Arthropod communities in a selenium-contaminated habitat with a focus on ant species

Abstract

The selenium contamination event that occurred at Kesterson Reservoir (Merced Co., CA) during the 1970-80s is a frequently cited example for the negative effects of contamination on wildlife. Despite the importance of arthropods for ecosystem services and functioning, relatively little information is available as to the impacts of pollution on arthropod community dynamics. We conducted surveys of the arthropod community present at Kesterson Reservoir to assess the impacts of selenium contamination on arthropod diversity, with a focus on ant species richness, composition and density. Trophic groups were compared to determine which arthropods were potentially receiving the greatest selenium exposure. Plant samples were analyzed to determine the selenium content by site and by location within plant. Soil concentrations varied across the study sites, but not across habitat types. Topsoil contained higher levels of selenium compared to core samples. Plants contained similar concentrations of selenium in their leaves, stems and flowers, but flowers contained the greatest range of concentrations. Individuals within the detritivores/decomposers and predators accumulated the greatest concentrations of selenium, whereas nectarivores contained the lowest concentrations. Species composition differed across the sites: Dorymyrmex bicolor was located only at the site containing the greatest soil selenium concentration, but Solenopsis xyloni was found at most sites and was predominant at six of the sites. Selenium concentrations in ants varied by species and collection sites. Nest density was also found to differ across sites, but was not related to soil selenium or any of the habitat variables measured in our study. Selenium was not found to impact species richness, but was a significant variable for the occurrence of two out of the eight native species identified.

Evidence for the transfer of a soil‐borne contaminant from plants to ants via an aphid mediator

“…Mogren et al (2013) found that levels of arsenic transferred to predators differed based on their feeding strategy, where preying mantids consuming entire arsenic-laden mosquitoes accumulated higher levels than spiders that consumed only internal mosquito body fluids. Species-specific accumulation patterns of heavy metals have also been described for ants residing in the same habitat (Rabitsch, 1997;De La Riva et al, 2017), suggesting possible differences in both metal regulation and diet preferences. Exposure levels may also differ seasonally, depending on the source of the contaminant available in the environment, such as changes in floral nectar availability or herbivore populations.…”

A higher taxonomic richness does not ensure the functional resilience of saproxylic beetle communities in evergreenQuercusforests

“…significant differences using the nonparametric Kruskal-Wallis test (Ostertagová et al, 2014;De La Riva et al, 2017).…”

“…Finally, to analyse trait patterns between parks, the selected traits were first weighted according to the number of individuals per trap (community weighted mean; Watts & Mason, 2015). Due to the data's non-normality, we then looked for significant differences between parks using the nonparametric Kruskal-Wallis test (Ostertagová et al, 2014;De La Riva et al, 2017).…”