Consumer Responses to Experimental Pulsed Subsidies in Isolated versus Connected Habitats

Area of Science:

• Ecology
• Island biogeography
• Animal behavior

Background:

• Resource pulses can increase consumer abundance via diet shifts, aggregation, and reproduction.
• Previous studies on large islands showed lizard (Anolis sagrei) abundance increases after seaweed deposition, driven by diet shifts and aggregation.

Purpose of the Study:

• To investigate how resource pulse frequency and magnitude affect lizard diet and abundance on small, isolated islands versus large islands.
• To compare ecological responses to resource pulses in connected versus isolated habitats.

Main Methods:

• Manipulated seaweed resource pulse frequency and magnitude on small islands and in plots on large islands.
• Monitored lizard diet and numerical abundance over a 4-year period.
• Compared responses between small (isolated) and large (connected) island systems.

Main Results:

• Seaweed addition consistently increased lizard abundance on small islands, irrespective of pulse frequency or magnitude.
• No significant numerical response was detected in lizard populations on large islands, despite increased marine resource consumption.
• Persistent abundance increases on small islands may be linked to population establishment and enhanced overwinter survival.

Conclusions:

• Habitat connectivity is crucial for ecological responses to resource pulses.
• Disaggregation and changes in survivorship are significant, potentially underappreciated, drivers of pulse-associated dynamics.
• Island isolation can lead to persistent population increases following resource pulses, unlike in connected habitats where other factors may regulate populations.