Vapour pressure deficit during growth has little impact on genotypic differences of transpiration efficiency at leaf and whole‐plant level: an example from Populus nigra L.

Poplar genotypes differ in transpiration efficiency (TE) at leaf and whole‐plant level under similar conditions. We tested whether atmospheric vapour pressure deficit (VPD) affected TE to the same extent across genotypes. Six Populus nigra genotypes were grown under two VPD. We recorded (1) ¹³C content in soluble sugars; (2) ¹⁸O enrichment in leaf water; (3) leaf‐level gas exchange; and (4) whole‐plant biomass accumulation and water use. Whole‐plant and intrinsic leaf TE and ¹³C content in soluble sugars differed significantly among genotypes. Stomatal conductance contributed more to these differences than net CO₂ assimilation rate. VPD increased water use and reduced whole‐plant TE. It increased intrinsic leaf‐level TE due to a decline in stomatal conductance. It also promoted higher ¹⁸O enrichment in leaf water. VPD had no genotype‐specific effect. We detected a deviation in the relationship between ¹³C in leaf sugars and ¹³C predicted from gas exchange and the standard discrimination model. This may be partly due to genotypic differences in mesophyll conductance, and to its lack of sensitivity to VPD. Leaf‐level ¹³C discrimination was a powerful predictor of the genetic variability of whole‐plant TE irrespective of VPD during growth.     

Isolation and characterization of EST‐derived microsatellite loci from the fungal wheat pathogen Phaeosphaeria nodorum

Eleven polymorphic microsatellite loci and one minisatellite locus originating from expressed sequence tag (EST) libraries of Phaeosphaeria (syn. Stagonospora) nodorum were isolated and characterized. The satellite markers were used to genotype isolates from field populations collected in China, North America and South Africa. The number of alleles per locus ranged from two to 15. Genotype diversity ranged from 87.5 to 95.3 and gene diversity from 0.1 to 0.8. The variable levels of polymorphism within and among populations of P. nodorum renders these 12 satellite loci ideal markers for population genetic analysis of P. nodorum.     

CONSUMER PERCEPTION OF WHEY AND SOY PROTEIN IN MEAL REPLACEMENT PRODUCTS

ABSTRACT

Meal replacement products including protein bars, shakes and powdered drinks have increased in demand and sales. The objective of this study was to assess the consumer perception of protein content and type and product claims for meal replacement beverages and bars. The impact of exercise frequency on product perception was also investigated. Focus groups were conducted with exercisers and nonexercisers. An adaptive conjoint analysis survey was subsequently developed and conducted (n = 138 consumers, ages 18–35 years). Relative importance of product attributes was determined through a realistic trade‐off scenario. Utility scores were extracted and rescaled by the zero‐centered differences method, and two‐way analysis of variance was conducted to identify the differences between exercise frequency and product attributes. Both groups preferred bars to beverages, and no clear preferences were observed for protein type, which was consistent with focus group results of low knowledge/understanding of specific proteins. All respondents valued the products with low‐fat/fat‐free, calcium, all‐natural, protein, vitamin/mineral, heart health and muscle‐building claims. Exercisers viewed muscle‐building claims as more important than nonexercisers. Nonexercisers viewed heart health, calcium and vitamin/mineral claims as more important than exercisers. Three distinct consumer clusters were identified, and both exercise groups were found in all three clusters, although exercise frequency influenced membership in two of the three clusters (P < 0.05). These findings can be used to develop and market meal replacement products to specific consumer groups while leveraging their specific and unique needs.

PRACTICAL APPLICATIONS

Conjoint analysis provides a useful model of how consumers think during the purchase process and an understanding of the motivation for purchase through the testing of possible claims or product attributes. By applying this method to the purchase process of meal replacement bars and beverages, those in the field of development of these products can benefit from this information by being able to understand the motivation for purchase by the targeted consumer.     

Spatial scale affects bioclimate model projections of climate change impacts on mountain plants

Plant species have responded to recent increases in global temperatures by shifting their geographical ranges poleward and to higher altitudes. Bioclimate models project future range contractions of montane species as suitable climate space shifts uphill. The species–climate relationships underlying such models are calibrated using data at either ‘macro’ scales (coarse resolution, e.g. 50 km × 50 km, and large spatial extent) or ‘local’ scales (fine resolution, e.g. 50 m × 50 m, and small spatial extent), but the two approaches have not been compared. This study projected macro (European) and local models for vascular plants at a mountain range in Scotland, UK, under low (+1.7 °C) and high (+3.3 °C) climate change scenarios for the 2080s. Depending on scenario, the local models projected that seven or eight out of 10 focal montane species would lose all suitable climate space at the site. However, the European models projected such a loss for only one species. The cause of this divergence was investigated by cross‐scale comparisons of estimated temperatures at montane species' warm range edges. The results indicate that European models overestimated species' thermal tolerances because the input coarse resolution climate data were biased against the cold, high‐altitude habitats of montane plants. Although tests at other mountain ranges are required, these results indicate that recent large‐scale modelling studies may have overestimated montane species' ability to cope with increasing temperatures, thereby underestimating the potential impacts of climate change. Furthermore, the results suggest that montane species persistence in microclimatic refugia might not be as widespread as previously speculated.     

Patterns of invertebrate biodiversity across a natural edge

Abstract Most ecologists are comfortable with the notion of habitats as recognizable entities and also with situations where the junction between two adjacent habitats forms a discrete edge. Such edges form naturally because of sharp changes in important edaphic, geomorphological, climatic or chemical properties to which plants, in particular, respond. Less clear is the effect of such edges on assemblages of mobile organisms, especially invertebrates that operate at relatively small spatial scales. The objective of the present study was to sample invertebrate composition across a natural edge between a well‐developed riparian habitat on fluvial sands and a saltbush habitat developed on a stony gibber plain in a semi‐arid region of New South Wales, Australia. A total of 150 pitfall traps on five 1‐km‐long transects that straddled the edge produced more than 13 000 adult specimens from 21 ordinal invertebrate taxa. A total of 10 446 beetle, ant, wasp, fly and springtail specimens were further sorted into 426 morphospecies. Comparisons and estimates of trends in abundance and richness were made, along with computation of multivariate dissimilarity and permutation statistics, to determine if the land system edge was coincident with changes in invertebrate abundance and composition. These analyses were unable to detect disjunctions in diversity coincident with the edge. The data suggest that many taxa are either present consistently in both habitats or are mostly found in one habitat but ‘leak’ several hundred metres across into the other. Few taxa were unique to either habitat. The result is that assemblage composition for invertebrates changes gradually over distances of up to 400 m either side of the edge and that the distance to a recognizable change in composition is taxon dependent. Even sharp habitat edges, as defined by discrete changes in soils and plants, are not edges but broad transition zones for many invertebrate taxa. There are several implications of these results, especially for landscape ecology.     

Carbon source accounting for fish using combined DNA and stable isotope analyses in a regulated lowland river weir pool

Determining the source and flow of carbon, energy and nutrients through food webs is essential for understanding ecological connectivity and thus determining the impact of management practices on biodiversity. We combined DNA sequencing, microarrays and stable isotope analyses to test whether this approach would allow us to resolve the carbon flows through food webs in a weir pool on the lower Murray River, a highly impacted, complex and regulated ecosystem in southern Australia. We demonstrate that small fish in the Murray River consume a wide range of food items, but that a significant component of carbon and nitrogen entering the food web during dry periods in summer, but not spring, is derived from nonconventional sources other than in-channel primary producers. This study also showed that isotopic analyses alone cannot distinguish food sources and that a combined approach is better able to elucidate food-consumer dynamics. Our results highlight that a major river ecosystem, stressed by reduced environmental flows, can rapidly undergo significant and previously undetected changes that impact on the ecology of the system as a whole.     

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 relationship between the Rubisco reaction mechanism and models of photosynthesis*

Abstract. A new model of photosynthesis published recently in this journal (H. Farazdaghi & G. E. Edwards, Plant, Cell and Environment (1988) 11 , 789–798; 799–809) clams to have a more complete mechanistic basis than currently used models based on the paper of G. D. Farquhar, S. von Caemmerer & J. A. Berry (Planta (1980) 149 , 78–90). In this paper, we examine the validity of the new kinetic expression for the rate of CO₂ fixation by Rubisco, and the derivation of an equation for photosynthetic CO₂ assimilation as a function of light intensity and CO₂ concentration presented in the new model. In addition, we compare measured response curve of photosynthesis to CO₂ and light with simulated curves using alternative models. We conclude that the new model is mechanistically misleading and, empirically, overestimates the extent to which light and CO₂ co-limit the rate of photosynthesis under most physiological conditions.     

Native oak chloroplasts reveal an ancient divide across Europe

Glacial refugia and postglacial migration are major factors responsible for the present patterns of genetic variation we see in natural populations. Traditionally postglacial history has been inferred from fossil data, but new molecular techniques permit historical information to be gleaned from present populations. The chloroplast tRNA^Leu1 intron contains regions which have been highly conserved over a billion years of chloroplast evolution. Surprisingly, in one of these regions which has remained invariant for all photosynthetic organisms so far studied, we have found intraspecific site polymorphism. This polymorphism occurs in two European oaks, Quercus robur and Q. petraea , indicating hybridisation and introgression between them. Two distinct chloroplast types occur and are distributed geographically as eastern and western forms suggesting that these oaks are each derived from at least two separate glacial refugia.