SignificanceDate palm (Phoenix dactylifera L.) is one of the oldest tree crop species in the world and is a major fruit crop of arid regions of the Middle East and North Africa. We use whole-genome sequence data from a large sample of P. dactylifera and its wild relatives to show that hybridization between date palms and Phoenix theophrasti Grueter—a species endemic to the Eastern Mediterranean—is associated with the diversification of date palm.

Plumbaginaceae is characterized by a history of multiple taxonomic rearrangements and lacks a broad molecular phylogenetic framework. Limonium is the most species‐rich genus of the family with ca. 600 species and cosmopolitan distribution. Its center of diversity is the Mediterranean region, where ca. 70% of all Limonium species are endemic. In this study, we sample 201 Limonium species covering all described infrageneric entities and spanning its wide geographic range, along with 64 species of other Plumbaginaceae genera, representing 23 out of 29 genera of the family. Additionally, 20 species of the sister family Polygonaceae were used as outgroup. Sequences of three chloroplast (trnL‐F, matK, and rbcL) and one nuclear (ITS) loci were used to infer the molecular phylogeny employing maximum likelihood and Bayesian analyses. According to our results, within Plumbaginoideae, Plumbago forms a non‐monophyletic assemblage, with Plumbago europaea sister to Plumbagella, while the other Plumbago species form a clade sister to Dyerophytum. Within Limonioideae, Ikonnikovia is nested in Goniolimon, rejecting its former segregation as genus distinct from Goniolimon. Limonium is divided into two major clades: Limonium subg. Pteroclados s.l., including L. sect. Pteroclados and L. anthericoides, and L. subg. Limonium. The latter is divided into three well‐supported subclades: the monospecific L. sect. Limoniodendron sister to a clade comprising a mostly non‐Mediterranean subclade and a Mediterranean subclade. Our results set the foundation for taxonomic proposals on sections and subsections of Limonium, namely: (a) the newly described L. sect. Tenuiramosum, created to assign L. anthericoides at the sectional rank; (b) the more restricted circumscriptions of L. sect. Limonium (= L. sect. Limonium subsect. Genuinae) and L. sect. Sarcophyllum (for the Sudano‐Zambezian/Saharo‐Arabian clade); (c) the more expanded circumscription of L. sect. Nephrophyllum (including species of the L. bellidifolium complex); and (d) the new combinations for L. sect. Pruinosum and L. sect. Pteroclados subsect. Odontolepideae and subsect. Nobiles.

Summary The complex nature of species boundaries has been a central topic in evolutionary biology ever since Darwin. Despite numerous separate studies on reproductive isolation and hybridization, their relationship remains underinvestigated. Are the strengths and asymmetries of reproductive barriers reflected in the extent and directionalities of interspecific genetic exchange? We combined field, experimental, and molecular data to quantify strengths and asymmetries of sympatric reproductive barriers and hybridization between florally heteromorphic primroses. We also assessed whether generalist pollinators discriminate between different floral cues and contribute to reproductive isolation, a long‐debated topic. Sympatric reproductive isolation is high but incomplete, and most phenotypic intermediates are genetic F1 hybrids, whereas backcrosses are rare, revealing low interspecific gene flow. Species integrity rests on multiple barriers, but ethological isolation is among the strongest, demonstrating that even generalist pollinators crucially contribute to the maintenance of species boundaries. Furthermore, reproductive barriers are weaker for Primula veris and short‐styled plants, results corroborated by molecular data. Thus, in florally heteromorphic systems, both species‐ and morph‐dependent asymmetries affect permeability of species boundaries. Our study illustrates how the interactions between complex floral syndromes and pollinators shape species boundaries in unique, previously undescribed ways.

The role of environment and the relative significance of endogenous versus exogenous selection in shaping hybrid zones have been crucial issues in the studies of hybridization. Recent advances in ecological niche modeling (ENM) offer new methodological tools, especially in combination with the genotyping of individuals in the hybrid zone. Here, we study the hybrid zone between the widely known spices Origanum onites and Origanum vulgare ssp. hirtum in Crete. We analyze the genetic structure of both parental taxa and their hybrid Origanum × intercendens using AFLP markers on 15 sympatric and 12 allopatric populations and employ ecological niche modeling and niche similarity tests to study their niche patterns. We complement these analyses with seed viability measurements. Our study revealed that the hybridizing taxa O. onites and O. vulgare ssp. hirtum and the resulting genotypic classes showed geographical and environmental niche similarities based on the predictions of ENMs and the subsequent similarity tests. The occurrence of the hybrid zone is not directly dependent on environmental factors which favor the fitness of the hybrid compared to the parental taxa, but rather on aspects such as historical factors and management practices, which may contribute to the localization and maintenance of the contact zone between parental species. Our results suggest that if a minimum required niche differentiation between genotypic classes is not achieved, environmental dependence might not have a prominent role on the outcome of the hybridization.

The Mediterranean realm, comprising the Mediterranean and Macaronesian regions, has long been recognized as one of the world’s biodiversity hotspots, owing to its remarkable species richness and endemism. Several hypotheses on biotic and abiotic drivers of species diversification in the region have been often proposed but rarely tested in an explicit phylogenetic framework. Here, we investigate the impact of both species-intrinsic and -extrinsic factors on diversification in the species-rich, cosmopolitan Limonium, an angiosperm genus with center of diversity in the Mediterranean. First, we infer and time-calibrate the largest Limonium phylogeny to date. We then estimate ancestral ranges and diversification dynamics at both global and regional scales. At the global scale, we test whether the identified shifts in diversification rates are linked to specific geological and/or climatic events in the Mediterranean area and/or asexual reproduction (apomixis). Our results support a late Paleogene origin in the proto-Mediterranean area for Limonium, followed by extensive in situ diversification in the Mediterranean region during the late Miocene, Pliocene, and Pleistocene. We found significant increases of diversification rates in the “Mediterranean lineage” associated with the Messinian Salinity Crisis, onset of Mediterranean climate, Plio-Pleistocene sea-level fluctuations, and apomixis. Additionally, the Euro-Mediterranean area acted as the major source of species dispersals to the surrounding areas. At the regional scale, we infer the biogeographic origins of insular endemics in the oceanic archipelagos of Macaronesia, and test whether woodiness in the Canarian Nobiles clade is a derived trait linked to insular life and a biotic driver of diversification. We find that Limonium species diversity on the Canary Islands and Cape Verde archipelagos is the product of multiple colonization events followed by in situ diversification, and that woodiness of the Canarian endemics is indeed a derived trait but is not associated with a significant shift to higher diversification rates. Our study expands knowledge on how the interaction between abiotic and biotic drivers shape the uneven distribution of species diversity across taxonomic and geographical scales.