Accounting for multiple dimensions of biodiversity to assess surrogate performance in a freshwater conservation prioritization

Abstract

Although freshwater ecosystems support a disproportionately large number of species, decision-support tools for prioritizing protected area efforts have mostly been implemented in marine and terrestrial environments. Systematic conservation planners rely on surrogate metrics to represent unsampled elements of biodiversity, yet few studies have considered the potential benefits associated with prioritizing multiple dimensions of freshwater biodiversity across multiple organism groups. In this study, we first evaluated relationships among patterns of taxonomic richness, functional diversity, functional redundancy, and biotic integrity for freshwater fish and benthic macroinvertebrate communities in the Congaree Biosphere Region, South Carolina, USA. We then used the decision-support tool Marxan to explore a potential trade-off between the number of organism groups sampled (i.e., taxonomic extent) and the multidimensional nature of biodiversity. Our central findings indicated that the processes driving patterns of taxonomic and functional diversity among organism groups were complementary, with direct implications for the evaluation of surrogate performance. Our results also suggest that within-taxa variation among measures of taxonomic and functional diversity may be more important to consider than the taxonomic representation of multiple organism groups. That is, we may be able to enhance the efficiency of conservation planning efforts by using available datasets in a more comprehensive way, as surrogate performance was largely mediated by the variation among metrics. Through the continued development of functional trait databases, we may be able to enhance the efficiency of data collection efforts and promote the timely and sustainable development of conservation strategies.