New Caledonian Araucaria

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New Caledonian Araucaria plants show the world’s strongest diversity for this genus. In New Caledonia there are 14 endemic Araucaria species, out of 20 living species in total. These trees mostly occur in scattered groups in open areas where they face less competition.

The island is a famous hotspot for life, with about 75% of its plant species found nowhere else on Earth. Araucaria trees in New Caledoniamostly grow on ultramafic soils, which are poor in nutrients and high in heavy metals like nickel and cobalt. This tough soil helps explain why many Araucaria species are found in specialized places rather than everywhere.

Scientists debate why so many Araucaria species exist there. One idea: New Caledonia hosts ancient “relic” species from when the land was part of Gondwana. Another idea: many species arose recently after the island formed, through rapid diversification.

Geological history helps frame the question. New Caledonia was once connected to Gondwana and separated from Australia about 80 million years ago. It probably sank under the sea in the Paleocene to Eocene, and recolonization may have occurred after the island re-emerged in the Oligocene. This pattern points to the possibility of a fairly recent origin for many of its Araucaria species.

Taxonomy and genetics have shed light on relationships. In the late 1940s and early 1950s, scientists described several New Caledonian Araucaria species and grouped them by branch patterns. In 1998, genetic studies using the RBCL gene confirmed four main sections within Araucaria and showed that New Caledonian species form a single, closely related group within the Eutacta section. The data also suggest a recent split from a common ancestor, with A. heterophylla (from Norfolk Island) being a sister group to the New Caledonian species.

A 2012 study using AFLP markers and other analyses strengthened the idea of recent diversification in New Caledonia. It also hinted at a coastal genetic group and the possibility of cryptic (hidden) species.

In 2016, researchers described Araucaria goroensis as the 14th endemic species in New Caledonia. It was initially mistaken for A. muelleri, but it has larger leaves and different cone features.

Overall, the origin of New Caledonian Araucaria remains complex. The evidence points toward relatively recent diversification, with some ongoing cryptic diversity, rather than a single ancient dispersal from Australia.