Trade-offs, spatial heterogeneity, and the maintenance of microbial diversity.
Specialization and concomitant trade-offs are assumed to underlie the non-neutral coexistence of lineages. Trade-offs across heterogeneous environments can promote diversity by preventing competitive exclusion. However, the importance of trade-offs in maintaining diversity in natural microbial assemblages is unclear, as trade-offs are frequently not detected in artificial evolution experiments. Stressful conditions associated with patches of heavy-metal enriched serpentine soils provide excellent opportunities for examining how heterogeneity may foster genetic diversity. Using a spatially replicated design, we demonstrate that rhizobium bacteria symbiotic with legumes inhabiting contrasting serpentine and nonserpentine soils exhibit a trade-off between a genotype's nickel tolerance and its ability to replicate rapidly. Furthermore, we detected adaptive divergence in rhizobial assemblages across soil type heterogeneity at multiple sites, suggesting that this trade-off may promote the coexistence of phenotypically distinct bacterial lineages. Trade-offs and adaptive divergence may be important factors maintaining the tremendous diversity within natural assemblages of bacteria.
The Department of Integrative Biology, University of California, Berkeley, California 94720, USA. ssporter@berkeley.edu
Stephanie S
SS
Porter
Kevin J
KJ
Rice
D000222:Adaptation, Physiological / Q000187:drug effects / Q000235:genetics; D044822:Biodiversity; D019143:Evolution, Molecular; D014644:Genetic Variation; D000070116:Lotus / Q000235:genetics / Q000502:physiology; D029902:Medicago / Q000235:genetics / Q000502:physiology; D009532:Nickel / Q000032:analysis / Q000494:pharmacology; D012231:Rhizobium / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D013312:Stress, Physiological; D013559:Symbiosis / Q000235:genetics
D012987:Soil; D009532:Nickel