Gene dispersal processes shape demographic and microevolutionary dynamics of tree species. Gene dispersal patterns can be studied by spatially explicit methods. Spatial genetic structure (SGS), summarized in the Sp statistic, provides indirect estimates of gene dispersal across generations for a known or assumed population effective density. Sp is modulated by exogenous and endogenous factors including the mating system that can be assessed using outcrossing rates (t m ). Knowledge on t m and Sp are particularly important for the conservation of species in fragmented biomes such as seasonally dry tropical forests (SDTF). The main aim of this review was to evaluate putative drivers of Sp and t m , and their consequences for gene dispersal in tree species from SDTF. We reviewed 59 genetic studies on SDTF tree species published between 2000 and 2020 and extracted data on propagule dispersal, successional stages, seasonality, mating system, population density, landscape features, type of molecular markers, pairwise kinship in the first distance class (F 1 ), Sp statistic, mean gene dispersal distance (σ g ), and multilocus outcrossing rates (t m ). Sp was significantly associated with the mating system where Sp(outcrossing) > Sp(mixed-mating), and population density where Sp was higher in high-density populations. Outcrossing rate was significantly associated with the type of propagule dispersal, where t m was higher in populations of plants pollinated by wind, and in those with animal-mediated seed dispersal, t m (zoochory) > t m (anemochory) > t m (autochory), and with successional stage where t m (late-successional) > t m (pioneer). These factors are relevant to inform management actions in conservation and restoration projects. Thus, the knowledge on the determinants of gene dispersal processes can help to rescue SDTF through sustainable management.

& Key message A remnant population of Anadenanthera colubrina var. cebil in Northern Argentina showed a mixed mating system, high genetic diversity, and moderate spatial genetic structure, which was stronger in saplings than in adults. Demographic history analyses revealed an ancient population expansion. Despite high genetic diversity, high inbreeding suggests caution in the use of this stand as seed source. & Context Information on fine-scale spatial genetic structure (FSGS) and demographic history is essential to determine which mechanisms are responsible for population persistence and evolution. This is particularly important in fragmented biomes, such as the seasonally dry tropical forests. & Aims To assess the level of genetic diversity and population genetic structure in a remnant population of A. colubrina var. cebil, and to evaluate the influence of historical and contemporary environmental change on the genetic constitution of this population. & Methods Eight microsatellites were typed in 60 adults and 59 saplings. The existence of (non-spatial) genetic clusters was evaluated using STRUCTURE and PCAs. FSGS was evaluated by kinship analyses and sPCA. MCMCglmm models were used to provide insights into factors underlying FSGS. Demographic history was studied using bottleneck statistics and approximate Bayesian computation. & Results We found high levels of genetic diversity and high inbreeding. Genetic structure was stronger in saplings than in adult trees, probably due to assortative mating, and was not explained by altitude or DBH. Demographic analyses suggested an ancient population expansion. & Conclusion Patterns of inbreeding and relatedness suggest a mixed mating system. High genetic diversity and moderate genetic structure suggest long-term population viability. High inbreeding suggests caution when using this stand as a source of material for reforestation.