Connectivity of seagrass populations through gene flow along eastern Australia

Connectivity as able to be evaluated using novel genetic markers were developed for three seagrass species–Halophila ovalis, Thalassia hemprichii, Zostera muelleri. These markers provided sufficient resolution to determine... [ view full abstract ]

Connectivity as able to be evaluated using novel genetic markers were developed for three seagrass species–Halophila ovalis, Thalassia hemprichii, Zostera muelleri. These markers provided sufficient resolution to determine clonality i.e. we are able to detect individual plants. We evaluated population structure and connectivity gradients of these species on the eastern coast of Australia.
These species exhibit three different levels of population isolation that reflect the species resilience strategies. Thalassia hemprichii (turtlegrass), reaches its southern limit in the central GBR, has populations that are increasingly clonal towards the southern limit of its distribution, the most southern site achieving uni-clonality. Zostera muelleri reaches its northern distributional limit in the Torres Strait and populations there were found to be highly clonal.
Connectivity was unexpectedly low and we must infer at the sampled scale (Torres Strait to southern GBR) they are regionally isolated. Sites with small numbers of individuals (i.e. larger clones) are at greater risk from stressors, due to low genetic diversity. Due to the relatively limited regional scale of gene flow detected we need to evaluate smaller scales of population connectivity to assess the adaptability of species to changing environmental conditions.
Increasing temperature from southern to northern GBR has contributed to latitudinal variation in species composition and genetic diversity. Future warming will lead to changes in species ranges and their genetic diversity.