Systematics and phylogeography of the Mediterranean Helichysum pendulum complex (Compositae) inferred from nuclear and chloroplast DNA and morphometrics analyses

Multiple factors related to complex geomorphological and climatic history, in addition to biological factors such as hybridization, hinder the definition of some Mediterranean plant groups. The existence of controversial taxonomic treatments, the possible hybridization events involved, and its unknown evolutionary history, make the Helichrysum pendulum complex of H. sect. Stoechadina an ideal model to understand general processes of Mediterranean plant systematics and evolution. The mosaic range of the complex, which is distributed over several islands and continental areas in the western-central Mediterranean Basin, provides an opportunity to investigate how past connections and disconnections between landmasses may have determined the current geographic distribution of genetic variation in this area. The cpDNA region rpl32-trnL intergenic spacer and the nrDNA region ETS were sequenced for 1-8 individuals from each of the 44 populations sampled, covering all taxa and the whole geographic range of the complex. These individuals were analysed together with a broad sampling of the remaining members of sect. Stoechadina. In addition, detailed multivariate analyses of morphological characters were performed for the whole section and for the H. pendulum complex. Considering together distinctive genetic and morphological traits, our species concept is presented and discussed in a context of integrative taxonomy, and five species are recognized within the complex: H. errerae, H. melitense, H. pendulum, H. saxatile and H. valentinum. The first three species are recognizable by qualitative and quantitative morphological traits, and are genetically distinguishable from the rest as shown by the molecular markers analysed. The two last species are reported here to have a putative ancient hybrid origin and are also genetically distinguishable from the rest but morphologically recognisable only by quantitative characters. Phylogenetic relationships shown by nuclear and chloroplast markers, and an intermediate morphology between the two putative parental taxa, point to H. pendulum and H. italicum as the putative parental taxa for H. saxatile, and H. pendulum and H. stoechas as putative parental taxa for H. valentinum. In a discriminant analysis of the five species, 97.8% of all individuals were classified correctly. The high level of haplotype and ribotype diversity observed in North Africa indicates that this region is either the area of origin of the complex or a secondary contact zone. Our results suggest that the complex colonized several islands and migrated through the Gibraltar and Sicilian Straits during phases of low sea level, favoured by local dispersal events that promoted its gradual range expansion. The occurrence of the complex in the Balearic Islands, which have remained isolated even during low sea level phases, could be explained by stochastic long-distance dispersal events

Evolution, biogeography and systematics of the genus Cymbalaria Hill

Des de temps ancestrals la diversitat d’éssers vius del planeta ha fascinat i intrigat la humanitat. Com s’originen les espècies? Com han assolit la distribució geogràfica actual? En les darreres dècades, el gran avenç de les tècniques de sistemàtica molecular ha permès anar resolent aquests interrogants de manera satisfactòria. En aquesta tesi, desenvolupem un estudi sistemàtic del gènere Cymbalaria, un grup de plantes rupícoles endèmiques de la conca Mediterrània. Hem utilitzat principalment tècniques moleculars de filogènia i filogeografia i anàlisis morfològiques per inferir la seva història evolutiva i biogeogràfica, i proposar una nova classificació taxonòmica des de la perspectiva de la taxonomia integrativa. Cymbalaria va originar-se al voltant de 4 milions d’anys i va diversificar durant i després de l’establiment del clima mediterrani per mitjà de processos d’especiació al·lopàtrica, simpàtrica i poliploide. Com a mínim, dues dispersions a llarga distància des de Còrsega-Sardenya a les Balears van ocórrer, tot i no observar-se adaptacions específica a la dispersió en aquest cas. Les barreres marines han interromput exitosament el flux genètic en alguns casos, estimulant l’especiació al·lopàtrica, mentre que, en altres, les espècies han aconseguit mantenir el flux genètic entre poblacions separades pel mar. Les fluctuacions del nivell del mar del Pleistocè probablement van contribuir a la distribució actual dels tàxons i van afavorir l’especiació. La combinació de dades moleculars i morfològiques ens han permès apropar la classificació del gènere al concepte de taxonomia integrativa i identificar els caràcters morfològics amb valor diagnòstic. Així doncs, proposem una nova circumscripció per C. fragilis per incloure poblacions que, degut a l’ornamentació de les llavors, s’havien identificat com a C. aequitriloba. Per altra banda, descrivim la nova subespècie parafilètica C. muelleri subsp. villosa, de la qual s’originà per especiació anacladogenètica C. muelleri subsp. muelleri. Així, discutim la importància de reconèixer tàxons no monofilètics, que són el reflex d’una història evolutiva que no sempre produeix relacions purament dicotòmiques entre les espècies. Finalment, proposem un nou tractament taxonòmic per a les espècies de la Mediterrània oriental, en què dividim l’antiga C. microcalyx en quatre espècies, descrivim la nova espècie C. spetae i proposem dues noves combinacions.Since ancient times the diversity of life forms has fascinated and intrigued humanity. How do species originate? How did they achieve their present geographic distributions? In the last decades, the progress of molecular systematics tools has allowed for successfully answering these questions. In this thesis, we perform a systematic study of the genus Cymbalaria, a group of rupicolous plants endemic to the Mediterranean Basin. Mainly, we used phylogenetic and phylogeographic methods and morphological analyses to infer their evolution and biogeographic history, and to propose a new taxonomic classification from the perspective of integrative taxonomy. Our results show that Cymbalaria originated ca. 4 million years ago and diversified during and after the establishment of Mediterranean type climate, through allopatric, sympatric and polyploid speciation. At least, two long-distance dispersal events from Corsica-Sardinia to the Balearic Islands occurred, although no apparent adaptations for dispersal exist in this case. Marine barriers successfully interrupted gene flow and allowed allopatric speciation to take place in some cases, while, in others, species successfully maintained gene flow between populations separated by the sea. Pleistocene sea-level fluctuations could have contributed to the present distribution of taxa and triggered speciation. By combining molecular and morphological data, we bring the classification of Cymbalaria closer to the integrative taxonomy concept and identify valuable diagnostic morphological characters. Here, we propose a new circumscription of C. fragilis to include specimens misidentified as C. aequitriloba due to the variability of seed ornamentation. Also, we describe the new paraphyletic subspecies C. muelleri subsp. villosa, from which C. muelleri subsp. muelleri originated through anacladogenetic speciation. Thus, we discuss the need for recognizing non-monophyletic taxa, since evolution does not always result in purely dichotomous branching patterns. Finally we suggest a new taxonomic treatment for the eastern Mediterranean species, in which we split C. microcalyx into four species, describe the new species C. spetae and propose two new combinations