Relative growth rate and biomass allocation in 20 Aegilops (Poaceae) species

This paper analyses relationships between relative growth rate ( rgr ), seed mass, biomass allocation, photosynthetic rate and other plant traits as well as habitat factors (rainfall and altitude) in 20 wild species of Aegilops L. and one closely related species of Amblyopyrum (Jaub. & Spach) Eig., which differ in ploidy level (diploid, tetraploid and hexaploid). The plants were grown hydroponically for 20 d in a growth chamber. The relationships between parameters were calculated either using the phylogenetic information (phylogenetically independent contrasts, PIC) or without using the phylogenetic information (trait values of taxa, TIP). The results using the two approaches were very similar, but there were a few exceptions in which the results were different (e.g. rgr vs. seed mass). Specific leaf area ( sla ) was positively correlated with leaf area ratio ( lar ) and negatively correlated with net assimilation rate ( nar ), which together resulted in the absence of a correlation between sla and rgr . Leaf photosynthetic rates (expressed on a mass or area basis) showed no correlation with rgr . rgr was positively correlated with the stem mass ratio and negatively with root mass ratio. Species with a lower d. wt percentage have a higher rgr . Aegilops species from locations with higher annual rainfall invested less biomass in roots and more in shoots (leaves and stems) and had a higher rgr . Diploid species had a lower seed mass and initial mass than the hybrids (tetraploid and hexaploid species), but there was no correlation of rgr with ploidy level. Polyploid species, which have higher seed mass, occur at a higher altitude than diploid species. Our results show that variation in rgr in Aegilops and Amblyopyrum spp. is associated mainly with variation in biomass allocation (proportion of biomass in stems and roots) and d. wt percentage, and not with variation in sla , leaf photosynthetic rates or seed mass.     

Genetic,morphological, and dietary changes associated with novel habitat colonisation in the Canary Island endemic grasshopper Acrostira bellamyi

1. The large flightless grasshopper Acrostira bellamyi Uvarov, endemic to the island of La Gomera (Canary Islands), inhabits two different environments: the xeric euphorb shrubland, as is typical for congeneric Canarian species, and the humid laurel forest, a novel habitat for the genus. 2. We investigate genetic, morphological, and ecological variation among individuals of A. bellamyi from the two habitats. DNA sequence data were used to evaluate whether grasshoppers from the two environments represent distinct lineages. Morphological and trophic analyses were performed to assess phenotypic differentiation between the two different habitats. 3. Population genetic analyses support the hypothesis that the euphorb shrubland is the ancestral habitat for this species. Female laurel forest specimens are larger than those inhabiting the euphorb shrubland, and some external body parts exhibit significant morphometric differences between the two populations. Diet of shrubland individuals is completely different from that of laurel forest individuals. Although in each habitat they consume the most abundant plants, individuals are able to select food plants, which appear to be explained by their nutrient content. 4. Our results suggest that A. bellamyi has colonised laurel forest from shrubland, and that this habitat shift has resulted in genetic, morphological, and ecological changes, perhaps as an adaptation to this new habitat.     

Effects of three modern insecticides, pyriproxyfen, spinosad and tebufenozide, on survival and reproduction of Chrysoperla carnea adults

Three novel insecticides, pyriproxyfen, spinosad and tebufenozide, were evaluated for their effect on survival and reproduction of Chrysoperla carnea adults using two methods of exposure: direct contact and ingestion. Pyriproxyfen and tebufenozide proved to be harmless to adult survival, whereas spinosad 72 h after treatment reduced the number of adults by 39.8% and 87.2% in topical and ingestion treatment at the maximum concentration recommended (800 mg a.i. litre^?1). Fecundity was not affected irrespective of the insecticide or time of application (before or after the onset of oviposition). Concerning fertility, only pyriproxyfen exerted a negative effect on hatching when the eggs were deposited by females treated by ingestion in the post‐oviposition period at the highest concentration tested (150 mg a.i. litre^?1).     

N2 Fixation (C2H2-Reducing Activity) and Leghaemoglobin Content during Nitrate- and Water-Stress-Induced Senescence of Medicago sativa Root Nodules

Nitrate and water stress were used to induce senescence in rootnodules of alfalfa (Medicago sativa L. cv. Aragon). Nodule senescencewas assessed by determinations of the nitrogenase (C₂H₂-reducing)activity, and the leghaemoglobin (LHb) and total soluble proteincontents of the nodules. Nodules responded similarly to and water stress in many respects, but there was a significant difference.All parameters of nodule activity, expressed on the basis ofnodule dry weight (DW), consistently decreased following treatmentwith or during drought; there was a significant interaction (synergism) between the inhibitory effects of and water stress on nitrogenase activity, but sucheffects were merely additive in the case of LHb content or LHb/solubleprotein ratio. However, caused the selective decay of LHb with respect to other nodular soluble proteins,whereas the decrease of LHb during water stress was due to ageneral inhibition of protein synthesis and to an increasedproteolytic activity in the nodule cytosol rather than to aspecific proteolysis of LHb. Key words: Leghaemoglobin, Medicago saliva, nitrogen fixation, root nodule senescence, water stress     

Population fluctuations of mosquitoes in the non-seasonal tropics

Abstract.

• 1 Seasonal and annual fluctuations in abundance of a number of species of mosquitoes were studied in a relatively non-seasonal climate near Almirante, Panama.
• 2 The fluctuations observed were large, but did not have a period of 1 year and should be classified as non-seasonal.
• 3 At each site the various species were not synchronous in their fluctuation pattern, but the fluctuations of each species were synchronous over an area of at least 4 km long, in spite of large differences in habitat.
• 4 Changes in abundance from year to year observed in these mosquitoes are large compared with those of insects, including mosquitoes, in other areas of Panama.
• 5 The importance of such large and unpredictable fluctuations in abundance for planning control measures is discussed.

     

Combining geometric morphometrics and pattern recognition to identify interspecific patterns of skull variation: case study in sympatric Argentinian species of the genus Calomys (Rodentia: Cricetidae: Sigmodontinae)

Sympatric species of vesper mice Calomys laucha and Calomys musculinus are difficult to discriminate, especially in natural history collections where they are identified by external body measurements and cranial characteristics. Accurate identification of these two species can be important because only one of them, C. musculinus , is a Junin virus reservoir, the aetiological agent of the Argentine Hemorragic Fever. Research has focused into the development of molecular techniques to unambiguously identify these species. We apply statistical procedures from the field of pattern recognition to three-dimensional geometric morphometric data based on skull landmarks to identify sympatric species C. laucha , C. musculinus and Calomys venustus . Pattern recognition techniques correctly identified the three species without any prior information on specimen identity. By contrast to expectations, C. venustus differed from the other two species mainly on the basis of shape and not by its centroid size. The main sources of difference between C. laucha and C. musculinus were of shape, specifically localized at the landmarks defined by: (1) the sutures between the premaxillaries, the nasals and the frontals; (2) the sutures between the parietals, the frontals and the squamosals; and (3) the suture between the parietals and the interparietal. Nevertheless, allometries dominate the patterns of interspecific variation between these latter species and may partly explain past identification difficulties. Morphological evolution is discussed. The need for objective methods to define phenotypic clusters is highlighted with respect to the need for fast and precise biodiversity assessments.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 365–378.     

Number of individuals and molecular markers to use in genetic differentiation studies

Molecular markers are frequently used to study genetic variation among individuals within or between populations. Differences in marker banding patterns can be used to verify if individuals do, or do not, represent distinct groups or populations. Only in 2005, more than 500 studies used molecular markers to group individuals in clusters. Such studies make use of an arbitrary number of molecular markers from each of an arbitrary number of individuals presumed to represent distinct genotypes. However, the greater the genetic variation, the more likely a larger number of individuals and markers will be needed to capture a population's genetic signature. The numbers of both, markers and individuals included thus affect the way in which individuals are organized through cluster analyses, thereby affecting the conclusions drawn. Here we present a method that provides statistical criteria to verify that individual and marker sample sizes are sufficient to accurately depict genetic differentiation among different populations. Our method uses a resampling technique to assess the reproducibility of obtaining a particular grouping pattern for specific data sets. It thus, allows to estimate the robustness of the results obtained without including additional individuals, or markers.     

Development of polymorphic microsatellite markers for the Eucalyptus leaf pathogen Mycosphaerella nubilosa

Mycosphaerella nubilosa is one of the most important Eucalyptus leaf pathogens, causing premature defoliation and stunting of growth. The aim of this study was to develop polymorphic microsatellite markers for M. nubilosa. Fifteen primer sets were developed and evaluated for polymorphism. Two primers were monomorphic, three primers did not amplify the desired region and 10 primer pairs were polymorphic. These microsatellite markers will be applied to population biology studies of M. nubilosa collections from several countries. These studies will promote an understanding of the genetics and the global movement of M. nubilosa that is severely limiting plantation development.