Abstract
The grasshopper genus Caledonula, endemic to New Caledonia, was studied to understand the evolution of species distributions in relation to climate and soil types. Based on a comprehensive sampling of 80 locations throughout the island, the genus was represented by five species, four of which are new to science, of which three are described here. All the species have limited distributions in New Caledonia. Bioclimatic niche modelling shows that all the species were found in association with a wet climate and reduced seasonality, explaining their restriction to the southern half of the island. The results suggest that the genus was ancestrally constrained by seasonality. A molecular phylogeny was reconstructed using two mitochondrial and two nuclear markers. The partially resolved tree showed monophyly of the species found on metalliferous soils, and molecular dating indicated a rather recent origin for the genus. Adaptation to metalliferous soils is suggested by both morphological changes and radiation on these soils. The genus Caledonula is therefore a good model to understand the origin of microendemism in the context of recent and mixed influences of climate and soil type.
Highlights
New Caledonia, located in the south-west Pacific, is considered one of the major hotspots of biodiversity [1]
Except for one specimen showing contradictory information on the labels (GPS data indicates the top of Mont Do, whereas it is labelled as being from the base of Mont Do), all specimens identified as C. fuscovittata are from non-ultramafic soils only
New Caledonia has recently undergone a change in biogeographical status, from Gondwanan refuge to old Darwinian island [8]
Summary
New Caledonia, located in the south-west Pacific, is considered one of the major hotspots of biodiversity [1]. Recent phylogenetic studies, in concordance with all geological studies, showed that the diversification of the fauna and flora in New Caledonia is much more recent than expected [7,8,9] and started 37 Mya after long episodes of total submergence in the Palaeocene and in the Eocene [10,11,12,13,14,15]. One major feature of New Caledonian biodiversity is its strong endemism [8,16,17]. Regional endemism, including relicts, is extremely high, since many species or even whole groups are only found on Grande Terre [5]. Microendemism was found to be a dynamic feature, resulting from very recent diversification through allopatric speciation and evolving later towards less restricted distributions [23]
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