Geographic variation in apparent competition between native and invasive Phragmites australis

Area of Science:

• Ecology
• Invasive Species Biology
• Community Ecology

Background:

• Apparent competition, an indirect interaction mediated by shared natural enemies, significantly influences ecological communities.
• Its role in driving species invasions and latitudinal variation in interaction strength remains underexplored.

Purpose of the Study:

• To investigate apparent competition between native and invasive Phragmites australis lineages.
• To determine if the strength of this interaction varies with latitude.

Main Methods:

• Field experiments were conducted at four sites along the U.S. Atlantic Coast.
• Native and invasive P. australis were cross-transplanted, and herbivore damage was assessed for four guilds (stem-feeders, leaf-miners, leaf-chewers, aphids).

Main Results:

• Apparent competition was confirmed for both native and invasive P. australis, excluding leaf-chewers.
• Native plants experienced significantly higher aphid and stem-feeding/leaf-mining herbivore loads in invasive patches, indicating negative impacts.
• The strength of apparent competition against native P. australis decreased with increasing latitude.

Conclusions:

• Invasive P. australis negatively affects native P. australis through apparent competition, which can be as important as enemy release for invasion success.
• Apparent competition's strength can vary geographically, potentially influencing invasion dynamics across different latitudes.