Development of 14 polymorphic microsatellite loci for Ficus tikoua (Moraceae).

PREMISE OF THE STUDY: Polymorphic microsatellite markers were developed to facilitate studies on the fine-scale population genetic structure of Ficus tikoua (Moraceae), a prostrate shrub known to have highly restricted gene flow. METHODS AND RESULTS: Microsatellite primers were developed using the biotin-streptavidin capture method and scanned for polymorphism within 76 individuals sampled from three natural F. tikoua populations. Fourteen loci were shown to be polymorphic, with allele numbers ranging from three to 16. The observed and expected heterozygosity in the three populations ranged from 0 to 1 and from 0 to 0.87, respectively. Substantial divergence was found among the populations at some loci. All loci can be successfully amplified in at least eight other Ficus species, indicating good transferability within the genus. CONCLUSIONS: The 14 microsatellite loci will be a helpful tool for assessing the fine-scale genetic structure of F. tikoua.

Extremely high proportions of male flowers and geographic variation in floral ratios within male figs of Ficus tikoua despite pollinators displaying active pollen collection.

Most plants are pollinated passively, but active pollination has evolved among insects that depend on ovule fertilization for larval development. Anther-to-ovule ratios (A/O ratios, a coarse indicator of pollen-to-ovule ratios) are strong indicators of pollination mode in fig trees and are consistent within most species. However, unusually high values and high variation of A/O ratios (0.096-10.0) were detected among male plants from 41 natural populations of Ficus tikoua in China. Higher proportions of male (staminate) flowers were associated with a change in their distribution within the figs, from circum-ostiolar to scattered. Plants bearing figs with ostiolar or scattered male flowers were geographically separated, with scattered male flowers found mainly on the Yungui Plateau in the southwest of our sample area. The A/O ratios of most F. tikoua figs were indicative of passive pollination, but its Ceratosolen fig wasp pollinator actively loads pollen into its pollen pockets. Additional pollen was also carried on their body surface and pollinators emerging from scattered-flower figs had more surface pollen. Large amounts of pollen grains on the insects' body surface are usually indicative of a passive pollinator. This is the first recorded case of an actively pollinated Ficus species producing large amounts of pollen. Overall high A/O ratios, particularly in some populations, in combination with actively pollinating pollinators, may reflect a response by the plant to insufficient quantities of pollen transported in the wasps' pollen pockets, together with geographic variation in this pollen limitation. This suggests an unstable scenario that could lead to eventual loss of wasp active pollination behavior.