Article

Pollinator activity can have a major effect on the reproductive success of plant species, not only assuring their survival but also influencing gene flow and hybridization between species. N. cavanillesii is considered a threatened species in Portugal with only two reported populations, forming highly-fragmented, isolated patches. This autumnal flowering species develops small yellow flowers with a short perianth tube and an inconspicuous corona, allowing total exposure of the sexual structures. Although N. cavanillesii is self-compatible and self-pollinated, crosspollination processes are favoured and necessary to promote higher fruit set (50%). N. serotinus is distributed along the Mediterranean coast and in Portugal is considered a common species. Its fragrant flowers are white and have a very short yellow corona and a long, narrow perianth tube that hides the sexual organs. Self-pollination processes are favoured, although this species can also set fruits by cross-pollination. Floral visitors are necessary to promote self-crossings. N. serotinus has an average fruit set of about 70%. In Portugal, these two species are sympatric and their flowering periods overlap. Artificial crossings revealed weak reproductive barriers that do not prevent interspecific crosses especially when N. cavanillesii is the receptor species. However, in natural conditions, hybridization events are reduced by the activity of different pollinators. N. cavanillesii flowers are mainly visited by the hymnoptera, Halictus sp., while N. serotinus is mostly visited by the coleoptera, Meligethes sp. Only the hymenoptera, Megachile sp. is common to both species, but less than 3% of the visits are shared between these two species. The present study shows that these two co-generic species, which are well-adapted to the same environment, have developed divergent reproductive strategies, minimizing pollinator competition and assuring survival outside the main Mediterranean flowering season.