A test of Tyler’s Line – response of chironomids to a pH gradient in Tasmania and their potential as a proxy to infer past changes in pH

1. Tyler’s Line delimits two distinct limnological provinces that reflect differences in climate, geology and vegetation in Tasmania. Lakes west of Tyler’s Line are typically acidic and dystrophic with relatively shallow euphotic zones, whereas eastern lakes are circumneutral and oligotrophic or ultra‐oligotrophic, allowing deeper penetration of light. Consequently, Tyler’s Line defines a boundary where species assemblages change over a relatively short distance. 2. A survey of 48 Tasmanian lakes was undertaken to identify indicator taxa of the two limnological provinces and breakpoints along the pH gradient where shifts in taxa occur. Chironomidae (Diptera) were used because they are ideal candidates for lake classification. 3. Three independent methods (geographical position, piecewise linear regression, two‐way indicator species analysis) verified that chironomids accurately reflect the environmental variables defining Tyler’s Line at lake and catchment scales. Chironomid genera are often speciose, and members of the same genus can have markedly different responses to a given environmental variable. Although the types of taxa changed along the pH gradient, richness did not. This finding contrasts with many studies from the northern hemisphere but accords with other studies from Australia. 4. Models of pH, developed using both partial least squares and weighted averaging partial least squares, can be used to understand past natural variability of pH in Tasmania and to test hypotheses regarding the timing, magnitude and source of contamination in impacted aquatic ecosystems.     

Protein composition of unusual tobacco mosaic virus strains

Amino acid analyses have been made of the proteins of single-lesion isolates of five strains of tobacco mosaic virus (TMV) differentiated by Lycopersicon hosts. These hosts differed in their genetical control of resistance to TMV, and the virus strains had therefore survived specific selection pressures. Two of the five strains differed in their amino acid composition from type TMV and from all other tomato strains of TMV previously examined. Symptoms induced by the five strains in four tomato lines and in Nicotiana tabacum cvs White Burley and Kawala are described.     

Comparative study of the breeding success of Whooper Swans Cygnus cygnus nesting in upland and lowland regions of Iceland

The study assessed the reproductive success at different stages of the breeding season of Whooper Swans Cygnus cygnus from two geographically distinct areas of Iceland, one an upland and the other a lowland region. Censuses made at both sites indicated that the majority of the birds did not attempt to breed and that annual recruitment came from 30 to 40% of the population. Individual females tended to lay more eggs in the lowlands, with a mean clutch-size of 4.7 eggs, compared with 3.8 eggs per clutch in the highlands. A mean brood-size of 3.1 cygnets was obtained at both the highland and the lowland sites in August but the highland cygnets were significantly smaller and lighter. The difference in cygnet size could be attributable to one or a combination of factors including age differences and habitat variables. Lowland adults were significantly heavier than those from the highlands, which reinforced the view that habitat quality was superior at the lowland site. There was no difference in the feather length recorded for adult swans moulting in the two study areas, indicating that the moult occurred concurrently in the highlands and lowlands. The number of cygnets lost per brood between ringing and resighting in the wintering range was significantly higher for the highland swans, although the number of highland families relocated was small. The results indicate that birds from different breeding areas may contribute disproportionately to the percentage of juveniles reared annually in the population.     

Regional and local (road verge) effects on size and fecundity in Banksia menziesii

Abstract Banksia menziesii is a tree at the mesic end (Swan Coastal Plain) of its range and a shrub at the xeric end (Eneabba Plain). Plants at the xeric end produced, on average, as many cones, set 2.3 times as many seeds and stored 8.8 times as many viable seeds in the crown, as those at the mesic end. Plants on road verges had, on average, 2.5 times larger crowns than those at least 50 m further from the road. Road edge plants produced, on average, 2.5 times as many cones, set 3.1 times as many seeds and stored 3.7 times as many viable seeds as non-edge plants. Greater fecundity at the xeric end, including the road verges, could help offset the greater incidence of adult deaths and the reduced likelihood of seedling recruitment after fire at Eneabba.     

Neoselachian sharks from the Callovian–Oxfordian (Jurassic) of Ogrodzieniec,Zawiercie Region,southern Poland

Abstract: Callovian and Oxfordian strata in Ogrodzieniec near Zawiercie, southern Poland, have yielded two shark tooth assemblages that collectively include 14 neoselachian taxa. A previously unrecognised member of the Orectolobiformes, Akaimia altucuspis gen. et sp. nov., is described and characterised by a dentition remarkably similar to modern wobbegong sharks (Orectolobidae) by convergence. The assemblages also include the first anterior teeth ever found of the palaeospinacid ‘Synechodus’prorogatus Kriwet, in addition to teeth from two other palaeospinacids, Sphenodus spp., four different orectolobiforms, two hexanchids and Protospinax spp. These shark tooth assemblages contribute to the poorly known Callovian and Oxfordian neoselachian faunas and indicate that the diversity was higher than previously appreciated, particularly within the Orectolobiformes.