A Study in Endemism: Silene diclinis

Silene diclinis (Lag.)M. Lainz is a dioecious endemic with a highly restricted distribution in south-eastern Spain. The sparse literature on the plant is summarised before referring to the results of a study of S. diclinis in the wild. A new description of the species is presented and its taxonomic affinities discussed. Details of the flowering time of S. diclinis, possible pollinators and its population age structure are set out and its wild habitat described. Before examining the possible origin of the distribution of S. diclinis, an attempt is made to clarify the various classifications of endemism that have been widely used in the literature. It is considered that since these classifications are generally based on the supposed origins of endemics they do not form a sound basis for the examination of evidence in individual cases. Types of evidence that can be used to throw light on the history of individual endemics are examined and include evidence gained from experimental taxonomy, pollen and macrofossil analysis and ecological studies. Unfortunately, in the case of S. diclinis there is no direct evidence referring to its past. One hypothesis, based on present distribution and on a consideration of Mediterranean Cenozoic palaeoenvironments, is put forward to explain the present restriction of S. diclinis. Finally, the genetic situation in a restricted endemic population, the future of S. diclinis and conservation measures are discussed.