Seed and pollen dispersal shape large-scale population dynamics in a timber tree species of Central African rain forests

Seed and pollen dispersal plays a crucial role in species persistence by shaping populations on a large scale. However, empirical studies linking small-scale dispersal to large-scale patterns are scarce. We analysed the reproductive ecology of Staudtia kamerunensis (Myristicaceae), a tree species widespread in Central Africa, with the aim of linking its reproductive ecology to its large-scale population dynamics, characterised by a range expansion in the Congo Basin. We investigated gene flow and dispersal using parentage analyses and fine-scale spatial genetic structure in two landscape types, a closed-canopy forest and a forest-savanna mosaic. We found a deficit in regeneration despite fair seed production in the closed-canopy forest. Staudtia kamerunensis is a self-compatible monoecious species (8% selfed progeny), although the decay of inbreeding with age highlights inbreeding depression. Pollen dispersal (dp = 580 m) was more extensive than seed dispersal in the closed-canopy forest, where we detected a significant fine-scale spatial genetic structure (Sp = 0.0083), while gene flow was more extensive in the fragmented forest. The median diameter for reproduction was dbh50 = 58 cm whereas trees reproduce efficiently from 40 cm. This study provides insight into the reproductive ecology and dispersal of S. kamerunensis, revealing patterns that are consistent with previous studies on its population dynamics. Our results also provide insights to maintain healthy populations. We recommend a minimum cutting diameter of 60 cm or regulation to maintain at least 50% of the original reproductive potential after logging operation to preserve the reproductive potential of natural populations.