Investigating Plant–Bird Co-Occurrence Patterns in Mediterranean Wetlands: Can They Reveal Signals of Ecosystem Connectivity?

Interspecific biotic interaction is believed to be a fundamental phenomenon in ecology. However, despite the increasing efforts, interaction mechanisms are still not clearly understood. We compiled a database of 323 birds and 844 vascular plants in 30 wetlands from Sardinia. This was complemented with seed dispersal features and plant structures (suitability for nesting), and with site-level traits, such as wetland surface area, distance from the sea, percentage of open water, protection level, and number of human impacts. The percentage of non-random co-occurrences was then measured, and the relative importance of each trait in determining it was modelled. We found that non-random co-occurrences among sites decreased with the site extent and increase with the percentage of open water, bird zoochory was positively correlated with co-occurrences, nesting birds showed higher rates of co-occurrence than non-nesting birds, and plants with habits suitable for nesting displayed more co-occurrences than the rest of the plants. These results are a small contribution to the complex topic of species co-occurrence and connectivity within an ecosystem. Species co-occurrence is a promising but debatable approach that may provide insightful clues to species interactions within ecological systems.