Differences in beta diversity between exotic and native grasslands vary with scale along a latitudinal gradient

Area of Science:

• Ecology
• Conservation Biology
• Biodiversity Research

Background:

• Beta diversity, a key component of biodiversity, is less understood than alpha and gamma diversity.
• Biotic homogenization theory suggests exotic species reduce beta diversity at large scales, but impacts at smaller scales remain unclear.

Purpose of the Study:

• To investigate how exotic plant species influence beta diversity at multiple spatial scales (biome, region, site).
• To compare beta diversity in exotic-dominated versus native-dominated grasslands within the tallgrass prairie region.

Main Methods:

• Plant species abundances were sampled in 42 grasslands across a latitudinal gradient.
• Beta diversity was analyzed at three nested scales: biome-wide, within regions, and within sites.
• Comparisons were made between exotic-dominated and native-dominated (remnant) grasslands.

Main Results:

• Exotic-dominated grasslands exhibited altered beta diversity compared to native grasslands at all scales.
• At the largest scale (biome), exotic grasslands showed higher beta diversity due to varied exotic species composition across the latitudinal gradient.
• At smaller scales, exotic grasslands showed lower beta diversity within sites and variable differences within regions (higher in the south, lower in the north).

Conclusions:

• Exotic species can unexpectedly alter beta diversity patterns across spatial scales.
• The identity and abundance of exotic species, along with landscape connectivity, play crucial roles in shaping beta diversity.
• Findings challenge simple predictions of biotic homogenization and highlight the complexity of exotic species impacts on biodiversity.