Sara Martín-Hernanz

Indian populations of Helianthemum (Cistaceae), previously identified as H. lippii, are re-evaluated here using an integrative approach combining morphology, molecular systematics based on plastid (ndhF, psbA-trnH, trnL-trnF) and nuclear (ITS) DNA sequences, and cytogenetic data. The morphological traits and phylogenetic results suggest a close relationship with a Helianthemum lineage from the southern Arabian Peninsula and the Horn of Africa, particularly with H. citrinum. The Indian plants are described here as H. citrinum subsp. kachchhicum. The phylogenetic reconstructions provided evidence that this subspecies likely originated from a recent dispersal event from the southern Arabian Peninsula around 120,000 years ago. Overall, this study carries significant biogeographical and evolutionary implications and highlights the limited understanding of Helianthemum beyond its Mediterranean biodiversity hotspot.

Island biotas often show highly uneven species richness among lineages, influenced by clade age, diversification rates, and/or spatio-ecological limits. However, disentangling these drivers has been challenging due to the lack of comprehensive datasets across multiple lineages in the same geographical arena. The flora of the Canary Islands includes hundreds of plant lineages with contrasting species richness and harbours the highest number of species that evolved their woodiness in-situ (“insular woodiness”). Here, we present a phylogenomic reconstruction for Canary Island angiosperms and show that diversity unevenness in the flora is not driven by lineage age but by trait-dependent diversification and spatio-ecological limits. Our phylogenomic dataset, based on 1,244 newly generated and 501 published DNA sequences for 669 Canary Island species and 771 closely related mainland taxa, allows us to simultaneously study 435 plant lineages (∼50% of total). Applying dynamic stochastic modelling, we find the flora is shaped by high extinction and colonisation rates, maintaining a macroevolutionary equilibrium. Additionally, insular woody lineages exhibit higher diversification rates than the remaining flora. Our results suggest the uneven diversity of a highly dynamic insular region can be explained by the interaction of trait evolution and ecological constraints, providing insights into island biodiversity dynamics.

The sclerophyllous syndrome is characterized by well‐defined traits (evergreen coriaceous leaves, inconspicuous flowers, and fleshy fruits). It has been hypothesized that lineages displaying the sclerophyllous syndrome show lower speciation rates than non‐sclerophyllous lineages after the establishment of the mediterranean climate. Daphne gnidium displays sclerophyllous traits and some differentiation into three subspecies (gnidium, mauritanica, maritima), but the spatio‐temporal origin of this taxonomic group is unknown due to the lack of a time‐calibrated phylogeny of the whole genus. Here, we inferred phylogenetic relationships and divergence times of Daphne (32 species, 238 samples) and other genera of Thymelaeaceae (16 genera, 38 species, 34 samples) using the internal transcribed spacer (ITS), which revealed that the current circumscription of Daphne is profoundly polyphyletic because some species are nested within the genera Wikstroemia and Edgeworthia. In contrast, D. gnidium formed a well‐supported clade as recognized in taxonomic accounts (subgenus Spachia). We found morphological and phylogenetic support for Daphne mauritanica as a monophyletic lineage sister to D. gnidium. Divergence between D. gnidium and D. mauritanica appears to have predated the establishment of seasonally dry conditions, which supports a pre‐mediterranean temporal origin of the lineage. A phylogeographical analysis within D. gnidium based on 66 nrDNA (ITS) and 84 cpDNA (rps16, trnV) sequences agreed with the low differentiation of the species in the Pleistocene despite its large distribution range. Altogether, D. gnidium illustrates one more example of the sclerophyllous syndrome with no speciation after the onset of the mediterranean climate.

In this study we assessed karyotype size and symmetry for a comprehensive taxonomic and geographic representation of Helianthemum and reconstructed chromosome number evolution in the genus. Using root tips, we photographed mitotic metaphase spreads to obtain chromosome number, total haploid (monoploid) length of the chromosome set (THL), karyotype formula, Stebbins’ classification of karyotype asymmetry, interchromosomal coefficient of variation of chromosome length (CVCL) and intrachromosomal mean centromeric asymmetry (MCA) using MATO (Measurement and Analysis Tools). We found that shifts in chromosome number are not a major driver in the evolution of Helianthemum, whose chromosome number evolved at a constant rate of single chromosome gain or loss. Karyotype asymmetry is very low and little variable in all taxonomic categories studied, with a predominance of metacentric and submetacentric small to medium-sized chromosomes about 3 μm at the genus level. However, total karyotype length varies from 16.91 μm to 47.84 μm at the species level, with a cytogenetic signature that is not conserved within subgenera and most sections. Overall, H. subg. Plectolobum shows both the longest and the most symmetrical karyotypes. We hypothesize that the variation in karyotype size in Helianthemum is likely a consequence of chromosome rearrangements that have occurred under selective pressures.

Premise: Divergence of floral morphology and breeding systems are often expected to be linked to angiosperm diversification and environmental niche divergence. However, available evidence for such relationships is not generalizable due to different taxonomic, geographical and time scales. The Palearctic genus Helianthemum shows the highest diversity of the family Cistaceae in terms of breeding systems, floral traits, and environmental conditions as a result of three recent evolutionary radiations since the Late Miocene. Here, we investigated the tempo and mode of evolution of floral morphology in the genus and its link with species diversification and environmental niche divergence.Methods: We quantified 18 floral traits from 83 taxa and applied phylogenetic comparative methods using a robust phylogenetic framework based on genotyping‐by‐sequencing data.Results: We found three different floral morphologies, putatively related to three different breeding systems: type I, characterized by small flowers without herkogamy and low pollen to ovule ratio; type II, represented by large flowers with approach herkogamy and intermediate pollen to ovule ratio; and type III, featured by small flowers with reverse herkogamy and the highest pollen to ovule ratio. Each morphology has been highly conserved across each radiation and has evolved independently of species diversification and ecological niche divergence.Conclusions: The combined results of trait, niche, and species diversification ultimately recovered a pattern of potentially non‐adaptive radiations in Helianthemum and highlight the idea that evolutionary radiations can be decoupled from floral morphology evolution even in lineages that diversified in heterogeneous environments as the Mediterranean Basin.

Background and Aims: The Canary Islands have strong floristic affinities with the Mediterranean Basin. One of the most characteristic and diverse vegetation belts of the archipelago is the thermophilous woodland (between 200 and 900 m.a.s.l.). This thermophilous plant community consists of many non-endemic species shared with the Mediterranean Floristic Region together with Canarian endemic species. Consequently, phytogeographic studies have historically proposed the hypothesis of an origin of the Canarian thermophilous species following the establishment of the summer-dry mediterranean climate in the Mediterranean Basin around 2.8 million years ago.Methods: Time-calibrated phylogenies for 39 plant groups including Canarian thermophilous species were primarily analysed to infer colonization times. In particular, we used 26 previously published phylogenies together with 13 new time-calibrated phylogenies (including newly generated plastid and nuclear DNA sequence data) to assess whether the time interval between stem and crown ages of Canarian thermophilous lineages postdates 2.8 Ma. For lineages postdating this time threshold, we additionally conducted ancestral area reconstructions to infer the potential source area for colonization.Key Results: A total of 43 Canarian thermophilous lineages were identified from 39 plant groups. Both mediterranean (16) and pre-mediterranean (9) plant lineages were found. However, we failed to determine the temporal origin for 18 lineages because a stem–crown time interval overlaps with the 2.8-Ma threshold. The spatial origin of thermophilous lineages was also heterogeneous, including ancestral areas from the Mediterranean Basin (nine) and other regions (six).Conclusions: Our findings reveal an unexpectedly heterogeneous origin of the Canarian thermophilous species in terms of colonization times and mainland source areas. A substantial proportion of the lineages arrived in the Canaries before the summer-dry climate was established in the Mediterranean Basin. The complex temporal and geographic origin of Canarian thermophilous species challenges the view of the Canary Islands (and Madeira) as a subregion within the Mediterranean Floristic Region.

TYPE OF ARTICLE: Original Article Time-calibrated phylogenies reveal mediterranean and pre-mediterranean origin of the thermophilous vegetation of the Canary IslandsSara Martín-Hernanz1, 2*, Manuel Nogales3, Luis Valente4, 5, Mario Fernández-Mazuecos6, 7, Fernando Pomeda-Gutiérrez1, Emilio Cano1, Patricia Marrero1, 3, Jens M. Olesen8, Ruben Heleno9, Pablo Vargas11Department of Biodiversity and Conservation, Real Jardín Botánico de Madrid - CSIC, Madrid, Spain. 2Departament of Plant Biology and Ecology, Faculty of Pharmacy, Universidad de Sevilla, Sevilla, Spain. 3Island Ecology and Evolution Research Group, Instituto de Productos Naturales y Agrobiología (IPNA-CSIC), San Cristóbal de La Laguna, Tenerife, Canary Islands, Spain. 4Naturalis Biodiversity Center, Leiden, The Netherlands. 5 Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands. 6Departament of Biology (Plant Biology), Faculty of Sciences, Universidad Autónoma de Madrid, Madrid, Spain.7Centro de Investigación en Biodiversidad y Cambio Global (CIBC-UAM), Universidad Autónoma de Madrid, Madrid, Spain. 8Department of Biology, Aarhus University, Aarhus C, Denmark. 9Centre for Functional Ecology, TERRA Associated Laboratory, Department of Life Sciences, University of Coimbra, Portugal.The article should be cited as: Sara Martín-Hernanz, Manuel Nogales, Luis Valente, Mario Fernández-Mazuecos, Fernando Pomeda-Gutiérrez, Emilio Cano, Patricia Marrero, Jens M. Olesen, Ruben Heleno, Pablo Vargas. Time-calibrated phylogenies reveal mediterranean and pre-mediterranean origin of the thermophilous vegetation of the Canary Islands. Authorea. DOI: 10.22541/au.165212305.54923019/v1 * For correspondence. E-mail sara.martin.hernanz@gmail.comRunning title: Origin of thermophilous plants from the Canary Islands Summary· Background and Aims The Canary Islands have strong floristic affinities with the Mediterranean Basin. One of the most characteristic and diverse vegetation belt of the archipelago is the thermophilous woodland (between 200 and 900 m). This thermophilous plant community consists of many non-endemic species shared with the Mediterranean Floristic Region together with Canarian endemic species. Consequently, phytogeographic studies have historically proposed the hypothesis of a origin of the Canarian thermophilous species following the establishment of the summer-dry mediterranean climate in the Mediterranean Basin around 2.8 million years ago.· Methods Time-calibrated phylogenies for 39 plant groups including Canarian thermophilous species were primarily analysed to infer colonization times. In particular, we used 26 previously-published phylogenies together with 13 time-calibrated phylogenies (including newly generated plastid and nuclear DNA sequence data) to assess whether the time interval between stem and crown ages of Canarian thermophilous lineages postdates 2.8 Ma. For lineages postdating this time threshold, we additionally conducted ancestral area reconstructions to infer the potential source area for colonization.· Key Results A total of 43 Canarian thermophilous lineages were identified from 39 plant groups. Both mediterranean (16) and pre-mediterranean (9) plant lineages were found. However, we failed to determine the temporal origin for 18 lineages because a stem-crown time interval overlaps with the 2.8 Ma threshold. The spatial origin of thermophilous lineages was also heterogeneous, including ancestral areas from the Mediterranean Basin (nine) and other regions (six).· Conclusions Our findings reveal an unexpectedly heterogeneous origin of the Canarian thermophilous species in terms of colonization times and mainland source areas. A substantial proportion of the lineages arrived in the Canaries before the summer-dry climate was established on the Mediterranean Basin. The complex temporal and geographical origin of Canarian thermophilous species challenges the view of the Canary Islands (and Madeira) as a subregion within the Mediterranean Floristic Region.Keywords: thermophilous woodland, Canary Islands, Mediterranean Floristic Region, colonization times, stem age, crown age, ancestral area, extinction

Molecular systematics requires the establishment of a robust phylogenetic framework including extensive geographical and taxonomic sampling. In this work, we proposed systematic changes in the genus Helianthemum based on phylogenetic trees obtained by both maximum likelihood and Bayesian analyses of GBS data. The implications of these phylogenetic results for the systematics of Helianthemum entail the establishment of a new subgenus and novel re-ascriptions of sections and species along with some nomenclatural novelties. The following new combinations are proposed: Helianthemum subg. Eriocarpum (Dunal) Martín-Hernanz, Velayos, Albaladejo & Aparicio; H. oelandicum subsp. conquense (Borja & Rivas Goday ex G.López) Martín-Hernanz, Velayos, Albaladejo & Aparicio; H. nummularium subsp. cantabricum (M.Laínz) Martín-Hernanz, Velayos, Albaladejo & Aparicio; H. nummularium subsp. tinetense (M.Mayor & Fern.Benito) Martín-Hernanz, Velayos, Albaladejo & Aparicio.