Intraspecific traits change biodiversity effects on ecosystem functioning under metal stress

Abstract

Studies investigating the impacts of biodiversity loss on ecosystem processes have often reached different conclusions, probably because insufficient attention has been paid to some aspects including (1) which biodiversity measure (e.g., species number, species identity or trait) better explains ecosystem functioning, (2) the mechanisms underpinning biodiversity effects, and (3) how can environmental context modulates biodiversity effects. Here, we investigated how species number (one to three species) and traits of aquatic fungal decomposers (by replacement of a functional type from an unpolluted site by another from a metal-polluted site) affect fungal production (biomass accumulation) and plant litter decomposition in the presence and absence of metal stress. To examine the putative mechanisms that explain biodiversity effects, we determined the contribution of each fungal species to the total biomass produced in multicultures by real-time PCR. In the absence of metal, positive diversity effects were observed for fungal production and leaf decomposition as a result of species complementarity. Metal stress decreased diversity effects on leaf decomposition in assemblages containing the functional type from the unpolluted site, probably due to competitive interactions between fungi. However, dominance effect maintained positive diversity effects under metal stress in assemblages containing the functional type from the metal-polluted site. These findings emphasize the importance of intraspecific diversity in modulating diversity effects under metal stress, providing evidence that trait-based diversity measures should be incorporated when examining biodiversity effects.

Predator richness increases the effect of prey diversity on prey yield

“…Negative values of DE and TDC reflect better growth in mixtures of species with low-monoculture yields at the expense of other species or without affecting other species, respectively. Contrary to most published studies to date 35,36 TDC contributed substantially to the observed responses in our microcosms. Fox 8 suggested that TDC effects arise from 'nested niches', if for instance niche overlap coincides with competitive release of subdominant species at altered diversity.…”

Aquatic Hyphomycete Communities Associated with Decomposing Alder Leaf Litter in Reference Headwater Streams of the Basque Country (northern Spain)

“…A possible explanation could be the ecological trophic redundancy of these fungi [43]. Additionally, this linkage seems to be variable when different impacts interact [34], masking the effects of these organisms on ecosystem functioning [24], especially when the community is exposed to several stresses [21,44].…”

Copper and zinc affect the activity of plasma membrane H+-ATPase and thiol content in aquatic fungi

“…Indeed, the sensitivity of these species varies when cultivated in different carbon sources (Azevedo et al, 2007;Azevedo & Cássio, 2010;present work). Although the background of the fungal species (or strain) may influence their responses to metal stress (Guimarães- Soares et al, 2007;Fernandes et al, 2011), this is not always the case. In our study, the species more tolerant to zinc (V. elodeae) was isolated from a clean stream, whilst the species more tolerant to copper (H. submersus) was isolated from a metal-polluted stream.…”