Phylogeography and niche modelling of the relict plant Amborella trichopoda (Amborellaceae) reveal multiple Pleistocene refugia in New Caledonia

Abstract

Amborella trichopoda Baill. (Amborellaceae, Amborellales), the sole living member of the sister group to all other extant angiosperms, is endemic to New Caledonia. We addressed the intraspecific phylogeography of Amborella by investigating whether its present population genetic structure could be related to its current and past habitats. We found moderate range-wide genetic diversity based on nuclear microsatellite data and detected four well-differentiated, geographically distinct genetic groups using Bayesian clustering analyses. We modelled the ecological niche of Amborella based on the current climatic and environmental conditions. The predictive ability of the model was very good throughout the Central East mainland zone, but Amborella was predicted in the northern part of the island where this plant has not been reported. Furthermore, no significant barrier was detected based on habitat suitability that could explain the genetic differentiation across the area. Conversely, we found that the main genetic clusters could be related to the distribution of the suitable habitat at the last glacial maximum (LGM, c. 21,000 years BP), when Amborella experienced a dramatic 96.5% reduction in suitable area. At least two lineages survived in distinct putative refugia located in the Massif des Lèvres and in the vicinity of Mount Aoupinié. Our findings finally confirmed the importance of LGM rainforest refugia in shaping the current intra- and interspecific diversity in New Caledonian plants and revealed the possibility of an as yet unreported refugium. The combination of niche modelling and population genetics thereby offered novel insight into the biogeographical history of an emblematic taxon.

Trait coordination, mechanical behaviour and growth form plasticity of Amborella trichopoda under variation in canopy openness

“…To understand the distribution of traits within a group, it is crucial to study as wide an array of lineages as possible. Among the flowering plants, Amborella trichopoda (Amborellaceae), a dioecious woody plant endemic to the moist forests of New Caledonia, has attracted the attention of plant science since the end of the last century, after several phylogenetic studies supported the position of Amborella as the single surviving representative of a lineage sister to all other extant angiosperms (Mathews and Donoghue 1999; Soltis et al 1999; Mathews and Donoghue 2000; Qiu et al 2000; Soltis et al 2000; Amborella Genome Project 2013; Poncet et al 2013). …”

The morphophysiological dormancy inAmborella trichopodaseeds is a pleisiomorphic trait in angiosperms

“…Secondly, our findings contribute to a growing picture of the ecophysiology of A. trichopoda within its endemic habitat of the New Caledonian rain forest. We thus add data on seed dormancy and germination to studies of photosynthesis (Feild et al, 2001), stomatal function (Rudall and Knowles, 2013), vascular function (Feild et al, 2000;Turgeon and Medville, 2011;Feild and Wilson, 2012), flowering time (Fourcade et al, 2015), pollination biology (Thien et al, 2009), seed physiology (Poncet et al, 2015), population structure (Thien et al, 2003;Poncet et al, 2013) and genetic diversity (Poncet et al, 2012). These diverse studies of A. trichopoda make a major contribution to the concerted reconstruction of the ecophysiological features of the first flowering plants (see Feild et al, 2004;Feild and Arens, 2007).…”

In situ observations of the basal angiosperm Amborella trichopoda reveal a long fruiting cycle overlapping two annual flowering periods

“…In a recent study, the ecological niche of A. trichopoda has been modelled on the basis of climatic and edaphic conditions that the species currently occupies (Poncet et al 2013). The absence of A. trichopoda in the northern part of the main island (Mont Panié), while the region was predicted as suitable for the species, suggests that the distribution of the species is partly shaped by constraints other than the current climate.…”

“…The key position of A. trichopoda in the phylogenetic tree of angiosperms led to high interest in research, such as in genomics (Bergthorsson et al 2004;Poncet et al 2013;Rice et al 2013;Zuccolo et al 2011), angiosperm evolution (Floyd and Friedman 2001;Friedman and Ryerson 2009;Soltis et al 2009;Williams 2009), reproductive biology (Bobrov et al 2005;Buzgo et al 2004;Endress and Igersheim 2000;Tobe et al 2000), physiology (Feild et al 2001;Feild et al 2000), and cytology (Oginuma Abstract Amborella trichopoda is the sole living angiosperm species belonging to the sister lineage of all other extant flowering plants. In the last decade, the species has been the focus of many phylogenetic, genomic and reproductive biology studies, bringing new highlights regarding the evolution of flowering plants.…”

“…Populations of A. trichopoda are distributed in the understory of rainforests located in the central mountain range of Grande Terre (Pillon 2009;Poncet et al 2013). Plants are functionally unisexual and populations are dioecious (Bailey and Swamy 1948;Endress 2001).…”