Declines in a ground-dwelling arthropod community during an invasion by Sahara mustard (Brassica tournefortii) in aeolian sand habitats

• Published in: Biological invasions Vol. 16; no. 8; pp. 1675 - 1687
• Main Authors: Hulton VanTassel, Heather L., Hansen, Anne M., Barrows, Cameron W., Latif, Quresh, Simon, Margaret W., Anderson, Kurt E.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.08.2014; Springer; Springer Nature B.V
• Subjects: Animal, plant and microbial ecology; Applied ecology; Arthropoda; Arthropods; Biodiversity; Biological and medical sciences; Biomedical and Life Sciences; Brassica tournefortii; Community ecology; Community structure; Compaction; Conservation, protection and management of environment and wildlife; Developmental Biology; Ecology; Freshwater & Marine Ecology; Fundamental and applied biological sciences. Psychology; General aspects; Habitats; Indigenous plants; Introduced plants; Introduced species; Life Sciences; Nonnative species; Original Paper; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking; Plant ecology; Plant Sciences; Plant species; Predators; Rape plants; Sand; Species richness; Africa; Sahara; USA, California, Coachella Valley; USA, California; Community structure; Arid environments; Invasive species impacts; Bottom-up effects; Aeolian sand dunes; Sand; Arid environment; Invasion; Bottom up control; Brassica; Invasive species; Soil fauna; Cruciferae; Animal community; Dicotyledones; Angiospermae; Spermatophyta; Habitat; Desert; Environmental monitoring; Dunes; Environmental protection
• ISSN: 1387-3547; 1573-1464
• DOI: 10.1007/s10530-013-0616-7

Sahara Mustard ( Brassica tournefortii ; hereafter mustard), an exotic plant species, has invaded habitats throughout the arid southwestern United States. Mustard has reached high densities across aeolian sand habitats of southwestern deserts, including five distinct sand habitats in the eastern Coachella Valley, California. We examined trends in ground-dwelling arthropod community structure concurrent with mustard invasion in 90 plots within those habitats from 2003 to 2011 (n = 773 plot·years). We expected arthropod communities to respond negatively to mustard invasion because previous work documented significant negative impacts of mustard on diversity and biomass of native plants, the primary resource base for many of the arthropods. Arthropod abundance and species richness declined during the study period while mustard cover increased, and arthropod metrics were negatively related to mustard cover across all plots. When controlling for non-target environmental correlates (e.g. perennial frequency and precipitation) and for potential factors that we suspected of mediating mustard effects (e.g. native cover and sand compaction), negative relationships with mustard remained statistically supported. Nevertheless, arthropod richness’s relationship decreased slightly in strength and significance suggesting that mechanistic pathways may be both direct (via habitat structure) and indirect (via native cover suppression and sand compaction). However, mechanistic pathways for mustard effects, particularly on arthropod abundance, remain unclear. Most arthropod taxa, including most detritivores, decreased through time and were negatively related to mustard cover. In contrast, many predators were positively related to mustard. In total, our study provides substantial evidence for a negative effect of Sahara mustard on the structure of a ground-dwelling arthropod community.