Updating the Phylogenetic Dating of New Caledonian Biodiversity with a Meta-analysis of the Available Evidence

Abstract

For a long time, New Caledonia was considered a continental island, a fragment of Gondwana harbouring old clades that originated by vicariance and so were thought to be locally ancient. Recent molecular phylogenetic studies dating diversification and geological data indicating important events of submergence during the Paleocene and Eocene (until 37 Ma) brought evidence to dismiss this old hypothesis. In spite of this, some authors still insist on the idea of a local permanence of a Gondwanan biota, justifying this assumption through a complex scenario of survival by hopping to and from nearby and now-vanished islands. Based on a comprehensive review of the literature, we found 40 studies dating regional clades of diverse organisms and we used them to test the hypothesis that New Caledonian and inclusive Pacific island clades are older than 37 Ma. The results of this meta-analysis provide strong evidence for refuting the hypothesis of a Gondwanan refuge with a biota that originated by vicariance. Only a few inclusive Pacific clades (6 out of 40) were older than the oldest existing island. We suggest that these clades could have extinct members either on vanished islands or nearby continents, emphasizing the role of dispersal and extinction in shaping the present-day biota.

Figure 1

Estimated crown age of New Caledonian clades from 40 selected studies (purple: arthropods, green: plants, red: vertebrates, grey: molluscs). Dotted lines indicate confidence intervals when available. A–C: tectonic/geodynamic model of the evolution of the Eocene accretion/subduction complex of New Caledonia; (a–c): reconstruction of the convergence of the Norfolk Ridge and the Loyalty Arc. A-C and a-c are not to scale and redrawn from.

Figure 2

Accumulated likelihood of being older than 37 Ma (±3 Ma). Numbers on the X-axis refer to the Clade ID in Table 1. Purple: arthropods, green: plants, red: vertebrates, grey: molluscs.

Figure 3

Estimated crown age of the New Caledonian and Pacific island clades from the 40 selected studies. Dotted lines indicate confidence intervals when available. Purple: arthropods, green: plants, red: vertebrates, grey: molluscs.

Figure 4

Accumulated likelihood of the inclusive Pacific Group being older than 37 Ma (±3 Ma), from studies where crown age and Pacific insular age differ (n = 10). Numbers on the X-axis refer to the Clade ID in Table 1. Purple: arthropods, green: plants, red: vertebrates, grey: molluscs.