Biological surrogates are overrated as a guide to ‘predicting’ biodiversity, according to an analysis of surrogate effectiveness in marine systems.

Camille Mellin, a CERF Marine Biodiversity Hub postdoctoral student with the Australian Institute of Marine Science, led the analysis of expert knowledge and 264 published ‘tests’ of surrogate effectiveness. More than one third of the tests analysed had found no evidence of a relationship between surrogate and target biodiversity. Even when a relationship was evident, surrogate predictive power was often weak.

Surrogates can be physical or biological. An example of a biological surrogate is the number of species of a particular taxon present in an area related to a biodiversity parameter of interest, such as the total number of species.

Biological surrogates are gaining popularity as substitutes for biodiversity patterns, particularly in diverse marine systems where field surveys can be expensive. Areas of conservation concern might then be prioritised based on relative measures of differences among them, rather than on a full description of their biodiversity. But surrogates lack consistency in definition, in scale, and in the estimation of their effectiveness.

Dr Mellin and her colleagues found that spatial scale, habitat, type of surrogate and the statistical method used for its construction all influenced surrogate effectiveness. The best performers were higher-taxa surrogates at a 10-kilometre scale, in low-complexity marine habitats such as soft bottoms, and which used multivariate-based methods.

The analysis provides a benchmark for the reliable use and development of biological surrogacy, which will benefit from careful choice and specification of methods tailored either to prediction or planning. Its recommendations include:

• select surrogates based on the target taxa of interest;
• match the surrogate to an explicit objective;
• use representation-based methods for designing protected areas;
• use congruence-based methods where data are scarce;
• use a surrogate that is faster/cheaper to sample than the target; and
• test the spatial and temporal stability of surrogate effectiveness.

This paper indicates the pitfalls of a casual choice of surrogates for scientific research, planning or management. Surrogates need to be matched to the research or management question and tested for discrimination and reliability before they are used in earnest.
 

Photo:  Coral reef.  Copyright AIMS

Related information:

CERF Marine Biodiversity Hub

Mellin C., Delean S., Caley J., Edgar G., Meekan M., et al. (2011). Effectiveness of Biological Surrogates for Predicting Patterns of Marine Biodiversity: A Global Meta-Analysis. PLoS ONE 6(6): e20141. doi:10.1371/journal.pone.0020141