Variation in the reproductive strategy of a lichenized fungus along a climatic gradient

Onset of reproduction and reproductive allocation patterns are key components of plant reproductive strategies. Life history theory predicts that plants in adverse environments for juvenile performance start reproduction at smaller sizes and exhibit higher reproductive allocation compared to their counterparts in favourable environments. Life history theory will gain in generality if its predictions are shown to apply to a broad range of organisms and modes of reproduction. This study tested whether the asexual reproductive strategy of a lichenized fungus changed along a climatic gradient.

The variation in threshold size for asexual reproduction and asexual reproductive allocation of the lichen Lobarina scrobiculata was assessed in 18 populations (9665 individuals) along a climatic gradient spanning 800 km in latitude in Southern Europe. Using generalized linear models and standardized major axis regressions, the allometric relationships and the associated variation in climatic factors according to the changes in the threshold size for reproduction and reproductive allocation patterns were assessed.

The onset of reproduction was size-dependent and the reproductive allocation increased with individual size. Both the threshold size for reproduction and the reproductive allocation varied along the rainfall gradient. A lower threshold size for reproduction and higher reproductive allocation in drier, adverse locations were found. Therefore, populations in drier locations fitted the predictions of life history theory for sexually reproducing organisms in adverse environments for juvenile performance.

This study highlights the applicability of the life history theory to fungi and to modes of reproduction other than sexual reproduction. Based on the intraspecific variation in the asexual reproductive strategy of a fungal organism with climatic factors, these findings expand the scope of life history theory predictions and increase our understanding of life history diversity and reproductive strategies across environments.