Summary1. Seed reproduction of a plant species is strongly affected by the spatial structures of its population through gene flow patterns. We assessed the effects of the spatial arrangement of genetically compatible mates on the seed set and gene flow of a heterostylous perennial species, Primula sieboldii E. Morren (Primulaceae), using a patchy experimental population. 2. Seed set was significantly higher in patches containing opposite-morph genets than in patches without opposite-morph genets. Pollen flow within patches explained 76·9% of total pollen flow, while 13·5% was ascribed to pollen flow between patches. Mean and maximum pollen dispersal distances within the experimental population were 7·23 and 89 m, respectively. 3. Mean and maximum seed dispersal distances were 10·4 and 23·0 cm, respectively. 4. Our results suggest a profound effect of the spatial arrangement of compatible mates within the patchy population on seed set and gene flow. Investigations using experimental populations in combination with molecular markers will provide highly effective means for evaluating the influences of spatial structures on plant gene flow and reproduction, and will also provide valuable information for conservation efforts.

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To detect plant specialization to pollinator insects and to further examine the ‘pollination syndrome’ hypotheses, flowering angiosperms and insect visitors were recorded in a northern maritime grassland community. Associations between plant species and insect groups were analyzed using binomial tests based on census data obtained from two sites over 3 years. ‘Preference to an insect group by a plant species’ was expressed as a significant deviation of the actual proportion (i.e. the proportion of the number of flower visits by the insect group to the plant species in the total number of visits to the plant species) of the expected proportion (i.e. the proportion of the number of visits by the insect group in the total visits during its flowering period). ‘Preference to a plant species by an insect group’ was similarly expressed using the number of flowers of the plant species visited by the insect group. Most significant preferences varied temporally or spatially. Variability in the preferences is suggested to have resulted from temporal and spatial variations in the abundance and species composition of both flowers and insects. However, in species showing variable preferences, significant specialization in the pollinator insect group (i.e. relatively constant, mutual preferences) were demonstrated for seven and five plant species at the two study sites, respectively. Most specializations were found in associations with bumblebees. ‘Bumblebee specialists’ were significantly well represented in the flower shape types ‘gullet’ and ‘flag’ and the flower color types ‘violet’, which supports the ‘pollination syndrome’ theory.

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