Data from: Investigating the spatial, demographic, and genetic structures of Cylicodiscus gabunensis Harms, a light-demanding African timber species

Most Central African rainforest canopies consist of light-demanding tree
species that hold high commercial value but also suffer locally from
regeneration deficits, raising concerns about the sustainability of
logging. Regeneration is influenced by factors such as past perturbations
(including human activity), mating systems, and seed/pollen dispersal
processes that impact demographic, spatial, and genetic structures within
populations. To gain a better understanding of these interactions, we
studied the spatial distribution and trunk diameter structure
of Cylicodiscus gabunensis (Fabaceae) - a
wind-dispersed, insect-pollinated, timber species - in three plots ranging
from 400 to 839 ha situated in various environmental contexts
(e.g. forest types and elephant densities) across Central Africa. We also
genotyped adults and juveniles using microsatellite markers to analyze the
spatial genetic structure of each population and infer the selfing rate,
seed and pollen dispersal capacities and selection gradients using
the ‘neighborhood model’. The selfing rate was low (3 –
4 %), and seed dispersal distances
(ds = 184 m) were much shorter than pollen
dispersal distances (dp > 2 km). The
three populations displayed contrasted spatial, demographic and genetic
structures. One population showed no spatial aggregation or genetic
structure, and a multimodal diameter structure indicating pulses of
regeneration events. Two populations showed strong spatial aggregation and
genetic structures. One exhibited a unimodal diameter structure indicating
one ancient pulse of regeneration, while the other displayed a
'reverse J-shaped' diameter structure, typical of ongoing
regeneration. In the latter, reproductive success appeared leptokurtic,
three mother trees accounting for over 90 % of the regeneration
and no tree below the minimum cutting diameter implemented by logging
companies had offspring. The idiosyncratic nature of population
characteristics observed in C. gabunensis suggests that, for
sustainable management, a nuanced approach is needed. This involves
protecting productive seed trees in areas where natural regeneration is
occurring and actively supporting regeneration in areas exhibiting
deficits, especially in contexts with low elephant densities.