A putative case of honeyeater-driven sympatric speciation associated with corolla shape shift resulting in a new New Caledonian Oxera species

Abstract

While conducting a population genetic study aiming at refining previous conclusions about cladogenesis in the Oxera genus (Lamiaceae) in New Caledonia, we uncovered an unexpected result for the well-known Oxera palmatinervia Dubard species. To better understand the preliminary molecular results that revealed two distinct sister species, we performed extensive field studies in order to sample, measure, hand-pollinate, and observe the flower and fruit visitors on different populations of O. palmatinervia and other species of the “robusta” clade. We found flower morphology differences to be congruent with the molecular results, so that we propose to describe a new species as O. sympatrica Gâteblé & Karnadi sp. nov. The differences in flower morphology between the two species, which can grow in true sympatry and flower at the same time of the year, are striking so that flower visitors and pollination syndromes were investigated as far as possible. We find that two species of honeyeaters Glycifohia undulata and Philemon diemenensis are likely the preferred pollinators, respectively, of O. palmatinervia and O. sympatrica sp. nov. because of their respective sizes, bill and tongue lengths, and behavior. Even though, to date, it cannot be proven that initial speciation of both Oxera occurred in sympatry, today's sympatry is observed along with a remarkable supposed coevolution pollination syndrome. The new species is fully described, mapped, evaluated against Red List criteria, and illustrated. Pollination syndromes are discussed and illustrated.

Keywords

honeyeater / New Caledonia / new species / Oxera / pollination syndrome / speciation

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2025 The Author(s). Journal of Systematics and Evolution published by John Wiley & Sons Australia, Ltd on behalf of Institute of Botany, Chinese Academy of Sciences.