Abstract
Several hypotheses have been proposed to explain the rich floristic diversity in regions characterised by nutrient-impoverished soils; however, none of these hypotheses have been able to explain the rapid diversification over a relatively short evolutionary time period of Grevillea, an Australian plant genus with 452 recognised species/subspecies and only 11 million years of evolutionary history. Here, we hypothesise that the apparent evolutionary success of Grevillea might have been triggered by the highly efficient use of key nutrients. The nutrient content in the seeds and nutrient-use efficiency during early seedling growth of 12 species of Grevillea were compared with those of 24 species of Hakea, a closely related genus. Compared with Hakea, the Grevillea species achieved similar growth rates (root and shoot length) during the early stages of seedling growth but contained only approximately half of the seed nutrient content. We conclude that the high nutrient-use efficiency observed in Grevillea might have provided a selective advantage in nutrient-poor ecosystems during evolution and that this property likely contributed to the evolutionary success in Grevillea.
Highlights
Several hypotheses have been proposed to explain the rich floristic diversity in regions characterised by nutrient-impoverished soils; none of these hypotheses have been able to explain the rapid diversification over a relatively short evolutionary time period of Grevillea, an Australian plant genus with 452 recognised species/subspecies and only 11 million years of evolutionary history
Our study aimed to provide unique insights into the potential mechanisms underlying the evolutionary success of Grevillea
For the 24 Hakea and 12 Grevillea species that yielded a sufficient number of germinants for growth comparisons, the time period to expand the first true leaves was similar, Grevillea plants had significantly fewer leaves after growing for 100 days
Summary
Several hypotheses have been proposed to explain the rich floristic diversity in regions characterised by nutrient-impoverished soils; none of these hypotheses have been able to explain the rapid diversification over a relatively short evolutionary time period of Grevillea, an Australian plant genus with 452 recognised species/subspecies and only 11 million years of evolutionary history. Mediterranean climate regions, such as those in southwest Western Australia (SWA), the South African Cape region, and the Mediterranean Basin, have diverse species and endemic rich flora and are considered globally significant[1,2]. Species have developed diverse morphological and physiological adaptations to limited nutrient availability in order to successfully establish in nutrient-limited soils[10,11,12,13] These species typically exhibit highly efficient photosynthetic phosphorus use[14]. Our study aimed to provide unique insights into the potential mechanisms underlying the evolutionary success (i.e., high diversification rate) of Grevillea
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