Increasing global aridity destabilizes shrub facilitation of exotic but not native plant species

LUCERO, JACOB E.; FILAZZOLA, ALESSANDRO; CALLAWAY, RAGAN M.; BRAUN, JENNA; GHAZIAN, NARGOL; HAAS, STEPHANIE; MIGUEL, M. FLORENCIA; OWEN, MALORY; SEIFAN, MERAV; ZULIANI, MARIO; LORTIE, CHRISTOPHER J.

Global Ecology and Conservation

Elsevier

Año: 2022 vol. 40

2351-9894

Earth’s dryland (hyper-arid, arid, semi-arid, and dry sub-humid) ecosystems face increasingaridity and invasion by exotic plant species. In concert, these global changes threaten thebiodiversity, ecosystem functioning, and economic viability of drylands worldwide, with criticalimplications for environmental quality and human wellbeing. Positive interactions (facilitation)from shrubs can buffer native plant communities against increasing aridity, but this couldbackfire if exotic species are facilitated more than natives. Thus, understanding how native andexotic plant species respond to shrub facilitation along aridity gradients is essential for predictingthe ecological consequences of concomitant aridification and exotic plant invasion in changingdrylands. Here, we performed meta-analyses using 152 independent studies to compare thepositive effects of shrubs on native vs. exotic plant species across Earth’s dryland ecosystems thatvary in aridity. Globally, shrubs facilitate the abundance, diversity, reproduction, and survival ofnative plant species but do not consistently facilitate any measure of exotic plant performance. Asaridity increases, shrub effects on native species do not change, but shrub effects on exotic species become more negative. Thus, across dryland ecosystems globally, shrubs facilitate more measures of native plant performance than exotic plant performance, and as aridity increases, shrub facilitation remains stable for native species but transitions towards resistance for exotic species. At the global scale, dryland aridification may pose a greater threat to exotic species than native species, as much as shrubs and their interactions remain intact.