Welsh Journals

THE FLORA ON YNYS SEIRIOL (PUFFIN ISLAND), WITH SOME NOTES OF THE EFFECTS OF MYXOMATOSIS. WILLIAM S. LACEY Department of Botany, University College of North Wales, Bangor. INTRODUCTION YNYS SEIRIOL lies off the most easterly part of Anglesey (V-c. 52), separated by a deep channel which is less than half a mile wide. It is a small island, being only about 1200 yards long by 300 yards wide, and is composed entirely of Carboniferous Limestone, which reaches a maximum height of 193 ft. above the sea. Like most small off-shore islands, Ynys Seiriol has an interest quite out of proportion to its size. It has attracted the attention of naturalists since quite early times. Pennant, for example, visited the island in the 18th century, and a hundred years before him John Ray had also been there to record what he saw of the bird life and the plants. Indeed, it seems very likely that the fauna and flora were studied long before Ray's time, for the island has a long history of occupation by man. Remains of Early Christian ecclesiastical buildings and old walled gardens are still to be seen there. Most earlier writers have commented on the composition of the flora of Ynys Seiriol. As might be expected, this includes a maritime element, but, in addition, it is characterised, partly by the occurrence of several species which almost certainly owe their presence to introduction by man, and partly by the very small total number of species present. The available records show that until 1956 this has never exceeded a hundred species. The poverty of the flora is explained, in part at least, by the grazing effects of rabbits, which appear to have been present on the island, in fluctuating numbers, for a very long time (Phillips, 1894 Lacey, 1949). In 1955, however, the spread of myxomatosis to the island resulted in a drastic reduction of the rabbit population and this was followed by a very marked change in the flora, first noticed in 1956. It now seems opportune to put the pre-myxomatosis flora on record, together with records for the first year after the spread of myxo- matosis, so that the subsequent composition of the flora can be compared with the original, and further changes noted. METHOD OF PRESENTATION OF RECORDS Three separate species lists are given for flowering plants and ferns. These are (1) the first published Flora of Puffin Island, 1888-1892 (Herdman, 1890 Phillips, 1894). This list includes several doubtful records and records of undetermined species which cannot now be checked. Several comments are included in parenthesis at the appropriate points in the list.