Rapid morphological change in stream beetle museum specimens correlates with climate change

Abstract 1. Climate change has been occurring at unprecedented rates and its impacts on biological populations is beginning to be well documented in the literature. For many species, however, long‐term records are not available, and trends have not been documented. 2. Using museum specimens from southern USA, we show that the stream‐dwelling beetle Gyretes sinuatus has shown an 8% increase in body size and change in body shape (fineness ratio) from 1928 to 1988. Any directional morphological change observed over time could be an indicator of a microevolutionary response. 3. During these 60 years, there have also been changes in temperature, precipitation, and location of collection sites. Unlike the global trend, mean annual temperature in the region has decreased, and furthermore, total annual precipitation has increased. By investigating how these various ecological and geographical variables may affect body size and shape, we can examine which pressures may promote larger and/or thinner beetles. 4. Results indicate that mean annual temperature was the most predictive variable for the change in size and shape. We suggest there is an adaptive role for temperature on body size and shape of stream dwelling organisms. 5. We found that museum specimens can be invaluable resources of information when collection date and location information is available. We promote the use of such specimens for future studies of the morphological response to climate change.     

The effects of temperature, pH and water hardness on winter starvation of young-of-the-year smallmouth bass, Micropterus dolomieui Lacepede

Year-class strength in northern populations of smallmouth bass is strongly influenced by winter starvation of young-of-the-year. We examined starvation among young bass under both winter and summer light and temperature conditions. During starvation, body condition declines to a specific level and then the fish dies. Body condition at death is a well defined function of body size that remains relatively constant over a wide range of environmental conditions. Starvation rate varies systematically with body size, temperature, pH and water hardness. Available stored energy increases more rapidly with body size than starvation rate. Therefore, lifetime under starvation conditions tends to increase with increasing body size. The Q₁₀ for starvation rate over the temperature range 2.5-8° C is 2.2. Starvation rate increases as pH declines from 7.0-4.9: the rate at pH 4.9 is ∼ 1.25 times the rate at pH 7 Starvation rate decreases as Ca concentration increases from 1 mgl⁻¹ to 80mgl⁻¹: the rate at 80 mg Ca 1⁻¹ is ∼0.80 times the rate at 1 mgl⁻¹.     

SEXUAL SIZE DIMORPHISM AND REPRODUCTIVE INVESTMENT BY FEMALE SPIDERS: A COMPARATIVE ANALYSIS

We investigate the association between female reproductive investment, absolute size, and sexual size dimorphism in spiders to test the predictions of the fecundity-advantage hypothesis. The relationships between absolute size and sexual size dimorphism and aspects of female reproductive output are examined in comparative analyses using phylogenetically independent contrasts. We provide support for the idea that allometry for sexual dimorphism is the result of variation in female size more so than male size. Regression analyses suggest selection for increased fecundity in females. We argue that fecundity selection provides the only general explanation for the evolution of sexual size dimorphism in spiders.     

Phytase expression in transgenic soybeans: stable transformation with a vector-less construct

A minimal linear gene cassette (35S-phytase gene-nos) with T-DNA borders was acquired by PCR and directly introduced into soybean through the pollen tube pathway. A total of 13% of T₁ plants were positive for phyA by specific PCR. Southern blot analyses showed that phyA insertions were harbored stably in T₂ progeny. Phytase expression level increased 2.5-fold over a 6-week period; its highest activity was 150 U/mg protein, compared to 56 U/mg protein in untransformed controls. Activity of phytase increased to 125 FTU/kg in T₃ transgenic seeds as compared to 64 FTU/kg in wild-type plants.     

Preparation of a monolithic capillary column with immobilized alpha-mannose for affinity chromatography of lectins

A simple method for the preparation of an affinity monolithic (also called continuous bed) capillary column for alpha-mannose-specific lectins is described. 2-Hydroxyethyl methacrylate in combination with (+)-N,N -diallyltartardiamide (DATD) and piperazine diacrylamide (PDA, 1,4-bisacryloyl-piperazine) as crosslinkers, were used as monomers for the monolith. After oxidation of DATD with periodate, alpha-mannose with spacer was bound to the aldehyde groups of the polymeric skeleton via reductive amination to form an affinity column for the separation, enrichment or binding studies of mannose-specific lectins. The permeability of the column was excellent. The porosity of the monolith was investigated by scanning electron microscope (SEM) and inverse size exclusion chromatography (ISEC). The affinity of the monolith was evaluated by frontal analysis (FA) and fluorescence microscopy (FM) using fluorescently labeled concanavalin (Con A). Frontal affinity chromatography showed a specific interaction of two different lectins with the alpha-mannose-modified monolith. According to FM the affinity sites were evenly distributed over the monolithic bed.     

The use of Quantitative Agarose Gel Electrophoresis for rapid analysis of the integrity of protein-DNA complexes

Recent biochemical studies evaluated the affinity of histones to DNA in the context of nucleosome core particle (NCP). These have indicated a concentration-dependence for nucleosome stability. However, when studying chromatin the preferred templates are nucleosome arrays (NA) and not the NCP. Biochemical methods are poorly suited for structural analysis of chromatin. To overcome that technical hindrance, and investigate the effect of concentration on stability of the histone-DNA interactions, we have applied the multigel Quantitative Agarose Gel Electrophoresis (QAGE) method to in vitro-assembled nucleosomal arrays. The results demonstrated the method to be extremely valuable for the evaluation of the effect of low concentration on NA. However, QAGE is a fairly time-demanding and complex method. To maximize the efficiency of use of this technology, we devised a protocol that allowed for multiple sets of templates to be analyzed simultaneously. Briefly, samples can be loaded at regular intervals and analyzed individually for their molecular composition. The technique presented in this study describes the calibration steps and proof of concept necessary to validate the use of multiple loading of multigel to evaluate the composition of nucleosomal arrays as a function of concentration.     

Cost of sexually embracing a large female offset by the number of eggs fertilized for small male Bufo bufo L.

When pairing with high quality females, a male increases its fitness through an increased number and/or quality of sired offsprings. In anurans, size has often been used as a measure of female quality. In the present study, we examined the effects of pairing with large females for small males in the common toad, Bufo bufo . For the first time in anurans, we show a fitness cost for males to maintain amplexus with a large female. Indeed, although we did not detect any effect of male size on male pairing success in a first breeding event in the presence of other competing males, when males that were successful in the first breeding event were tested for a second time, male pairing success strongly decreased when they had been first paired with a large female. However, the higher fecundity of large females (1.52-fold more than that of small females) may override this pairing cost, especially because high fertilization rate was not linked to male/female body size ratio. Indeed, we did not detect any difference in egg fertilization success between small males paired with large and small females. Our results suggest that predictable cues of female reproductive value exist in common toads, thus meeting a prerequisite of the occurrence of male mate choice. Male mate choice, probably underestimated in anurans, may be particularly important in species where the breeding season is short and the number of mating events for a male is limited. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 755–762.     

Geographical and within-population variation in the globeflower–globeflower fly interaction: the costs and benefits of rearing pollinator’s larvae

Interspecific interactions can vary within and among populations and geographical locations, and this variation can influence the nature of the interaction (e.g. mutualistic versus antagonistic) and its evolutionary stability. Globeflowers are exclusively pollinated by flies whose larvae feed only on their seeds. Here we document geographical variability in costs and benefits in globeflowers in sustaining their pollinating flies throughout the range of this arctic-alpine European plant over several years. A total of 1,710 flower heads from 38 populations were analysed for their carpel, egg and seed contents. Individual and population analyses control for the confounding influences of variation in both: (1) population traits, such as fly density and egg distribution among flower heads; and (2) individuals traits, such as carpel and egg numbers per flower head. Despite considerable variation in ecological conditions and pollinator densities across populations, large proportions (range 33–58%) of seeds are released after predation, with a benefit-to-cost ratio of 3, indicating that the mutualism is stable over the whole globeflower geographical range. The stability of the mutualistic interaction relies on density-dependent competition among larvae co-developing in a flower head. This competition is revealed by a sharp decrease in the number of seeds eaten per larva with increasing larval number, and is intensified by non-uniform egg distribution among globeflowers within a population. Carpel number is highly variable across globeflowers (range 10–69), and flies lay more eggs in large flowers. Most plants within a population contribute to the rearing of pollinators, but some pay more than others. Large globeflowers lose more seed to pollinator larvae, but also release more seed than smaller plants. The apparent alignment of interests between fly and plant (positive relationship between numbers of seeds released and destroyed) is shown to hide a conflict of interest found when flower size is controlled for.