Figure 1. Map of the Upper Lough Erne (ULE) system showing the geographical location of the system and the studied lakes (loughs) and the recorded abundances of Elodea canadensis during 2008-2009 (circles). The size of the circles represents an abundance scale of 0-5, where 5 is maximum abundances and 0 (red circle) apparent absence. Superscripts numbers indicate the lake group that each lake belongs. The lake groups were selected according to the water flow direction:Group 1 , lakes directly connected to the central lake (ULE) via the River Erne flow; Group 2 , lakes with a direct lateral connection to the ULE; and Group 3 , lakes connected laterally to the ULE via one or more intermediate lakes. Water layers obtained from Ordnance Survey Northern Ireland https://www.nidirect.gov.uk/services/osni-online-map-shop and reproduced with the permission of Land & Property Services © Crown Copyright 2018.