title: Highly divergent mussel lineages in isolated Indonesian marine lakes.
abstract: Marine lakes, with populations in landlocked seawater and clearly delineated contours, have the potential to provide a unique model to study early stages of evolution in coastal marine taxa. Here we ask whether populations of the musselBrachidontesfrom marine lakes in Berau, East Kalimantan (Indonesia) are isolated from each other and from the coastal mangrove systems. We analyzed sequence data of one mitochondrial marker (Cytochrome Oxidase I (COI)), and two nuclear markers (18S and 28S). In addition, we examined shell shape using a geometric morphometric approach. The Indonesian populations ofBrachidontesspp. harbored four deeply diverged lineages (14-75% COI corrected net sequence divergence), two of which correspond to previously recorded lineages from marine lakes in Palau, 1,900 km away. These four lineages also showed significant differences in shell shape and constitute a species complex of at least four undescribed species. Each lake harbored a different lineage despite the fact that the lakes are separated from each other by only 2-6 km, while the two mangrove populations, at 20 km distance from each other, harbored the same lineage and shared haplotypes. Marine lakes thus represent isolated habitats. As each lake contained unique within lineage diversity (0.1-0.2%), we suggest that this may have resulted fromin situdivergence due to isolation of founder populations after the formation of the lakes (6,000-12,000 years before present). Combined effects of stochastic processes, local adaptation and increased evolutionary rates could produce high levels of differentiation in small populations such as in marine lake environments. Such short-term isolation at small spatial scales may be an important contributing factor to the high marine biodiversity that is found in the Indo-Australian Archipelago.
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA, USA; Department of Marine Animal Ecology, Wageningen University & Research, Wageningen, The Netherlands; Department of Marine Biodiversity, Naturalis Biodiversity Center, Leiden, The Netherlands.
authors.forename: Leontine E
authors.initials: LE
authors.lastname: Becking
authors.affiliation: Department of Marine Animal Ecology, Wageningen University & Research, Wageningen, The Netherlands; Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Christiaan A
authors.initials: CA
authors.lastname: de Leeuw
authors.affiliation: Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam , Amsterdam , The Netherlands.
authors.forename: Bram
authors.initials: B
authors.lastname: Knegt
authors.affiliation: Department of Marine Animal Ecology, Wageningen University & Research , Wageningen , The Netherlands.
authors.forename: Diede L
authors.initials: DL
authors.lastname: Maas
authors.affiliation: Department of Marine Biodiversity, Naturalis Biodiversity Center , Leiden , The Netherlands.
authors.forename: Nicole J
authors.initials: NJ
authors.lastname: de Voogd
authors.affiliation: Faculty of Fisheries and Marine Sciences, Mulawarman University , Samarinda , East Kalimantan , Indonesia.
authors.lastname: Abdunnur
authors.affiliation: Faculty of Fisheries and Marine Sciences, Mulawarman University , Samarinda , East Kalimantan , Indonesia.
authors.forename: Iwan
authors.initials: I
authors.lastname: Suyatna
authors.affiliation: Department of Marine Biodiversity, Naturalis Biodiversity Center, Leiden, The Netherlands; Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Katja T C A
authors.initials: KT
authors.lastname: Peijnenburg
keywords: Anchialine; East Kalimantan; Geometric morphometrics; Mytillidae; Phylogeography; Speciation