Promising yet variable performance of cross-taxon biodiversity surrogates: a test in two marine habitats at multiple times

Abstract

Surrogates are a potential solution to the often-cited problem of there being insufficient information for biodiversity assessments or conservation planning. Cross-taxon surrogacy is the ability of a group of well-known taxa to represent variation in other poorly known taxa. To date, tests of the effectiveness of cross-taxon surrogacy in marine environments have yielded variable results and a significant qualification to the outcomes of tests that have demonstrated surrogacy is the near absence of tests for its persistence through time. This study tested for cross-taxon surrogacy and its persistence through time for three surrogates (crustaceans, molluscs, polychaetes). We used data on biodiversity variables and species assemblages of the surrogates and their targets that had been collected during multiple sampling events over 2.5 yr in two habitats (seagrass, unvegetated sediment) in a large bay in south-eastern Australia. We tested surrogacy by fitting a series of linear models using generalized least squares for biodiversity variables and by Mantel tests of dissimilarity matrices of species assemblages. We also tested whether the type of data transformation affected Mantel tests. We found that each of the groups were effective surrogates for some but not all biodiversity variables (with molluscs or polychaetes being effective surrogates for species richness in both habitats), that none of the groups were effective surrogates for species assemblages, and that the outcomes of Mantel tests of dissimilarity matrices of surrogates and their targets were unaffected by the data transformation used. We conclude that while our results for surrogacy for biodiversity variables are promising the inconsistent results from other studies argues for caution about their application beyond the area and context in which they were assessed. The lack of evidence that we found for surrogates of species assemblages, and similar lack of evidence from other studies, suggests that assemblage-level surrogates are unlikely to be useful in biodiversity surveys.

Living and dead bivalves are congruent surrogates for whole benthic macroinvertebrate communities in Puget Sound

“…However, polychaetes were closely followed in Puget Sound by bivalves, both alive and dead, in total abundance and were very distantly trailed by malacostracans despite this group being second-ranked in richness in the Puget Sound regional dataset (second row, Figure 4). In general, taxonomic subsetting has been generally found to be less effective, reliable, and/or consistent as a method of surrogacy than has taxonomic sufficiency (coarsening), based on other studies using the same clades as examined here (e.g., Włodarska-Kowalczuk and Kêdra, 2007;Bevilacqua et al, 2009;Mellin et al, 2011;Gladstone et al, 2020;Kokesh et al, 2022). Nonetheless, given the observed variation among subsets in their robustness to taxonomic coarsening, we would suggest that the ability of a subset to preserve whole-fauna patterns be assessed prior to putting this (or any other) surrogacy method into practice.…”

“…"Subsetting" on the other hand refers to narrowing the scope of information, for example by focusing on a "taxonomic subset" (a singular clade, functional guild, or other group of interest) or on a "numerical subset" of the whole fauna (e.g., the first 100 individuals picked from the sample, as is common in micropaleontology). Other forms of surrogacy include "cross-taxon" approaches in which one group of taxa serves as a proxy for another, completely independent group (Mellin et al, 2011;Gladstone et al, 2020). A death assemblage, which is not part of the living fauna, could be considered a cross-taxon surrogate that is also a temporally coarser sample than the corresponding living assemblage.…”

Taxonomic surrogates for long-term macrobenthic community monitoring: an application with community trajectory analysis

“…Olsgard & Somerfield 2000, Wodarska-Kowalczuk & Kedra 2007, Kokesh et al 2022. However, in contrast with most studies on temporal dynamics which used non-metric multidimensional scaling (nMDS), sometimes combined with Mantel tests (Gladstone et al 2020), a method that has been subject to criticisms (Legendre et al 2015), we assessed the effectiveness of taxonomic surrogacy with a method explicitly designed to quantitatively evaluate temporal dynamics.…”

Annelid Diversity: Historical Overview and Future Perspectives

“…Annelids are a major component of the marine benthos and terrestrial realm, and they comprise species with different tolerances to stress. Consequently, they have been considered as good bioindicators in environmental monitoring (e.g., [32][33][34]) and surrogates for marine biodiversity [35,36] biomarkers (e.g., [37][38][39][40]).…”