Species delimitation and phylogeography of African tree populations of the genus Parkia (Fabaceae)

Ahossou, Oscar D.; Daïnou, Kasso; Janssens, Steven; Triest, Ludwig; Hardy, Olivier J.

doi:10.1007/s11295-020-01463-x

Cited by 13 publications

(12 citation statements)

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“…Our analyses revealed a strong phylogeographical structure in S. kamerunensis , indicating past population fragmentation. This result is congruent with a number of studies that identified signals of past fragmentation in other rain forest species from Africa (Abeele et al, 2021; Ahossou et al, 2020; Daïnou et al, 2014). While phylogeographical signatures of past population fragmentation are often reported in Guineo‐Congolian tree species, species responses to climatic oscillations in Lower Guinea are largely idiosyncratic (Helmstetter, Béthune, et al, 2020b).…”

Section: Discussionsupporting

confidence: 91%

“…Moreover, existing studies usually had a limited number of samples from Congolia, covered a fraction of the region, or did not include the full plastome (Daïnou et al, 2014; Migliore et al, 2019; Piñeiro et al, 2017). However, population genetic studies based on nuclear single sequence repeats generally showed that Lower Guinea hosts a higher number of genetic clusters than Congolia (Abeele et al, 2021; Ahossou et al, 2020: Daïnou et al, 2014). These trends support the hypothesis that Lower Guinea maintained higher diversity owing to forest refugia, while Congolia underwent higher levels of species and lineages extinctions during adverse climatic periods.…”

Section: Discussionmentioning

confidence: 99%

“…Many species diverged prior to the Pleistocene (Couvreur et al, 2021), while those originating during the Pleistocene mainly belong to clades that were already undergoing diversification, making it unlikely that the Pleistocene refugia mechanism was the main driving force of their speciation (Couvreur et al, 2021). Nevertheless, phylogeographical studies applying molecular dating on certain Guineo‐Congolian tree species have revealed strong population structure with genetically distinct groups (Abeele et al, 2021; Ahossou et al, 2020), which diverged during the Pleistocene (Boom et al, 2021; Couvreur et al, 2021). This suggests that recent climatic oscillations likely had a major impact on differentiation at an intraspecific level, highlighting the necessity of investigating intraspecific biodiversity to better understand the impact of Pleistocene oscillations on the rain forest.…”

Section: Introductionmentioning

confidence: 99%

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Spatially explicit phylogeographical reconstruction sheds light on the history of the forest cover in the Congo Basin

Matvijev

Dellicour

Kaymak

et al. 2022

Journal of Biogeography

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Aim The impact of Pleistocene climatic oscillations on the biodiversity of African tropical rain forests remains poorly understood, and the Congo Basin is particularly understudied. We aim to elucidate how Pleistocene climatic oscillations shaped lowland tropical rain forests by investigating the intraspecific diversity and evolutionary history of a widespread tree species. Location Guineo‐Congolian rain forest, Central Africa. Taxon Staudtia kamerunensis Warb. (Myristicaceae). Methods We used genome skimming combined with maximum likelihood and Bayesian inference to infer the plastid phylogeny. We estimated the time of speciation and differentiation, genetic diversity, and we employed a continuous phylogeographical approach to infer the dispersal history of its plastid lineages. Results We sequenced an average of 5,827,783 reads per sample, and the reconstructed reference plastome had a mean depth of 73.3. We identified five plastid lineages that diverged during the Early or Middle Pleistocene and are parapatric, suggesting past population fragmentation. Four lineages are endemic to Lower Guinea, and one spans the Congo Basin. We found contrasting patterns of expansion in the two regions, with a rapid and recent range expansion of the Congolian lineage in the last 200,000 years, while the spread of the Lower Guinean lineages was substantially slower. Main conclusion The contrasting demographic histories between eastern and western lineages, associated with contrasted levels of plant species richness and rates of endemism, suggest that forest cover was more stable in Lower Guinea during the Late Pleistocene than in Congolia, where the biodiversity might have been eroded before the forest re‐expanded in the Congo basin. This study illustrates how a continuous phylogeographical inference approach, mostly applied so far for inferring the spread of fast‐evolving pathogens over months or years, can provide new insights to reconstruct the dispersal history of tropical tree species over thousands or millions of years.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spatially explicit phylogeographical reconstruction sheds light on the history of the forest cover in the Congo Basin

Matvijev

Dellicour

Kaymak

et al. 2022

Journal of Biogeography

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“…The division of the Lower Guinean and Congolian bioregions [ 3 , 4 ], which is based on the distribution of endemic species, seems to be supported by the distribution of intraspecific genetic diversity within S. zenkeri . Additionally, the overall premise that Lower Guinea has a higher diversity and rate of endemism than Congolia in terms of species diversity [ 1 ], is also confirmed at the intraspecific level for S. zenkeri in terms of allelic diversity (Table 1 ), a pattern also occurring in the tree Parkia bicolor [ 32 ]. The current study is the first to document this differential distribution of intraspecific genetic diversity in plants, which could be explained by a more drastic reduction of the forest cover in Congolia compared to Lower Guinea.…”

Section: Discussionmentioning

confidence: 84%

Evidence of past forest fragmentation in the Congo Basin from the phylogeography of a shade-tolerant tree with limited seed dispersal: Scorodophloeus zenkeri (Fabaceae, Detarioideae)

et al. 2021

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Background Comparative phylogeographic studies on rainforest species that are widespread in Central Africa often reveal genetic discontinuities within and between biogeographic regions, indicating (historical) barriers to gene flow, possibly due to repeated and/or long-lasting population fragmentation during glacial periods according to the forest refuge hypothesis. The impact of forest fragmentation seems to be modulated by the ecological amplitude and dispersal capacities of each species, resulting in different demographic histories. Moreover, while multiple studies investigated the western part of Central Africa (Lower Guinea), few have sufficiently sampled the heart of the Congo Basin (Congolia). In this study, we look for genetic discontinuities between populations of the widespread tropical tree Scorodophloeus zenkeri Harms (Fabaceae, Detarioideae) in Central Africa. Additionally, we characterize genetic diversity, selfing rate and fine-scale spatial genetic structure within populations to estimate the gene dispersal capacity of the species. Results Clear intraspecific genetic discontinuities occur throughout the species’ distribution range, with two genetic clusters in Congolia and four in Lower Guinea, and highest differentiation occurring between these bioregions. Genetic diversity is higher in Lower Guinea than Congolia. A spatial genetic structure characteristic of isolation by distance occurs within the genetic clusters. This allowed us to estimate gene dispersal distances (σg) for this outcrossing species with ballistic seed dispersal, which range between 100 and 250 m in areas where S. zenkeri occurs in high densities, and are in the low range of σg values compared to other tropical trees. Gene dispersal distances are larger in low density populations, probably due to extensive pollen dispersal capacity. Conclusions Fragmentation of S. zenkeri populations seems to have occurred not only in Lower Guinea but also in the Congo Basin, though not necessarily according to previously postulated forest refuge areas. The lower genetic diversity in Congolia compared to Lower Guinea parallels the known gradient of species diversity, possibly reflecting a stronger impact of past climate changes on the forest cover in Congolia. Despite its bisexual flowers, S. zenkeri appears to be mostly outcrossing. The limited dispersal observed in this species implies that genetic discontinuities resulting from past forest fragmentation can persist for a long time before being erased by gene flow.

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“…Recent genetic studies on, for example, Prunus africana (Mihretie et al, 2015), Parkia spp. (Ahossou et al, 2020), or Scorodophloeus zenkeri (Abeeele et al, 2021), did not include records from the Itombwe Massif. A genetic study on Milicia spp.…”

Section: Discussionmentioning

confidence: 99%

Tree diversity and carbon stocks in the Itombwe Mountains of eastern DR Congo

et al. 2021

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Our ecological understanding of tropical montane forests in Africa is still limited, particularly in the Albertine Rift. Because of a greater role of environmental filtering at higher elevations, tree species' richness and aboveground biomass (AGB) is expected to decrease with increasing elevation. However, broader scale patterns are complex and different patterns have also been observed in different mountains. We established eight permanent 1-ha plots in Itombwe Mountains and sampled all trees ≥10 cm diameter following standard RAINFOR protocols to investigate tree species' richness, forest structure, and estimated AGB. We also collected and analyzed soil samples to establish how these affected AGB. We identified over 120 tree species, 12 of which were of international conservation concern according to IUCN criteria. Species richness was significantly negatively correlated with elevation. AGB ranged from 268 Mg/ha (submontane) to 396 Mg/ha (middle montane forests), and it was significantly positively correlated with elevation, soil organic matter, and soil organic C and N. We compare Itombwe with other montane forests in the Albertine Rift, to demonstrate their high floristic diversity, high abundance of large stems, and high AGB, insights which are crucial for the future management of these unique forests.

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Species delimitation and phylogeography of African tree populations of the genus Parkia (Fabaceae)

Cited by 13 publications

References 98 publications

Spatially explicit phylogeographical reconstruction sheds light on the history of the forest cover in the Congo Basin

Spatially explicit phylogeographical reconstruction sheds light on the history of the forest cover in the Congo Basin

Evidence of past forest fragmentation in the Congo Basin from the phylogeography of a shade-tolerant tree with limited seed dispersal: Scorodophloeus zenkeri (Fabaceae, Detarioideae)

Tree diversity and carbon stocks in the Itombwe Mountains of eastern DR Congo

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