An integrative taxonomic study of Santolina (Asteraceae) from southern France and north‐eastern Spain reveals new endemic taxa

Abstract

Santolina is a clear example of a genus lying in an alpha‐taxonomic status, with species accepted only based on qualitative morphological descriptions. In particular, taxonomic issues still need to be resolved for Santolina populations from southern France and north‐eastern Spain, and so, we carried out an integrative taxonomic study involving morphometrics, cypsela morphometrics, niche overlap, and phylogenetic analysis based on six plastid markers (trnH‐psbA, trnL‐trnF, trnQ‐rps16, rps15‐ycf1, psbM‐trnD, and trnS‐trnG). Our results revealed that the current taxonomic circumscription is not adequate. In particular, the Santolina populations at the foothills of eastern Pyrenees, previously included in the variability of Santolina benthamiana, have to be considered as a distinct species, namely, Santolina intricata. In addition, despite their high phylogenetic relatedness, S. benthamiana s.str. and Santolina ericoides can still be considered as distinct species due to clear morphological and ecological differentiation. Finally, we demonstrated that three different subspecies can be recognized in Santolina decumbens, a species endemic to Provence. For one of these subspecies, due to its extremely restricted distribution range, conservation issues are pointed out.

A Morphometric Analysis of the Santolina chamaecyparissus Complex (Asteraceae)

“…Therefore, albeit the tetraploid populations were detected in central-eastern Spain and the only known hexaploid population was detected in south-eastern Spain [22,27], we deem that the current shortage of chromosome data, in proportion to the wide distribution range, does not allow for speculation about a possible allopatric distribution of the two cytotypes. The absence of morphological distinctiveness between the two cytotypes agrees with their sister relationship observed in the phylogenetic tree provided by Giacò and collaborators [25]. Based on the current knowledge, the case of S. villosa does not fit with any of the cases presented by Soltis and collaborators [28], in which chromosome races may be worth of taxonomic distinction.…”

“…As regards the latter, a nomenclatural revision [1] and a karyomorphological study [22] raised several taxonomic issues that have been later clarified using integrated taxonomic approaches. In particular, De Giorgi and collaborators [23] focused on polyploid Santolina populations from Corsica and Sardinia, Giacò and collaborators [24] on diploid continental Italian species, while Giacò and collaborators [25] untangled the systematic relationships of diploid populations occurring in southern France and north-eastern Spain. Santolina insularis (Gennari ex Fiori) Arrigoni has been synonymized with S. corsica [23], whereas new taxa have been recognized in France and Spain [25]: S. intricata Jord.…”

A Comprehensive Approach to Improving Endemic Plant Species Research, Conservation, and Popularization

“…However, the taxonomy of this complex was very unstable in the past, mostly because all species were circumscribed based only on qualitative morphological observations. A research project was recently conducted to clarify the systematics and taxonomy of the S. chamaecyparissus complex using an integrative taxonomic approach, involving nomenclature, cytogenetics, morphometry, cypsela morpho-colorimetry, molecular systematics, and niche analysis [70][71][72][73][74]. For the purposes of the project, all species were sampled for a total amount of 27 populations, including all known type localities and populations with an uncertain taxonomic position.…”

Betula mcallisteri sp. nov. (sect. Acuminatae, Betulaceae), a new diploid species overlooked in the wild and in cultivation, and its relation to the widespread B. luminifera

“…To delineate species more reliably, an integrated approach has been increasingly adopted, combining morphological, molecular, and (or) cytogenetic data ( Fujita et al., 2012 ; Alors et al., 2016 ; Newton et al., 2020 ; Giacò et al., 2022 ; Wang et al., 2022 ). The advantage of using an integrated approach for species delimitation is that it overcomes the subjective species concepts ( Hey, 2006 ; Hausdorf, 2011 ; Carstens et al., 2013 ) .…”