Origins of the fern genus Hymenophyllum (Hymenophyllaceae) in New Caledonia: Multiple independent colonizations from surrounding territories and limited in situ diversification

• Published in: TAXON
• Main Authors: Rio, Cédric Del, Hennequin, Sabine, Rouhan, Germinal, Ebihara, Atsushi, Lowry II, Porter P., Dubuisson, Jean-Yves, Gaudeul1, Myriam
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2017
• Subjects: Plant Science; Ecology, Evolution, Behavior and Systematics; New Zealand; Pacific; Antarc*; Antarctica
• Online Access: http://dx.doi.org/10.12705/665.4; https://onlinelibrary.wiley.com/doi/pdf/10.12705/665.4

Abstract Based on a worldwide dataset of molecular sequence data from three plastid DNA markers ( rbcL , rbcL ‐ accD ‐ accD , rps4 ‐ trnS ) obtained from 109 species of Hymenophyllum (Hymenophyllaceae), we investigated the systematics and bioge‐ographic origins of the New Caledonian (NC) members of this fern genus, which were thought to include 16 species with 10 endemics. Located in the southwest Pacific, NC is a continental Gondwanan island that was long supposed to harbour phylogenetic relicts. However, molecular and geological data suggest that the current flora and fauna are the result of recent colonizations that occurred after total submersion (during the Eocene) and subsequent re‐emersion of NC ca. 37 Ma. Our molecular phylogenetic results, complemented by morphological observations of herbarium specimens, show the existence of a new species that was as yet undescribed, and suggest that a previously recognized variety should be elevated to the rank of species to avoid species polyphyly. These two species, which are recognizable based on several morphological features, are endemic to NC: (i) Hymenophyllum soriemersum sp. nov. is sister to the other NC endemic H. dimidiatum and (ii) H. neo‐caledonicum comb. & stat. nov, previously described as a variety within H. lyallii , was retrieved as a distinct lineage. We also confirmed the synonymy of H. streptophyllum and H. subdimidiatum (both previously considered as endemic to NC) with the more widely distributed H. javanicum and H. holochilum , respectively. These synonymies were previously hypothesised based on morphology alone. New Caledonia thus has as total of 17 Hymenophyllum species, 12 (71%) of which are endemics. Biogeographic inferences based on the results of our phylogenetic analyses suggest that Hymenophyllum originated in New Zealand ca. 49.8 Ma (95% HPD: 40.7–59.5 Ma). Its spatio‐temporal history may in part have been influenced by vicariance (with potential exchange via the Antarctica land bridge that persisted between Australia and South ...