THE REPRODUCTIVE-BIOLOGY AND BREEDING SYSTEM OF ERICA-ANDEVALENSIS CABEZUDO AND RIVERA (ERICACEAE), AN ENDANGERED EDAPHIC ENDEMIC OF SOUTHWESTERN SPAIN - IMPLICATIONS FOR ITS CONSERVATION

Erica andevalensis CABEZUDO et RIVERA is a strict edaphic endemic of F l Andevalo (Huelva province, S Spain), an ancient pyrite mining exploi tation area characterized by elevated concentrations of heavy metals a nd acid sulphates in the local soils and rivers. The reproductive biol ogy of this heather has been studied in terms of flower longevity, nec tar secretion, pollinators, and fruit- (flower to fruit) and seed- (ov ule to seed) setting under natural, experimental bagging and greenhous e conditions. Additionally, hand-pollination (self- and cross-pollinat ion) has been performed in the greenhouse. Flower longevity was high, close to 24 d in greenhouse conditions; nectar secretion was scarce wi th a daily mean volume of 0.25 mu l and 0.03 mg of sugar. Apis mellife ra, Anthidium sp., Andrena sp. and Lysandra sp. have been captured vis iting the flowers of E. andevalensis. Mean number of ovules per flower was high, ca. 77, and was statistically independent of population, in dividual plant and inflorescence. The mean average fertility (74%) als o varied at these three levels. Fruit and seed set in natural populati ons were high, with values ca. 87% for fruiting; in the field the mean number of seeds per fruit was close to 57. The exclusion of insects ( i.e. pollinators) in the field lowered Very signigicantly fruit- and s eed-set, while in the greenhouse absolutely no fruit or seed has occur red spontaneously. Hand-pollination experiments produced significantly lower rates of seeds/fruit compared to plants in the field, but there was no effect of cross- versus self-pollination. Erica andevalensis i s therefore a self-compatible not-selfing species. From a conservation point of view, this species is in a ''good reproductive health'', it produces high numbers of fruit and seed set under natural conditions. Therefore, no intrinsic reproductive threat is apparent. Nevertheless, the fidelity to its environment appears to be sharply endangering the future of this remarkable heather.