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Mol Ecol. 2019 Jun;28(12):3119-3134. doi: 10.1111/mec.15138. Epub 2019 Jun 10.

Seed and pollen dispersal distances in two African legume timber trees and their reproductive potential under selective logging.

Author information

1
Evolutionary Biology and Ecology Unit, CP 160/12, Faculté des Sciences, Université Libre de Bruxelles, Brussels, Belgium.
2
TERRA Teaching and Research Centre, Forest is Life, Gembloux Agro-Bio Tech, Université de Liège, Gembloux, Belgium.
3
Nature Forest Environment, Freelance in Tropical Forestry, Porcheresse, Belgium.
4
DIADE, IRD, Univ Montpellier, Montpellier, France.
5
Bioversity International, Forest Genetic Resources and Restoration Programme, Sub-Regional Office for Central Africa, Messa, Yaoundé, Cameroon.
6
Nature+ asbl, Wavre, Belgium.

Abstract

The natural regeneration of tree species depends on seed and pollen dispersal. To assess whether limited dispersal could be critical for the sustainability of selective logging practices, we performed parentage analyses in two Central African legume canopy species displaying contrasted floral and fruit traits: Distemonanthus benthamianus and Erythrophleum suaveolens. We also developed new tools linking forward dispersal kernels with backward migration rates to better characterize long-distance dispersal. Much longer pollen dispersal in D. benthamianus (mean distance dp  = 700 m, mp  = 52% immigration rate in 6 km2 plot, s = 7% selfing rate) than in E. suaveolens (dp  = 294 m, mp  = 22% in 2 km2 plot, s = 20%) might reflect different insect pollinators. At a local scale, secondary seed dispersal by vertebrates led to larger seed dispersal distances in the barochorous E. suaveolens (ds  = 175 m) than in the wind-dispersed D. benthamianus (ds  = 71 m). Yet, seed dispersal appeared much more fat-tailed in the latter species (15%-25% seeds dispersing >500 m), putatively due to storm winds (papery pods). The reproductive success was correlated to trunk diameter in E. suaveolens and crown dominance in D. benthamianus. Contrary to D. benthamianus, E. suaveolens underwent significant assortative mating, increasing further the already high inbreeding of its juveniles due to selfing, which seems offset by strong inbreeding depression. To achieve sustainable exploitation, seed and pollen dispersal distances did not appear limiting, but the natural regeneration of E. suaveolens might become insufficient if all trees above the minimum legal cutting diameter were exploited. This highlights the importance of assessing the diameter structure of reproductive trees for logged species.

KEYWORDS:

African rainforest; forestry; gene dispersal; mating system; parentage analysis; sustainable management

PMID:
31141237
DOI:
10.1111/mec.15138
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