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Straube N.,Zoologische Staatssammlung Munich | Straube N.,Friedrich - Schiller University of Jena | Lampert K.P.,Ruhr University Bochum | Geiger M.F.,Zoologisches Forschungsmuseum Alexander Koenig Bonn | And 2 more authors.
Journal of Fish Biology | Year: 2016

In this study, two parthenogenetic events within a family of the whitespotted bambooshark Chiloscyllium plagiosum are reported. A captive female produced multiple parthenogens. Unexpectedly, a single specimen of a total of nine parthenogens displayed external claspers characterizing the male sex in chondrichthyans. Upon dissection, internal sexual organs of this specimen were malformed or absent; however, the presence of claspers in this study challenges the as yet assumed sex determination system in this shark species. Even more remarkable was that one of the female parthenogens reproduced asexually again producing viable offspring. As far as is known, this is the first genetically confirmed evidence for second-generation facultative parthenogenesis in vertebrates. These results support the evolutionary significance of parthenogenesis as an alternative to sexual reproduction. © 2016 The Fisheries Society of the British Isles. Source

Ahrens D.,Natural History Museum in London | Schwarzer J.,Zoologisches Forschungsmuseum Alexander Koenig Bonn | Schwarzer J.,University of Bern | Schwarzer J.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | And 2 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2014

Extant terrestrial biodiversity arguably is driven by the evolutionary success of angiosperm plants, but the evolutionary mechanisms and timescales of angiosperm-dependent radiations remain poorly understood. The Scarabaeoidea is a diverse lineage of predominantly plant- and dung-feeding beetles. Here, we present a phylogenetic analysis of Scarabaeoidea based on four DNA markers for a taxonomically comprehensive set of specimens and link it to recently described fossil evidence. The phylogeny strongly supports multiple origins of coprophagy, phytophagy and anthophagy. The ingroupbased fossil calibration of the tree widely confirmed a Jurassic origin of the Scarabaeoidea crown group. The crown groups of phytophagous lineages began to radiate first (Pleurostict scarabs: 108 Ma; Glaphyridae between 101 Ma), followed by the later diversification of coprophagous lineages (crown-group age Scarabaeinae: 76 Ma; Aphodiinae: 50 Ma). Pollen feeding arose even later, at maximally 62 Ma in the oldest anthophagous lineage. The clear time lag between the origins of herbivores and coprophages suggests an evolutionary path driven by the angiosperms that first favoured the herbivore fauna (mammals and insects) followed by the secondary radiation of the dung feeders. This finding makes it less likely that extant dung beetle lineages initially fed on dinosaur excrements, as often hypothesized. © 2014 The Author(s) Published by the Royal Society. All rights reserved. Source

Eberle J.,Zoologisches Forschungsmuseum Alexander Koenig Bonn | Walbaum W.,Zoologisches Forschungsmuseum Alexander Koenig Bonn | Warnock R.C.M.,Smithsonian Institution | Fabrizi S.,Natural History Museum in London | Ahrens D.,Natural History Museum in London
Molecular Phylogenetics and Evolution | Year: 2015

Left-right asymmetry is a frequently encountered phenomenon in the copulation organs of insects. While various causes have been proposed for genital asymmetry, we raise the question of whether asymmetry might facilitate, or even accelerate, morphological divergence of genitalia between species. We tested this hypothesis in the scarab chafer genus Schizonycha, which comprises species with symmetric as well as asymmetric male genitalia. Morphometric analyses were conducted in the context of their phylogeny, inferred from mitochondrial and nuclear ribosomal DNA sequence data (cox1, rrnL, and 28S) for a sample of 99 South African specimens. , including 34 species and 5 outgroup taxa. Trees were reconstructed with maximum likelihood and Bayesian analysis. The extent of asymmetry and the variation of male copulation organs were analyzed with Generalized Procrustes analysis (GPA), by quantifying shape divergence of the parameres. We found a continuous transition in the degree of asymmetry among the investigated species. Ancestral state reconstruction revealed multiple origins and a high degree of evolutionary plasticity of paramere asymmetry in Schizonycha. However, no significant correlation between evolutionary rates of paramere shape divergence and the degree of paramere asymmetry was found, and so we conclude that asymmetric genitalia in Schizonycha do not increase the rate of genital shape divergence. © 2015 Elsevier Inc. Source

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