Isozyme Evidence for Natural Hybridization in Phlomis (Lamiaceae): Hybrid Origin of the RareP.xmargaritae

Phlomisxmargaritae is a rare and sterile hybrid taxon foundin a single endangered population in southern Spain. It waspreviously described as a morphologically intermediate hybrid,putatively between Phlomis purpurea and P. composita. The presentstudy used allozymes as molecular markers to assess the hybrididentity ofP.xmargaritae . Ten putative loci from seven enzymesystems were resolved: five were monomorphic and fixed acrossall taxa studied and the rest (Aat-1, Aat-2, 6-Pgdh-2, Pgi andPgm) were polymorphic in at least one taxon. The two parentaltaxa are fixed for different alleles at 6-Pgdh-2 and show distinctallelic frequency differences for four other loci. Phlomisxmargaritaedisplays fixed heterozygous phenotypes for four of the fivepolymorphic loci, these being composed of combinations of thealleles found in the parental taxa. No unique alleles were detectedin P.xmargaritae. We conclude that this taxon is of hybrid originand confirm the identity of the parental taxa involved. It isfurther suggested that this population is composed of individualsthat are recent F₁hybrids that have not undergone backcrossingor introgression. Global conservation measures are necessaryfor the whole hybrid system in this location since further continuousassessment could reveal the evolutionary input of hybridizationin Phlomis.Copyright 2000 Annals of Botany Company Endangered species, genetic diversity, isozyme variation, hybrid species, Phlomisxmargaritae, plant conservation, population genetics, Lamiaceae, Spain.