Terrestrial food web of the Malpelo Fauna and Flora Sanctuary, Colombia: An analysis from a topological approach

Abstract

Malpelo Island is the largest marine protected area (MPA) in the Colombian Pacific; however, the lack of information regarding its ecological dynamics suggests that management and conservation strategies are developed from an individual approach (species or groups of species) and not from an ecosystem one. This study analyzes the terrestrial food web of Malpelo Island, Colombia, based on topological analysis (e.g., centrality). The food web was constructed from 27 nodes representing the main trophogroups, which consist of species or functional groups. Malpelo Island had a food web of four steps with a maximum separation among all trophogroups and trophic pathways, with two steps in average length. Furthermore, the food web was divided into three food web compartments, with a recurrence of connectivity patterns dominated by apparent and exploitative competition, followed by tri-trophic chains and omnivory. Five key trophogroups control the energy flow throughout the food web (detritus, the land crab Johngarthia malpilensis, the lizard Anolis agassizi, the Malpelo dotted galliwasp Diploglossus millepunctatus, and the Nazca booby Sula granti). The high importance of detritus suggests that bottom-up processes act as a control and regulation mechanism of trophic flows. The low number of food web compartments and a high recurrence of specific connectivity patterns in the Malpelo Island terrestrial ecosystem evidence different ecological processes centered on five trophogroups, allowing stability against disturbances. In addition, the simulation of trophogroup removal (randomly or directed) suggests that food web can be vulnerable to structural alterations in their properties, which may have consequences on the resilience of this ecosystem. This study contributes to the knowledge of the trophic dynamics of Malpelo Island, providing a potential tool for management and conservation measures from an ecosystemic approach.