Soil conservation in Polylepis mountain forests of Central Argentina: Is livestock reducing our natural capital?

Mountain forests and their soils provide ecological services such as maintenance of biodiversity, provision of clean water, carbon capture and forage for livestock rearing, which is one of the principal economic activities in mountain areas. However, surprisingly little is known about livestock impact in South American mountain forest soils. With the aim of understanding how livestock and topography influence patterns of forest cover, soil compaction, soil loss and soil chemical properties, we analysed these parameters in 100 Polylepis australis woodland plots situated in the humid subtropical mountains of Central Argentina. We used distance from the nearest ranch as an objective index of historical livestock impact and measured standard topographic variables. Our main results reveal that distance from ranch in all cases partly explains tree canopy cover, soil loss, soil compaction and soil chemical properties; suggesting a strong negative effect of livestock. Intermediate altitudes had more tree canopy cover, while landscape roughness – a measure of the variability in slope inclination and aspect – was negatively associated to soil impedance and acidity, and positively associated to soil organic matter content. Finally, flatter areas were more acid. We conclude that livestock has had a substantial influence on forest soil degradation in the Mountains of Central Argentina and possibly other similar South American mountains. Soil degradation should be incorporated into decision making when considering long‐term forest sustainability, or when taking into account retaining livestock for biodiversity conservation reasons. Where soil loss and degradation are ongoing, we recommend drastic reductions in livestock density.     

Biochemical evidence of the expression of two major histocompatibility complex class I genes on bovine peripheral blood mononuclear cells

For a long time, the bovine major histocompatibility complex (MHC) (BoLA) class I region was characterized, rather uniquely among mammalian species, as having one expressed locus. Recent reports have suggested otherwise. Selective immunoprecipitation and molecular characterization of products enable a decisive answer to the question of whether there is indeed more than one locus expressed. Therefore, we characterized serologically defined w10 encoding haplotypes in European and African cattle by immunoprecipitation of [35S]-methionine-labelled peripheral blood mononuclear cells (PBMC), followed by one- and two-dimensional isoelectric focusing (1D/2D-IEF) of cell lysates. Monoclonal antibodies (mAb) used were directed against either human class I monomorphic determinants (W6/32 and B1.1G6) or bovine polymorphic determinants expressed on products encoded by serologically defined w10 encoding haplotypes of Boran and Friesian cattle. Sequential immunoprecipitations with W6/32 and B1.1G6 using lysates of PBMC of British Friesian cattle, revealed that from this haplotype W6/32 precipitated one product, whereas B1.1G6 precipitated two products. The product precipitated in addition appeared to be the one that was selectively precipitated by the mAb directed against polymorphic determinants on a product of w10 encoding haplotypes. Additionally, peptide maps of protease V8-digested precipitates showed that this particular 'w10' associated product was distinctly different from the product recognized by W6/32. Thus, we suggest that the two products are distinct gene products and that the product with higher pI is associated with the serologically defined A-locus product, whereas the product with lower pI is the putative second locus product. In the African Boran breed, variants of the serologically defined w10 specificity were found on the basis of IEF typing. These variants appeared to be associated with different second locus products. Therefore, we conclude that serologically defined w10 encoding haplotypes encode at least two independent class I locus products, expressed on normal bovine PBMC. In IEF analysis the additional use of mAb recognizing polymorphic determinants on serologically defined A-locus products highly facilitated the detection and typing of second locus products.     

Intraspecific variation in wing and pupal melanization in copper butterflies (Lepidoptera: Lycaenidae)

Melanin is a widespread pigment causing variation in skin darkness, with darker phenotypes typically reaching higher equilibrium temperatures than lighter ones. Therefore, selection is expected to favour darker phenotypes in colder environments. In the present study, we show intraspecific variation in pupal (and wing) melanization along an altitudinal gradient in two species of copper butterflies. Both, pupal and wing melanization increased with increasing altitude. Consistent with the thermal melanism hypothesis, darker (high-altitude) pupae reached higher equilibrium temperatures than paler (low-altitude) ones. However, as temperature differences were rather small despite pronounced differences in melanization, we cannot rule out that factors (e.g. ultraviolet protection, disease resistance) other than temperature comprise the principal selective agents. Mechanistically, variation in melanization might be related to variation in hormone titres, as demonstrated by low-altitude pupae showing higher ecdysteroid and juvenile hormone titres compared to high-altitude ones. Furthermore, we report sex differences in wing melanization, with males being darker than females, which is potentially related to a higher flight activity of males.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 301–312.     

Energetics of reproduction: consequences of divergent selection on egg size, food limitation, and female age for egg composition and reproductive effort in a butterfly

Using lines artificially selected on egg size and being subjected to a restricted and an unrestricted feeding treatment, we examined the relationships between egg size, egg number, egg composition, and reproductive investment in the butterfly Bicyclus anynana . Despite a successful manipulation of egg size, correlated responses to selection in larval time, pupal mass, pupal time, longevity, fecundity, or the amount of energy allocated to reproduction were virtually absent. Thus, there was no indication for an evolutionary link between offspring size and reproductive investment. Egg composition, in contrast, was affected by selection, with larger eggs containing relatively more lipid and water, but less protein and energy compared to smaller eggs. Hence, females producing large eggs did not have to sacrifice fecundity due to adjustments in egg composition. Food limitation per se caused only minor changes in egg composition, and there was no general reduction in egg provisioning with female age. The latter was restricted to food-limited females, whereas egg quality remained remarkably similar throughout the females' life in control groups. We conclude that neglecting changes in biochemical egg composition, depending on genetic background, food availability, and female age, may introduce substantial error when estimating reproductive effort, and may ultimately lead to invalid conclusions.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 403–418.     

Habitat invasion risk assessment based on Landsat 5 data,exemplified by the shrub Rosa rubiginosa in southern Argentina

Prediction of invasive species spread helps to plan management actions. We performed a risk assessment by quantifying habitat invasibility, predicted the potential distribution of an invasive species using the Maxent modelling program and confirmed patterns using detailed field studies. Our study was conducted in southern Argentina, Patagonia, where large areas are already invaded by the European shrub Rosa rubiginosa. A total of 163 R. rubiginosa locations served as ground truth data, and predictors were obtained from the spaceborne sensor Landsat 5. Based on the Maxent Method (area under the receiver operating characteristic curve 0.8), the habitat invasibility map covered about 5000 km². Our model revealed that R. rubiginosa has the potential to invade 36% of the area along a steep precipitation gradient (target region 600–1400 mm per year). The Tasseled Cap brightness index and the normalized vegetation index explained most of the variance in our model, followed by the Tasseled Cap greenness and wetness indices, which can be interpreted as indicators of disturbance. Highest levels of invasibility were predicted for urban areas, along roads and rivers, on pastures, in Austrocedrus chilensis forests and inside Nothofagus dombeyi forest gaps. Detailed field assessments of rose cover performed in seven habitat types supported these results: rose cover significantly decreased with increasing tree cover (P < 0.01). Our data revealed that the occurrence of R. rubiginosa is not connected to a certain habitat type, but that it thrives in open patches following habitat disturbance. Our approach is a widely applicable, cost‐free remote sensing method that can serve as a risk assessment tool for alien plant species invasion of habitats.     

Ant specificity and behaviour in mutualisms with epiphytes: the case of Lecanopteris (Polypodiaceae)

Seven species of the fern Lecanopteris: L. sinuosa, L. sarcopus, L. mirabilis, L. curtisii, L. pumila, L. celebica and L. damaedii are regularly inhabited by ants of five species: Iridomyrmex cordatus, I. murinus, Crematogaster treubi, C. difformis and Camponotus pallidas. Inhabitation is not obligate; either party can survive without the other, but ferns without ants are rare in their natural habitat. The total recorded diversity of ants in Lecanopteris is 31 species, 20 of which were only recorded once.
All five regularly inhabiting ant species kept larvae in the domatium (82% of Lecanopteris specimens examined). The major ant species inhabiting Lecanopteris deposited debris in the domatium, segregated from their brood (90% of Lecanopteris specimens). Iridomyrmex murinus did not build carton around the rhizomes, but the other major inhabitants constructed runways in 79% of Lecanopteris specimens. Goccid cultivation was variable within ant and plant species: I murinus tended them in 50% of specimens, and homopterans were also recorded with Crematogaster treubi (39%), C. bomeensis (27%) and I cordatus (16%). A high frequency of ant colonies inhabiting Lecanopteris , keeping larvae, depositing debris, building carton runways, and occasionally keeping coccids has been established. Specificity of ant species is high within a population of Lecanopteris , or a given habitat or geographical area, but outside the ranges of regular inhabitants other ant occupants are found. Comparable data from other genera of ant-epiphytes with domatia show similar diversity of inhabitance over geographical areas; no data are available within single plant populations.