Global biogeography of mating system variation in seed plants.

Latitudinal gradients in biotic interactions have been suggested as causes of global patterns of biodiversity and phenotypic variation. Plant biologists have long speculated that outcrossing mating systems are more common at low than high latitudes owing to a greater predictability of plant-pollinator interactions in the tropics; however, these ideas have not previously been tested. Here, we present the first global biogeographic analysis of plant mating systems based on 624 published studies from 492 taxa. We found a weak decline in outcrossing rate towards higher latitudes and among some biomes, but no biogeographic patterns in the frequency of self-incompatibility. Incorporating life history and growth form into biogeographic analyses reduced or eliminated the importance of latitude and biome in predicting outcrossing or self-incompatibility. Our results suggest that biogeographic patterns in mating system are more likely a reflection of the frequency of life forms across latitudes rather than the strength of plant-pollinator interactions.

Pollinator-mediated reproductive isolation among dioecious fig species (Ficus, Moraceae).

The extent of isolation among closely related sympatric plant species engaged in obligate pollination mutualisms depends on the fitness consequences of interspecies floral visitation. In figs (Ficus), interspecific gene flow may occur when pollinating wasps (Agaonidae) visit species other than their natal fig species. We studied reproductive isolation in a clade of six sympatric dioecious fig species in New Guinea. Microsatellite genotyping and Bayesian clustering analysis of the fig community indicated strong reproductive barriers among sympatric species. A total of 1-2% of fig populations consisted of hybrid individuals. A new experimental method of manipulating fig wasps investigated the reproductive consequences of conspecific and heterospecific pollinator visitation for both mutualists. Fig wasps introduced to Ficus hispidioides pollinated and oviposited in receptive figs. Seed development and seedling growth were largely comparable between conspecific and heterospecific crosses. Heterospecific pollinator fitness, however, was significantly less than that of conspecific pollinators. Heterospecific pollinators induced gall formation but offspring did not develop to maturity in the new host. Selection on pollinators maintaining host specificity appears to be an important mechanism of contemporary reproductive isolation among these taxa that could potentially influence their diversification.

Development and characterization of microsatellite loci in dioecious figs (Ficus, Moraceae).

PREMISE OF THE STUDY: Microsatellite markers for dioecious fig species, Ficus bernaysii King (section Sycocarpus), Ficus pachyrrhachis K. Schum. & Lauterb. (section Sycocarpus), and Ficus copiosa Steud. (section Sycidium) were developed to estimate gene flow among closely related fig species. METHODS AND RESULTS: Loci were developed from tri- and tetranucleotide-enriched genomic libraries. The six most repeatable and scorable loci for F. bernaysii and F. pachyrrhachis were characterized in 50 individuals each of five species from section Sycocarpus. Four primer pairs from F. copiosa were screened in 50 individuals each of two species from section Sycidium. Observed heterozygosity ranged from 0.53 to 0.93 in loci developed from F. bernaysii, 0.25 to 0.86 in loci developed from F. pachyrrhachis, and 0.68 to 0.87 in loci developed from F. copiosa. CONCLUSIONS: Amplification across the two Ficus sections was observed in seven of the ten total primer pairs.