Indicator-species and coarse-filter approaches in conservation appear insufficient alone

Because resources are finite, conservation practices can be based on shortcuts (i.e., a quicker way to a desired outcome). For example, indicator species are often used as a shortcut to justify conservation at greater organizational levels (i.e., communities, ecosystems, landscapes). Conversely, "coarse-filter" approaches to protect landscapes are often assumed to conserve organizational levels nested within that landscape. But is conservation biology fundamentally different from other applied sciences, in which shortcuts appear rare or absent? To evaluate this question requires a rarity; much data across organizational levels in numerous well-defined systems. We used data collected in vernal pools (N = 61) in greater San Diego, California and seasonal wetlands (N = 70) in Florida. Data for plant species of concern, plant community diversity, ecosystem function, and landscape integrity were evaluated using partial least-squares structural equation models. Three a priori alternative models for each of the indicator species and coarse-filter approaches were tested, where models varied in complexity and included shortcuts between organizational levels. We found little support for shortcuts connecting distant levels, but species of concern and community diversity were always significantly and strongly interrelated. We conclude that species of concern often predict community diversity (and vice versa) but shortcuts between more distant organizational levels are hard to find. Given that study systems here were numerous, discrete and relatively small (i.e., well-described), we expect that effective shortcuts will be difficult to demonstrate for many other systems that do not share all those attributes. Thus we suggest that regional ensemble conservation goals and approaches will be more often effective than relying on assumed conservation shortcuts with little evidence.