Cryptic kelp: Identifying the processes driving divergence within an ecologically important Australian kelp species, Durvillaea potatorum

Speciation in marine ecosystems can be driven by allopatric and/or ecological divergence. Identifying which processes have underpinned speciation events provides insight into patterns of marine dispersal, connectivity and... [ view full abstract ]

Speciation in marine ecosystems can be driven by allopatric and/or ecological divergence. Identifying which processes have underpinned speciation events provides insight into patterns of marine dispersal, connectivity and diversity. Southern bull kelp, Durvillaea potatorum, is an ideal model organism to study the relative influences of historic geographic isolation or ecological divergence on diversification. D. potatorum is an important ecosystem engineer endemic to exposed rocky shores in southeastern Australia. Previous genetic investigation has indicated the presence of cryptic species within D. potatorum. The divergence, and subsequent speciation, between the ‘eastern’ and ‘western’ lineages may be linked to ecological processes or historic geographical separation. My Honours research uses an integrated approach combining molecular, ecological, morphological and histological techniques to investigate and describe cryptic species within D. potatorum and to determine the underlying processes that have resulted in speciation. In February this year, 228 individuals were collected from seven sites around Tasmania’s eastern and western coasts. Sites were selected to provide a range of wave, depth and latitudinal gradients, to cover the range of morphological variability and to include locations where lineages are found sympatrically or independently. For every individual morphological characteristics, such as stipe length, were measured, the depth and exposure level recorded and thallus tissue samples taken for genetic and histology analyses of reproductive structures. Genetic sequencing of mitochondrial (COI) and nuclear (28S) markers will be used to identify which samples belong to each lineage, assess whether hybridisation has occurred, and measure intraspecific variation. Morphological and ecological character differences, and any correlation with the spatial distribution both within and across sites, between the two lineages will be analysed by a range of techniques including non-metric multidimensional scaling and analysis of similarities. This research will resolve taxonomic uncertainty within an ecologically and economically important macroalga, and shed light on the drivers of speciation in coastal marine ecosystems of southeastern Australia.