Ecological impacts of invasive African olive (Olea europaea ssp. cuspidata) in Cumberland Plain Woodland,Sydney, Australia

African olive (Olea europaea ssp. cuspidata) is a small evergreen tree which has become highly invasive at a landscape scale in the western Sydney and Hunter Valley regions of New South Wales, Australia. African olive invasion results in the formation of a dense and permanent mid‐canopy in grassy woodland vegetation. We investigated the relationship between African olive and native species establishment, abundance and diversity, using field surveys and a manipulative shading experiment. There were 78% fewer native species beneath African olive canopy in the field compared to uninvaded woodland sites. The shading experiment showed that simulated dense African olive shade levels produced the lowest dry weight for the three native species studied, with simulated canopy edge light providing optimal conditions for the native shrub Bursaria spinosa and African olive. Dense African olive shade levels produced the highest mortality rate for native species; however, African olive was able to maintain an 88% survival rate under dense canopy shade. This study confirms the adaptability of African olive and its capacity to decrease native plant diversity and substantially modify native vegetation at the community level.     

Life stage specific variation in the occupancy of ponds by Litoria aurea,a threatened amphibian

Breeding aggregations are a reproductive strategy to increase mate finding opportunity. However, because aggregations skew the distribution of mature animals through conspecific attraction, rather than resource availability, the distribution of breeding sites may be reduced, so that not all suitable breeding sites are used. To examine the relationship between landscape and reproductive strategies of a threatened frog, Litoria aurea, we studied its distribution at Sydney Olympic Park over two breeding seasons. We aimed to: (i) determine the distribution and predictors of breeding ponds; and (ii) assess the significance of dispersal in the juvenile age‐class. We found that the distribution of the calling males was highly skewed and occurred in large, well‐connected ponds. Despite this, breeding ponds were not aggregated; pond size was the single factor explaining the distribution of breeding ponds. Juvenile frogs dispersed from breeding ponds and were not associated with a specific pond characteristic. Less breeding occurred in the second season during which fewer ponds were used for breeding including many different ponds from the previous year. These changes suggest that breeding effort and breeding pond choice are dynamic and therefore knowledge of the factors that drive breeding events will be a powerful tool in managing species, particularly in light of changing climatic regimes.     

Systematics of the tribe Podalyrieae (Fabaceae) based on DNA, morphological and chemical data

Phylogenetic relationships among nine genera and 28 species of the southern African tribe Podalyrieae were estimated from sequences of the internal transcribed spacer (ITS) of nuclear ribosomal DNA as well as morphological and chemical data. Morphological and ITS sequence data produced cladograms with similar topologies, both supporting the monophyly of Podalyrieae (excluding Hypocalyptus ). The combined data sets indicate that subtribe Xiphothecinae are monophyletic, but embedded within Podalyriinae. The high degree of congruence between previous taxonomic hypotheses and those based on DNA data provides further evidence for the utility of ITS sequences in studying phylogeny.  © 2002 The Linnean Society of London , Botanical Journal of the Linnean Society , 2002, 139 , 159–170.     

Systematics of Vitaceae from the viewpoint of plastid rbcL DNA sequence data

A phylogenetic analysis of plastid rbcL DNA sequences for 20 species of Vitaceae s.l. (including Leeaceae) and eight outgroups from Dilleniaceae and Santalales is presented. Patterns of floral and vegetative morphology and ontogeny within the family are compared to the phylogenetic trees produced. Despite the limited sampling of large and variable genera, there is a good correspondence with hypothesized floral and vegetative ontogenetic trends, with Leea and Ampelopsis ancestral, Cissus and Ampelocissus intermediate and Vitis most derived. A clade containing Parthenocissus , Tetrastigma , Cyphostemma and Vitis is found in all shortest trees. Cyphostemma and Parthenocissus are shown to be closely related to Vitis , to which clade Tetrastigma and Cayratia comprise the sister clade. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 138 , 421–432.     

Changes in fire regime break the legacy lock on successional trajectories in Alaskan boreal forest

Predicting plant community responses to changing environmental conditions is a key element of forecasting and mitigating the effects of global change. Disturbance can play an important role in these dynamics, by initiating cycles of secondary succession and generating opportunities for communities of long‐lived organisms to reorganize in alternative configurations. This study used landscape‐scale variations in environmental conditions, stand structure, and disturbance from an extreme fire year in Alaska to examine how these factors affected successional trajectories in boreal forests dominated by black spruce. Because fire intervals in interior Alaska are typically too short to allow relay succession, the initial cohorts of seedlings that recruit after fire largely determine future canopy composition. Consequently, in a dynamically stable landscape, postfire tree seedling composition should resemble that of the prefire forest stands, with little net change in tree composition after fire. Seedling recruitment data from 90 burned stands indicated that postfire establishment of black spruce was strongly linked to environmental conditions and was highest at sites that were moist and had high densities of prefire spruce. Although deciduous broadleaf trees were absent from most prefire stands, deciduous trees recruited from seed at many sites and were most abundant at sites where the fires burned severely, consuming much of the surface organic layer. Comparison of pre‐ and postfire tree composition in the burned stands indicated that the expected trajectory of black spruce self‐replacement was typical only at moist sites that burned with low fire severity. At severely burned sites, deciduous trees dominated the postfire tree seedling community, suggesting these sites will follow alternative, deciduous‐dominated trajectories of succession. Increases in the severity of boreal fires with climate warming may catalyze shifts to an increasingly deciduous‐dominated landscape, substantially altering landscape dynamics and ecosystem services in this part of the boreal forest.     

Regulation of maturation-promoting factor by protein kinase C in Chaetopterus oocytes

Summary

We present the results of a variety of studies showing that activation of protein kinase C (PKC) in oocytes of Chaetopterus pergamentaceus results in germinal vesicle breakdown (GVBD). Phorbol esters and diacylglycerol can initiate a morphologically normal GVBD accompanied by a spectrum of associated biochemical processes, including increased protein phosphorylation, a shift in protein synthesis and activation of a protein kinase, maturation promoting factor (MPF). MPF activation is essential for GVBD in response to phorbol esters. In addition, inhibitors of PKC can block naturally-induced GVBD. We also present evidence that PKC can phosphorylate p34^cde2, the catalytic subunit of MPF and that phosphorylation by PKC increases the histone H1 kinase activity of immunoprecipitated MPF. Immunoblot studies show that Chaetopterus oocyte p34^cdc2 is not tyrosine phosphorylated prior to the initiation of GVBD, indicating that activation of MPF at GVBD in this species does not require p80^cdc25, the activator of MPF at mitosis. These results suggest that PKC is an essential regulator of GVBD which can directly phosphorylate and regulate p34^cdc2. Since PKC is the intracellular receptor for and is directly activated by tumor-promoters, tumor promotion might involve acceleration of the cell cycle through modification of the enzymatic activity of MPF by PKC.     

Passive aerodynamic stabilization by beetle elytra (wing covers)

Summary. Most beetles extend their elytra laterally during flight, where they can act as fixed airfoils; typically, such elytra are held at a pronounced dihedral angle. We fixed extended elytra of June beetles (Scarabaeidae: Melolonthinae) and tiger beetles (Cicindelidae) over a range of dihedral angles (-10° to 45°) and towed them in a water tunnel. We also towed them with flexed elytra (i.e. in the resting position). (Reynolds number was used to maintain dynamic similarity with air.) We measured the maximum rolling angle and the lateral oscillation rate as two indices of stability. There was no relationship between oscillation rate and dihedral angle, or between maximum roll angle and dihedral angle. At all dihedral angles tested, however, beetles were much more stable than when they were towed with the elytra flexed. We also included a third beetle type, flower beetle (Scarabaeidae: Cetoniine), which normally flies with flexed elytra. We measured stability indices for these beetles with elytra only in the flexed position. When all beetles were tested with flexed elytra, flower beetles showed no difference in maximum roll angle, but more stability in oscillation rate than the other two beetle types.     

Chloroplast DNA variation and hybridization between invasive populations of Japanese knotweed and giant knotweed (Fallopia, Polygonaceae)

Chloroplast inheritance and the direction of hybridization have been investigated in some invasive weeds from the genus Fallopia. PCR RFLP analysis of the tmK intron has been used to identify markers that distinguish between the chloroplast genomes of British samples of F. japonica var. japonica, F. japonica var. compacta and F. sachalinensis. Maternal inheritance of chloroplast DNA has been observed in controlled crosses and in hybrid seed from known maternal parents. PCR RFLP analysis of wild hybrids between F. japonica var. japonica and either F. japonica var. compacta or F. sachalinensis indicates that F. japonica var. japonica is the maternal parent of all of its hybrids, consistent with the apparent male-sterility of this taxon in Britain. Hybrids between F. japonica var. compacta and F. sachalinensis show the chloroplast haplotype of one or other of the parents, consistent with bi-directional hybridization.     

Postfledging Survival of Laysan Ducks

ABSTRACT Precise and unbiased estimates of demographic parameters are necessary for effective population monitoring and to parameterize population models (e.g., population viability analyses). This is especially important for endangered species, where recovery planning and managers' decisions can influence species persistence. In this study, we used mark—recapture methods to estimate survival of fledged juveniles (hatch-yr [HY]) and adult (after-hatch-yr [AHY]) Laysan ducks (Anas laysanensis), an endangered anatid restricted to Laysan Island in the northwestern Hawaiian Islands. To better understand population dynamics, we examined how survival varied as a function of Laysan duck density during 1998–2004. Using random effects models, we also quantified process variation in survival, thereby quantifying the appropriate source of variation for future population models. The dataset supported variation in survival that was time (yr), age (AHY vs. HY), and sex specific. Due to small sample sizes, we did not examine time specificity in the survival of HY ducks. Survival of HY ducks was 0.832 (SE = 0.087) for females (n = 21) and 0.999 (SE < 0.001) for males (n = 15) during 1998–2001. Trends in time and density lacked support as sources of variation in the survival of AHY ducks during 1998–2004. After-hatch-year survival ranged from 0.792 (SE = 0.033) to 0.999 (SE < 0.001). Where we modeled survival as a random effect, annual survival for AHY females was 0.881 (SE = 0.017) and process variation (σ_s) was 0.034. For AHY males, annual survival (μ_s) was 0.906 (SE = 0.019) and process variation (σ_s) was 0.040. This information will improve existing population viability analysis models for Laysan ducks. We believe that monitoring the source and translocation populations will be paramount for increasing our understanding of Laysan duck dynamics, recovery planning, and population management.