Genetic connectivity of the seagrass Thalassia hemprichii in the Kimberley and Pilbara, Western Australia

The seagrass Thalassia hemprichii is a foundation species and widely distributed in the Indo-Pacific. It inhabits intertidal and subtidal areas along the tropical coast of Western Australia, from the Muiron Islands in the... [ view full abstract ]

The seagrass Thalassia hemprichii is a foundation species and widely distributed in the Indo-Pacific. It inhabits intertidal and subtidal areas along the tropical coast of Western Australia, from the Muiron Islands in the Pilbara to the Kimberley in the north, and is a key food source for dugongs and green turtles. Due to its buoyant fruits, it has the potential to disperse over 100’s of km. This study aims to investigate the population connectivity in the Kimberley, provide insight into their resilience and contribute to the design and spatial management of seagrass in the region. We collected seagrass samples from 13 meadows in the Kimberley and 3 meadows in the Pilbara. Genetic variability, population structure and gene flow were analysed based on 16 polymorphic microsatellite loci. We presented our preliminary results here. There was little evidence of connection between the Pilbara and Kimberley populations; these formed two distinct clusters, suggesting that the Pilbara and the Kimberley are discrete management units. We also detected three significant sub-populations clusters within the Kimberley. However, the clustering pattern did not coincide well with the meadows’ geographical situation, in which two meadows separated only 8km were found in different clusters. This pattern was in conjunction with the very low levels of gene flow detected between these meadows. Connectivity within the Kimberley was characterized by a predominantly north-to-south direction of gene flow that is in contrast with the south-to-north direction of gene flow among meadows within the Pilbara. Hydrodynamic factors might be responsible in determining the pattern of connectivity in this region. We also found clones (identical individuals = multi locus genotypes) that were shared among populations. This finding indicated that the seagrass connectivity was also facilitated potentially by vegetative dispersal and clonal growth.