Phylogenetic relationships of <em>Erysimum</em> (Brassicaceae) from the Baetic Mountains (SE Iberian Peninsula)

Abstract

The Baetic mountains, located in the southern Iberian Peninsula, is a major hotspot of biodiversity in the Mediterranean Basin, constituting one of the most important glacial refugia for vascular plants in Europe. Despite their relatively limited extension, the Baetic Mountains contain almost 50% of the total endemic Erysimum species in the Iberian Peninsula. The broadly distributed Erysimum genus has diversified profusely in the Mediterranean region, with more than a hundred species described in the area, out of a total of c. 200 species included in the genus. We used two plastid DNA regions (ndhF and trnT-L) and one nuclear DNA region (ITS1-5.8S rDNA-ITS2), with 3,556 bp total length, to carry out phylogenetic analysis by Bayesian inference, maximum likelihood and maximum parsimony, in order to explore the evolutionary relationships between the Erysimum species inhabiting these ranges. Analyses of concatenated sequences from the two genomes identified two main clades with no overlap in species composition so that samples from the same species fell within the same major clade. The phylogenetic relationships depicted by those two clades do not give support to the E. nevadense group, previously proposed on taxonomic grounds. In addition, our results indicated recurrent changes in flower colour in the Baetic Erysimum species although, alternatively, reticulate evolution, which is suggested by incongruent position of taxa in the different trees, may have also affected this trait. Las cordilleras Béticas, localizadas en el sudeste de la Península Ibérica, representan una importante zona para la biodiversidad de la cuenca mediterránea, constituyendo uno de los refugios glaciares más destacados de plantas vasculares en Europa. A pesar de su extensión relativamente limitada, las cordilleras Béticas albergan casi el 50% del total de las especies endémicas de Erysimum de la Península Ibérica. Erysimum es un género ampliamente distribuido, que se ha diversificado profusamente en la región mediterránea, con más de un centenar de especies descritas en dicha área, del total de las alrededor de 200 especies incluidas en el género. Usamos dos regiones de ADN plastidial (ndhF y trnT-L) y una región de ADN nuclear (ITS1-5.8S rDNA-ITS2), con una longitud total de 3.556 pb, para llevar a cabo análisis filogenéticos mediante inferencia bayesiana, máxima verosimilitud y máxima parsimonia, con el fin de explorar las relaciones evolutivas entre las especies de Erysimum que habitan en éstas cordilleras. El análisis de secuencias concatenadas de los dos genomas identifica dos clados principales y las muestras de la misma especie aparecen siempre en un clado o en el otro pero no en ambos. Las relaciones filogenéticas que indican esos dos clados no apoyan la circunscripción del grupo taxonómico E. nevadense, previamente definido en dicho género. Además, los análisis indican cambios recurrentes en el color floral de las especies de Erysimum que habitan los Sistemas Béticos aunque la evolución reticulada, que sugiere la posición de algunos ...

Decision letter: Independent evolution of ancestral and novel defenses in a genus of toxic plants (Erysimum, Brassicaceae)

“…However, while we have been unsuccessful in reconstructing the exact evolutionary history of the genus, we nevertheless believe our species tree captures key aspects of its phylogenetic relationships, particularly in respect to closely related species and geographic clades.In our species tree, the three annual species, E. repandum, E. incanum, and E. wilczekianum grouped together as a well-supported monophyletic clade sister to all other Erysimum species. These species co-occur geographically with several perennial Erysimum species, but they are largely isolated Within the Spanish clade, species from southeastern Spain exhibited closer relatedness to Moroccan species than to species from northeastern or northwestern Spain, loosely matching more fine-scale evaluations of species relatedness in this region(Abdelaziz et al 2014). Therefore, even though none of these clades were supported by high gene concordance factors, the main topology of our species tree captured an apparently meaningful pattern of closely related species commonly occurring in close geographic proximity.Clustering of species by dissimilarities in glucosinolate profiles revealed distinct groups of chemically similar species, largely corresponding to nine chemotypes determined by the predicted function of few major-effect glucosinolate genes.…”

“…Specifically, if these are allopolyploid rather than autopolyploid species, discordance could be introduced by our methodological approach for gene selection, which randomly retained only a single copy for each identified orthologous gene with multiple copies. This same problem could also have inflated the estimation of hybridization by our HyDe analysis, although a high rate of gene flow is likely, at least among geographically close species (Abdelaziz et al 2014). More fundamentally, the high levels of gene discordance also highlight the limitations of simple bifurcating species trees to represent the significantly more complicated network of splits and reticulate evolutionary events that is likely the true history of the genus Erysimum (Marhold and Lihová 2006 In contrast, clustering of species by dissimilarities in cardenolide profiles revealed fewer distinct groups of chemically similar species, suggesting that the considerably more complex cardenolide chemotypes may be controlled by many minor-effect genes.…”

Faculty Opinions recommendation of Independent evolution of ancestral and novel defenses in a genus of toxic plants (Erysimum, Brassicaceae).

“…Specifically, if these are allopolyploid rather than autopolyploid species, discordance could be introduced by our methodological approach for gene selection, which randomly retained only a single copy for each identified orthologous gene with multiple copies. This same problem could also have inflated the estimation of hybridization by our HyDe analysis, although a high rate of gene flow is likely, at least among geographically close species (Abdelaziz et al, 2014). More fundamentally, the high levels of gene discordance also highlight the limitations of simple bifurcating species trees to represent the significantly more complicated network of splits and reticulate evolutionary events that is likely the true history of the genus Erysimum (Marhold and Lihová, 2006).…”

Genomic Resources for Erysimum spp. (Brassicaceae): Transcriptome and Chloroplast Genomes

“…It is widely distributed in the Northern Hemisphere and has been the focus of active research in ecology, evolution, and genetics (Gómez and Perfectti, 2010;Gómez, 2012;Valverde et al, 2016). Despite long-standing interest in Erysimum, its taxonomy has yet to be properly established, partly due to a complex and reticulated evolutionary history that renders phylogenetic reconstructions highly challenging (Ancev, 2006;Marhold and Lihová, 2006;Abdelaziz et al, 2014;Gomez et al, 2014;Moazzeni et al, 2014;Züst et al, 2020).…”