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