Biology subjects

Depecker, J.

Publications and source records attributed to Depecker, J..

8 recordsLinked to original sources

bioRxiv2024

Phylogenetic and functional compositional shifts associated with selective logging and forest regrowth in tropical rainforests of the Congo Basin

Background and aimsTropical rainforests constitute a globally important biome severely threatened by anthropogenic activities. Accounting for the phylogenetic and functional dimensions can provide insights into how anthropogenic activities affect tree species community assembly. Here, we aimed to assess the effects of selective logging and forest regrowth on the tree composition in the Yangambi region (Democratic Republic of the Congo), as compared to reference undisturbed old-growth forest by incorporating phylogenetic and functional information. MethodsWe measured the phylogenetic and functional alpha-diversity and dissimilarity of undisturbed old-growth, disturbed old-growth, and regrowth rainforests by sampling species abundances and key traits related to usefulness (wood density), vegetative (specific leaf area), and reproductive (fruit type) functions. Then, we evaluated the association between phylogenetic and functional dissimilarity to unravel potential drivers underlying changes in the community composition. Key resultsPhylogenetic and functional dissimilarities resulted in a consistent compositional separation of the disturbed old-growth forests and regrowth forests from the undisturbed old-growth forests, with this separation clearly associated with key functional traits. Compared to undisturbed old-growth forests, disturbed old-growth forests subjected to selective logging did not diverge in terms of both phylogenetic and functional diversity and structure. However, regrowth forests displayed increased levels of phylogenetic diversity and comparable functional diversity as undisturbed old-growth forests. ConclusionsSelective logging and forest regrowth have not led to an overdispersion or clustering of phylogenetic lineages nor functional traits in the tropical rainforests in the Congo Basin, rather, these anthropogenic activities brought an altered phylogenetic and functional community composition which may have serious implications for the stability of these ecosystems.

ecology↗

bioRxiv2024

Comparative pollinator conservation potential of coffee agroforestry relative to coffee monoculture and tropical rainforest in the DR Congo

Animal-pollination is crucial in the reproduction of many crops grown in the tropics, including the self-incompatible Robusta coffee. Coffea canephora Pierre ex A. Froehner. is indigenous to the Congo basin where it is growing in the rainforest understorey yet providing very low yields. Cultivation therefore mainly occurs in either unshaded monocultures or in agroforestry systems. Here we surveyed the Diptera (true flies) and Hymenoptera (bees) communities that are putative coffee pollinating organisms in the Yangambi region in DR Congo, and we assessed the comparative benefits of coffee agroforestry and monocultures to the coffee pollinator community. To assess a base line value of pollinator conservation value of the agroforestry system, we also compared it with natural rainforest. Using white pan traps, we identified 9,597 specimens. Natural rainforest harboured a higher number of individuals, as well as a higher number of species than both agroforestry and coffee monoculture systems, with no differences between the latter two land-uses. The Simpson diversity and Pielous evenness on the other hand did not differ among land-uses. Furthermore, we observed different responses in species richness and diversity to land-use between Diptera and Hymenoptera. Our analyses of pollinator community composition showed a high dissimilarity between natural rainforest and the two cultivation systems, without significant differences between the latter land-uses. Specifically, the community composition of the agroforestry and coffee monoculture systems were totally different, rather than a subset of the community composition of the natural rainforest. Our study indicates that rehabilitation of agricultural land through intercropping fruit trees may not always enhance the pollinator community and that the studied agroforestry system falls short of matching the pollinator conservation potential found in natural rainforests. A more optimal selection of tree species intercropped with coffee may both enhance the conservation value of the agroforestry system and the provisioning of pollination services.

ecology↗

bioRxiv2024

Leaf functional trait evolution and its putative climatic drivers in African Coffea species

Background and AimsLeaf traits are known to be strong predictors of plant performance and can be expected to (co)vary along environmental gradients. We investigated the variation, integration, environmental relationships, and evolutionary history of leaf functional traits in the genus Coffea L., typically a rainforest understory shrub, across Africa. A better understanding of the adaptive processes involved in leaf trait evolution can inform the use and conservation of coffee genetic resources in a changing climate. MethodsWe used phylogenetic comparative methods to investigate the evolution of six leaf traits measured from herbarium specimens of 58 African Coffea species. We added environmental data and data on maximum plant height for each species to test trait-environment correlations in various (sub)clades, and we compared continuous trait evolution models to identify variables driving trait diversification. Key ResultsA substantial leaf trait variation was detected across the genus Coffea in Africa, which was mostly interspecific. Of these traits, stomatal size and stomatal density exhibited a clear trade-off. We observed low densities of large stomata in early branching lineages and higher densities of smaller stomata in more recent taxa, which we hypothesise to be related to declining CO2 levels since the mid-Miocene. Brownian Motion evolution was rejected in favour of White Noise or Ornstein-Uhlenbeck models for all traits, implying these traits are adaptively significant rather than driven by pure drift. The evolution of leaf area was likely driven by precipitation, with smaller leaves in dryer climates across the genus. ConclusionsGenerally, Coffea leaf traits appear to be evolutionarily labile and governed by stabilising selection, though evolutionary patterns and correlations differ depending on the traits and clades considered. Our study highlights the importance of a phylogenetic perspective when studying trait relationships across related taxa, as well as the consideration of various taxonomic ranges.

evolutionary biology↗

bioRxiv2023

Cultivated Robusta coffee meets wild Coffea canephora: Evidence of cultivated-wild hybridisation in the Democratic Republic of the Congo

Background and aimsPlant breeders are increasingly turning to crop wild relatives (CWRs) to ensure global food security amidst a rapidly changing environment. However, CWR populations are confronted with various human-induced threats, including hybridisation with their nearby cultivated crops, posing a significant threat to the wild gene pool. Here, we focussed on Robusta coffee in the Yangambi region in the DR Congo, where cultivated Robusta coffee coexists with its wild relative (Coffea canephora), creating ample opportunity for genetic exchange. We examined the geographical distribution of cultivated Robusta coffee plants and the incidence of hybridisation between cultivated and wild individuals within the rainforest. MethodsWe used Genotyping-by-Sequencing data from 471 C. canephora individuals across various locations, including natural rainforests, home gardens, and the INERA Coffee Collection, a Robusta coffee field genebank. Our analyses involved establishing robust diagnostic fingerprints that differentiate cultivated from wild coffee, identifying cultivated-wild hybrids and mapping their geographical position. Key resultsWe identified cultivated genotypes and cultivated-wild hybrids in zones with clear anthropogenic activity, and where Robusta coffee cultivated in the home gardens may serve as a source for crop-to-wild gene flow. We found relatively few hybrids and backcrosses in the rainforests, which is so far likely not sufficient for the stable incorporation of alleles from the cultivated gene pool into the CWR gene pool. ConclusionsThe cultivation of Robusta coffee in close proximity to its wild gene pool has led to cultivated genotypes and cultivated-wild hybrids appearing within the natural habitats of C. canephora. Yet, given the high overlap between the cultivated and wild gene pool, together with the relatively low frequency of hybridisation, our results indicate that the overall impact in terms of risk of introgression remains limited so far. Nevertheless, it is important to continue monitoring crop-to-wild gene flow to safeguard the wild gene pool of C. canephora.

ecology↗

bioRxiv2023

Characterization of the genetic composition and establishment of a core collection for the INERA Robusta coffee (Coffea canephora) field genebank from the Democratic Republic of the Congo

Cultivation of Robusta coffee is likely to gain importance because of its high disease resistance and climate envelope, but substantial effort must be made to improve its cupping quality and other agronomic traits. Robusta coffee genetic resources conserved in field genebanks can play an important role in this context, but many of them are limited and poorly characterized. In this study, we aimed to characterize the genetic composition of the historically important but until recently neglected INERA Coffee Collection in Yangambi (Democratic Republic of the Congo) and to propose a Robusta core collection. We combined genome-wide GBS marker sets with a novel versatile multiplex amplicon sequencing (HiPlex) screening assay, for the genetic screening of the INERA Coffee Collection and created tools for future genetic screening. A set of 730 coffee shrubs in the collection were genotyped at 86 HiPlex loci and 263 unique genetic fingerprints were identified. Representative fingerprints were compared to Lula cultivars, Luki cultivars, Congolese subgroup A, and wild genotypes growing in the rainforest of the Yangambi region. The majority of the unique genetic fingerprints were identified as Lula cultivars but also four Congolese subgroup A and nine wild genotypes were found in the collection. Twenty-five percent of the unique genetic fingerprints had a hybrid identity which could result from seed-based propagation of the collection or natural cross-pollination. Moreover, eight unique genetic fingerprints were frequently identified as a parent and these may correspond to the ancient selected mother plants, or direct descendants thereof, of which seed material was widely distributed from 1930 to 1960 for the creation of coffee plantations. Finally, to delineate core collections we tested the maximization strategy and genetic distance method for the INERA Coffee Collection, and proposed i) a core collection conserving the loci diversity of the collection, i.e. 100 accessions and ii) a core collection holding the highest genetic distances between the accessions, i.e. 10 accessions. Our study provides a method for the genetic characterization of Robusta coffee collections in general and contributes to the revaluation and exploitation of the Robusta coffee genetic resources in the Democratic Republic of the Congo in particular.

plant biology↗

bioRxiv2022

Genetic diversity and structure in wild Robusta coffee (Coffea canephora A. Froehner) populations in Yangambi (DR Congo) and their relation with forest disturbance

Degradation and regeneration of tropical forests can strongly affect gene flow in understorey species, resulting in genetic erosion and changes in genetic structure. Yet, these processes remain poorly studied in tropical Africa. Coffea canephora is an economically important species, found in the understorey of tropical rainforests of Central and West Africa, and the genetic diversity harboured in its wild populations is vital for sustainable coffee production worldwide. Here, we aimed to quantify genetic diversity, genetic structure, and pedigree relations in wild C. canephora populations, and we investigated associations between these descriptors and forest disturbance and regeneration. Therefore, we sampled 256 C. canephora individuals within 24 plots across three forest categories in Yangambi (DR Congo), and used genotyping-by-sequencing to identify 18 894 SNPs. Overall, we found high genetic diversity, and no evidence of genetic erosion in C. canephora in disturbed old-growth forest, as compared to undisturbed old-growth forest. Additionally, an overall heterozygosity excess was found in all populations, which was expected for a self-incompatible species. Genetic structure was mainly a result of isolation-by-distance, reflecting geographical location, with low to moderate relatedness at finer scales. Populations in regrowth forest had lower allelic richness than populations in old-growth forest and were characterised by a lower inter-individual relatedness and a lack of isolation-by-distance, suggesting that they originated from different neighbouring populations and were subject to founder effects. Wild Robusta coffee populations in the study area still harbour high levels of genetic diversity, yet careful monitoring of their response to ongoing forest degradation remains required.

ecology↗

bioRxiv2021

Effects of forest disturbance and regeneration on tree species composition and traits in DR Congo

Despite their key role in biodiversity conservation, forests of the Congo Basin are increasingly threatened by human activities. Whereas deforestation is very conspicuous, it remains challenging to monitor the impact of forest degradation under a more or less intact canopy. Likewise, the outcomes of forest regeneration following agricultural abandonment remain poorly studied in the Congo Basin. Here, we surveyed 125 vegetation quadrats across 25 forest inventory plots in the Yangambi region, and based on historical land-use maps. We aimed to assess both the impact of anthropogenic disturbance and forest recovery on tree species diversity, tree functional traits, community composition, canopy cover, and forest structure, as compared to undisturbed old-growth forest. We found that undisturbed old-growth forest harboured more tree individuals, particularly individuals with a smaller diameter, as well as species with a higher wood density when compared to both disturbed old-growth and regrowth forest. Moreover, species diversity was highest in disturbed old-growth forest. Tree species composition was significantly different between undisturbed old-growth forest and the other two forest categories. Our findings indicate that anthropogenic disturbance results in a degraded forest structure and may reduce the forests ability to store carbon. Whereas species diversity recovered 60 years after agricultural abandonment, species composition remained different from undisturbed old-growth forest. Our study illustrates the need for more extensive vegetation surveys in the Congo Basin in order to quantify the effects of human disturbance under a closed canopy.

ecology↗

bioRxiv2021

Genetic diversity of wild and cultivated Coffea canephora in northeastern DR Congo and the implications for conservation.

PremiseMany cultivated coffee varieties descend from Coffea canephora, commonly known as Robusta coffee. The Congo Basin has a century long history of Robusta coffee cultivation and breeding, and is hypothesized to be the region of origin of many of the cultivated Robusta varieties. Since little is known about the genetic composition of C. canephora in this region, we assessed the genetic diversity of wild and cultivated C. canephora shrubs in the Democratic Republic of the Congo. MethodsUsing 18 microsatellite markers, we studied the genetic composition of wild and backyard-grown C. canephora shrubs in the Tshopo and Ituri provinces, and from the INERA Yangambi Coffee Collection. We assessed genetic clustering patterns, genetic diversity, and genetic differentiation between populations. Key resultsGenetic differentiation was relatively strong between wild and cultivated C. canephora shrubs, and both gene pools harbored multiple unique alleles. Strong genetic differentiation was also observed between wild populations. The level of genetic diversity in wild populations was similar to that of the INERA Yangambi Coffee Collection, but local wild genotypes were mostly missing from that collection. Shrubs grown in the backyards were genetically similar to the breeding material from INERA Yangambi. ConclusionsMost C. canephora that is grown in local backyards originated from INERA breeding programs, while a few shrubs were obtained directly from surrounding forests. The INERA Yangambi Coffee Collection could benefit from an enrichment with local wild genotypes, to increase the genetic resources available for breeding purposes, as well as to support ex situ conservation.

genetics↗