Molecular phylogeny of the Notostraca

Abstract

a b s t r a c tWe used a combined analysis of one nuclear (28S rDNA) and three mitochondrial markers (COI, 12S rDNA, 16S rDNA) to infer the molecular phylogeny of the Notostraca, represented by samples from the six continents that are inhabited by this group of branchiopod crustaceans. Our results confirm the monophyly of both extant notostracan genera Triops and Lepidurus with good support in model based and maximum parsimony analyses. We used branchiopod fossils as a calibration to infer divergence times among notostracan lineages and accounted for rate heterogeneity among lineages by applying relaxed-clock models. Our divergence date estimates indicate an initial diversification into the genera Triops and Lepidurus in the Mesozoic, most likely at a minimum age of 152.3-233.5 Ma, i.e., in the Triassic or Jurassic. Implications for the interpretation of fossils and the evolution of notostracan morphology are discussed. We further use the divergence date estimates to formulate a biogeographic hypothesis that explains distributions of extant lineages predominantly by overland dispersal routes. We identified an additional hitherto unrecognised highly diverged lineage within Lepidurus apus lubbocki and three additional previously unknown major lineages within Triops. Within T. granarius we found deep differentiation, with representatives distributed among three major phylogenetic lineages. One of these major lineages comprises T. cancriformis, the T. mauritanicus species group and two hitherto unrecognised T. granarius lineages. Samples that were morphologically identified as T. granarius diverged from the most basal 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 fossils that are currently attributed to the extant T. cancriformis. We thus elevate T. cancriformis minor to full species status as Triops minor Trusheim, 1938 and include in this species the additional Upper Triassic samples that were attributed to T. cancriformis. We further elevate T. cancriformis permiensis to full species status as Triops permiensis Gand et al., 1997.

Updated checklist and distribution of large branchiopods (Branchiopoda: Anostraca, Notostraca, Spinicaudata) in Tunisia

“…further emphasized the noteworthy cryptic diversity lumped under this binomen. Korn et al (2013) even demonstrated that T. granarius is paraphyletic with respect to the remaining congeneric species, thus further highlighting the need for a revision of the taxon. Other references: Seurat (1922), Longhurst (1955), Turki and Turki (2010).…”

“…Mantovani et al 2009, Korn et al 2013, further evidence is needed in order to clarify which of the populations presently attributed to this subspecies might actually refer to the former L. lubbocki described by Brauer (1873). The situation is complicated by the fact that L. a. lubbocki turned out to be paraphyletic with respect to the remaining species in the genus hitherto studied via molecular tools (see Figs. 1 and 2 in Korn et al 2013). Furthermore, no specimens from the type locality have ever been investigated using modern methods, so that a possible taxonomical re-instatement should await a profound re-investigation of Circum-Mediterranean populations.…”

“…Large branchiopod nomenclature was based on Korn et al ( , 2010Korn et al ( , 2013 and for the Notostraca, and on Belk and Brtek (1995) and Rogers (2013) for the Anostraca, with the only exception of Phallocryptus spinosus (Milne-Edwards, 1840). In fact, the halophilic thamnocephalid originally described as Branchipus spinosus by Milne-Edwards (1840), transferred to the genus Branchinecta Verrill, 1869 by Simon (1886) and later to the genus Branchinella Sayce, 1903by Daday (1910, was convincingly demonstrated to belong to the genus Phallocryptus Biraben, 1951 by Rogers (2003).…”

“…Although recent molecular evidence suggests that this taxon probably deserves species status (e.g. Mantovani et al 2009, Korn et al 2013, further evidence is needed in order to clarify which of the populations presently attributed to this subspecies might actually refer to the former L. lubbocki described by Brauer (1873). The situation is complicated by the fact that L. a. lubbocki turned out to be paraphyletic with respect to the remaining species in the genus hitherto studied via molecular tools (see Figs. 1 and 2 in Korn et al 2013).…”

How do freshwater organisms cross the “dry ocean”? A review on passive dispersal and colonization processes with a special focus on temporary ponds

“…Moreover, dispersal often occurs through multiple processes and vectors (Higgins et al, 2003). In this review, we will put a special focus on temporary water bodies, since these ecosystems represent biodiversity hotspots (Williams et al, 2001;Zacharias et al, 2007) and their functioning and conservation strictly depends on the dispersal and colonization abilities of their biota (Sahuquillo & Miracle, 2013;Marrone et al, 2013;Korn et al, 2013). Moreover, temporary ponds, alternating flooded and dry phases, add the duration of their ponding phase as a further temporal dimension to their ''insular features'' (Ebert & Balko, 1987;NaselliFlores & Barone, 2012).…”