Evidence from peroxidase polymorphism on the taxonomy and reproduction of some Sorbus populations in south‐west England

Peroxidase isoenzymes in stem tissue were investigated by polyacrylamide gel electrophoresis in Sorbus populations mainly from Devon, south-west England, A total of 16 bands were recognized, of which 10 were variable between individuals or populations. The sexual diploid species S. aucuparia, S. aria and S. torminalis showed individual variation within populations. Six polyploid microspecies, S. anglica, S. porrigentiformis, S. rupicola, S. vexans, S. subcuneata and S. devoniensis, and an extensive unnamed rupicola-like population on the coast of north Devon and west Somerset, consisted of individuals of essentially identical phenotype (with a few recognizable minor variants). Every microspecies had a distinctive peroxidase phenotype but S. porrigentiformis from Devon was not identical with a specimen from Leigh Woods, Bristol. Microspecies of the S. aria group have various combinations of seven bands which occur in diploid S. aria populations. S. anglica combines 'S. aria' bands with a prominent band from S. aucuparia. S. subcuneata and S. devoniensis possess four or five of the 'S. aria' bands, together with two bands which are apparently constant in S. torminalis; S. intermedia also has a peroxidase phenotype related to these species.