Phylogeny, biogeography and ecological diversification of New Caledonian palms (Arecaceae)

Abstract

Background and Aims The geographic origin and evolutionary mechanisms underpinning the rich and distinctive New Caledonian flora remain poorly understood. This is due 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 may 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 were 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 derive 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. Geographic and ecological transitions associated with speciation events differed across time and genera. Substrate transitions were more frequently associated with older than younger events. Conclusions Neighbouring areas and a mosaic of local habitats shaped New Caledonia’s palm flora, 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 further unpick the mechanisms underpinning New Caledonian palm endemism.

Early Cretaceous Origin and Evolutionary History of Palms (Arecaceae) inferred from 1,033 Nuclear Genes and a New Synthesis of Fossil Evidence

“…CC-BY-NC-ND 4.0 International license made available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is Eiserhardt et al, 2022;Hodel et al, 2021;Pérez-Calle, Bellot et al, 2024;Sâm et al, 2023) and from the outgroup genus Dasypogon (Dasypogonaceae; Li et al, 2021). See Supplementary Methods and Table S1 for details.…”

“…Leaf tissue from silica-dried or herbarium specimens was sampled for at least one species from each of the 184 genera currently recognized in the family (Baker & Dransfield, 2016;Bellot et al Eiserhardt et al, 2022;Hodel et al, 2021;Pérez-Calle, Bellot et al, 2024;Sâm et al, 2023) and from the outgroup genus Dasypogon (Dasypogonaceae; Li et al, 2021). See Supplementary Methods and Table S1 for details.…”

“…: Antonelli et al, 2017;Cássia-Silva et al, 2019;Faurby et al, 2016;Onstein et al, 2017;Torres Jiménez et al, 2023). However, the classification of palms has subsequently evolved, with some genera split, others merged and new ones discovered as new-to-science (Baker & Dransfield, 2016;Eiserhardt et al, 2022;Hodel et al, 2021;Pérez-Calle, Bellot et al, 2024;Sâm et al, 2023), rendering the existing synthesis incomplete. Moreover, phylogenomic methods have entirely superseded previous approaches applied to palms, through plastome sequencing Chen et al, 2022;Comer et al, 2015;Yao et al, 2023) and targeted sequencing of nuclear genes (Cano et al, 2022;Comer et al, 2016;de La Harpe et al, 2019;Eiserhardt et al, 2022;Escobar et al, 2022;Helmstetter et al, 2020;Heyduk et al, 2016;Kuhnhäuser et al, 2021;Loiseau et al, 2019;Pérez-Calle, Bellot et al, 2024;Sanín et al, 2022;Torres Jiménez et al, 2021).…”