Did Polyommatus icarus (Lepidoptera: Lycaenidae) have distinct glacial refugia in southern Europe? Evidence from population genetics

Pleistocene climatic oscillations strongly influenced the genetic composition of many species which are often divided into several genetic lineages. In this context, we studied the allozymes of a common and widely distributed butterfly, the common blue Polyommatus icarus, over a large part of Europe. The species had a rather high genetic diversity within populations with a strikingly high mean number of alleles per locus (2.98). In contrast, differentiation between populations was very low ( F _ST: 0.0187). Only a marginal trend of decline in genetic diversity from the south to the north was observed. Isolation-by-distance existed on a European scale ( r =  0.826), but not at a regional level. Regional differentiation between populations in western Germany was extremely low ( F _ST: 0.0041). It is probable that P. icarus was widely distributed in the Mediterranean region during the last ice age and expanded into central Europe in the postglacial period without major genetic erosion. Moderate present and past gene flow in an intact metapopulation structure may have occurred on local, regional and perhaps even continental scales.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80 , 529–538.     

A PANEL PERFORMANCE PROCEDURE IMPLEMENTED IN R

Monitoring performance is essential for the efficient use of a sensory panel both during training and while carrying out product assessments. We present a concise procedure to monitor panel performance based on classical statistical methods. The program includes tests for the ability to discriminate between products, repeatability of assessments, scale use, agreement between panelists and a principal component analysis map of panelist means across attributes. The algorithm is implemented in R – a state‐of‐the‐art, freely available statistical software package. The program output is summarized in graphs and tables. This easily applicable panel performance procedure is aimed at improving sensory practice, especially in areas where the use of highly complex systems is not feasible.     

Vegetative reproduction by species with different adaptations to shallow-flooded habitats

In shallow flooded parts of rich fens Mentha aquatica might thrive in deeper water than Epilobium hirsutum but previous experiments have provided no clear indication that the flooding tolerance of these species differs. In this study we investigated, by measuring growth, biomass allocation and vegetative reproduction, whether the impact of water level on vegetative reproduction might produce different lower boundaries on water level gradients. There was a striking contrast between biomass production at high water levels and the field distribution of both species. After 18 wk, the mean biomass of E. hirsutum grown in waterlogged and flooded conditions was 82% and 54%, respectively, of the mean biomass production of drained plants. Biomass of waterlogged and flooded M. aquatica was reduced to 57% and 37% in drained conditions. Waterlogged and flooded E. hirsutum had swollen stem bases and invested a high proportion of biomass in adventitious roots. Stems of M. aquatica did not swell, formed few adventitious roots and maintained an equal proportion of below-ground roots at all water levels. The effect of water level on vegetative reproduction corresponded well with the lower hydrological boundaries of both species. When waterlogged and flooded, most rhizomes of E. hirsutum emerged from above-ground parts of the stem base and were oriented in an upward direction. Plants in flooded soil allocated less biomass to rhizomes and also reduced the number and size of rhizomes. Rhizome formation of M. aquatica on the other hand was not directly affected by water level and only depended on plant size. These differences in vegetative reproduction are discussed in relation to the different abilities of both species to oxygenate their below-ground roots. It was concluded that the mode of adaptation to soil flooding might also affect vegetative reproduction and, therefore, a species' ability for long-term persistence in soil-flooded habitats.     

Flooding tolerance of Carex species in relation to field distribution and aerenchyma formation

The flooding tolerance of Carex species was studied in relation to their field distribution and their capacity to form root aerenchyma under controlled conditions. In an alpine meadow, six Carex species were selected which were distributed in a clear zonation correlating with water content of the soil. Carex sempervirens and C. ferruginea were only found on nonflooded soil, the latter species preferring moister conditions. Carex davalliana and C. nigra were both associated with water-saturated soil, whereas C. limosa and C. rostrata preferred partially submerged conditions. Carex davalliana and C. limosa were bound to flooded soils with a relatively high redox potential and horizontally flowing groundwater. Carex rostrata and C. nigra grew in stagnant soil-flooded conditions with low soil redox potentials. The amount of aerenchyma in the roots of all species increased when grown in oxygen-deficient stagnant agar. This increase in root porosity, combined with increased root diameter, presumably improved internal aeration of the roots. Although all species survived experimental soil flooding, partial submergence was lethal to C. sempervirens and, surprisingly, also to the wetland species C. davalliana. Carex ferruginea showed a reduced growth rate during partial submergence. The three other species, all wetland plants, reached highest biomass production under soil-flooded and partially submerged conditions, with slower growth on free-draining soil. It is concluded that aerenchyma is not constitutive in the Carex species under study, and is best developed in Carex species from wetlands. Species with less aerenchyma perform poorly when soil-flooded, but conditions of partial submergence could even affect species with a considerable amount of root aerenchyma.     

Flight characteristics of birds:

This is the first part of a study on flight characteristics of birds and presents an annotated list of flight speeds of 139 western Palearctic species. All measurements were taken with the same tracking radar and corrected for wind influence according to radar-tracked wind-measuring balloons. Graphical presentation of the birds' air speeds emphasizes the wide variation of speeds within species and allows easy comparison between taxonomic groups, species, and types of flight. Unlike theoretical predictions, speeds increase only slightly with size. The larger species seem to be increasingly limited to speeds close to their speed of minimum power consumption V_mp',. Released birds, apparently reluctant to depart with migratory speed, fly at considerably lower speeds than migrating conspecifics. While large birds seem to be limited to speeds around V _mp', smaller birds seem to be capable of selecting between various speeds, approaching predicted V _mp, when tending to remain airborne at low cost, but flying at much higher speeds when tending to make best progress at low cost (around predicted speed of maximum range V _mr,). Predictions of air speeds by aerodynamic models proved to be too low for small birds because the models do not account for the gain in speed attained by the reduction in profile drag during bounding flight of small passerines. The models predict excessive speeds for large birds because the power output available for flight seems to decline much more with size than previously assumed.     

Molecular phylogeny of the endemic East African flightless grasshoppers Altiusambilla Jago, Usambilla (Sjöstedt) and Rhainopomma Jago (Orthoptera: Acridoidea: Lentulidae)

Abstract.  A molecular phylogeny of endemic flightless grasshoppers is presented for the three Lentulidae genera Altiusambilla Jago, 1981 , Usambilla Sjöstedt, 1909 and Rhainopomma Jago, 1981 based on DNA sequences (16S rRNA locus). Parsimony, distance and likelihood reconstructions were performed using different assumptions on sequence evolution. The generated phylogenies agree in almost all parts of the calculated trees and support the monophyly of the observed genera. It was shown that Usambilla and Rhainopomma are more closely related to each other, Altiusambilla being a separate clade. However, the investigated East African lentulid genera are clearly separated from South African taxa, underlining the monophyly of East African genera. Usambilla olivacea is re-established. Populations of Rhainopomma montanum from the Taita Hills of Kenya and from the West Usambara mountains of Tanzania are two separate species not closely related to each other. Rhainopomma samples from the North Pare mountains of Tanzania belong to a hitherto undescribed species.     

The genetics of bird migration: stimulus, timing, and direction

The extent to which genetic factors are directly involved in the control of bird migration and the mode of inheritance involved has been studied systematically over the past 15 years in the Blackcap Sylvia atricapilla by cross-breeding and selective breeding. Results have also been obtained from a few experimental and field studies on Robins Eritfiacus rubecula, Blackbirds Turdus merula and Song Sparrows Melospiza melodia. Cross-breeding of migrants with nonmigrants has resulted in the partial transmission of migratory activity into the F, generation indicating that the urge to migrate is inherited and is based on a multilocus system with a threshold for expression. Migratoriness and sedentariness in obligate partial migrants is probably inherited in a similar way, suggesting that the decision to migrate also has a strong genetic basis. Both traits can be selected to phenotypic uniformity within 3–6 generations indicating an extremely high evolutionary potential. Orientation behaviour can also be transmitted to the offspring of a nonmigratory population by cross-breeding. Cross-breeding individuals with different migratory directions produced offspring with phenotypically intermediate directional preferences, suggesting that the migratory direction is also a predominantly heritable character. In the current development of novel migratory habits in those Central European Blackcaps that now winter in the British Isles, the inheritance of the novel migratory direction may be crucial. Genetic variation in migratory events seems to be sufficient to allow for many microevolutionary processes.     

Somatic Hybridization of Nitrate Reductase Deficient Mutants of Nicotiana tabacum by Protoplast Fusion

Protoplasts were isolated from two mutant cell lines of Nicotiana tabacum L. cv. Gatersleben and fused with the aid of polyethylene glycol. Both mutants lacked nitrate reductase and were thus auxotrophic for reduced nitrogen. The fusion resulted in a high frequency of hybrid cells which were detected by their regained ability to grow in media containing nitrate as sole nitrogen source. Thus, the two mutants were found to complement each other in the hybrids. In control experiments, back mutation and cross-feeding were excluded as possible explanations for the occurrence of cell lines utilizing nitrate. A total of 1061 hybrid lines capable of sustained proliferation were isolated. Some of them were further characterized with respect to nitrate reductase activity, chlorate sensitivity, chromosome number, and shoot formation. The results demonstrate that protoplast fusion can be used for the genetic analysis of cell variants of higher plants and that nitrate reductase-deficient mutants provide efficient selective systems for hybrid cells.     

Odour–genes covariance within a natural population of subterranean Spalax galili blind mole rats

Previous research, using habituation techniques with multiple rodent species as subjects, has demonstrated (from kin to across species) the greater perceptual similarity in the qualities of individual odours of more closely genetically related individuals ('odour–genes covariance', abbreviated 'OGC'). This predictable relationship between individual genotypes and individual odours has only been assessed in rodents in which the genetic similarities and dissimilarities are known either through laboratory breeding or by selecting odour donors from different populations or species. To study OGC within a natural population of rodents, we genotyped Spalax galili blind mole rats using ten microsatellite markers, and conducted pairwise genetic distance comparisons to estimate genetic similarity and to calculate the relatedness coefficient between pairs of individuals. We then used habituation-generalization techniques to assess whether perceived odour similarities covaried with the genetic similarities we had identified. Indeed, animals treated odours from genetically closer donors as more similar than odours from less genetically similar donors. The results suggest an accurate and subtle ability to resolve genetically determined odour distinctions among familially unrelated animals within a population. Graded differential responses to conspecific odours based on degrees of similarity between other individuals' odours and one's own have been demonstrated in kinship and species discriminations and preferences. The evidence presented here provides the basis for hypothesizing a similar process that could promote optimal outbreeding and inclusive fitness within populations of conspecifics. The evolutionary implications of these findings are discussed.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 483–490.     

High microbial activity on glaciers: importance to the global carbon cycle

Cryoconite holes, which can cover 0.1–10% of the surface area of glaciers, are small, water-filled depressions (typically <1 m in diameter and usually <0.5 m deep) that form on the surface of glaciers when solar-heated inorganic and organic debris melts into the ice. Recent studies show that cryoconites are colonized by a diverse range of microorganisms, including viruses, bacteria and algae. Whether microbial communities on the surface of glaciers are actively influencing biogeochemical cycles or are just present in a dormant state has been a matter of debate for long time. Here, we report primary production and community respiration of cryoconite holes upon glaciers in Svalbard, Greenland and the European Alps. Microbial activity in cryoconite holes is high despite maximum temperatures seldom exceeding 0.1 °C. In situ primary production and respiration in cryoconites during the summer is often comparable with that found in soils in warmer and nutrient richer regions. Considering only glacier areas outside Antarctica and a conservative average cryoconite distribution on glacial surfaces, we found that on a global basis cryoconite holes have the potential to fix as much as 64 Gg of carbon per year (i.e. 98 Gg of photosynthesis minus 34 Gg of community respiration). Most lakes and rivers are generally considered as heterotrophic systems, but our results suggest that glaciers, which contain 75% of the freshwater of the planet, are largely autotrophic systems.