Browsing by Author "Serrao, Ester A."
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- eDNA metabarcoding for diet analyses of green sea turtles (Chelonia mydas)Publication . Díaz-Abad, Lucía; Bacco-Mannina, Natassia; Madeira, Fernando Miguel; Neiva, João; Aires, Tânia; Serrao, Ester A.; Regalla De Barros, Aissa; Patrício, Ana Rita; Frade, P. R.Understanding sea turtle diets can help conservation planning, but their trophic ecology is complex due to life history characteristics such as ontogenetic shifts and large foraging ranges. Studying sea turtle diet is challenging, particularly where ecological foraging observations are not possible. Here, we test a new minimally invasive method for the identifcation of diet items in sea turtles. We fngerprinted diet content using DNA from esophageal and cloacal swab samples by metabarcoding the 18S rRNA gene. This approach was tested on samples collected from green turtles (Chelonia mydas) from a juvenile foraging aggregation in the Bijagós archipelago in Guinea-Bissau. Esophagus samples (n=6) exhibited a higher dietary richness (11±5 amplicon sequence variants (ASVs) per sample; average±SD) than cloacal ones (n=5; 8±2 ASVs). Overall, the diet was dominated by red macroalgae (Rhodophyta; 48.2±16.3% of all ASVs), with the main food item in the esophagus and cloaca being a red alga belonging to the Rhodymeniophycidae subclass (35.1±27.2%), followed by diatoms (Bacillariophyceae; 7.5±7.3%), which were presumably consumed incidentally. Seagrass and some invertebrates were also present. Feeding on red algae was corroborated by feld observations and barcoding of food items available in the benthic habitat, validating the approach for identifying diet content. We conclude that identifcation of food items using metabarcoding of esophageal swabs is useful for a better understanding of the relationships between the feeding behavior of sea turtles and their environment.
- Seagrass connectivity on the west coast of Africa supports the hypothesis of grazer-mediated seed dispersalPublication . Tavares, Ana I; Assis, Jorge; Patrício, A. R.; Ferreira, Rogério; Cheikh, Mohamed Ahmed Sidi; Bandeira, Salomao; Regalla, Aissa; Silva Dos Santos, Iderlindo Jorge; Potouroglou, Maria; Nicolau, Suzana; Teodosio, MA; Almada, Carmen; Santos, Rui; Pearson, Gareth Anthony; Serrao, Ester A.Population connectivity influences the distribution of genetic diversity and divergence along a species range, as the likelihood of extinction or differentiation increases in isolated populations. However, there is still poor understanding of the processes mediating interpopulation dispersal in marine species that are sessile and lack planktonic life stages. One such case is the seagrass species Halodule wrightii, which produces basal seeds, although detached plants can drift. Along the tropical western coast of Africa, this species occurs in distant discontinuous habitats, raising the question of how interpopulation dispersal is mediated. The species is a key source of ecosystem functions including feeding large migratory grazers. This study aims to infer whether genetic differentiation of the seagrass H. wrightii along the western coast of Africa supports a hypothesis of predominant transportation of rafting seagrass by ocean currents, versus the hypothesis of biotic vectors of dispersal. Additional hypotheses were addressed concerning range-wide clonality and genetic diversity, assessed with microsatellite markers on populations of the west coast of Africa from Mauritania to Angola. Population genetic diversity and structure were compared with predictions from biophysical models of dispersal by oceanographic currents. The genetic data revealed low divergence among most populations, in strong contrast with predictions of very low probability of connectivity mediated by currents along the western African coastline. Moderate to high genotypic diversity showed important seed recruitment, but genetic and genotypic diversities were lower at range edges. Populations north and south of the equator were differentiated, and remarkably, so were neighboring equatorial populations despite their proximity. These results reveal independent sources of colonization of meadows in these islands, which are major habitat for migratory grazing green turtles, also supporting the hypothesis of biotically mediated seed transport. The importance of seagrass for conservation of endangered macrofauna has been widely reported; here we report evidence supporting the reciprocal role, that macrofauna protection can also plays a role in long-term survival and reproductive success of seagrass.