Which Factors Determine Spatial Segregation in the South American Opossums (Didelphis aurita and D. albiventris)? An Ecological Niche Modelling and Geometric Morphometrics Approach

Didelphis albiventris and D. aurita are Neotropical marsupials that share a unique evolutionary history and both are largely distributed throughout South America, being primarily allopatric throughout their ranges. In the Araucaria moist forest of Southern Brazil these species are sympatric and they might potentially compete having similar ecology. For this reason, they are ideal biological models to address questions about ecological character displacement and how closely related species might share their geographic space. Little is known about how two morphologically similar species of marsupials may affect each other through competition, if by competitive exclusion and competitive release. We combined ecological niche modeling and geometric morphometrics to explore the possible effects of competition on their distributional ranges and skull morphology. Ecological niche modeling was used to predict their potential distribution and this method enabled us to identify a case of biotic exclusion where the habit generalist D. albiventris is excluded by the presence of the specialist D. aurita. The morphometric analyses show that a degree of shape discrimination occurs between the species, strengthened by allometric differences, which possibly allowed them to occupy marginally different feeding niches supplemented by behavioral shift in contact areas. Overlap in skull morphology is shown between sympatric and allopatric specimens and a significant, but weak, shift in shape occurs only in D. aurita in sympatric areas. This could be a residual evidence of a higher past competition between both species, when contact zones were possibly larger than today. Therefore, the specialist D. aurita acts a biotic barrier to D. albiventris when niche diversity is not available for coexistence. On the other hand, when there is niche diversification (e.g. habitat mosaic), both species are capable to coexist with a minimal competitive effect on the morphology of D. aurita

Analysis of Differential Transcript Expression Reveals Time-Dependent Leaf Responses to Sclerotinia seclerotiorum in Wild and Cultivated Sunflower

The necrotrophic pathogen Sclerotinia sclerotiorum is a causal agent of rot diseases in sunflower and is described as one of the most damaging pathogens of cultivated sunflower. Resistance to this pathogen is found in some genotypes of wild sunflower in particular characterised by significantly reduced lesion lengths in capitulum, stems and leaves. This study was conducted to characterise transcriptomic alterations during interaction of host and pathogen in lesion-surrounding areas of the leaf using differential display RT-PCR and to compare molecular responses between a resistant and a susceptible genotype. Leaves were examined during the first stages of pathogenesis (dpi 2, 3 and 4) after inoculation with S. sclerotiorum. By means of computational analysis of fluorescently labelled expression data, expression patterns were evaluated and significant differentially expressed transcripts were selected. The expression profile revealed that a response measured by the number of significant differentially expressed transcripts differed between the resistant and susceptible genotype in timing. Nine differentially expressed transcripts were successfully sequenced of which two transcripts originated from the mRNA population of the pathogen, two transcripts were derived from the susceptible cultivar of Helianthus annuus and five transcripts were isolated from the resistant genotype of Helianthus maximiliani. Semi-quantitative real-time PCR was accomplished to verify the significant differential expression of the potentially resistance-associated transcripts coumarate-CoA-ligase and cysteine protease transcript in the resistant H. maximiliani accession and differential expression of a chlorophyll-a/b-binding-protein and an S-adenosyl-methionine-synthetase transcript originating from the susceptible H. annuus cultivar

New records of the red-rumped mouse Juliomys pictipes (Osgood, 1933) (Rodentia: Sigmodontinae) in coastal Atlantic forest of Paraná, southern Brazil

http://dx.doi.org/10.5007/2175-7925.2014v27n1p159 Juliomys pictipes is a Sigmodontinae rodent endemic to the Atlantic Forest. Herein, we report the first records of the species on the coast of the state of Paraná, filling a gap in the species’ distribution. Records at low altitudes in the eastern part of the Serra do Mar confirm that the coastal mountains are not a barrier to the species’ distribution.http://dx.doi.org/10.5007/2175-7925.2014v27n1p159 Juliomys pictipes is an Atlantic Forest endemic Sigmodontinae rodent. Herein we report the first records of the species in the coast of the state of Paraná, filling a gap in the species distribution. Records at low altitudes at the eastern part of the Serra do Mar confirms that the coastal mountains are not a barrier to the species distribution