Putative speciation events in Lamellodiscus (Monogenea: Diplectanidae) assessed by a morphometric approach

In the present study, we used morphometry as a proxy to study the microevolution of generalist Lamellodiscus (Monogenea, Diplectanidae) species, comprising gill parasites of sparid fish. We investigated 147 individuals, belonging to nine described species, regrouped in four morphotypes. Morphometric measurements were taken on sclerotized parts of the attachment organ. The formation of groups on the basis of the global morphometry within a host species, or between several host species, was assessed using both exploratory analyses (principal component analysis and clustering analysis) and statistical tests. We showed that: (1) for three out of four morphotypes, the global morphometry was significantly different according to host species used, and (2) the coexistence of two populations of Lamellodiscus elegans on Diplodus sargus could reflect an ongoing intra‐host speciation event. We suggest that generalist Lamellodiscus are undergoing specialization on their different hosts, which may lead to speciation. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 559–569.     

Functional diversity is positively associated with biomass for lake diatoms

1. Recent work has emphasised the benefit of using functional measures when relating biodiversity to ecosystem functioning. In this study, we investigated the extent to which functional and taxonomic diversity might be related to summed biovolume in community assemblages of 212 species of diatoms collected from 65 temperate lakes in western and central Quebec, Canada. 2. We quantified functional diversity as both the total path‐length of a functional dendrogram (FD) and the variance in species traits (TV) for a given community. Selected traits included both size and responses to a set of environmental variables known to be influential for diatom communities. 3. Species richness, as well as both FD and TV, was positively associated with total diatom biovolume at the level of the entire diatom community, suggesting that diversity in response types (particularly to total phosphorus and pH) is important for diatom community production. 4. Although functional measures of diversity did not provide enhanced explanatory power over species richness, we argue that an exploration of functional traits potentially allows greater insight into the mechanisms underlying biodiversity–ecosystem functioning relations, indicating which traits might be most influential in driving community biomass production.     

Radial growth response of four dominant boreal tree species to climate along a latitudinal gradient in the eastern Canadian boreal forest

To address the central question of how climate change influences tree growth within the context of global warming, we used dendroclimatological analysis to understand the reactions of four major boreal tree species –Populus tremuloides, Betula papyrifera, Picea mariana, and Pinus banksiana– to climatic variations along a broad latitudinal gradient from 46 to 54°N in the eastern Canadian boreal forest. Tree‐ring chronologies from 34 forested stands distributed at a 1° interval were built, transformed into principal components (PCs), and analyzed through bootstrapped correlation analysis over the period 1950–2003 to identify climate factors limiting the radial growth and the detailed radial growth–climate association along the gradient. All species taken together, previous summer temperature (negative influences), and current January and March–April temperatures (positive influences) showed the most consistent relationships with radial growth across the gradient. Combined with the identified species/site‐specific climate factors, our study suggested that moisture conditions during the year before radial growth played a dominant role in positively regulating P. tremuloides growth, whereas January temperature and growing season moisture conditions positively impacted growth of B. papyrifera. Both P. mariana and P. banksiana were positively affected by the current‐year winter and spring or whole growing season temperatures over the entire range of our corridor. Owing to the impacts of different climate factors on growth, these boreal species showed inconsistent responsiveness to recent warming at the transition zone, where B. papyrifera, P. mariana, and P. banksiana would be the most responsive species, whereas P. tremuloides might be the least. Under continued warming, B. papyrifera stands located north of 49°N, P. tremuloides at northern latitudes, and P. mariana and P. banksiana stands located north of 47°N might benefit from warming winter and spring temperatures to enhance their radial growth in the coming decades, whereas other southern stands might be decreasing in radial growth.     

Organisation de type tétracoralliaire des rides septales de Palaeacis (Cnidaria, Carbonifére)

Plusquellec, Y., Lafuste, J. & Webb, G. E. 1990 10 15: Organisation de type tétracoralliaire des rides septales de Palaeacis (Cnidaria, Carbonifére). Lethaia, Vol. 23, pp. 385–397. Oslo. ISSN 0024–1164. Precedemment signalée chez Kerforneidictyum (Pleurodictyforme dévonien), la rare disposition des rides septales suivant un mode tétracoralliaire est décrite chez un Palaeack sp. du Viséen d'Algérie et chez P. cuneiformis subsp. A du Viseen d'Australie. Chez Palaeacis sp. sont mises en evidence une ride septale cardinale forte en position externe opposée à une ride antipode déterminant un plan de symétrie bilatérale; de part et d'autre une zone systématiquement confuse marque l'emplacement des rides alaires. La reconnaissance des périantipodes prête à discussion et ce secteur présente une originalité certaine par rapport à celui des Tétracoralliaires. Chez P. cuneiformis subsp. A, une coupe transversale montre la présence de quatre rides proéminentes qui fusionnent dans I'axe du corallite et I'existence d'une symétrie bilatérale. La position systématique du genre Palaeacis est discutée: son attribution aux Tétracoralliaires est exclue, ancun caractére n'est incompatible avec le statut de Tabulé, la création d'une unité taxon-omique nouvelle regroupant Palaeacis, Trachypsammia et les Pleurodictyformes est envisageable mais actuellement prématurée. ? Palaeacis, Tabulata, Rugosa, rides septales, systématique, relations deparenré, Viséen. The tetracoral pattern of septal ridges described in Kerforneidictyum (Devonian Pleurodictyum-like coral) is scar'ce in the Tabulata, but has been found in Palaeacis sp. from the Visean of Algeria and in P. cuneiformis subsp. A from the Visean of Australia. Palaeacis sp. shows a strong cardinal septal ridge in peripheral position, just opposite the counter ridge. thus creating a plane of bilateral symmetry: an area on both sides. which is always blurred, indicates the position of the alar ridges. counter-lateral ridges are not easily identified and yield differing interpretation. Compared with the Rugosa this area presents distinctive features. In P. cuneiformis subsp. A, a transverse section exhibits four well-developed septal ridges that coalesce in the axis of the corallite with obvious bilateral symmetry. The systematic position of the genus Palaeacis is questioned: Rugosa it is not; it may belong to Tabulata: however, erecting a new higher taxon for Palaeacis, Trachypsammia and other Pleurodictyum-like corals is premature at our present state of knowledge. ? Palaeacis, Tabulata, Rugosa, septal ridges, systematic. affinities, Visean.     

Isolation and characterization of polymorphic microsatellites in Parnassius apollo and Euphydryas aurinia (Lepidoptera)

Microsatellite loci were developed from Parnassius apollo and Euphydryas aurinia, two endangered Palaearctic butterfly species. Respectively, six and five polymorphic loci were characterized from an enriched partial genomic library. Genetic diversity range from three to 25 alleles for the first species and from seven to 21 for the second. Although the presence of null alleles is suspected, these polymorphic loci are likely to provide important information on the fine scale genetic structure among populations of these species.     

A stable isotopic investigation into the causes of decline in a sub-Antarctic predator, the rockhopper penguin Eudyptes chrysocome

The rockhopper penguin (Eudyptes chrysocome) is a conspicuous apex marine predator that has experienced marked population declines throughout most of its circumpolar breeding distribution. The cause(s) for the declines remain elusive, but the relatively large spatio‐temporal scale over which population decreases have occurred implies that ecosystem‐scale, at‐sea factors are likely to be involved. We employ stable isotope analyses of carbon (¹³C/¹²C, expressed as δ¹³C) and nitrogen (¹⁵N/¹⁴N, δ¹⁵N) in time‐series of rockhopper penguin feather samples, dating back to 1861, in order to reconstruct the species' ecological history. Specifically, we examine whether rockhopper penguin population decline has been associated with a shift towards lower primary productivity in the ecosystem in which they feed, or with a shift to a diet of lower trophic status and lower quality, and we use long‐term temperature records to evaluate whether shifts in isotope ratios are associated with annual variations in sea surface temperature. Having controlled temporally for the Suess Effect and for increases in CO₂ concentrations in seawater, we found that overall, δ¹³C signatures decreased significantly over time in rockhopper penguins from seven breeding sites, supporting the hypothesis that decreases in primary productivity, and hence, carrying capacity, for which δ¹³C signature is a proxy, have been associated with the decline of penguin populations. There was some evidence of a long‐term decline in δ¹⁵N at some sites, and strong evidence that δ¹⁵N signatures were negatively related to sea surface temperatures across sites, indicative of a shift in diet to prey of lower trophic status over time and in warm years. However, a site‐by‐site analysis revealed divergent isotopic trends among sites: five of seven sites exhibited significant temporal or temperature‐related trends in isotope signatures. This study highlights the utility of stable isotope analyses when applied over relatively long timescales to apex predators.     

Tooth morphology of Echimyidae (Rodentia,Caviomorpha): homology assessments,fossils, and evolution

Echimyidae constitute the most important radiation of caviomorph rodents in the Neotropical region, represented by 20 extant genera and several extinct species. Both in extant and fossil forms, this diversity is reflected by a significant morphological variation found in crown structures of the cheek teeth. Different hypotheses of primary homology have been proposed for these structures, which, in turn, support diverse dental evolutionary hypotheses. In this contribution we inspect the main structures (cusps and lophids) of the lower deciduous teeth and molars in extinct and extant Echimyidae, and establish their topological correspondences. Comparisons with cusps and lophids of Erethizontidae are emphasized. We explore the testing of alternative primary hypotheses of lophid correspondences in a cladistic context. Following a ‘dynamic’ approach, we select the hypothesis of primary homology, which produced the more parsimonious results, and evaluate the evolutionary transformations of the dental characters analysed. In this context, the phylogenetic relationships of living Myocastor coypus (Molina, 1782) with the extinct Tramyocastor and Paramyocastor are tested. Our results indicate that pentalophodonty is the derived condition for the lower molars in Echimyidae, that trilophodonty evolved independently at least three times during the evolutionary history of these rodents, and that tetralophodonty represents the plesiomorphic condition. This study shows that dental evolution in echimyids can be better understood when occlusal structures are expressed as reliably comparable characters, and when fossils are taken into account. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 164 , 451–480.