Impact of a mouth parasite in a marine fish differs between geographical areas

Considerable variation exists in parasite virulence and host tolerance which may have a genetic and/or environmental basis. In this article, we study the effects of a striking, mouth‐dwelling, blood‐feeding isopod parasite (Ceratothoa italica) on the life history and physiological condition of two Mediterranean populations of the coastal fish, Lithognathus mormyrus. The growth and hepatosomatic index (HSI) of fish in a heavily human‐exploited population were severely impacted by this parasite, whereas C. italica showed negligible virulence in fish close to a marine protected area. In particular, for HSI, the parasite load explained 34.4% of the variation in HSI in the exploited population, whereas there was no significant relationship (0.3%) between parasite load and HSI for fish in the marine protected area. Both host and parasite populations were not differentiated for neutral genetic variation and were likely to exchange migrants. We discuss the role of local genetic adaptation and phenotypic plasticity, and how deteriorated environmental conditions with significant fishing pressure can exacerbate the effects of parasitism. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 842–852.     

Multiple refugia and barriers explain the phylogeography of the Valais shrew,Sorex antinorii (Mammalia: Soricomorpha)

The aim of the present study was to investigate the genetic structure of the Valais shrew (Sorex antinorii) by a combined phylogeographical and landscape genetic approach, and thereby to infer the locations of glacial refugia and establish the influence of geographical barriers. We sequenced part of the mitochondrial cytochrome b (cyt b) gene of 179 individuals of S. antinorii sampled across the entire species' range. Six specimens attributed to S. arunchi were included in the analysis. The phylogeographical pattern was assessed by Bayesian molecular phylogenetic reconstruction, population genetic analyses, and a species distribution modelling (SDM)‐based hindcasting approach. We also used landscape genetics (including isolation‐by‐resistance) to infer the determinants of current intra‐specific genetic structure. The phylogeographical analysis revealed shallow divergence among haplotypes and no clear substructure within S. antinorii. The starlike structure of the median‐joining network is consistent with population expansion from a single refugium, probably located in the Apennines. Long branches observed on the same network also suggest that another refugium may have existed in the north‐eastern part of Italy. This result is consistent with SDM, which also suggests several habitable areas for S. antinorii in the Italian peninsula during the LGM. Therefore S. antinorii appears to have occupied disconnected glacial refugia in the Italian peninsula, supporting previous data for other species showing multiple refugia within southern refugial areas. By coupling genetic analyses and SDM, we were able to infer how past climatic suitability contributed to genetic divergence of populations. The genetic differentiation shown in the present study does not support the specific status of S. arunchi. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 864–880.     

Nesting strategies affect altitudinal distribution and habitat use in Alpine dung beetle communities

1. Dung beetles are key contributors to a suite of ecosystem services. Understanding the factors that dictate their distributions is a necessary step towards preventing negative impacts of biodiversity loss. 2. Alpine dung beetle communities were analysed along altitudinal gradients to assess how different components of the community, defined in terms of nesting strategy [dung‐ovipositing Aphodiidae (DOAs), soil‐ovipositing Aphodiidae (SOAs) and two paracoprid (PAR) groups, Geotrupidae and Scarabaeidae] and parameters relevant to dung removal rates (species richness, total biomass and functional diversity), are distributed, and to identify to which environmental factors they respond. 3. Species richness declined with altitude. There was no significant variation in functional diversity or total biomass in relation to altitude. There were significant variations when considered by nesting group: DOA species richness and biomass decreased, SOA biomass increased, and Geotrupidae biomass showed a non‐linear trend, as altitude increased. 4. Functional diversity and total species richness were positively related to vegetation cover. DOA species richness was highest in forest and scrub; SOA species richness was highest in grassland and PAR species richness was lowest in rocky areas. 5. Dung beetle species show different trends in species richness and biomass depending on nesting strategy. Management to promote the dung beetle community should include maintenance of a mosaic of habitat types. Given the likely importance of species richness and biomass to ecosystem functioning, and the complimentary effect of different dung beetle groups, such a strategy may protect and enhance the ecosystem services that Alpine dung beetles provide.     

Myriapod metamerism and arthropod segmentation

Outstanding progress in understanding segmentation of tracheate arthropods (Atelocerata), i.e. Chilopoda, Diplopoda, Pauropoda, Symphyla and Insecta, has been gained through experimental studies carried out on a single, very derivative organism, i.e. Drosophila. We stress the need for a broader comparative approach. We have studied the segmental structure of the trunk in geophilomorph centipedes, where we can identify morphogenetic units of two, four, eight or 16 segments. Accordingly, we sketch an improved model for arthropod segmentation, with the following initial steps: (a) biochemical marking of a very few repetitive units (eosegments); (b) iterative duplications of this first periodicity, until the embryo acquires an array of biochemical markings matching the whole number of segments of the future larva or juvenile specimen; (c) transpatterning, stabilization and interpretation of this 'segmental' arrangement; (d) possible repatterning, to give a final repetitive pattern we define as metasegmental. Finally, we express some doubt about the homology between annelid and arthropod segmentation.     

Phylogeography of European sea bass in the north‐east Atlantic: a correction and reanalysis of the mitochondrial DNA data from Coscia & Mariani (2011)

The re‐analysis of mtDNA sequence data on sea bass (Dicentrarchus labrax) in the north‐east Atlantic revealed the presence of a ‘slippage error’ in the alignment of the mitochondrial DNA (mtDNA) control region sequences. This induced an overestimation of the genetic variability within this species, and hence the inference of a striking multi‐clade partitioning of D. labrax populations within this area. After correction, the existence of highly distinct D. labrax haplogroups in Atlantic areas does not hold anymore, but the robust dichotomy between a single Mediterranean and a single Atlantic subgroup is confirmed. Here we present the new results related to the amended mtDNA control region alignment, and also summarize the key message in relation to the microsatellite data, which are unaffected by this revision. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 455–458.     

Trophic dynamics within a hybrid zone – interactions between an abundant cyprinid hybrid and sympatric parental species

1. Recent proliferation of hybridisation in response to anthropogenic ecosystem change, coupled with increasing evidence of the importance of ancient hybridisation events in the formation of many species, has moved hybridisation to the forefront of evolutionary theory. 2. In spite of this, the mechanisms (e.g. differences in trophic ecology) by which hybrids co‐exist with parental taxa are poorly understood. A unique hybrid zone exists in Irish freshwater systems, whereby hybrid offspring off two non‐native cyprinid fishes often outnumber both parental species. 3. Using stable isotope and gut content analyses, we determined the trophic interactions between sympatric populations of roach (Rutilus rutilus), bream (Abramis brama) and their hybrid in lacustrine habitats. 4. The diet of all three groups displayed little variation across the study systems, and dietary overlap was observed between both parental species and hybrids. Hybrids displayed diet, niche breadth and trophic position that were intermediate between the two parental species while also exhibiting greater flexibility in diet across systems.