Neglected vegetative characters in field identification at the supraspecific level in woody plants: phyllotaxy, serial buds, syllepsis and architecture

Some taxonomic characters may escape observation when only a small part of the vegetative body of the plant is examined. For this reason, these characters are likely to be overlooked. Phyllotaxy varies in most cases from the trunk to branches. Serial buds, when they exist, may be lacking in the axil of some leaves. Syllepsis is easier to see on the trunk than on twigs. Architectural models are established after appropriate observation of the whole plant or, better, with different individuals of the same species. Nevertheless, many of these characters can be readily observed and frequently help to identify a woody plant without its flowers or fruits. Some interpretations concerning systematics and evolutionary biology are also given.     

Carbohydrate Metabolism in Drought-Stressed Leaves of Pigeonpea (Cajanus cajan)

Pigeonpea is a tropical grain-legume, which is highly dehydrationtolerant. The effect of drought stress on the carbohydrate metabolismin mature pigeonpea leaves was investigated by withholding waterfrom plants grown in very large pots (50 kg of soil). The moststriking feature of drought-stressed plants was the pronouncedaccumulation of D-pinitol (1D-3-methyl-chiro-inositol), whichincreased from 14 to 85 mg g^–1 dry weight during a 27d stress period. Concomitantly, the levels of starch, sucroseand the pinitol precursors myo-inositol and ononitol all decreasedrapidly to zero or near-zero in response to drought. The levelsof glucose and fructose increased moderately. Drought stressinduced a pronounced increase of the activities of enzymes hydrolysingsoluble starch (amylases) and sucrose (invertase and sucrosesynthase). The two anabolic enzymes sucrose phosphate synthase(sucrose synthetic pathway) and myo-inositol methyl transferase(pinitol synthetic pathway) also showed an increase of activityduring stress. These results indicate that pinitol accumulatedin pigeonpea leaves, because the carbon flux was diverted fromstarch and sucrose into polyols. Key words: Drought, polyols, pinitol, sucrose, starch, pigeonpea     

Declining body size in an endangered large mammal

Body size affects almost every aspect of the biology of a species. According to the ‘resource rule’, decreasing resource availability (e.g. prey density) will lead to a reduction in body size or, alternatively, a decline in mass‐independent energy expenditure. In the present study, we provide a test of this hypothesis, assessing the effect of significantly decreasing prey density on endangered African wild dog (Lycaon pictus) body size and energy expenditure over a 20‐year period. As predicted from the ‘resource rule’, decreasing resource availability resulted in energetic re‐allocation: wild dogs' body size decreased significantly (both shorter and slimmer), whereas our fitness‐related measure of energy expenditure (i.e. litter size) remained constant over time. A phenotypic change of up to 17% within 20 years, as found in the present study, appears to be unprecedented in a nonharvested large mammal, thus advancing the emerging field of eco‐evolutionary dynamics. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 8–12.     

How river structure and biological traits influence gene flow: a population genetic study of two stream invertebrates with differing dispersal abilities

1. Determined by landscape structure as well as dispersal‐related traits of species, connectivity influences various key aspects of population biology, ranging from population persistence to genetic structure and diversity. Here, we investigated differences in small‐scale connectivity in terms of gene flow between populations of two ecologically important invertebrates with contrasting dispersal‐related traits: an amphipod (Gammarus fossarum) with a purely aquatic life cycle and a mayfly (Baetis rhodani) with a terrestrial adult stage. 2. We used highly polymorphic markers to estimate genetic differentiation between populations of both species within a Swiss pre‐alpine catchment and compared these results to the broader‐scale genetic structure within the Rhine drainage. Landscape genetic approaches were used to test for correlations of genetic and geographical structures and in‐stream barrier effects. 3. We found overall very weak genetic structure in populations of B. rhodani. In contrast, G. fossarum showed strong genetic differentiation, even at spatial scales of a few kilometres, and a clear pattern of isolation by distance. Genetic diversity decreased from downstream towards upstream populations of G. fossarum, suggesting asymmetric gene flow. Correlation of genetic structure with landscape topography was more pronounced in the amphipod. Our study also indicates that G. fossarum might be capable of dispersing overland in headwater regions and of crossing small in‐stream barriers. 4. We speculate that differences in dispersal capacity but also habitat specialisation and potentially the extent of local adaptation could be responsible for the differences in genetic differentiation found between the two species. These results highlight the importance of taking into account dispersal‐related traits when planning management and conservation strategies.