Abstract
BackgroundDecreases in mate and/or pollinator availability would be expected to affect the selective pressure on plant mating systems. An increase in self-fertilization may evolve to compensate for the negative effects of pollination failure. However, the benefit of selfing in variable pollination environments depends on the relative fitnesses of selfed and outcrossed progeny. We investigated the potential for selfing to provide reproductive assurance over the lifetime of a long-lived perennial species and its variation between plant patches of various sizes. Patch size is likely to affect mate and pollinator availabilities, thereby affecting pollination success and the rate of selfing. We estimated fruit and seed set, reproductive assurance, self-compatibility, the multilocus patch selfing rate and lifetime inbreeding depression in natural patches of Rhododendron ferrugineum (Ericaceae), a mass-flowering species characterized by considerable patch size variation (as estimated by the total number of inflorescences).ResultsOpen seed set declined linearly with increasing patch size, whereas pollinator-mediated seed set (emasculated flowers) was not significantly affected. Progeny array analysis indicated that the selfing rate declined with increasing patch size, consistent with greater reproductive assurance in small sparse patches than in large, dense patches. However, fruit set and adult fitness decreased with decreasing patch size, with an estimated mean lifetime inbreeding depression of 0.9 (obtained by comparing F values in adults and progenies).ConclusionsLifetime inbreeding depression strongly counteracts the advantage of reproductive assurance due to selfing in this long-lived species. The poor fitness of selfed offspring should counteract any evolution towards selfing, despite its potential to alleviate the negative consequences of pollen limitation. This study highlights the need to estimate lifetime inbreeding depression, together with mating system and pollination parameters, if we are to understand the actual benefit of selfing and avoid the overestimation of reproductive assurance.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-014-0243-7) contains supplementary material, which is available to authorized users.
Highlights
Decreases in mate and/or pollinator availability would be expected to affect the selective pressure on plant mating systems
Open seed set from intact flowers was significantly greater than that of emasculated flowers, consistent with significant reproductive assurance
Reproductive assurance and selfing rate estimates for patches of different sizes We found that autogamy significantly increased seed set, as previously shown for other systems [41,42,43,44]
Summary
Decreases in mate and/or pollinator availability would be expected to affect the selective pressure on plant mating systems. Pollination failure may promote the evolution of selfing, which can provide reproductive assurance by increasing seed production when pollinators and/or mates are scarce [5,6]. Reproductive assurance is one of the most longstanding and widely accepted explanations for the evolution of selfing and the maintenance of mixed mating systems [7,8,9,10,11]. If both pollinators and mates are limiting, reproductive assurance can occur through autonomous selfing [9,10]. In conditions of pollen limitation, selfing would be selected for ID values below (1 - e) / 2, where e is the fraction of ovules remaining unfertilized [17,18]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
