Wolf Predation Among Reintroduced Przewalski Horses in Hustai National Park,Mongolia

ABSTRACT Depredation by wolves (Canis lupus) could threaten survival of reintroduced wild Przewalski horses (Equus ferus przewalskii) in Hustai National Park (HNP), Mongolia. We conducted scat analysis, spatial analyses of kills, and interviews to study prey species selection and temporal and spatial factors that characterize prey choices of wolves. Diet of wolves in HNP was comprised of >50% of livestock. Diet composition varied during the year, with more livestock taken in winter. Wildlife species were selected over livestock species. From available livestock species domestic horses were predated most, whereas red deer (Cervus elaphus) and marmot (Marmota sibirica) were the preferred wildlife species. Our spatial analyses showed an unexpected significant positive relation between number of domestic horses killed and distance to the park, as well as a significant negative relation with number of gers (tents) in the area. Compared to randomly selected comparison sites (n = 36), we found Przewalski foal kills (n = 36) at sites that were closer to the forest, at higher altitudes, with lower shrub cover, higher forest cover, and higher red deer density. If the negative trend of deer numbers continues and if herdsmen protect their livestock more vigorously, depredation of wild Przewalski horses by wolves will rise. Therefore, a large red deer population could be pivotal in improving the conservation status of Przewalski horses.     

Response of plant species and life form diversity to variable fire histories and biomass in the jarrah forest of south‐west Australia

Frequent fires reduce the abundance of woody plant species and favour herbaceous species. Plant species richness also tends to increase with decreasing vegetation biomass and cover due to reduced competition for light. We assessed the influence of variable fire histories and site biomass on the following diversity measures: woody and herbaceous species richness, overall species richness and evenness, and life form evenness (i.e. the relative abundance or dominance among six herbaceous and six woody plant life forms), across 16 mixed jarrah (Eucalyptus marginata) and marri (Corymbia calophylla) forest stands in south‐west Australia. Fire frequency was defined as the total number of fires over a 30‐year period. Overall species richness and species evenness did not vary with fire frequency or biomass. However, there were more herbaceous species (particularly rushes, geophytes and herbs) where there were fewer shrubs and low biomass, suggesting that more herbaceous species coexist where dominance by shrubs is low. Frequently burnt plots also had lower number and abundance of shrub species. Life form evenness was also higher at both high fire frequency and low biomass sites. These results suggest that the impact of fire frequency and biomass on vegetation composition is mediated by local interactions among different life forms rather than among individual species. Our results demonstrate that measuring the variation in the relative diversity of different woody and herbaceous life forms is crucial to understanding the compositional response of forests and other structurally complex vegetation communities to changes in disturbance regime such as increased fire frequency.     

The role of electrogenic xylem pumps in K+ absorption from the zylem of Vigna unguiculata: the effects of auxin and fusicoccin

Abstract We tested the hypothesis that electrogenic ion pumps, working at the parenchyma symplast/xylem interface of pea hypocotyls, provide the driving force for K⁺ uptake from the xylem. Solutions of known composition were perfused through a hypocotyl segment. The K⁺ activity of the solution flowing out of the xylem (K⁺_out) increased (i.e. K⁺ uptake decreased) when aerobic respiration was inhibited by lack of O₂, and this was preceded by a decrease in V_px (electrical potential difference between parenchyma symplast and xylem). Perfusion with auxin (1AA) and fusicoccin (FC) stimulated the electrogenic activity of the ‘xylem pumps’ (111 and 205% respectively) and stimulated uptake of K ⁺ from the xylem (with 71% and 29% respectively). The close correlation between xylem pump activity and K⁺ uptake corroborated the aforementioned hypothesis. Interestingly, inhibition of pump activity by anoxia was incomplete in the presence of FC. It is thought that FC increases the affinity of the ATP-requiring xylem pump for ATP, thus ensuring that ATP production during fermentation is sufficient to fuel the pump in the absence of O₂.     

Activity areas and daily movements of an arboreal monitor lizard,Varanus tristis (Squamata: Varanidae) during the breeding season

During the breeding season, in the western Great Victoria Desert, Western Australia, male Varanus tristis move greater daily distances (186.5 m) than females (99.7 m) and have larger activity areas (40.3 ha vs 3.7 ha). V. tristis retreat predominantly to live and dead upright Eucalyptus gongylocarpa (marble gum) trees that have hollows in their trunks and limbs. There is no observable difference between males and females in their preferred habitat, but females are found more frequently in a lesser number of preferred retreats during the breeding season.