Identifying insect and arachnid indicator taxa for impacts and management in coastal landscapes

Insects and arachnids are abundant and diverse, respond to key human impacts and support a diversity of key ecological functions. They are therefore widely recognised as effective surrogates for ecosystem condition. Their efficacy as indicators and surrogates in coastal dunes has, however, rarely been quantified, but might be instructive in guiding management in these often highly impacted coastal ecosystems. In this study, we (1) tested the effects of spatial and habitat drivers on the abundance of key insect and arachnid groups, and (2) used these patterns to identify viable management surrogates for impacts and management actions. We surveyed insect, arachnid and plant assemblages in coastal dunes at 20 sites on the Sunshine Coast in central eastern Australia. We have identified indicators for habitat condition and indicators for impact, and taxa that could be used to measure restoration outcomes. Crucially, five indicator groups also met criteria for being umbrella species, as management actions that increase their abundance would confer benefits to most other insect and arachnid taxonomic groups. We identified seven indicator groups (five insect and two arachnid), and each were affected by multiple spatial and habitat metrics, with metrics quantifying the composition and structure of vegetation communities being the most important predictors of most indicator’s distributions. Implications for insect conservation: We highlight the importance of understanding subtleties in spatial patterns and the unique set of spatial and environmental conditions that each group requires when identifying suitable indicator taxa for use in the conservation and management of coastal dunes.