title: A morphological and phylogenetic investigation into divergence among sympatric Australian southern bull kelps (Durvillaea potatorum and D. amatheiae sp. nov.).
abstract: Genetic analyses can reveal a wealth of hitherto undiscovered cryptic biodiversity. For co-occurring and morphologically similar species, the combination of molecular, ecological and morphological analyses provides an excellent opportunity for understanding some of the processes that can lead to divergence and speciation. The Australian endemic brown macroalga Durvillaea potatorum (Phaeophyceae) was examined with a combination of genetic and morphological approaches to confirm the presence of two separate species and to infer the processes that led to their divergence. A total of 331 individuals from 11 sites around coastal Tasmania were collected and measured in situ for a range of morphological and ecological characteristics. Tissue samples were also collected for each individual to allow genetic analyses using mitochondrial (COI) and nuclear (28S) markers. Genetic analyses confirmed the presence of two deeply divergent clades. The significant morphological differentiation, despite high levels of intra-lineage variability, further supported their recognition as distinct species. We describe a new species, D. amatheiae sp. nov., which is characterised by a narrower and proportionately shorter stipe, shorter total length, and higher number of stipitate lateral blades and branches than D. potatorum (sensu stricto). The occurrence of both species in sympatry along Tasmania's eastern and western coasts, as well as their contrasting patterns of haplotype diversity, supports a hypothesis of geographical isolation, allopatric speciation and subsequent secondary contact in response to sea level and ocean current change throughout the Pleistocene glaciation cycles. This research contributes to resolving the phylogenetic relationships, taxonomy and evolution of the ecologically keystone kelp genus Durvillaea.
authors.affiliation: Fenner School of Environment and Society, Australian National University, Building 141, Linnaeus Way, Acton ACT 2601, Australia. Electronic address: xweber@palaeome.org.
authors.forename: Xénia A
authors.initials: XA
authors.lastname: Weber
authors.affiliation: Institute for Marine and Antarctic Studies, University of Tasmania, GPO Box 252-49, Hobart, Tasmania 7001, Australia.
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Edgar
authors.affiliation: Fenner School of Environment and Society, Australian National University, Building 141, Linnaeus Way, Acton ACT 2601, Australia.
authors.forename: Sam C
authors.initials: SC
authors.lastname: Banks
authors.affiliation: Department of Zoology, University of Otago, 340 Great King Street, Dunedin 9016, New Zealand.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Waters
authors.affiliation: Fenner School of Environment and Society, Australian National University, Building 141, Linnaeus Way, Acton ACT 2601, Australia.
authors.forename: Ceridwen I
authors.initials: CI
authors.lastname: Fraser
mesh_terms: D001315:Australia; D001483:Base Sequence; D004272:DNA, Mitochondrial / Q000235:genetics; D017753:Ecosystem; D014644:Genetic Variation; D005843:Geography; D006239:Haplotypes; D044423:Kelp / Q000145:classification* / Q000235:genetics*; D015999:Multivariate Analysis; D010802:Phylogeny; D061350:Sympatry / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial
keywords: Cryptic species; Hybridisation; Macroalgae; Marine; Phenotypic plasticity; Phylogeography