Patterns of biodiverse, understudied groups do not mirror those of the surrogate groups that set conservation priorities: a case study from the Mid-Atlantic Coastal Plain of eastern North America

We conducted biodiversity inventories of lichens, woody plants, and sedges at 32 sites on the Mid-Atlantic Coastal Plain of eastern North America between November 2012 and June 2015. Each site comprised a single, uniform habitat, consisting of either Coastal Plain Floodplain forest, Coastal Plain Flatwood swamp, Coastal Plain Oak-Pine forest, Maritime forest, Mixed Mesic Hardwood forest, or Tidal forest. We compared alpha diversity and community assemblages of each organismal group across the sites, and compared selected minimal reserve sets in order to visualize biodiversity patterns and assess whether specific components of vascular plants (sedges and woody plants) serve as an effective surrogate for lichens. Woody plants provide a direct substrate for lichen growth, but there is no significant correlation between the alpha diversity of these groups. For conserving maximal species richness among the studied groups, lichens outperform the sedges and woody plants as the best surrogate group for building minimum reserve sets, even though vascular plants are more commonly used as a surrogate. Likewise, sedge alpha diversity does not correlate with lichens, or with woody plants. Although no group is an effective indicator for high alpha diversity sites of other organisms, a significant correlation between the community assemblages of lichens and woody plants suggests that protecting varied types of plant communities might serve as a workable surrogate for protecting lichens. The lack of congruence between species richness patterns across organismal groups suggests that the mechanisms that shape patterns of diversity are not identical, and that identifying and incorporating specific biodiversity indicators for understudied groups in conservation policy is necessary to ensure their protection.