A project undertaken at the Centre for Integrative Legume Research, School of Biological Sciences, Monash University, and supervised by Dr Kathryn Hodgins
Australian grasslands are unique ecosystems harbouring many endemic species. In south-eastern Australia, less than 1% of native grasslands remain, in dwindling remnant patches. Ecological restoration seeks to reverse this historic tide of degradation, but the challenges are many. We have used native grass species in the _Bothriochloa_genus as a test case to develop genomics resources and methods to aid managers when making planting decisions. There has been limited development of methods to integrate genomic information with future climate predictions to provide tangible recommendations to managers who are actively sourcing seeds. Our study tackles this knowledge gap.
We first conducted experiments by growing a diverse array of genotypes originating from a broad climatic gradient in multiple environments. We found evidence consistent with adaptation to local climate, whereby biomass traits correlated with historic patterns of aridity, particularly in early life stages. This suggests that the choice of genotype may impact establishment success depending on the local planting environment. These data have allowed us to identify seed sources that when utilised for restoration may make the grassland more resilient to predicted future drought conditions.
We completed the first high quality genome assembly of an Australian native grass used in restoration. Further, we identified an ancient whole genome duplication in the genus. The genome assembly and annotation will provide resources needed to do genomics studies to find signals of local adaptation to climate related factors. It will also facilitate the identification genetic differences among populations that may result in outbreeding depression, and hence should not be mixed during restoration. This genomic resource will aid in developing the genus as a newsystem for studying the utility of genomics for assisted gene flow in grasses.
We sequenced DNA from 40 populations across southeast Australia to assess the adaptive genetic landscape of these Bothriochloa species. This information is being integrated with ecological modelling to assess adaptive variation in restoration stocks with respect to future climates. We will then integrate the genomic, phenotypic and climate information to predict the impacts of different climate change scenarios. Decision analysis will be used to make planting recommendations based on the outcome of the simulations.
We used evolutionary simulations to examine how adaptation along climatic gradients impacts population persistence in the face of climate change and how different seed sourcing strategies may mitigate extinction. A key result is that the genetic basis of multiple traits can evolve in ways that can prevent assisted gene flow from rescuing populations from extinction. This can be the case when selective forces that drive local adaptation shift in contrasting ways with climate change.