Distribution and habitats of Erica mackayana and Erica × stuartii (Ericaceae): new insights and ideas regarding their origins in Ireland

Abstract

Erica mackayana has an unusual disjunct distribution in Europe, as it occurs only in Ireland and northern Spain and is thus known as a Hiberno-Lusitanian species. In Ireland, it is confined to localised areas in the west coast counties of Donegal, Mayo, Galway, and Kerry, where it occurs in lowland, or Atlantic, blanket bog habitat. Detailed mapping, in all of the six known Irish sites, of the distribution of E. mackayana and its hybrid with E. tetralix, E. × stuartii here shown for the first time, reveals a specific pattern of occurrence especially for E. mackayana. This species very rarely occurs more than 1 km from a track or road, whereas the hybrid is more widespread throughout the adjacent bog. Since E. mackayana does not set seed in Ireland and therefore relies on vegetative propagation, its spread at any site is limited, though much increased by human activity. All the sites are in relatively remote areas near the Atlantic coast, and we suggest here that E. mackayana may well have been introduced to Ireland through trade, possibly even smuggling, of goods from northern Spain.