English   español  
Por favor, use este identificador para citar o enlazar a este item: http://hdl.handle.net/10261/93244
logo share SHARE logo core CORE   Add this article to your Mendeley library MendeleyBASE

Visualizar otros formatos: MARC | Dublin Core | RDF | ORE | MODS | METS | DIDL
Exportar a otros formatos:

Greener pastures? High-density feeding aggregations of green turtles precipitate species shifts in seagrass meadows

AutorKelkar, Nachiket; Arthur, Rohan ; Marbà, Núria ; Alcoverro, Teresa
Palabras claveSeagrass meadows
Seagrass species shifts
Direct and apparent competition
Green turtles
Herbivory pressure
Historical baselines
Plant–herbivore interactions
Fecha de publicación2013
CitaciónJournal of Ecology 101 : 1158-1168 (2013)
Resumen1. Historical declines of marine megaherbivores have led to a view of seagrass communities structured largely by abiotic disturbance and plant competition. There is, however, growing recognition of the significance of top-down control through herbivory, on seagrass ecosystem processes, raising the question of how meadows functioned under historically high populations of megaherbivores. 2. We assess the impacts of such intense herbivory on seagrass meadow composition in the Lakshadweep islands (India), where high-density feeding aggregations of green turtles have persisted for over a decade. We use a series of complementary approaches: (i) natural herbivory exclosures (ii) published data on seagrass composition before and after turtles established (at one atoll: Agatti) and (iii) present species composition along a turtle herbivory gradient over multiple atolls. 3. Long-term natural exclosures in Agatti indicated that sustained turtle grazing caused clear shifts in species dominance from the long-lived, higher-successional Thalassia hemprichii to the relatively short-lived, pioneering species Cymodocea rotundata (dominant in grazed areas). T. hemprichii was the dominant species c. 20 years ago but is now restricted to areas within exclosures in Agatti, and to the least grazed meadows (<5%) in other atolls. 4. We conducted field experiments to identify possible mechanisms by which herbivory mediated direct or apparent competitive interactions between seagrass species. To verify if grazing reduced growth rates of T. hemprichii in comparison with C. rotundata, we conducted clipping experiments in 1m2 plots, simulating turtle herbivory on equal shoot proportions of both species. After 4 months, T. hemprichii shoot density showed major declines in clipped vs. control plots, but C. rotundata shoot density remained relatively unaffected. 5. To test whether selective grazing on T. hemprichii facilitated C. rotundata, we established paired seagrass preference experiments. Turtles had clear preferences for T. hemprichii (64%), but also grazed on C. rotundata. 6. Synthesis. Taken together, our results show that high-impact turtle herbivory changes seagrass composition, precipitating dominance shifts in grazed meadows by mediating direct and apparent competition. Given the crucial role of megaherbivores in seagrass meadow functioning, our results suggest that past meadows may have had natural functional limits to megaherbivore densities that they could sustainably support.
Descripción11 páginas, 7 figuras, 3 tablas.
Versión del editorhttp://dx.doi.org/10.1111/1365-2745.12122
Aparece en las colecciones: (IMEDEA) Artículos
(CEAB) Artículos
Ficheros en este ítem:
Fichero Descripción Tamaño Formato  
accesoRestringido.pdf15,38 kBAdobe PDFVista previa
Mostrar el registro completo

NOTA: Los ítems de Digital.CSIC están protegidos por copyright, con todos los derechos reservados, a menos que se indique lo contrario.