Coefficients of conservatism and plant traits

Many plant species are limited to habitats relatively unaffected by anthropogenic disturbance, so protecting these undisturbed habitats is essential for plant conservation. Coefficients of conservatism (C values) are numeric values assigned to plant species to indicate their sensitivity to anthropogenic disturbance, and these values are increasingly used to prioritize natural areas for conservation and monitor restoration outcomes. Assigning these values is highly subjective, quantitative links between C values and a plant species’ ecology would vastly improve the assignment of C values.

Illustration of representative plant species across a range of coefficients of conservatism. Species illustrated include (from left to right): Conyza canadensis, Ambrosia artemisiifolia, Chamaecrista fasciculata, Monarda fistulosa, Asclepias tuberosa, Ratibida pinnata, Baptisia alba, Silphium integrifolium, Veronicastrum virginicum, Amorpha canescens and *Sporobolus heterolepis*. Image credit: J. Ferguson.

In a study published in AoBP, Bauer et al. tested whether there are consistent differences in life histories between species with high and low C values. To do so they grew seedlings of 54 plant species in a greenhouse and measured traits related to life history trade-offs (including total biomass, root:shoot ratio, flowering biomass, number of leaves, proportion of dead leaves, leaf thickness, height, seed dimensions and seed mass). They also grew plants with and without mycorrhizal fungi as a test of these species’ reliance on this mutualism. Life history traits were correlated with C values, indicating that coefficients of conservatism are closely linked to a plant species’ life history strategy. Plants with high C values and a slow life history were more responsive to mutualisms with mycorrhizal fungi. Overall, these results connect C values with life-history trade-offs, indicating that high C value species tend to share a suite of traits associated with a slow life history. Relative growth rate, long-lived leaves and root:shoot ratios were significantly correlated with C values, and so could in the future allow for a more quantitative, and less subjective, estimation of a species’ vulnerability to disturbance.

The authors of this study and the illustrator of the image above can be found on Twitter:
@jonathantbauer, @MycoBloom, and @JuliaFpaintsbio