*Corresponding author. E-mail: mbosch@farmacia.far.ub.es Biological Journal of the Linnean Society, 2002, 76, 79–90. With 6 figures INTRODUCTION The genus Petrocoptis A. Braun ex Endl., endemic to the north of the Iberian Peninsula, comprises a set of perennial chasmophyte (rock fissure plants) microspecies specialized in colonizing vertical calcare- ous rocks and caves (Montserrat & Fernández-Casas, 1990); this genus has been recently interpreted as a subgenus of Silene (Mayol & Rosselló, 1999). During the last decade, some studies on floral biology and pollination of several species of Petrocoptis (Guitián & Sánchez, 1992; García, 1993; García, Antor & Villar, 1993; Navarro, Guitián & Guitián, 1993; Guitián, Sánchez & Guitián, 1994; Guitián & Navarro, 1996; Navarro, 1996; Guitián et al., 1997; Navarro & Guitián, 2002) suggested the existence of two patterns of pollination syndromes within the genus: (i) species pollinated by bees (melitophylous) with zygomorphic, pink and relatively large flowers, with high nectar production and facultative xenogamy and (ii) species pollinated by flies (miophylous) with actinomorphic, white, and relatively small flowers, with low nectar production and facultative autogamy. Given this © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 76, 79–90 79 Pollination ecology of the pre-Pyrenean endemic Petrocoptis montsicciana (Caryophyllaceae): effects of population size M. BOSCH*, J. SIMON, A. M. ROVIRA, J. MOLERO and C. BLANCHÉ GReB, Laboratori de Botànica, Facultat de Farmàcia, Universitat de Barcelona, Avda. Joan XXIII sn, 08028 Barcelona, Catalonia, Spain Received 23 April 2001; accepted for publication 18 January 2002 Petrocoptis montsicciana (Caryophyllaceae) is a threatened pre-Pyrenean endemic that grows exclusively on caves and walls of limestone. We studied its pollination ecology by monitoring phenology and by evaluating pollen and nectar production, pollinator activity (frequency and behaviour of visitors), quantity and quality of pollination ser- vices, pollen/ovule ratio, and seed set in response to insect exclusion and self-compatibility tests. We also analysed the effect of population size on reproductive mechanisms by comparing a large and a small population. Flowers of P. montsicciana produced nectar and were visited by Hymenoptera (79.7%), Diptera (11.5%), and Lepidoptera (8.8%). The most frequent pollinators (60.6% of total visits) were long-tongued bees of the genus Anthophora. Both popu- lations had a similar range of pollinators. We found a correlation between the number of visited flowers and the number of open flowers per census; 88.7% of pollen grains deposited on the stigmas were conspecific and the main competitor was another chasmophyte plant, Antirrhinum molle. Bagged flowers set seeds but significantly less so than hand-self-pollinated and control flowers. Thus, although self-compatible and self-pollinated, entomophilous pollination of P. montsicciana is required in order to explain c. 10–40% of total seed set, in accordance with P/O ratio estimations. Bagged flowers from the small population set significantly more seeds than the large one. Visi- tation rates were lower in the small population, but, unexpectedly, showed higher stigmatic pollen loads and similar or higher seed set. These results suggest an increase of spontaneous selfing rates in the small population, proba- bly favoured by a smaller flower size, which can not only assure reproductive success when pollinators are scarce, but also provide additional potential to adapt to climatic changes. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 76, 79–90. ADDITIONAL KEYWORDS: Anthophora – chasmophyte plant – competition – floral rewards – self- compatibility – self-pollination – seed set – stigmatic pollen load. Downloaded from https://academic.oup.com/biolinnean/article-abstract/76/1/79/2639716 by guest on 13 June 2020