Growth & Development

Variation in reproduction and genetic diversity across seagrass meadows in Western Australia

How do reproductive effort, genetic diversity and mating systems vary across the range of a seagrass population?

Seagrasses are ancient marine flowering plants, of which most species complete their life cycle entirely underwater. Globally, 24 % of species are classified as ‘threatened’ or ‘near-threatened’ on the IUCN’s Red List, with the rate of decline continuing to increase due to human activities including climate change. Plant species including seagrasses reproduce using sexual (seeds) and asexual (vegetative) means which can vary across a species range. Populations at the edges of their geographical range tend to have lower genetic diversity, smaller effective population sizes and limited connectivity relative to centralised populations. Edge populations are also likely to be better adapted to more extreme conditions for future survival and resilience in warming environments. However, they may also be most at risk of extinction from changing climate.

Posidonia australis inflorescences emerging from the leaf canopy. Male anthers (brownish to red) on hermaphroditic flowers mature from the base of each inflorescence upwards. Image credit: A. Rossen.

In their new study published in AoBP, Sinclair et al. compare sexual reproduction, genetic diversity and the mating system in Posidonia australis seagrass meadows from Western Australia, specifically at Shark Bay World Heritage Site on the northern edge of the species’ range and in Perth metropolitan waters in the centre of the range. Flower and fruit production were two orders of magnitude lower in Shark Bay meadows and they had lower genetic diversity and a mixed mating system when compared with meadows in Perth. These results indicate that seagrass restoration in Shark Bay may benefit from sourcing plant material from multiple reproductive meadows to increase outcrossed pollination and seed production for natural recruitment. Ongoing research into the role of adaptation, acclimation and plasticity in range edge seagrass meadows may shed light on how these meadows with reduced sexual reproduction and outcrossing rates may overcome additional challenges across a salinity gradient under changing climates.

Research highlight

Elizabeth Sinclair completed a Bachelor of Science with honours at the Australian National University and a PhD in Zoology from The University of Western Australia. An extended post-doctoral position in the United States covered a broad range of species from terrestrial and aquatic environments, researching genetic structure at different spatial scales and taxonomic levels. On returning to Australia in 2003, Liz has applied her skills to addressing conservation and restoration issues for Western Australia’s terrestrial and now marine plants.

Liz is an evolutionary biologist. Her current research focuses on genomic diversity, gene expression and adaptation in changing marine environmental conditions for Shark Bay’s large temperate seagrasses. This research contributes to an understanding of the processes impacting on marine connectivity across the Australian continental shelf ecosystems and makes an important contribution to the development of benthic biodiversity conservation planning and restoration practices.

>