Diversity and Cytogenomic Characterization of Wild Carrots in the Macaronesian Islands

Abstract

The Macaronesian islands constitute an enormous reservoir of genetic variation of wild carrots (subtribe Daucinae; Apiaceae), including 10 endemic species, but an accurate understanding of the diversification processes within these islands is still lacking. We conducted a review of the morphology, ecology, and conservation status of the Daucinae species and, on the basis of a comprehensive dataset, we estimated the genome size variation for 16 taxa (around 320 samples) occurring in different habitats across the Macaronesian islands in comparison to mainland specimens. Results showed that taxa with larger genomes (e.g., Daucus crinitus: 2.544 pg) were generally found in mainland regions, while the insular endemic taxa from Azores and Cabo Verde have smaller genomes. Melanoselinum decipiens and Monizia edulis, both endemic to Madeira Island, showed intermediate values. Positive correlations were found between mean genome size and some morphological traits (e.g., spiny or winged fruits) and also with habit (herbaceous or woody). Despite the great morphological variation found within the Cabo Verde endemic species, the 2C-values obtained were quite homogeneous between these taxa and the subspecies of Daucus carota, supporting the close relationship among these taxa. Overall, this study improved the global knowledge of DNA content for Macaronesian endemics and shed light into the mechanisms underpinning diversity patterns of wild carrots in the western Mediterranean region.

Combining genome size and pollen morphology data to study species relationships in the genus Daucus (Apiaceae)

“…To date, the two most extensive cytogenomic studies on the genus Daucus have been conducted by Nowicka et al [ 32 ] and Roxo et al [ 33 ]. Nowicka et al [ 32 ] investigated the nuclear DNA content in the collection of diploid members of Daucus from different parts of the world, whereas Roxo et al [ 33 ] estimated the 2C values for 16 taxa of the subtribe Daucine from the Macaronesian islands. The results of these works, combined with our findings, revealed an over 3.8-fold variation of the nuclear DNA content within Daucus .…”

“…Cultivated carrot has a relatively small genome of approximately 473 Mb per haploid genome [28,29]. In the genus Daucus, nuclear DNA content estimates by flow cytometry have been reported for several wild species and subspecies, as well as cultivated carrots, revealing great variation in the 2C DNA amount (0.847-3.019 pg) [30][31][32][33].…”

Genome size variation within Crithmum maritimum: Clues on the colonization of insular environments

“…Statistical analyses and descriptive statistics were performed using R v4.2.21 software (R Core Team, 2020 ). We followed the same general approach already outlined by our team in a previous paper (Roxo et al, 2021 ), which is summarized below.…”

“…In the second scenario, we included a biogeographic model, a latitude model, a longitude model, an altitude model, a bioclimatic model (including the principal components extracted from a PCA applied to the 19 bioclimatic variables), a full model including all the previous factors, as well as other models resulting from its simplification. We implemented this analysis with the GLM function of R, following previous work in this area by our team, namely Ávila et al ( 2018 ), Parelho et al ( 2021 ), and Roxo et al ( 2021 ) (see references therein). Model selection was based on the maximum likelihood approach using the Akaike's information criterion (AIC).…”

Comparative Fruit Morphology and Anatomy of Wild Relatives of Carrot (Daucus, Apiaceae)

“…Most Daucus species are diploids with chromosome numbers of 2n = 16, 18, 20, or 22; however, some tetra-and hexaploids 2 of 17 have also been reported [15,17,18]. Regarding the genome size within the genus, nuclear DNA content estimates based on flow cytometry are available for several wild species and subspecies, as well as for many cultivated carrots, ranging from 0.920 to 3.228 pg/2C DNA [19][20][21].…”