (USFQ) as well as Jill Stewart (UNC) and Juan Pablo Muñoz (GSC/USC). The book will be inclusive and accessible by the broader island community including scientists, managers, residents, tourists, and government and non-government organizations.

While the most obvious goal of organizing the World Summit on Island Sustainability is to celebrate the 10th Anniversary of the GSC and the UNC-USFQ Galapagos Initiative, other goals will be addressed through special opportunities created as part of our operational planning of the World Summit.

For instance, we seek to elevate and highlight the Galapagos in the island conservation discourse, seeking to interact with other island networks in more obvious and conspicuous ways to benefit the Galapagos Islands, the UNC-USFQ Galapagos Initiative, and the world. We will seize the opportunity to further develop the I2N2 – International Islands Network-of-Networks. Further, we wish to highlight and emphasize multiple visions of a sustainable future for the Galapagos Islands and we cannot do this alone. Therefore, engaging the Ecuadorian Ministry of Environment, the Ministry of Tourism, the Government Council of Galapagos, the Galapagos National Park, and local Galapagos authorities, including government and non-government organizations and local citizen groups, is imperative.

The Galapagos Science Center on San Cristobal Island, Galapagos

Borrowing from Hawaii’s and Guam’s Green Growth Program and the Global Island Partnership, we wish to examine existing global programs that emphasize island sustainability and their incorporation into life, policies, and circumstances in the Galapagos Islands. We will also seek to enhance our connections with the institutional members of our International Galapagos Science Consortium and expand the Consortium through the recruitment of other member institutions. We will also work to benefit islands and their local communities by working with citizen groups as well as important NGOs who seek to improve the natural conditions in the Galapagos and diminish the impact of the human dimension on the future of Galapagos’ ecosystems.

Lastly, we will use the World Summit to benefit UNC & USFQ and our constituencies through a strong and vibrant communication plan about the World Summit, creating corporate relationships as sponsors, identifying funding goals through donors, and benefiting our study abroad program for student engagement in the Galapagos Islands. We plan to develop and issue a Galapagos Sustainability Communique after the World Summit that includes the vision and insights of all its participants for a sustainable Galapagos with applicability to global island settings.

We are eager to hear your perspective and have you join us at the World Summit on Island Sustainability!