Cryptic adaptive radiation in tropical forest trees in New Caledonia.
The causes of the species richness of tropical trees are poorly understood, in particular the roles of ecological factors such as soil composition. The nickel(Ni)-hyperaccumulating tree genus Geissois (Cunoniaceae) from the South-west Pacific was chosen as a model of diversification on different substrates. Here, we investigated the leaf element compositions, spatial distributions and phylogeny of all species of Geissois occurring on New Caledonia. We found that New Caledonian Geissois descended from a single colonist and diversified relatively quickly into 13 species. Species on ultramafic and nonultramafic substrates showed contrasting patterns of leaf element composition and range overlap. Those on nonultramafic substrates were largely sympatric but had distinct leaf element compositions. By contrast, species on ultramafic substrates showed similar leaf element composition, but occurred in many cases exclusively in allopatry. Further, earlier work showed that at least three out of these seven species use different molecules to bind Ni. Geissois qualifies as a cryptic adaptive radiation, and may be the first such example in a lineage of tropical forest trees. Variation in biochemical strategies for coping with both typical and adverse soil conditions may help to explain the diversification and coexistence of tropical forest trees on similar soil types.
Tropical Conservation Biology and Environmental Science, University of Hawai'i at Hilo, 200 West Kawili Street, Hilo, HI, 96720, USA.
Yohan
Y
Pillon
c/o Herbarium, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AE, UK.
Helen C F
HCF
Hopkins
IMBE UMR CNRS 7263/IRD 137, Institut de Recherche pour le Développement, 98848, Nouméa, New Caledonia.
Frédéric
F
Rigault
Laboratoire de botanique et d'écologie végétale appliquées, Herbarium NOU, UMR AMAP, Institut de Recherche pour le Développement, 98848, Nouméa, New Caledonia.
Tanguy
T
Jaffré
Tropical Conservation Biology and Environmental Science, University of Hawai'i at Hilo, 200 West Kawili Street, Hilo, HI, 96720, USA.
Elizabeth A
EA
Stacy
D000222:Adaptation, Physiological / Q000235:genetics*; D044822:Biodiversity; D019684:Magnoliopsida / Q000235:genetics* / Q000378:metabolism; D009510:New Caledonia; D009532:Nickel / Q000378:metabolism*; D010802:Phylogeny; D018515:Plant Leaves / Q000378:metabolism*; D012987:Soil / Q000737:chemistry*; D013045:Species Specificity; D014197:Trees / Q000235:genetics* / Q000378:metabolism; D014329:Tropical Climate
D012987:Soil; D009532:Nickel
New Caledonia; adaptive radiation; aluminium (Al) hyperaccumulator; island; nickel (Ni) hyperaccumulator; rainforest trees; serpentine; ultramafic