Flowering and Fruiting Characteristics and Phenology of an Endemic Monoecious Tree in a Fragmented African Rainforest Landscape

Premise of research. The impact of forest fragmentation on plant phenology is poorly studied, especially in Africa. Here we evaluate the flower and fruit phenology of a monoecious understory tree species, Mesogyne insignis (Moraceae), in forest fragments and continuous forest. We relate our findings to the habitat fragmentation process and its impact on the reproduction and conservation of this unique tree species.Methodology. Monitoring of 60 trees in three fragments (each <30 ha) and three continuous forest sites allowed a description of development stages and durations for male and female inflorescences. Using observations of inflorescences and fruits at these trees, we evaluated differences between fragment and continuous forest habitats for the following: (i) duration of each development stage of male and female inflorescences; (ii) total duration of budding to anthesis of male and receptivity of female inflorescences; and, similarly for postanthesis and postfertilization; (iii) total flower production; (iv) flower abscission rates; and (v) number of male and female inflorescences per tree.Pivotal results. Habitat fragmentation had an apparent impact on floral phenology; the total duration from early budding to anthesis or receptivity showed that inflorescences took 3–4 d longer to reach anthesis or receptivity in continuous forest than in small, isolated fragments. However, following anthesis and receptivity, there were no habitat differences in the duration of each of the stages postanthesis and postfertilization for male and female inflorescences, respectively. Furthermore, there were no significant differences in the number of open inflorescences per tree between habitat types, but there were differences in the number of buds and the floral sex ratio. Continuous forest trees had a ratio of male to female inflorescences that was 1.85 times higher than that for trees in fragments. Similarly, there were more buds per tree in continuous forest as compared to fragments (172 ± 2.14 vs. 130 ± 3.23, respectively). Trees in fragments had slightly more of their flowers open, as a percentage of the total buds and flowers, than trees in continuous forest (39.4% ± 0.02% vs. 34.4% ± 0.01%).Conclusions. While there were no clear effects of habitat fragmentation on multiple phenological aspects of M. insignis, the longer period of time needed to produce fertile inflorescences of both sexes in continuous forest implicates the drier and more open understory conditions in fragments where water stress is predictably higher and, thus, speeds up flower development. Further, both the higher floral ratio and the higher number of buds in the continuous forest may signify greater floral resources and increased chances of reproductive success for those trees; however, it could also be that trees in both habitats make approximately the same number of buds and the trees in fragments are more advanced in their phenology. While this species appears to be able to adapt its reproductive phenology to tolerate habitat fragmentation, it remains unknown whether seed dispersal or recruitment may be impacted by this disturbance process.