Species delimitation in the genus Greenwayodendron based on morphological and genetic markers reveals new species

Abstract

Combining genetic and morphological markers is a powerful approach for species delimitation, much needed in tropical species complexes. Greenwayodendron (Annonaceae) is a widespread genus of trees distributed from West to East African rainforests. Two species and four infra‐specific taxa are currently recognized. However, preliminary genetic studies and morphological observations suggested the occurrence of additional species, undescribed to date. We tested species delimitation within Greenwayodendron by combining morphological and population genetics data. First, a visual inspection of about a thousand specimens suggested the existence of seven morphogroups: four of them occur in Central Africa and overlap in Gabon while three others are allopatric, occurring respectively in West Africa, East Africa, and the islands of São Tomé and Príncipe. Their morphological differentiation was confirmed by analysis of 27 morphological characters coded from 233 herbarium specimens. Second, after genotyping 800 samples at eight nuclear microsatellites, Bayesian clustering analyses (STRUCTURE) identified four genetic clusters corresponding to the well‐sampled morphogroups but failed to separate the three remaining morphogroups represented by few samples. However, we show that this is an inherent limit of the STRUCTURE algorithm, whereas factorial correspondence analysis (FCA) and pairwise FST and RST measures confirmed the genetic differentiation of all morphogroups. We considered that a clear genetic differentiation occurring between sympatric populations advocates for recognizing distinct species following the biological species concept. Our analyses highlight that the current taxonomic treatment of Greenwayodendron underestimates the total number of species. We identified two new species and support separation at the rank of species of two varieties (G. suaveolens subsp. suaveolens var. gabonica, G. suaveolens subsp. suaveolens var. suaveolens) and one subspecies (G. suaveolens subsp. usambaricum). The taxonomic status of specimens collected in São Tomé and Príncipe remains inconclusive, partly due to the limited fertile material available. Our study highlights the strength of combining morphological and population genetics data for discovering new taxa. Guidelines for using genetic clustering approaches in species delimitation are provided.

Unravelling the Phylogenomic Relationships of the Most Diverse African Palm GenusRaphia(Calamoideae, Arecaceae)

“…Different approaches could rely on more in-depth population level studies using more variable markers (e.g. microsatellites) combined with detailed morphometric measurements as has been done in other African tree species [45]. We show here that the Heyduk et al bait kit [26] is useful for understanding relationships within the Raphia genus and between species as in other groups [ ?…”

“…microsatellites) combined with detailed morphometric measurements as has been done in other African tree species, e.g. [48–50]. A better comprehension of the taxonomy and the phylogenetic relationships in Raphia represents a fundamental tool towards the proposal of conservation strategies aiming to characterize genetic and morphologic diversity in this ecological and economically important genus.…”

Morphological variability and genetic diversity in Carex buxbaumii and Carex hartmaniorum (Cyperaceae) populations

“…Studies on genetic variability among closely related species, the taxonomic distinctness of which is usually obliterated in their morphology, allow to assess the extent of inter- and intraspecific variation and to explore relationships between the species studied (e.g., Schönswetter et al, 2009 ; Szczepaniak & Cieślak, 2011 ; Hurry, Walsh & Murphy, 2012 ; Mosaferi et al, 2015 ; Janković et al, 2019 ). Assessment of the extent of morphological and genetic variability are important for identifying taxonomic boundaries, developing natural classification systems, and for reconstructing phylogenies (e.g., Giulietti et al, 2012 ; Flores-Rentería et al, 2013 ; Lissambou et al, 2019 ).…”

Molecular and morphological analyses clarify species delimitation and reveal a newBetulaspecies in sectionCostatae

“…Species delineation based on morphology may be confounded by intra-specific variation among populations and limited differentiation between closely-related species (Whittall et al, 2004; Leliaert et al, 2009; Wang et al, 2014b; Lissambou et al, 2019). Where species co-occur, this may be further exacerbated by introgression and hybridisation (Bacon et al, 2012; Andújar et al, 2014), or may be morphologically impossible due to cryptic speciation (Bickford et al, 2007; Fišer et al, 2018).…”