Increased Primary Production from an Exotic Invader Does Not Subsidize Native Rodents

Area of Science:

• Ecology
• Invasive Species Biology
• Food Web Dynamics

Background:

• Invasive plants can alter ecosystems by increasing primary productivity.
• Cheatgrass (Bromus tectorum) is an aggressive invader in the Great Basin Desert.
• Native granivorous small mammals are key consumers in desert ecosystems.

Purpose of the Study:

• To investigate the utilization of cheatgrass seeds by native granivorous small mammals.
• To determine the impact of cheatgrass invasion on seed rain and small mammal populations.
• To assess the role of consumer preference in the trophic integration of invasive resources.

Main Methods:

• Field experiments were conducted in the Great Basin Desert.
• Quantified cheatgrass seed rain density and biomass.
• Assessed small mammal abundance, richness, and diversity in response to seed additions.
• Analyzed small mammal food preferences.

Main Results:

• Cheatgrass invasion increased seed rain density by over 2000% and biomass by over 3500%.
• Small mammal populations showed no positive numerical response to increased cheatgrass seeds.
• Native granivores exhibited a preference for native grass seeds over cheatgrass seeds.

Conclusions:

• Increased primary productivity from invasive plants does not automatically subsidize higher trophic levels.
• Cheatgrass invasion may disrupt native food webs by providing less-preferred resources.
• Native consumer preferences can mediate the impact of invasive species on food webs.