Multiple dimensions of bacterial diversity unrelated to functioning, stability and multifunctionality

Bacteria are essential for many ecosystem services but our understanding of factors controlling their functioning is incomplete. While biodiversity has been identified as an important driver of ecosystem processes in macrobiotic communities, we know much less about bacterial communities. Due to the high diversity of bacterial communities, high functional redundancy is commonly proposed as explanation for a lack of clear effects of diversity. The generality of this claim has, however, been questioned. We present the results of an outdoor dilution-to-extinction experiment with four lake bacterial communities. We found no general effects of bacterial diversity in terms of effective number of species, phylogenetic diversity or functional diversity on (i) bacterial abundance, (ii) temporal stability of abundance, (iii) nitrogen concentration, or (iv) multifunctionality. A literature review of 21 peer-reviewed studies that used dilution-to-extinction to manipulate bacterial diversity corroborated our findings: only about 25% found positive relationships. Combined, these results suggest that bacterial communities are able to uphold multifunctional ecosystems even at extensive reductions in diversity.