Abstract

Symbioses such as lichens are potentially threatened by drastic environmental changes. We used the lichen Peltigera aphthosaa symbiosis between a fungus (mycobiont), a green alga (Coccomyxa sp.), and N-2-fixing cyanobacteria (Nostoc sp.)as a model organism to assess the effects of environmental perturbations in nitrogen (N) or phosphorus (P). Growth, carbon (C) and N stable isotopes, CNP concentrations, and specific markers were analyzed in whole thalli and the partners after 4months of daily nutrient additions in the field. Thallus N was 40% higher in N-fertilized thalli, amino acid concentrations were twice as high, while fungal chitin but not ergosterol was lower. Nitrogen also resulted in a thicker algal layer and density, and a higher C-13 abundance in all three partners. Photosynthesis was not affected by either N or P. Thallus growth increased with light dose independent of fertilization regime. We conclude that faster algal growth compared to fungal lead to increased competition for light and CO2 among the Coccomyxa cells, and for C between alga and fungus, resulting in neither photosynthesis nor thallus growth responded to N fertilization. This suggests that the symbiotic lifestyle of lichens may prevent them from utilizing nutrient abundance to increase C assimilation and growth.

Keywords

CN stable isotopes; lichen; nitrogen; Peltigera aphthosa (L; ) Willd; phosphorus; photosynthesis; resource allocation; symbiosis

Published in

Ecology and Evolution
2017, Volume: 7, number: 18, pages: 7420-7433
Publisher: WILEY

SLU Authors

• Näsholm, Torgny

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Ecology


Publication identifier

DOI: https://doi.org/10.1002/ece3.3257

Permanent link to this page (URI)

https://res.slu.se/id/publ/93275