Uncovering the genetic basis for growth rate variation in a dominant kelp speciesMacroalgal Traits

Samuel Starko¹, Celina Burkholz1¹, Jane Edgeloe¹, Antoine Minne¹, Karen Filbee-Dexter^1,2, David Wheeler³, Jacqueline Batley¹, Melinda Coleman^3,1, Thomas Wernberg^1,2

¹University of Western Australia, Australia - ²Institute of Marine Research, Norway - ³Coffs Harbour, Australia

Understanding the genetic architecture of functional traits can provide key insights into the ecological dynamics and adaptive potential of species. We investigated the genetic basis of variation in growth rate in the widespread and dominant kelp species, Ecklonia radiata. Kelps were tagged by SCUBA divers and their growth tracked in situ over the spring season where growth is maximal. Individual kelps were genotyped using reduced representation sequencing. We then employed genome-wide association (GWAS) analysis and latent factor mixed effect modelling (LFMM) to assess the genetic contribution to variation in growth rate. We found evidence, that growth rate is underpinned by a major genetic component, with more than half of variation in growth rate predicted by only 20 loci. Analysis of published transcriptomic data confirm that most of these loci are expressed or are linked to expressed putative genes. However, at this point these genes are mostly of unknown function and/or do not match well-known gene families, suggesting that regulation of growth rate in brown algae is different from pathways known from other multicellular eukaryotes. The potential for a strong, heritable genetic component driving variation in growth rate of kelp has important implications both for understanding natural dynamics of this critical group of species and for applied approaches such as selective breeding and aquaculture.