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Cutting Edge What’s new in the world of botanical research?
A butterfly using its long proboscis to access nectar
THE CUTTING EDGE
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RESEARCHERS WORKING WITH THE AUSTRALIAN INSTITUTE OF BOTANIC SCIENCE (AIBS) PUBLISH MORE THAN 90 PEER-REVIEWED ARTICLES EACH YEAR. PROFESSOR BRETT SUMMERELL HIGHLIGHTS A FEW RECENT RESEARCH PROJECTS.
DID FLOWERING PLANTS AND THEIR POLLINATORS CO-EVOLVE? Animals pollinate an estimated 87.5% of flowering plants (angiosperms), with insects pollinating an overwhelming majority. This relationship is obviously of huge ecological importance, and a critical concern in terms of the health and ecological* function of most ecosystems, particularly given that angiosperms and their insect pollinators dominate terrestrial ecosystems.
Both groups of organisms are extremely biodiverse. Angiosperms, for instance, are the most species-rich group of land plants, comprising at least 295,000 known species. Similarly, the chief pollinator orders of insects, beetles, butterflies and moths, bees and wasps, flies and thrips contain an estimated 800,000 described species.
Yasmin Asar and Simon Ho from the University of Sydney, and Hervé
Sauquet, Senior Research Scientist at AIBS, recently explored the evidence for co-evolution of flowering plants and their insect pollinators¹. Using a range of molecular markers and dating, combined with the fossil record, they were able to show that there was not congruence between the emergence and initial diversification of angiosperms and the origin and diversification of their key insect pollinators.
Many pollinating orders of insects emerged in the Paleozoic (541–252 million years ago) or early Mesozoic (252–66 million years ago) periods, predating the flowering plants by tens of
Insects and flowering plants interacted with explosive results following the Cretaceous–Paleogene mass extinction event, which occurred when the Chicxulub asteroid crashed into the Yucatán Peninsula of Mexico and resulted in the annihilation of non-avian dinosaurs.
millions of years. There is considerable fossil evidence demonstrating that these insects already had beneficial interactions with groups like conifers and cycads before the flowering plants started to diversify enormously. It was only after the Cretaceous–Paleogene mass extinction event (66 million years ago) that the diversifications of flowering plants and insects had explosive impacts on each other through their species interactions, including pollination.
ENHANCING THE GERMINATION OF RAINFOREST TREES With land clearing, climate change and invasive species threatening rainforests all over the world, seed banks and botanic garden collections are playing an increasingly important role in conserving these species. To do so effectively, we need to better understand how to store these seeds and then to germinate them. Genesha Liyanage, Cathy Offord and Karen Somerville from the Australian PlantBank, together with colleagues from the Australian Tropical Herbarium at James Cook University in Cairns and the Australian National Botanic Garden in Canberra, recently studied dormancy and germination in Tasmannia sp. Mt Bellenden Ker and Tasmannia membranea − two tropical montane rainforest tree species threatened by climate change − to develop a better understanding of dormancy in the species and the genus².
They discovered that while both species display morphophysiological dormancy,^ treatments that remove seedcoat resistance to embryo growth facilitate germination – i.e., making precision cuts (nicking) in the seed coat is an effective dormancy-breaking technique. This also suggests that these treatments may help improve germination in other species from the same genus. This knowledge will greatly aid the germination of seeds to implement ex situ and in situ conservation strategies.
Further studies on stratification conditions, and incubation in different combinations of light levels and temperature regimes may improve our understanding of dormancy-breaking cues in the species’ natural habitat. Additionally, through this project we will have access to some really special rainforest species that are risk of extinction due to climate change. We are understanding their seed biology as well as bringing them into living collections.
HAIRPIN BANKSIAS – HOW MANY SPECIES ARE THERE? The Hairpin Banksia are a very wellknown group of plants, exemplified by Banksia spinulosa, which was first scientifically described in 1793. The group has since been split into a number of species, including Banksia vincentia, B. neoangelica, that are more recently described, as well as the much older B. cunninghamii and B. collina.
Trevor Wilson, Maurizio Rossetto and a range of colleagues recently explored the genetic variability across this group with the aim of determining if they are all one species, or if in fact they are more than one³. They did this by collecting a very large amount of material across the full range of these “species” (thousands of kilometres) and using genomic analysis tools to determine genetic variability and if the different groups were significantly different from one another to warrant species designation.
They found that Banksia spinulosa represents two groups, each with an internal genetic structure that has been shaped through separation by biogeographic barriers. This structure conflicts with the existing taxonomy for the group and clearly supports that there should only be two species, best represented by B. spinulosa and B. cunninghamii. This would mean that B. collina, B. vincentia and B. neoangelica are not species and importantly that B. vincentia should be removed from the threatened species list.
Paper details: 1. Early diversifications of angiosperms and their insect pollinators: were they unlinked? Trends in Plant Science, 2022, doi.org/10.1016/j.tplants.2022.04.004. 2. Understanding seed dormancy and germination aids conservation of rainforest species from tropical montane cloud forest: a case study confirming morphophysiological dormancy in the genus Tasmannia. Australian Journal of Botany doi:10.1071/ BT22011. 3. A turn in species conservation for hairpin Banksias: Demonstration of oversplitting leads to a better management of diversity. American Journal of Botany AJB-D-22-00132R2.
* The relationships between living things and their environments. ^ In morphological dormancy, the embryo is underdeveloped or undifferentiated and takes a long time to germinate.
