A genetic determination of cryptic species (Copepoda: Calanoida) and their postglacial biogeography in North America

Allozyme electrophoresis of Hesperodiaptomus arcticus (Marsh) sensu lato at subarctic Churchill, Canada revealed significant deviations from random mating in several populations, as shown by the complete absence of certain heterozygous types. A broad geographic survey of 20 enzyme loci in 1077 individuals from 27 ponds at 11 arctic and alpine sites west of Hudson Bay demonstrated that there were three genetically distinct types. Morphological analysis of genetically classified populations uncovered consistent morphological differences that had been ignored previously. These morphological characteristics were used to reclassify preserved museum and private specimens from additional sites from the entire North American distribution of H. arcticus sensu lato. A detailed study of two of the distinct types co-occurring at Churchill showed reproduction timing and habitat differences consistent with reproductive isolation. I concluded that there are three species and each have different distributions. Most regions examined must have been repopulated by dispersal from glacial refugia after deglaciation. The nominal species is apparently restricted to western arctic localities in the vicinity of the Alaskan refugium while the other two putative taxa have dispersed widely into previously glaciated regions.     

Cultural Sharing and Cultural Theory: Some Findings of a Five-Society Study

The results of this study of the sharing of elements of culture concerned with family life among nuclear family members indicate that members of family statuses share no more with one another than they do with members of their society in general. The highest levels of sharing are found not within statuses but within families. In some family relationships it was found that high levels of sharing develop over time rather than being brought to the relationships from their outset, but this does not seem to be true of all family relationships. Differences in levels of sharing between families in the same society were found to be greater than differences between different societies. The status-centered model of cultural sharing as currently formulated appears a weak basis for a broader cultural theory because of its failure to account for important elements in cultural distribution not attributable to status membership alone , [cultural differences, culture, family, status, theory]     

Genetic and environmental influences on shape variation in the European sea bass (Dicentrarchus labrax)

This paper demonstrates the contribution of both genetic and environmental effects on cultured European sea bass shape. We used the progeny of five populations of sea bass, in a partly diallel design, to investigate the genetics of shape (estimated with geometric morphometrics) in European sea bass. This was done using a common garden experiment with microsatellite markers assignment to parents and populations to avoid confusion between genetic and environmental effects. Additionally, one of the populations was studied over four different aquaculture facilities to investigate the effects of environment on shape. For the first time in this species, shape‐related traits were linked with genetic variation. The first relative warp analysis axis clearly differentiated rearing sites, demonstrating that the main shape/weight effects are related to culturing conditions, thereby accounting for ecomorphologically related differences. The second axis strongly differentiated groups by parental origins; there was a good correlation between shape differences and geographic distances between broodstock sampling locations. High heritabilities of axes scores (0.40–0.55) showed high genetic variation for shape within populations. This study shows that variation in shape has a high genetic component in sea bass, both at the population level and within populations. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 427–436.     

Changing Sink Demand Affects the Area but not the Specific Activity of Assimilate Sources in Cantaloupe (Cucumis meloL.)

To better understand source-sink interactions, this work focusedon the influence of fruit number on leaf area and photosyntheticactivity in cantaloupe. To this end, flowers were removed over2 years on two Charentais cultivars to obtain single-fruit plantsand plants with an unrestricted fruit load (which set two tofive fruits and constituted control plants). At the whole plantscale, net photosynthesis was reduced by about 30% under highfruit load. At the leaf scale, a submodel of stomatal conductancewas fitted to the data and was included in a rectangular hyperbolamodel of leaf photosynthesis. Maximum leaf net photosynthesisaveraged 14.83 µmol CO₂m^-2s^-1at 1000 µmol quantam^-2s^-1. Light use efficiency was not affected by fruit loadand equalled 0.040 mol CO₂mol^-1quanta. Leaf area of plants withunrestricted fruit load decreased after 24 days from pollination,while the leaf area of single-fruit plants was still increasing.The decrease was due to production of fewer new leaves per day,whereas the number of senescent leaves and the size of individualleaves were not affected by the treatment. Under high fruitload, cultivar Galoubet developed a larger projected leaf areathan cultivar Talma. Thus it is concluded that: (1) large cantaloupefruits may divert a large amount of assimilates away from, andgrow at the expense of, the canopy; and (2) photosynthesis ofthe canopy was lowered because leaf area was reduced whereasphotosynthetic rate of leaves was not altered.Copyright 1998Annals of Botany Company. Cucumis meloL., fruit load, source-sink interactions, leaf photosynthesis, canopy photosynthesis, leaf area, SLA, source strength.     

New occurrences of the wood Protocupressinoxylon purbeckensis Francis: implications for terrestrial biomes in southwestern Europe at the Jurassic/Cretaceous boundary

Abstract:  Previously known from the Kimmeridgian–Portlandian of Dorset (UK) only, Protocupressinoxylon purbeckensis wood is reported here from the Kimmeridgian of Asturias (Spain) and Ajoie (Switzerland). The morphospecies taxonomy and nomenclature are discussed, and new supplementary illustrations are given. The P. purbeckensis tree was growing in dry strongly seasonal (tropophilous) environments, and the new occurrences suggest that such a climate prevailed on land all over southwestern Europe at the end of the Jurassic (Kimmeridgian sensu anglico – Portlandian). The review of fossil wood data indicates that such a stressful environment may have constrained terrestrial biocoenoses and their evolution at the Jurassic/Cretaceous boundary. But wood generic diversity curves are also strikingly similar to that drawn 20 years ago for nonmarine tetrapods, implying a fossil Lagerstätte effect.     

Postembryonic development of Tisbe gracilis (T. Scott) (Copepoda, Harpacticoida)

All six naupliar and five copepodite stages of Tisbe gracilis (T. Scott, 1895) are described. A key for the identification of the nauplius stages is given. The oral appendages of all copepodite stages are described. Sexual dimorphism is visible from the copepodite IV stage on.     

Two-Dimensional Solid-State NMR Applied to a Chimeric Potassium Channel

Solid-state NMR (ssNMR) represents a spectroscopic method to study membrane protein structure and dynamics in lipid bilayers. We present two-dimensional correlation experiments conducted on a fully [¹³C,¹⁵N] labeled version of a chimeric potassium (KcsA-Kv1.3) channel. Data obtained by using two different ion concentrations suggest a structural conservation of the selectivity filter region. SsNMR experiments conducted at two different temperatures point to differential molecular dynamics of the channel.