Assessment of congruency across invertebrate taxa and taxonomic levels to identify potential surrogates

Owing to the huge number of invertebrate species, the paucity of available data and lack of accessible resources to carry out comprehensive surveys of invertebrates, it is necessary for surrogates to be used to represent invertebrate biodiversity in conservation planning, and to make rapid biodiversity assessments. The selection of surrogates is a popular topic in the literature, but there is no consensus regarding the criteria for the selection of appropriate surrogates. This study investigates the use of species density and species assemblage patterns to identify potential coarse-filter surrogates at a local scale, to assess cross-taxon congruency and congruency across taxonomic levels and activity groups using nine invertebrate taxa: Lepidoptera (butterflies), Hymenoptera (Apoidea), Coleoptera (Cetoniinae), Orthoptera, Blattodea, Araneae (Araneidae, Thomisidae, Oxyopidae), Myriapoda (Diplopoda, Chilopoda) and Mollusca. Furthermore, differences in the observed congruency when using species density and species assemblage patterns were assessed. Although cross-taxon congruencies were observed, the relations were weak and therefore surrogates could not be selected. The use of higher taxa to represent lower taxa shows good potential as a surrogate, but only in species-poor genera or families and only in regions where the biodiversity is well documented. The use of species density and species assemblage patterns to determine congruency and select surrogates demonstrated different congruent relations with varying ρ-values. Furthermore, when selecting surrogates, a ρ-value of greater than 0.75 should be used as an optimal level of congruency; below this value the relation is likely to be weak, and if used as a surrogate, misinterpretation may occur. The lack of congruency between invertebrate taxa supports the use of a multi-taxa approach for the incorporation of invertebrates into conservation plans. When data permits, species assemblage patterns should be used in conjunction with measures of species density for conservation planning, in particular, when an ecosystem consists of diverse habitats and with high species turnover.