Search

Background and Aims The geographical origin and evolutionary mechanisms underpinning the rich and distinctive New Caledonian flora remain poorly understood. This is attributable to the complex geological past of the island and to the scarcity of well-resolved species-level phylogenies. Here, we infer phylogenetic relationships and divergence times of New Caledonian palms, which comprise 40 species. We use this framework to elucidate the biogeography of New Caledonian palm lineages and to explore how extant species might have formed. Methods A phylogenetic tree including 37 New Caledonian palm species and 77 relatives from tribe Areceae was inferred from 151 nuclear genes obtained by targeted sequencing. Fossil-calibrated divergence times were estimated and ancestral ranges inferred. Ancestral and extant ecological preferences in terms of elevation, precipitation and substrate were compared between New Caledonian sister species to explore their possible roles as drivers of speciation. Key Results New Caledonian palms form four well-supported clades, inside which relationships are well resolved. Our results support the current classification but suggest that Veillonia and Campecarpus should be resurrected and fail to clarify whether Rhopalostylidinae is sister to or nested in Basseliniinae. New Caledonian palm lineages are derived from New Guinean and Australian ancestors, which reached the island through at least three independent dispersal events between the Eocene and Miocene. Palms then dispersed out of New Caledonia at least five times, mainly towards Pacific islands. Geographical and ecological transitions associated with speciation events differed across time and genera. Substrate transitions were more frequently associated with older events than with younger ones. Conclusions Neighbouring areas and a mosaic of local habitats shaped the palm flora of New Caledonia, and the island played a significant role in generating palm diversity across the Pacific region. This new spatio-temporal framework will enable population-level ecological and genetic studies to unpick the mechanisms underpinning New Caledonian palm endemism. [ABSTRACT FROM AUTHOR]

Background: Over the past decade, phylogenomics has greatly advanced our knowledge of angiosperm evolution. However, phylogenomic studies of large angiosperm families with complete species or genus-level sampling are still lacking. The palms, Arecaceae, are a large family with ca. 181 genera and 2600 species and are important components of tropical rainforests bearing great cultural and economic significance. Taxonomy and phylogeny of the family have been extensively investigated by a series of molecular phylogenetic studies in the last two decades. Nevertheless, some phylogenetic relationships within the family are not yet well-resolved, especially at the tribal and generic levels, with consequent impacts for downstream research. Results: Plastomes of 182 palm species representing 111 genera were newly sequenced. Combining these with previously published plastid DNA data, we were able to sample 98% of palm genera and conduct a plastid phylogenomic investigation of the family. Maximum likelihood analyses yielded a robustly supported phylogenetic hypothesis. Phylogenetic relationships among all five palm subfamilies and 28 tribes were well-resolved, and most inter-generic phylogenetic relationships were also resolved with strong support. Conclusions: The inclusion of nearly complete generic-level sampling coupled with nearly complete plastid genomes strengthened our understanding of plastid-based relationships of the palms. This comprehensive plastid genome dataset complements a growing body of nuclear genomic data. Together, these datasets form a novel phylogenomic baseline for the palms and an increasingly robust framework for future comparative biological studies of this exceptionally important plant family. [ABSTRACT FROM AUTHOR]

With 178 species, palm subtribe Dypsidinae is one of the largest plant radiations on Madagascar. A well‐resolved species‐level phylogeny is required not only to unpick the drivers of this spectacular radiation, but also to define natural and useful generic limits in this taxonomically difficult group. The only recent taxonomic revision of Dypsidinae recognised just four genera, including the large genus Dypsis (currently with 172 species), which was considered impossible to divide further based on morphology alone. Here we describe the first comprehensively sampled species‐level phylogeny of Dypsidinae, including 157 described species (88% of the subtribe) as well as 10 samples of uncertain taxonomic identity (potentially new to science). Our tree is based on target sequence capture data for 161 nuclear DNA loci. The phylogenetic relationships recovered render Dypsis s.l. paraphyletic, requiring the resurrection of two previously synonymised genera. In total, we recognise six genera in Dypsidinae (Dypsis, Chrysalidocarpus, Marojejya, Vonitra, Lemurophoenix, Masoala), all of which are monophyletic and consistent with morphology. [ABSTRACT FROM AUTHOR]

Summary: Genome size varies 2400‐fold across plants, influencing their evolution through changes in cell size and cell division rates which impact plants' environmental stress tolerance. Repetitive element expansion explains much genome size diversity, and the processes structuring repeat 'communities' are analogous to those structuring ecological communities. However, which environmental stressors influence repeat community dynamics has not yet been examined from an ecological perspective.We measured genome size and leveraged climatic data for 91% of genera within the ecologically diverse palm family (Arecaceae). We then generated genomic repeat profiles for 141 palm species, and analysed repeats using phylogenetically informed linear models to explore relationships between repeat dynamics and environmental factors.We show that palm genome size and repeat 'community' composition are best explained by aridity. Specifically, Ty3‐gypsy and TIR elements were more abundant in palm species from wetter environments, which generally had larger genomes, suggesting amplification. By contrast, Ty1‐copia and LINE elements were more abundant in drier environments.Our results suggest that water stress inhibits repeat expansion through selection on upper genome size limits. However, elements that may associate with stress‐response genes (e.g. Ty1‐copia) have amplified in arid‐adapted palm species. Overall, we provide novel evidence of climate influencing the assembly of repeat 'communities'. [ABSTRACT FROM AUTHOR]

The date palm, Phoenix dactylifera , has been a cornerstone of Middle Eastern and North African agriculture for millennia. It was first domesticated in the Persian Gulf, and its evolution appears to have been influenced by gene flow from two wild relatives, P. theophrasti , currently restricted to Crete and Turkey, and P. sylvestris , widespread from Bangladesh to the West Himalayas. Genomes of ancient date palm seeds show that gene flow from P. theophrasti to P. dactylifera may have occurred by ∼2,200 years ago, but traces of P. sylvestris could not be detected. We here integrate archeogenomics of a ∼2,100-year-old P. dactylifera leaf from Saqqara (Egypt), molecular-clock dating, and coalescence approaches with population genomic tests, to probe the hybridization between the date palm and its two closest relatives and provide minimum and maximum timestamps for its reticulated evolution. The Saqqara date palm shares a close genetic affinity with North African date palm populations, and we find clear genomic admixture from both P. theophrasti , and P. sylvestris , indicating that both had contributed to the date palm genome by 2,100 years ago. Molecular-clocks placed the divergence of P. theophrasti from P. dactylifera / P. sylvestris and that of P. dactylifera from P. sylvestris in the Upper Miocene, but strongly supported, conflicting topologies point to older gene flow between P. theophrasti and P. dactylifera , and P. sylvestris and P. dactylifera. Our work highlights the ancient hybrid origin of the date palms, and prompts the investigation of the functional significance of genetic material introgressed from both close relatives, which in turn could prove useful for modern date palm breeding. [ABSTRACT FROM AUTHOR]

Summary: Seed size shapes plant evolution and ecosystems, and may be driven by plant size and architecture, dispersers, habitat and insularity. How these factors influence the evolution of giant seeds is unclear, as are the rate of evolution and the biogeographical consequences of giant seeds.We generated DNA and seed size data for the palm tribe Borasseae (Arecaceae) and its relatives, which show a wide diversity in seed size and include the double coconut (Lodoicea maldivica), the largest seed in the world. We inferred their phylogeny, dispersal history and rates of change in seed size, and evaluated the possible influence of plant size, inflorescence branching, habitat and insularity on these changes.Large seeds were involved in 10 oceanic dispersals. Following theoretical predictions, we found that: taller plants with fewer‐branched inflorescences produced larger seeds; seed size tended to evolve faster on islands (except Madagascar); and seeds of shade‐loving Borasseae tended to be larger.Plant size and inflorescence branching may constrain seed size in Borasseae and their relatives. The possible roles of insularity, habitat and dispersers are difficult to disentangle. Evolutionary contingencies better explain the gigantism of the double coconut than unusually high rates of seed size increase. [ABSTRACT FROM AUTHOR]

• Phylogenomic framework for a pantropical and economically important plant subfamily. • Targeted sequencing of almost one thousand nuclear genomic regions. • Systematic sampling representing the taxonomic diversity within all genera. • Phylogenetic backbone resolved with maximal support and low gene tree conflict. • Complex deep evolutionary histories of several subtribes revealed. Well-supported phylogenies are a prerequisite for the study of the evolution and diversity of life on earth. The subfamily Calamoideae accounts for more than one fifth of the palm family (Arecaceae), occurs in tropical rainforests across the world, and supports a billion-dollar industry in rattan products. It contains ca. 550 species in 17 genera, 10 subtribes and three tribes, but their phylogenetic relationships remain insufficiently understood. Here, we sequenced almost one thousand nuclear genomic regions for 75 systematically selected Calamoideae, representing the taxonomic diversity within all calamoid genera. Our phylogenomic analyses resolved a maximally supported phylogenetic backbone for the Calamoideae, including several higher-level relationships not previously inferred. In-depth analysis revealed low gene tree conflict for the backbone but complex deep evolutionary histories within several subtribes. Overall, our phylogenomic framework sheds new light on the evolution of palms and provides a robust foundation for future comparative studies, such as taxonomy, systematics, biogeography, and macroevolutionary research. [ABSTRACT FROM AUTHOR]