Invertebrate species at risk from Ash Dieback in the UK

Ash Dieback, a disease of Ash (Fraxinus excelsior) trees caused by the ascomycete, Hymenoscyphus pseudoalbidus, was first noticed in the UK in February 2012 and has since been found through much of the country. Evidence from elsewhere in Europe suggests that most infected Ash trees succumb to the disease and, hence, UK woodlands and landscapes are at risk of large scale changes. A wide range of taxa either depends on Ash or makes significant use of it and is likely to be detrimentally affected if the UK's Ash trees are seriously depleted. Invertebrate species that use Ash exclusively or are highly associated with the tree were identified from existing literature. We categorised 36 invertebrate species as "obligate" on Ash in the UK and a further 38 as "highly associated". Hemiptera, Diptera and Lepidoptera were the most significant groups amongst the obligate species with Coleoptera, Lepidoptera and Diptera dominating the highly associated species. Most obligate species are phytophagous in their use of Ash. Highly associated species were evenly split between those that are phytophagous and those classified as saproxylic with a smaller number of species employing a range of additional feeding strategies. Among highly associated species that are phytophagous, Privet (Ligustrum sp.) was the most frequent alternative plant used. This and other alternative trees and shrubs could be used to help mitigate the effects of Ash Dieback in limited localised situations, where rare species might be affected. Additional suggestions for managing the impact of Ash Dieback on invertebrates are discussed.