Wind direction and strength determine the genetic structure of an insect-pollinated plant across heterogeneous landscape

Aim: Dispersal of plant propagules and their genes is crucial for plant responses to landscape heterogeneities, yet the mechanisms behind this dispersal remain unclear. Ficus species depend on wind-borne fig wasps for pollination, but research on air flow effects on Ficus genetic structure has produced conflicting results. Our study aims to clarify the role of wind in shaping the genetic structure of such plants with wind-borne insect pollinators by examining how geomorphological complexity interacts with air movements to influence genetic structures. Location: Southwest China: Sichuan, Yunnan, Guangxi and Guizhou provinces. Taxon: Ficus tikoua Bur., Ficus, Moraceae. Methods: We sampled 56 Ficus tikoua sites across southwest China, characterized by high geomorphologic complexity. River basins and predominant winds were visualized across the sampled regions. Wind connectivity between sampled sites during the main pollination season was modeled based on hourly daily wind data. The maternal and biparental genetic structure of sites were reconstructed using chloroplast DNA (cpDNA) and nuclear SSR (nuSSR) markers. Links between genetic structure, location and wind parameters were estimated by Mantel or partial Mantel tests. Results: The plant’s maternal genetic structure was defined by river systems, with two distinct cpDNA groups located in the Yangtze and Pearl River basins respectively. The boundaries for nuclear variation were less clearly delimited geographically. Sites with mixtures of nuSSR groups were concentrated where prevailing winds arrive from several directions. Stronger between-site air flows increased nuSSR geneflow and genetic similarities, while populations receiving more wind flow were also more genetically variable. Main conclusions: Our study reveals how plant gene dispersal reflects air and water movements that in turn respond to geomorphologic complexity, thereby directly demonstrating the effects of wind on geneflow of plants with wind-borne insect pollinators. Wind data matching pollinator flight times and large sample sizes are crucial for testing wind effects.

Methods
Combined cpDNA sequences of each individual for Ficus tikoua. 

SSR genotype data generated using 13 loci that specific isolated for Ficus tikoua.

Regional daily wind speeds and directions averaged for 30 years were downloaded from MERRA-2 (https://disc.gsfc.nasa.gov/datasets?project=MERRA-2), while hourly daytime wind directions and speeds at 10 m above ground were downloaded from from Climate System Forecast Reanalysis (CFSR, http://cfs.ncep.noaa.gov).