Resin exudation and resinicolous communities on Araucaria humboldtensis in New Caledonia

Abstract

International audienceConifers of the endemic species Araucaria humboldtensis on Mont Humboldt in New Caledonia exhibit extensive resin exudation. The resin flows of these threatened trees are here shown to be induced by two beetle species, which bore into branches and branchlets, leading to abundant outpouring of resin, which gradually solidifies into often drop-shaped resin bodies. The exudate is colonized by a resinicolous and likely insect-vectored ascomycete, Resinogalea humboldtensis, which is only known from Mont Humboldt. The fungus grows into fresh resin and eventually develops ascomata on the surface of solidifying resin. The solidified resin is also colonized by another fungus, a dematiaceous hyphomycete. Based on protein coding (CO1, CAD, ArgK) and ribosomal (LSU) genes, the larger branch-boring beetle is a weevil of the tribe Araucariini, which represents the sister group of all other cossonine weevils. The smaller beetle species belongs to the longhorn beetles (Cerambycidae). The strong host specificity of the Araucariini, along with the occurrence of two unique fungi, suggests that the resin-associated community is native and has evolved on the endemic conifer host. The formation of large amber deposits indicates massive resin production in the past, but the environmental triggers of exudation in Mesozoic and Cenozoic ecosystems remain unclear. Our observations from Mont Humboldt support the notion that the occurrences of small drop-shaped amber pieces in Triassic to Miocene amber deposits were linked to ancient insect infestations

Production and preservation of resins – past and present

“…New Caledonian Araucaria humboldtensis exudes resin from beetle‐infested branches, with particular drop‐like morphologies (Fig. C, D; Beimforde et al, ), reminiscent of the Dolomites amber drops with arthropods entrapped (Schmidt et al, ) and those in French amber (Saint Martin et al, ; Néraudeau et al, ). The actual quantities observed are relatively small in terms of ‘geologically significant’ resin volumes, and are due to the low density of the Araucaria humboldtensis trees on Mont Humboldt.…”

“…Interestingly, Beimforde et al . () showed complex animal and fungal interactions with the resinous Araucaria humboldtensis in New Caledonia, where the fungi depend on long‐term resin flows, under natural conditions in a stable ecosystem that lacks fire. Overall, the amount of resin that could collect over time is not thought to be very extensive, but given larger resinous trees growing at a much higher density, such as with the pines attacked by bark beetles (see below), ‘geologically significant’ resin volumes are possible.…”

Morphological Convergence in Forest Microfungi Provides a Proxy for Paleogene Forest Structure

“…Some such insects are strong fliers and can transport ascospores over long distances directly into specific new microhabitats. Also, woodpeckers and other birds and even some mammals are likely to promote the dispersal of some calicioid species (Rikkinen, 1995(Rikkinen, , 2003aTuovila et al, 2011b;Messuti et al, 2012;Rikkinen et al, 2016;Beimforde et al, 2017a).…”

Two new ant species (Formicidae: Dorylinae, Ponerinae) from New Caledonia

“…One specimen was collected in 2010 by Maïa Berman during her PhD on ant ecology (Fire project) at Charles Darwin University (Australia) (Berman 2012). All other specimens were collected by VP in 2011, during experimental fieldwork for actuo-paleontological studies of resin-producing araucarian forests of New Caledonia (e.g., Beimforde et al 2017). Both samplings were conducted with permission obtained from the Direction de l'Environnement de la Province Sud (permit 1357-2010/ARR/DENV to Alan Andersen/Maïa Berman and 17778/DENV/SCB to VP).…”