Does a Species' Extinction-Proneness Predict Its Contribution to Nestedness? A Test Using a Sunbird-Tree Visitation...

Area of Science:

• Ecology
• Conservation Biology
• Network Theory

Background:

• Mutualistic networks, crucial for ecosystem stability, are often studied using insect-plant interactions.
• Theory predicts that species vulnerable to extinction disproportionately influence network nestedness.
• Empirical validation of this prediction across different ecological systems remains limited.

Purpose of the Study:

• To empirically test if extinction-prone species contribute more to nestedness in a sunbird-tree visitation network.
• To assess the applicability of existing network theory, primarily developed from insect-plant systems, to avian-plant mutualisms.
• To investigate the role of local abundance as a proxy for extinction risk in predicting contributions to network nestedness.

Main Methods:

• Constructed a sunbird-tree visitation network, using local abundance as a proxy for sunbird extinction risk.
• Analyzed the network structure to determine species' contributions to nestedness.
• Compared the contributions of locally rare (assumed extinction-prone) and common sunbird species.

Main Results:

• The sunbird-tree network exhibited weak nestedness.
• All sunbird species contributed similarly to the network's nestedness.
• Extinction proneness, indicated by local abundance, did not predict a species' contribution to nestedness.

Conclusions:

• The study's findings do not support the prediction that extinction-prone species drive nestedness in this tree-sunbird system.
• Network theory derived from insect-plant interactions may not be universally applicable to other mutualistic networks, such as those involving birds.
• The small network size might have limited statistical power, and other ecological factors could influence field-based network theory tests.