Transoceanic origin of microendemic and flightless New Caledonian weevils

Abstract

The origin of the astonishing New Caledonian biota continues to fuel a heated debate among advocates of a Gondwanan relict scenario and defenders of late oceanic dispersal. Here, we study the origin of New Caledonian Trigonopterus flightless weevils using a multimarker molecular phylogeny. We infer two independent clades of species found in the archipelago. Our dating estimates suggest a Late Miocene origin of both clades long after the re-emergence of New Caledonia about 37 Ma. The estimation of ancestral ranges supports an ancestral origin of the genus in a combined region encompassing Australia and New Guinea with subsequent colonizations of New Caledonia out of New Guinea in the mid-Miocene. The two New Caledonian lineages have had very different evolutionary trajectories. Colonizers belonging to a clade of foliage dwellers greatly diversified, whereas species inhabiting leaf-litter have been less successful.

Keywords: BioGeoBEARS; Curculionidae; Melanesia; Trigonopterus; flightless beetle biogeography; long-distance dispersal.

Figure 1.

Map of New Caledonia and sampling localities. Geographical map of the New Caledonian archipelago with a relief layer indicating terrane elevation. Pink dots indicate sampling localities where specimens of Trigonopterus used in this study were collected (see electronic supplementary material, appendix S1 for more details).

Figure 2.

Phylogenetic tree of New Caledonian Trigonopterus. Maximum-likelihood phylogeny inferred using IQ-TREE. The main clades are labelled. Support values of nodes are given with SH-aLRT (left) and ultrafast bootstrap (right). Brown lineages indicate an edaphic lifestyle, and green lineages indicate foliage dwellers; black lineages are with an ambiguous lifestyle . Pink boxes mark New Caledonian taxa. Labels of species illustrated to the left are underlined.

Figure 3.

Palaeobiogeography of New Caledonian Trigonopterus. BEAST chronogram presenting median age estimates for the Trigonopterus radiation (see electronic supplementary material, appendix S4 for the full chronogram with CI bars). The main clades are labelled as in figure 2 and their age estimates are detailed in table 1. For each species used in this study, the distribution as defined in the BioGeoBEARS analyses is given at the corresponding tip. The colours are coded following the map inserted at the bottom left corner of the figure and as indicated in the caption. The ancestral range estimation recovered in the preferred BioGeoBEARS analyses (DIVALIKE + j) is presented for every node of the phylogeny. Asterisks indicate that the estimated best ancestral range had more than 50% relative probability compared with other possible ancestral ranges (see electronic supplementary material, appendix S6 for more details). The photograph inserted at the bottom right corner highlights a specimen of Trigonopterus in natura (Queensland, Australia, Photo D. Yarrow).