Evidence for ecological speciation in the sister species Candidula unifasciata (Poiret, 1801) and C. rugosiuscula (Michaud, 1831) (Helicellinae, Gastropoda)

This paper studies the speciation of two land snail species in south-east France. By using two mitochondrial and one nuclear gene, the species are shown to be sister species within the larger clade of western European Candidula species. The species never occurred syntopically, but a narrow contact zone population was identified. Recent range expansions inferred from phylogeographical methods indicated that the present day distributions are not limited by the colonization capacity of the species. Analysis of environmental variables suggested distribution along an ecotone. The gastropod community is also correlated to this gradient. Morphometric shell analysis showed that the divergence between the sister species is a result of desiccation-resistant shell characters. We therefore conclude that the cause for the ecological speciation is most probably the establishment of the Mediterranean climate ≈ 3.2 mya. A model of ecological speciation with a moving ecotone is put forward.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 79, 611–628.     

Male copulation frequency and female competition for fertilizations in a promiscuous brood parasite, the Pin-tailed Whydah Vidua macroura

Male Pin-tailed Whydahs Vidua macroura copulate infrequently and terminate most courtship displays, even when females are highly receptive. Female sexual interference is aimed at preventing other females from copulating, and is nearly always successful.     

Courtship song and immune function in the field cricket Gryllus bimaculatus

It has been assumed that sexual ornaments have evolved to reveal males' health and vigour for females. Choosy females may indirectly use ornaments as an indicator of the presence and effectiveness of genes for resistance against parasites. In this study we tested whether females of the Mediterranean field cricket, Gryllus bimaculatus, can use courtship song as a cue for choosing males with high immunocompetence, measured as encapsulation rate of nylon implants and lytic activity of haemolymph. We found that female crickets preferred courtship songs from males with a high encapsulation rate. Female crickets also had a tendency to prefer courtship songs with high tick rate and long high-frequency tick duration. These preferred song components were positively correlated with encapsulation rate, but negatively correlated with lytic activity of the male. In contrast to previous studies of crickets, there was no correlation between male weight and encapsulation rate or lytic activity. There is some evidence in another cricket species that the ability to encapsulate pathogens is heritable. Thus, in light of this study it seems possible that by preferring males according to their courtship song, females might benefit by increasing the parasite resistance of their offspring.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 79 , 503–510.     

Relationship between microspatial population genetic structure and habitat heterogeneity in Pomatias elegans (O.F. Müller 1774) (Caenogastropoda, Pomatiasidae)

In the present study the population genetic structure of the terrestrial snail Pomatias elegans was related to habitat structure on a microspatial scale. The genetic variability of 1607 individuals from 51 sampling sites in five different populations in Provence, France, was studied with an allozyme marker using population genetic methods, Mantel tests and spatial autocorrelation techniques were applied to different connectivity networks accounting for the structural features of the landscape. It is suggested that the population structure is, to a large extent, a function of the habitat quality, quantified as population density, and of the spatial arrangement of the habitat in the landscape and not of the geographical distance per se . In fragmented habitats, random genetic drift was the prevailing force for sampling sites separated by a few hundred meters.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 76 , 565–575.     

Mechanism and Control of Initiation in the Translation of R17 RNA

A general model of initiation of protein synthesis based on experiments with R17 RNA as messenger proposes a two-stage mechanism, the first stage requiring dissociation into subunits and initiation factors, the second involving direct attachment of ribosomes.     

REVISION OF THE TYPE MATERIAL AND NOMENCLATURE OF MASTODONSAURUS GIGANTEUS (JAEGER) (TEMNOSPONDYLI) FROM THE MIDDLE TRIASSIC OF GERMANY

Abstract: The type material of Mastodonsaurus is revised and its complicated taxonomic history resolved. The genus was erected by Jaeger in 1828 without a species name, which was added subsequently by Holl (1829) who named the type species Mastodonsaurus jaegeri. The large tooth on which Jaeger based his Mastodonsaurus is chosen herein as lectotype of the type species. A smaller second individual, represented by a piece of an occiput, was also named by Jaeger in 1828 as Salamandroides giganteus and, owing to the find of a complete skull, was recognized in 1833 by the same author as belonging to the same species as the Mastodonsaurus. Therefore, Mastodonsaurus giganteus (Jaeger, 1828) is a senior subjective synonym of the type species M. jaegeri Holl, 1829. The precedence of the two generic names was chosen in 1834 by the first reviser, von Alberti, in favour of Salamandroides, but all later authors, including von Alberti himself, followed Jaeger, who decided in 1837 to retain the name Mastodonsaurus. The established usage of Mastodonsaurus is preserved formally herein (nomen protectum). The names Batrachosaurus Fitzinger, 1837, and Labyrinthodon Owen, 1841 are unjustified replacement names of Mastodonsaurus. The names M. jaegeri von Meyer, 1832, S. jaegeri von Alberti, 1834 and M. salamandroides Jaeger, 1837 are junior homonyms and synonyms of M. jaegeri Holl, 1829, and M. giganteus (Jaeger, 1828), respectively. A recent attempt to replace the universally used Capitosauroidea Watson, 1919 by the unused and newly elevated Mastodonsauroidea Lydekker, 1885 is rejected. Two older synonyms of Mastodonsauridae Lydekker, 1885 (nomen protectum) are rejected as unavailable (Labyrinthodontidae von Meyer, 1842 ) and nomen oblitum (Batrachosauridae Fitzinger, 1843), respectively. The holotype of Mastodonsaurus giganteus is reinstated and valid on the basis of three diagnostic features present: the tripartite posterior rim of the parasphenoid, a laterally pushed suture between the parasphenoid and basipterygoid, and a wide slit‐like eustachian tube opening. Mastodonsaurus is known from specimens representing a continuous growth series, now also encompassing the lectotype of Mastodonsaurus jaegeri, which until rather recently stood isolated from other specimens as the largest find by far.     

Recent drought stress leads to growth reductions in Larix sibirica in the western Khentey,Mongolia

Trends in air temperature and precipitation in the forest‐steppe ecotone of the western Khentey, northern Mongolia were studied and related to stem increment and shoot water relations in Mongolia's most common tree species, Siberian larch (Larix sibirica). The area has been subject to a significant increase of summer temperature and a decrease of summer precipitation during the last 47 years. Tree‐ring width series from >400 larch trees show a strongly decreasing annual increment since the 1940s. The onset of this decrease is independent of the age of the trees and, therefore, can be attributed to the increasing aridity in the 20th century. Simultaneously to the declining annual increment, regeneration of Siberian larch decreased as well; today regeneration is virtually lacking in the larch forests on mountain slopes of the western Khentey. Measurements of shoot water potentials during the growing season exhibited daily minimum water potentials close to the point of zero turgor for extended periods. The drought stress indicated by these results is in line with the current low annual increment. Trees in the forest interior were more severely stressed and grow more slowly than trees at the forest line to steppe. This is attributable to the recent increase in aridity, as the stand density and probably also the trees themselves in the forest interior are adapted to moister conditions, whereas the trees at the forest edge have always been exposed to a more extreme microclimate. The progressing increase in aridity during the 21st century that is predicted for the western Khentey, suggests a future decline of larch forests. A widespread increase of aridity predicted for most parts of the Mongolian forest belt, suggests even a supra‐regional decline of larch.     

Immune defence,a possible nonvisual selective factor behind the industrial melanism of moths (Lepidoptera)

It is generally believed that industrial melanism in Lepidoptera is mainly caused by differential predation by birds. In polluted areas, melanic individuals are favoured by natural selection because they are better camouflaged than pale moths on lichen‐free and sooty tree trunks. In this article, we show that, in the black arches moth (Lymantria monacha), melanic morphs have a stronger encapsulation response than pale morphs against nylon monofilament implants. This indicates that the melanic and pale morphs differ in the strength of their immune defence. The same chemical precursors and their end product, melanin pigment, are involved in the encapsulation response and in the external coloration. Thus, it seems that there may be two possible, not mutually exclusive, explanations for the frequency changes observed in the industrial melanism of moths. The dominant gene causes an increase in the amount of melanin pigment and its precursors. This increase causes two changes: an intensified immune defence as a form of improved encapsulation ability of foreign objects, and the well‐known protective dark coloration (a case of relational pleiotropy). It seems possible that industrial melanism is a by‐product of selection on the strength of immunity. In the field, these pleiotropic aspects are exceedingly difficult to distinguish from each other, and the factors may even be compensatory. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 831–838.     

A NEW SEA SPIDER (ARTHROPODA: PYCNOGONIDA) WITH A FLAGELLIFORM TELSON FROM THE LOWER DEVONIAN HUNSRÜCK SLATE, GERMANY

Abstract:  A new Lower Devonian sea spider (Arthropoda: Pycnogonida) from the Hunsrück Slate, Germany, is described as Flagellopantopus blocki gen. et sp. nov. This is only the sixth fossil pycnogonid species to be described. Its most remarkable and unique aspect is the long, flagelliform telson. Although our fossil apparently lacks chelifores (an apomorphy), the retained telson and the segmented trunk end behind the last pair of legs resolve F. blocki to a fairly basal position in the pycnogonid stem lineage. It probably lies between Palaeoisopus problematicus Broili, which has a lanceolate telson and the most trunk segments of any sea spider, and all other Silurian–Recent Pycnogonida. Our new material shows that at least two fossil pycnogonids retained a telson, albeit with very different morphologies, and further supports the idea that a greater diversity of body plans existed among the Palaeozoic pycnogonid taxa.