Puzzling out the reproductive biology of the endangered cat’s head rockrose (Helianthemum caput-felis, Cistaceae)

• We studied the reproductive biology of endangered Helianthemum caput-felis.
• Differences in fruit and seed set were found between island and inland populations.
• In the inland population, H. caput-felis was mainly an outbreeder.
• The studied species was mainly visited by hymenopteran and coleopteran species.
• H. caput-felis was the principal species in the insect pollen loads.

Helianthemum caput-felis is an endangered plant species growing in fragmented habitats in the western Mediterranean basin. Reproductive traits, breeding system and pollinator assemblage were studied in its largest known (mainland) European population to improve knowledge on the reproductive biology of the species. Hand-pollination experiments were carried out to determine the breeding system. Generalized linear mixed models (GLMM) were fitted to the data to evaluate the effect of treatment on fruit set and number of viable seeds per fruit. We also investigated the composition of the pollinator assemblage by direct observations, and studied their pollen load. Results were then compared to previous studies conducted in an island population. In the studied population, H. caput-felis is partially self-compatible, but mostly an outbreeder species, since outcrossed flowers produced many more fruits and seeds than self-pollinated ones. Conversely, pollination treatments did not affect reproductive output in the island population. We also found several differences between island and mainland composition of floral visitors, as it was expected. The study of pollen loads revealed that insects were mostly visiting H. caput-felis. Despite the low capacity to produce fruits with self-pollination, H. caput-felis presented no reproductive limitations in its main inland population. Reproductive characteristics along with differences among populations should be taken into account for adequate management and conservation practices.

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