Over the past century, the Brazilian Atlantic forest has been reduced to small, isolated fragments of forest. Reproductive isolation theories predict a loss of genetic diversity and increases in inbreeding and spatial genetic structure (SGS) in such populations. We analysed eight microsatellite loci to investigate the pollen and seed dispersal patterns, genetic diversity, inbreeding and SGS of the tropical tree Copaifera langsdorffii in a small (4.8 ha), isolated population. All 112 adult trees and 128 seedlings found in the stand were sampled, mapped and genotyped. Seedlings had significantly lower levels of genetic diversity (A ¼ 16.5 ± 0.45, mean±95% s.e.; H e ¼ 0.838±0.006) than did adult trees (A ¼ 23.2±0.81; H e ¼ 0.893±0.030). Parentage analysis did not indicate any seed immigration (m seeds ¼ 0) and the pollen immigration rate was very low (m pollen ¼ 0.047). The average distance of realized pollen dispersal within the stand was 94 m, with 81% of the pollen travelling o150 m. A significant negative correlation was found between the frequency and distance of pollen dispersal (r ¼ À0.79, Po0.01), indicating that short-distance pollinations were more frequent. A significant SGS for both adults (B50 m) and seedlings (B20 m) was also found, indicating that most of the seeds were dispersed over short distances. The results suggested that the spatial isolation of populations by habitat fragmentation can restrict seed and pollen gene flow, increase SGS and affect the genetic diversity of future generations.

Divergence at reproductive traits can generate barriers among populations, and may result from several mechanisms, including drift, local selection and co‐adaptation between the sexes. Intersexual co‐adaptation can arise through sexually antagonistic co‐evolution, a timely hypothesis addressed in animals but, to our knowledge, not yet in flowering plants. We investigated whether male and female population of origin affected pollen competition success, offspring fitness and sex ratio in crosses within/between six genetically differentiated populations of the white campion, Silene latifolia. Each female was crossed with pollen from one focus male from the same population, and pollen from two focus males from two distinct populations, both as single‐donor and two‐donor crosses against a fixed tester male with a 2‐h interpollination interval (n = 288 crosses). We analysed paternity with microsatellite DNA. Male populations of origin significantly differed for siring success and in vitro pollen germination rates. In vitro pollen germination rate was heritable. Siring success also depended on sex ratio in the female family of origin, but only in between‐population crosses. In some female populations, two‐donor crosses produced less female‐biased sex ratios compared with single‐donor crosses, yet in other female populations the reverse was true. Offspring sex ratio varied with donor number, depending on the female population. Within/between population crosses did not differ significantly in seed set or offspring fitness, nor were siring success and offspring fitness significantly correlated. Altogether this suggests reproductive divergence for traits affecting pollen competition in S. latifolia.

Significant molecular genetic divergence among populations of Silene latifolia, from the European native range is consistent with known limited seed and pollen flow distances, while significant quantitative genetic divergence among populations and clinal variation for age at first flowering suggest local adaptation.