The Impact of a Range-Shifting Predator Is Affected by Prey Preference and Composition

Area of Science:

• Marine ecology
• Invasive species research
• Climate change impacts

Background:

• Global biodiversity is shifting due to climate change, with species altering their ranges.
• Ecological impact studies often focus on invasive species traits, neglecting recipient community effects.
• Understanding how prey composition influences novel species impacts is crucial for ecological management.

Purpose of the Study:

• To investigate how prey composition affects the prey preferences and ecological impact of the range-shifting predatory whelk, *Mexacanthina lugubris*.
• To test if the presence of a second prey species (mussels) modifies the consumptive effects of *M. lugubris* on another prey species (barnacles).

Main Methods:

• A field experiment was conducted in southern California over 8 weeks.
• Predatory whelks (*Mexacanthina lugubris*) were caged at varying densities.
• Predation rates on mussels and barnacles (on bare rock and on mussels) were monitored.

Main Results:

• The predatory whelk *Mexacanthina lugubris* showed a preference for consuming barnacles on bare rock over barnacles on mussels and mussels.
• The presence of mussels altered the accessibility of barnacle prey to the whelks.
• *M. lugubris* consumed barnacles on bare rock first, then barnacles on mussels, and lastly mussels.

Conclusions:

• Prey composition significantly influences the impact of range-shifting predators.
• Mussels can act as a refuge for barnacles by altering predator accessibility, demonstrating apparent facilitation.
• Recipient community structure is vital for predicting and managing ecological consequences of species range shifts.