Effect of additional food and water on house mice in a semi‐arid agricultural environment in Australia

Abstract We tested the hypothesis that providing high‐quality food and water would increase reproduction, survival and population size in house mice living in a semi‐arid cropping environment in the mallee region of western Victoria, Australia, where outbreaks of house mice (Mus domesticus) occur irregularly. We employed a factorial design and applied treatments along internal fencelines (16 sites), adjacent to cropping areas, from November 2003 to July 2004. Population abundance was low during the experiment (0–26 mice per site), and the summer rainfall was below average. We confirmed that mice used the supplementary food and water through a reduction in weight of food containers over time and for water through the presence of Rhodamine B in blood samples and positive bands in whiskers. Abundant food was also available through grain spilt on the ground after harvest of the wheat and barley crops. There was some evidence of increased breeding on sites where water was added, but no effect of food or food and water in combination. Sites where free water was available had marginally higher populations over summer (～2 more mice on average; P = 0.07). This difference was well below any biologically meaningful effect. Mice were 0.9 g heavier on sites where water was added (P = 0.04), and were in better condition (P = 0.03). The addition of high‐quality food did not affect mouse population dynamics, and the addition of water resulted in only marginal responses for some demographic characteristics. We conclude that other factors appear to be important for limiting mouse population growth in summer and autumn.     

Influence of growing location and cultivar on Rhyzopertha dominica （Coleoptera： Bostrichidae） and Sitophilus oryzae （Coleoptera： Curculionidae） infestation of rough rice

Long-grain rice cultivars Cocodrie, Wells, and XP 723 grown in three locations （Hazen, MO; Essex and Newport, AR, USA）, and medium-grain rice cultivars Bengal and XP 713 grown in two locations （Jonesboro and Lodge Corner, AR, USA）, were harvested and assayed for susceptibility to Rhyzopertha dominica （F.） （Coleoptera： Bostrichidae）, the lesser grain borer, and Sitophilus oryzae （L.） （Coleoptera： Curculionidae）, the rice weevil, on rice held at 27℃, 57% and 75% relative humidity （RH）. Separate samples from the same harvest lots were also analyzed for the physical characteristics of brown rice yield, percentage whole kernels and kernel thickness. Progeny production and feeding damage of R. dominica were significantly different among long-grain cultivars within two of the three locations （P 〈 0.05）, but not for location or RH （P ≥ 0.05）, while progeny production of S. oryzae was different among cultivars, location, and RH （P 〈 0.05）. On medium-grain rice, both cultivar and location were significant for progeny production of R. dominica, but not RH, while cultivar and RH were significant for progeny production of S. oryzae, but not location. On both rice types, feeding damage of R. dominica followed the same trends and was always strongly positively correlated with progeny production （P 〈 0.05）, but for S. oryzae there were several instances in which progeny production was not correlated with feeding damage （P ≥ 0.05）. Physical characteristics of both rice types were statistically significant （P 〈 0.01） but actual numerical differences were extremely small, and were generally not correlated with progeny production of either species. Results indicate that the location in which a particular rice cultivar is grown, along with its characteristics, could affect susceptibility of the rice to R. dominica and S. oryzae.     

Coevolution of the glucose dehydrogenase gene and the ejaculatory duct in the genus Drosophila

The glucose dehydrogenase gene (Gld) in Drosophila melanogaster exhibits a unique spatial and temporal pattern of expression. GLD expression switches from a non-sex-limited state at the pupal stage to a male-limited state at the adult stage. At the adult stage, the enzyme is restricted to the ejaculatory duct. Within the genus Drosophila, the ejaculatory duct has undergone a simple morphological divergence. In order to determine whether correlated changes in GLD expression had occurred, GLD activity during the pupal and adult stages was determined for several Drosophila species. It was found that virtually all of the species exhibit pupal GLD activity, whereas only those species with an expanded ejaculatory duct express male-limited GLD. The results of interspecific genital imaginal disc transplantation experiments indicate that the expanded morphology and GLD expression do not require any species- or sex-specific diffusible factors. An apparent regulatory polymorphism exists within the D. takahashii species with respect to male-limited GLD expression.      

Early vascular land plants: proof and conjecture

Megafossil evidence does not fill the 'evolutionary gap' between land plants and their hypothetical green algal ancestors. Rare Late Silurian vascular plant megafossils provide little information about the morphological, physiological, biochemical, and ecological steps that preceded their evolution. Dissociated trilete spores, spore tetrads, cuticle- and tracheid-like structures far exceed the abundance and diversity of Silurian vascular plant megafossils, and appear millions of years before them. In reference to whole-bodied organisms, these or analogous structures belong to land plants or emergent aquatics; they may represent plants evolutionarily intermediate between green algae and descendent vascular plants at the bryophyte or pre-bryophyte stages. Changes in the cellular biochemistry of pre-Devonian land plants in response to the selective pressures of terrestrial life may have led to the origin of lignin and cutin, neither of which has any counterpart among the algae, and to the evolutionary surge of the vascular plants in the Early Devonian represented by the plant megafossil record. Positive correlation between abundance and diversity of trilete spores and shallow-water, nearshore sites reinforces conclusions based on morphology that a terrestrial flora existed well prior to the appearance of vascular plant megafossils.