Plant genetic diversity in the Canary Islands: A conservation perspective

The Canary Islands are an Atlantic volcanic archipelago with a rich flora o f similar to 570 endemic species. The endemics represent similar to 40% of the native flora of the islands, and similar to 20% of the endemics are in the E (endangered) category of the International Union for Conservation of Nature. A review of allozyme variation in 69 endemic species belonging to 1 8 genera and eight families is presented. The average species-level genetic diversity (H-T) at allozyme loci is 0.186, which is twice as high as the m ean reported for endemics of Pacific archipelagos. Possible factors contrib uting to this higher diversity are discussed, but the reasons remain obscur e. An average of 28% of the allozyme diversity within species resides among populations, indicating a high level of interpopulational differentiation. Studies of reproductive biology indicate that many of the endemic species are outcrossers. The high total diversity within species, the relatively hi gh differentiation among populations, and the outcrossing breeding systems have implications for species conservation. Decreased population sizes in o utcrossing species would promote biparental inbreeding and increase inbreed ing depression. The relatively high proportion of allozyme diversity among populations indicates that the most effective strategy for preserving genet ic variation in species is to conserve as many populations as possible. The genetic diversity in many Canary Island endemics is endangered by: (1) ove rgrazing by introduced animals, such as barbary sheep, goats, mouflons, rab bits, and sheep; (2) interspecific hybridization following habitat disturba nce or planting of endemics along roadsides or in public gardens; (3) compe tition with alien plant species; and (4) decline of population size because of urban development and farming.