By Carol Davit, Executive Director, Missouri Prairie Foundation
Photo: Penn-Sylvania Prairie by Bruce Schuette
The concept of plant species conservatism was developed for Missouri flora by Doug Ladd, formerly director of conservation science for The Nature Conservancy and recently published by Ladd and Thomas (2015). Ecological conservatism is based on native species responding differently to changes and alterations in the landscape, two tenets being: 1) some species can tolerate greater disturbances to their environment and respond differently than others, and 2) species have varying degrees of fidelity to intact natural communities, ecological processes, and natural disturbance regimes.
For plants, Thomas (2016a) describes the coefficient of conservatism (CC value) as a 0 to 10 value assigned to every native species indicating the likelihood that that species is part of a stable and relatively undisturbed natural community. Species with values of 0 to 3 show little connection with remnant natural habitats and will opportunistically occupy disturbed areas; for example, annual ragweed species (Ambrosia spp.) have a value of 0.
The matrix species of intact natural communities are those with values in the 4 to 6 range. Species with values of 7 through 10 are the conservative species, which show high fidelity to high quality stable natural communities (Ladd and Thomas 2015), for example Oklahoma grass pink orchid (Calopogon oklahomensis) has a value of 10. Given that these species with high CC values occur on rare and fragmented natural communities, their conservation significance is even more meaningful. Low CC value species are ubiquitous on the landscape and need no special conservation effort; however, the high CC value conservative species largely need native remnant habitats with significant ecological integrity if they are to be conserved in the landscape.
MPF prairies collectively support up to 350 native vascular plant species, with a range of 27 to 53 conservative species per site. Looking at the mean native CC value is perhaps a better indicator for comparison because of differences in size and physical characteristics of each site. In Missouri today most of the landscape has a mean native CC value below 3.0 (Ladd and Thomas 2015). In today’s landscape of highly fragmented natural communities, a site with a mean native CC value of near 4.0 or more is considered to hold a level of natural integrity that is missing in most areas, and MPF prairies currently have a mean native CC value of 3.8 to 5.4.
MPF has contracted with the Institute of Botanical Training for floristic integrity surveys since 2012 for several of its prairies. These surveys are designed not only to document the current state of the flora, but for comparison with future sampling to determine botanical changes over time, to assess effectiveness of management. They are available at www.moprairie.org.
