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Cutting Edge What’s new in the world of botanical research?
Acacia pycnantha
THE CUTTING EDGE
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RESEARCHERS WORKING WITH THE AUSTRALIAN INSTITUTE OF BOTANICAL SCIENCE PUBLISH MORE THAN 90 PEER-REVIEWED ARTICLES EACH YEAR. PROFESSOR BRETT SUMMERELL HIGHLIGHTS A FEW RECENT PROJECTS.
PLANT DIVERSITY CONSERVATION CHALLENGES A consortium of authors1 – including our own Senior Principal Research Scientist, Dr Cathy Offord – recently examined the contribution that living collections and seed banks based in botanic gardens around the world make to wild plant conservation and to tackling global challenges.
They focused on the advantages and limitations of conservation of plant diversity as both living material and seed collections, and the need for additional research and conservation measures, such as cryopreservation, to enable the long-term conservation of ‘exceptional species’ (such as rainforest species which are difficult to seed bank). In particular, they highlighted the importance of networks and sharing data and plant material.
The skill sets found within botanic gardens and seed banks complement each other and enable the development of integrated conservation (linking in situ and ex situ efforts). The authors demonstrated how botanic gardens and seed banks support integrated conservation and research for agriculture and food security, restoration and reforestation, as well as supporting local livelihoods.
They concluded that botanic gardens and seed banks are well placed to respond to the biodiversity crises, but their conservation efforts need to be massively scaled up and supported by long-term funding. In addition, activities need to be coordinated across institutions, sectors (government agencies, universities, NGOs, etc.), geographies, and political and cultural boundaries. GENOMIC INSIGHT INTO INDIGENOUS DISPERSALS Over millennia, Indigenous peoples have dispersed seeds (and other propagules) of non-crop plants through trade, seasonal migration or attending ceremonies. In the process, they have potentially increased the geographic range and abundance of many food species around the world.
Scientists are now exploring how genomic data might be used to reconstruct how and when this dispersal happened. This research will further highlight the importance of Indigenous people in moving plant species and the importance of plants in their cultures.
In an important new paper2 , Macquarie University PhD student Monica Fahey and colleagues sought to develop a simple and cost-effective strategy to screen out Australian
species with genomic patterns consistent with long-term widespread dispersal by humans and animals. Their strategy also aimed to identify “candidate” species in rainforests that show dispersal signals consistent with spread by Indigenous people.
Large-seeded rainforest species often evolved with now-extinct megafauna, and hence current distribution patterns may either reflect lack of dispersal, or dispersal patterns consistent with human intervention. Some of the key characteristics of spread by Indigenous people are that large-seeded rainforest species generally have greater betweenpopulation genomic divergence and occupy smaller geographic ranges than their small-fruited counterparts. This can be used as a screening strategy that employs simple genomic tests to identify signals of dispersal within long-lived non-crop plant species that may be attributed to Indigenous peoples.
The paper’s authors sought to investigate whether fleshy-fruited species with a known history of Indigenous use carry genomic patterns that are distinctive from expected signatures of widespread faunal dispersal. Their study identified several rainforest species that warrant further investigation.
EVOLUTION OF ACACIA LEAF ADAPTATIONS In Acacia, 90% of species have droughttolerant phyllodes as their adult foliage, with the remaining species having bipinnate leaves. This high preponderance of phyllodes is thought to be an adaptation to the drying of Australia as it moved north during the break-up of Gondwana and a response to the low nutrient soils occurring in most parts of the Acacia’s range.
Most Acacia species (commonly known as Wattle) start off producing bipinnate leaves as juveniles, but this changes quickly as they mature – an indication that bipinnate leaves was an ancestral state as is similar in many plants in the pea family.
The question posed in a recent paper3 by Dr Matt Renner and co-authors from the University of Sydney, Royal Botanic Gardens Victoria and the Global Biodiversity Information Facility in Denmark, is whether the 10% of species that have bipinnate leaves reflect the ancestral state or whether they have re-evolved in response to wetter environments.
Analysis suggests that the most recent common ancestor of Acacia had phyllodes as their adult foliage, and the transition to phyllodes preceded the radiation (i.e., the spread into new habitats) of Acacia.
Most ancestral nodes inferred as having bipinnate adult foliage had median age estimates of less than five million years (Ma), half having ages between 3 Ma and 1.5 Ma. Acacia lineages with bipinnate adult foliage diversified during the Pliocene, perhaps in response to wetter climatic conditions experienced by the continental margin during this period.
These results indicate that some species of wattle have indeed re-evolved bipinnate leaves in response to environmental conditions, which highlights the great adaptability of wattles. Such features may be important in a changing environment.
Glossary Phyllodes: Phyllodes are modified leaf stalks (or stems), which are leaf-like in appearance and function. In some plants (e.g., many wattles) they can become flattened and widened, while the leaf itself is reduced or disappears, and as a result the phyllode serves the purpose of the leaf. Bipinnate: The term pinnation derives from the Latin word pinna meaning 'feather'. In botany, pinnation refers to an arrangement of structures (such as leaflets, branches or lobes) at multiple points along a common axis. It's a feature seen in many palms, cycads and grevilleas. A bipinnate leaf is one in which the leaflets themselves are further subdivided in a pinnate fashion.
A selection of Acacia species (photographed by the Gardens' Systematic Botanist Dr Russell Barrett), showing variation in shoot, flower, phyllode and leaf morphology, not to scale. Clockwise from top left: A. buxifolia, A. varia, A. dimorpha, A. humifusa, A. platycarpa, A. coolgardiensis, A. translucens, A. paradoxa, A. gunnii, A. deltoidea. Bipinnate adult foliage illustrated in top right, others phyllodinous.
Paper details: 1. Elinor Breman, Daniel Ballesteros, Elena CastilloLorenzo, Christopher Cockel, John Dickie, Aisyah Faruk, Katherine O’Donnell, Catherine A. Offord, Samuel Pironon, Suzanne Sharrock and Tiziana Ulian (2021) Plant Diversity Conservation Challenges and Prospects—The Perspective of Botanic Gardens and the Millennium Seed Bank. Plants 2021, 10, 2371. doi.org/10.3390/plants10112371. 2. Monica Fahey, Maurizio Rossetto, Emilie Ens and Andrew Ford (2022) Genomic Screening to Identify Food Trees Potentially Dispersed by Precolonial Indigenous Peoples. Genes 2022, 13, 476. doi.org/10.3390/genes13030476. 3. Matt A. M. Renner, Charles S. P. Foster, Joseph T. Miller and Daniel J. Murphy (2021) Phyllodes and bipinnate leaves of Acacia exhibit contemporary continental-scale environmental correlation and evolutionary transition-rate heterogeneity. Australian Systematic Botany, 2021, 34, 595–608. doi.org/10.1071/SB21009.
