Thresholds Are in the Eye of the Beholder: Plants and Wildlife Respond Differently to Short‐Term Cattle Corrals

Rangelands are governed by threshold dynamics, and factors such as drought, wildfire, and herbivory can drive change across thresholds and between ecological states. Most work on this topic has focused on shifts in a single response variable, vegetation, and little research has considered how to reconcile responses of more than one variable to determine whether a system has undergone a genuine state change. In sub‐Saharan Africa, mobile overnight livestock corrals (bomas) can be used by managers to precipitate ecological transitions from areas dominated by bare ground to productive ecosystem hotspots (glades) that are attractive to wild herbivores. We asked how long bomas must be occupied by cattle before undergoing a state change, considering both plant and animal response variables, to glade ecosystem hotspots. We tested five durations of boma occupation: 0, 4, 7, 14, and 28 days. Each treatment was replicated five times, and we assessed vegetation as well as herbivore dung (as a proxy of use) at multiple time points over 3 yr following boma abandonment. Vegetation in 7‐, 14‐, and 28‐d boma duration treatments appeared to undergo a complete transition to glade‐like plant communities, whereas the shortest 4‐d treatment had not converted to a glade plant community by year 3. Wildlife responses appeared to lag behind vegetation responses, with transitions to glade‐like herbivore use occurring only in the longest duration (14‐ and 28‐d) treatments. Our results show that different response variables, when considered individually, may provide incomplete or misleading information about state changes. Although shorter‐occupied bomas might be effective for reducing bare ground, they may not attract enough wild herbivores to constitute crossing into an alternative state. Understanding threshold dynamics associated not only with vegetation responses but with a broader suite of response variables is challenging, but will provide a more complete representation of ecosystem function and greater opportunity for more successful ecosystem management

Subterranean archipelago: mitochondrial DNA phylogeography of stygobitic isopods (Oniscidea : Haloniscus) from the Yilgarn region of Western Australia

Copyright © CSIRO 2008The arid Yilgarn region of Western Australia contains numerous isolated calcrete aquifers, within which a diverse subterranean fauna has been discovered. Genetic and morphological studies of subterranean dytiscid beetles and amphipods have suggested that individual calcretes are equivalent to closed island habitats, which have been isolated for millions of years. Here we test this ‘subterranean island’ hypothesis further by phylogeographic analyses of subterranean oniscidean isopods (Haloniscus), using mitochondrial DNA (mtDNA) sequence data derived from the cytochrome c oxidase subunit I gene. Phylogenetic and population genetic analyses provided evidence for significant phylogeographic structuring of isopod populations, with evidence for at least 24 divergent mtDNA lineages, each restricted in their distribution to a single calcrete aquifer. The high level of divergence among calcrete populations (generally >25%) and several mtDNA lineages within calcretes (>16%) suggests that each lineage is likely to represent a distinct species. These analyses, together with comparative phylogeographic data from dytiscid beetles and amphipods, provide strong support for the ‘subterranean island’ hypothesis, applying to both air-breathing and fully aquatic arthropod groups. The finding of several epigean lineages that grouped with stygobitic Haloniscus populations, and the overall phylogeographic structure of populations, suggests that the majority of stygobitic species evolved within individual calcretes following independent colonisation by epigean ancestors.Steven J. B. Cooper, Kathleen M. Saint, Stefano Taiti, Andrew D. Austin and William F. Humphrey

Tailored disorder in calcite organization in tergite cuticle of the supralittoral isopod Tylos europaeus Arcangeli, 1938

The crustacean cuticle forms skeletal elements consisting of chitin-protein fibrils reinforced by amorphous and crystalline calcium carbonate and phosphate minerals. The edges of skeletal elements are of particular interest. They are subject to repeated strain and stress because they form transitions to the arthrodial membranes connecting them. These allow for relative movements of skeletal elements. In this study, we investigate structure, chemical composition, mineral organization and local mechanical properties of the anterior and posterior edges of the tergite cuticle in the conglobating beach isopod Tylos europaeus and compare these with the protective dorsal region of the tergites. The distribution of mineral phases at the edges resembles that of dorsal regions of the tergites. At the transition with the unmineralized arthrodial membrane the calcite containing distal exocuticle is replaced by epicuticular material and the subjacent cuticular layers containing amorphous calcium carbonate become enriched with amorphous calcium phosphate. At the edges, the local elastic modulus and hardness values are significantly lower compared to dorsal regions of the tergite cuticle, for both, the calcite and the amorphous mineral containing layers. The calcite within the tergite cuticle is assembled in different texture patterns: (i) almost random co-orientation, (ii) almost single crystalline calcite, and (iii) a graded organization. Calcite organization and co-orientation strength is highly variable, not only on very few tens of micrometres, but also between regions with different skeletal functionality. Our results show that besides structure and composition, patterns of calcite organization contribute to the hierarchical architecture and functionality of biological composites. © 2018 Elsevier Inc

Volatile compounds from different fruit parts of two cultivars of Cydonia oblonga

Quince is characterized as a fragrant fruit which, unlike other pomes (apple, pear) it is not used for fresh consumption due to its astringency and compactness, but only in its processed form (jams, jelly, distillery products, and nutraceutical compounds). As a consequence, there is little knowledge currently available concerning the characteristics of the fruit, and in particular its aromatic and chemotaxonomic patterns. In this work, carpometric, chemometric and spectrophotometric measurements were performed on quince fruits. VOCs emitted by different tissues or parts of the fruit were studied to describe its aromatic profile. The study was carried out on the fruits of an old, well-known cultivar (‘Gigante di Wranja’, commonly called ‘Wranja’) and a new Tuscan accession. Intact, halved and solely pulp (cubed) samples were evaluated for each individual fruit. Data obtained from VOC analysis through Proton Transfer Reaction Time-of-Flight Mass Spectrometer (PTR-ToF-MS) were evaluated by multivariate statistical analysis. The spectra obtained from the intact fruit samples showed a higher amount of masses corresponding to terpenes or terpenoid compounds, which fundamentally characterize the aroma of this type of fruit; these substances were found to be much less present in the VOCs emitted by the pulp, where high values of masses linked to the maturation processes were instead found