We used a combined analysis of one nuclear (28S rDNA) and three mitochondrial markers (COI, 12SrDNA, 16S rDNA) to infer the molecular phylogeny of the Notostraca, represented by samples from thesix continents that are inhabited by this group of branchiopod crustaceans. Our results confirm themonophyly of both extant notostracan genera Triops and Lepidurus with good support in model basedand maximum parsimony analyses. We used branchiopod fossils as a calibration to infer divergencetimes among notostracan lineages and accounted for rate heterogeneity among lineages by applyingrelaxed-clock models. Our divergence date estimates indicate an initial diversification into the genera Triopsand Lepidurus in the Mesozoic, most likely at a minimum age of 152.3–233.5 Ma, i.e., in the Triassic orJurassic. Implications for the interpretation of fossils and the evolution of notostracan morphology arediscussed. We further use the divergence date estimates to formulate a biogeographic hypothesis thatexplains distributions of extant lineages predominantly by overland dispersal routes. We identified anadditional hitherto unrecognised highly diverged lineage within Lepidurus apus lubbocki and three additionalpreviously unknown major lineages within Triops. Within T. granarius we found deep differentiation,with representatives distributed among three major phylogenetic lineages. One of these majorlineages comprises T. cancriformis, the T. mauritanicus species group and two hitherto unrecognised T. granariuslineages. Samples that were morphologically identified as T. granarius diverged from the mostbasal nodes within this major lineage, and divergence dates suggested an approximate age of 23.7–49.6 Ma for T. cancriformis, indicating the need for a taxonomic revision of Triassic and Permian fossilsthat are currently attributed to the extant T. cancriformis.We thus elevate T. cancriformis minor to full speciesstatus as Triops minor Trusheim, 1938 and include in this species the additional Upper Triassic samplesthat were attributed to T. cancriformis. We further elevate T. cancriformis permiensis to full speciesstatus as Triops permiensis Gand et al., 1997.
|Numero di pagine||13|
|Rivista||Molecular Phylogenetics and Evolution|
|Stato di pubblicazione||Published - 2013|
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