MARINE REPTILES FROM THE LOWER CRETACEOUS OF SOUTH AUSTRALIA: ELEMENTS OF A HIGH-LATITUDE COLD-WATER ASSEMBLAGE

Abstract: The Lower Cretaceous rocks of South Australia have yielded a diverse marine reptile assemblage of up to five families of plesiosaur (including a new cryptoclidid or cimoliasaurid, indeterminate elasmosaurids, a possible polycotylid, rhomaleosaurids, and pliosaurid) and one family of ichthyosaur (ophthalmosaurid). Other common associated vertebrates include chimaerids and osteichthyans. Sharks, dipnoans and dinosaurs are uncommon and marine turtles are notably absent. The main fossil‐producing strata belong to the Lower Aptian–Lower Albian Bulldog Shale although the Upper Albian Oodnadatta Formation has produced isolated elements. Both these units comprise finely laminated shaly mudstones and claystones deposited in a transgressive shallow coastal, epicontinental marine environment. Estimates of palaeolatitude place South Australia between 60° and 70°S, in the late Early Cretaceous. Sedimentary structures (including lonestone boulders and glendonites), fossils, isotope data and climatic modelling also indicate that seasonally cool–cold conditions (possibly with winter freezing) prevailed during deposition of the Bulldog Shale. This contrasts markedly with climate regimes typically tolerated by modern aquatic reptiles but suggests that some of the South Australian Mesozoic taxa may have possessed adaptations (including elevated metabolic levels and/or annual migration) to cope with low temperatures. A high proportion of juvenile plesiosaur remains in the Bulldog Shale might also indicate that nutrient‐rich cold‐water coastal habitats functioned as both ‘safe calving grounds’ and refuges for young animals prior to their entering the open sea as adults. The occurrence of plesiosaurs and ichthyosaurs in the high‐latitude Lower Cretaceous of southern Australia, along with plesiosaurs and mosasaurs in the Upper Cretaceous of South America, Antarctica, New Zealand and the Chatham Islands, demonstrates that Mesozoic marine reptiles utilized southern high‐latitude environments over a considerable period of time, and that these records do not represent casual occupation by isolated taxa.     

Glutamine- and Asparagine-Dependent Protein Synthesis in Maturing Legume Cotyledons Cultured in vitro

Legume cotyledons have been grown in sterile culture and shownto synthesize up to 16 mg protein in 5 d when supplied witheither asparagine or glutamine as sole nitrogen sources. Glutamate,nitrate, and ureides also served as nitrogen sources for proteinsynthesis but to a lesser extent. Methionine sulphoximine and azaserine inhibited asparagine-dependentprotein synthesis suggesting that ammonia is liberated fromasparagine which is reassimilated via glutamine synthetase andglutamate synthase.     

The Influence of Sowing Depth and Seed Size on Seedling Emergence Time and Relative Growth Rate in Spring Cabbage (Brassica oleracea var. capitata L.)

The effects of seed size and sowing depth on the time of seedlingemergence and on the growth of spring cabbage studied in greenhouseand field experiments. Seed size had little effect on seedlingemergence time, but plants derived from large seeds were largerthan those from small seeds. Increased sowing depth delayedseedling emergence and reduced seedling relative growth rate(RGR). To our knowledge, these effects of sowing depth on RGRindependent of inter-plant competition have not been reportedpreviously for any species. Sowing depth had no effect on thenet assimilation rate (NAR) of seedlings, indicating that thelower RGR of seedlings from deep sowings was associated witha low light interception by small cotyledons which in turn resultedfrom disproportionately low partitioning of assimilates to thecotyledons during pre-emergence growth in favour of producinghypocotyls of greater length. Brassica oleracea, specific leaf area, growth analysis, dry matter partitioning, light interception, cabbage, seed size, sowing depth, seedling emergence time, relative growth rate, net assimilation rate     

The Influence of Foliage Habit on Competition Between Carrot Plants

Carrot plants of a cultivated variety (cv. Chantenay Red Cored)and those of a wild type were grown in both pure and mixed populationsin which root competition was prevented. During early growth,cultivated plants competed effectively against the wild plants.Fifty days after sowing chitted seed, the mean weight of thestorage organs of the cultivated variety grown in mixed populationswas 56 per cent greater than the mean weight of cultivated storageorgans in a pure population. Subsequently, however, this competitiveadvantage diminished, this being associated with the developmentof tall flowering stems by the wild plants. The foliage habitof the vegetative cultivated plants was more erect than thatof the vegetative wild plants. This difference in foliage habitmight explain why the cultivated plants out-compete the wildplants. Daucus carota L., carrot, foliage habit, competition     

Six quantitative trait loci influence task thresholds for hygienic behaviour in honeybees (Apis mellifera)

Honeybee hygienic behaviour provides colonies with protection from many pathogens and is an important model system of the genetics of a complex behaviour. It is a textbook example of complex behaviour under simple genetic control: hygienic behaviour consists of two components – uncapping a diseased brood cell, followed by removal of the contents – each of which are thought to be modulated independently by a few loci of medium to large effect. A worker’s genetic propensity to engage in hygienic tasks affects the intensity of the stimulus required before she initiates the behaviour. Genetic diversity within colonies leads to task specialization among workers, with a minority of workers performing the majority of nest‐cleaning tasks. We identify three quantitative trait loci that influence the likelihood that workers will engage in hygienic behaviour and account for up to 30% of the phenotypic variability in hygienic behaviour in our population. Furthermore, we identify two loci that influence the likelihood that a worker will perform uncapping behaviour only, and one locus that influences removal behaviour. We report the first candidate genes associated with engaging in hygienic behaviour, including four genes involved in olfaction, learning and social behaviour, and one gene involved in circadian locomotion. These candidates will allow molecular characterization of this distinctive behavioural mode of disease resistance, as well as providing the opportunity for marker‐assisted selection for this commercially significant trait.     

Conservation value of low fire frequency in tropical savannas: Ants in monsoonal northern Australia

The conservation values of ‘old‐growth’ forests in landscapes subject to repeated disturbance by fire or logging have received considerable conservation attention. However, little is known of the conservation values of old‐growth sites in ecosystems with an evolutionary history of highly frequent disturbance. Here we address the value of low fire frequency (<1 fire/10 years) in tropical savannas, the world's most fire‐prone biome, in terms of ant biodiversity. We do this by comparing savanna ant communities within the Territory Wildlife Park (TWP) near Darwin in the Australian monsoonal tropics, which has experienced a low incidence of fire over 25 years due to active fire exclusion, with those of adjacent (outside) sites experiencing the ambient fire regime of burning every 2–5 years. Ants were sampled using terrestrial and arboreal pitfall traps at 16 sites, eight each inside and outside TWP. More than 16 000 ants were recorded during the study, representing a total of 98 ant species from 30 genera. More species in total were recorded outside (90) than inside (74) TWP, but there was no difference in mean site species richness or abundance, and overall species composition was similar. All species recorded inside TWP are common and widespread throughout the savanna landscapes of the broader region, in the absence of active fire exclusion. Low fire frequency at the Territory Wildlife Park therefore does not appear to have enhanced regional ant conservation values. Our findings reinforce the importance of targeting fire regimes that are clearly linked to positive conservation outcomes, rather than assuming a need for maximum ‘pyrodiversity’.