The incidence, distribution and expression of Australian grapevine yellows, restricted growth and late season leaf curl diseases in selected Australian vineyards

Surveys were conducted in four Chardonnay vineyards for 3 to 6 years and one Shiraz vineyard for 3 years to determine the yearly percentage of grapevines affected by Australian grapevine yellows disease (AGYd), restricted growth disease (RGd) and late season leaf curl disease (LSLCd). In each of the Chardonnay vineyards in each year, all three diseases were characterised by remission of disease in some grapevines, recurrence of disease in other grapevines and new observations of disease in previously unaffected grapevines. The pattern of temporal incidence of each disease was different between vineyards for the survey period. Although Koch's postulates have not been fulfilled, phytoplasmas are considered to be the most likely cause of AGYd. While some grapevines exhibited a combination of AGYd and RGd or AGYd and LSLCd, both RGd and LSLCd can occur independently of AGYd. Statistical analyses using log-linear models also indicated that RGd and LSLCd were not always associated with AGYd. Thus, it is possible that phytoplasmas are not the cause of RGd or LSLCd and their association is coincidental. Expression of AGYd in Shiraz grapevines occurred later in the season compared to Chardonnay. Very little recurrence of AGYd was observed in the Shiraz grapevines indicating that the variety Shiraz responds differently to phytoplasma infections, assuming that AGYd in Shiraz is a phytoplasma caused disease. RGd and LSLCd were not observed on any grapevines in the Shiraz vineyard.     

Studies on the transmission of velvet tobacco mottle virus by the mirid, Cyrtopeltis nicotianae

The minimum acquisition period of velvet tobacco mottle virus (VTMoV) by its mirid vector Cyrtopeltis nicotianae was about 1 min, with an increase in the rate of transmission (i.e. proportion of test plants infected) for acquisition periods up to 1000 min. Pre-acquisition starvation periods up to 18 h did not affect the rate of transmission. After an acquisition access period of 2 days, the minimum inoculation period was between 1 and 2 h and the rate of transmission increased with increasing inoculation time; when the acquisition access period was 1 h, or if vectors were fasted for 16 h after the 2 day acquisition, the rate of transmission was significantly lower. When mirids were transferred sequentially each day to a healthy plant after a 24 h acquisition feed, they transmitted intermittently for up to 10 days. Up to 50% of mirids transmitted after a moult and this was not due to the mirids probing the shed cuticles or exudates of infective insects. Mirids transmitted after a moult, following acquisition periods of 10, 100 or 1000 min. C. nicotianae transmitted solanum nodiflorum mottle virus (SNMV), sowbane mosaic virus (SoMV) and southern bean mosaic virus (SBMV), but not subterranean clover mottle virus (SCMoV), lucerne transient streak virus (LTSV), tobacco ringspot virus (TRSV), galinsoga mosaic virus (GMV), nor nicotiana velutina mosaic virus (NVMV). Tomato bushy stunt virus (TBSV) was transmitted to 1/58 test plants.     

Repeated unidirectional introgression towards Populus balsamifera in contact zones of exotic and native poplars

As the evolutionary significance of hybridization is largely dictated by its extent beyond the first generation, we broadly surveyed patterns of introgression across a sympatric zone of two native poplars ( Populus balsamifera , Populus deltoides ) in Quebec, Canada within which European exotic Populus nigra and its hybrids have been extensively planted since the 1800s. Single nucleotide polymorphisms (SNPs) that appeared fixed within each species were characterized by DNA-sequencing pools of pure individuals. Thirty-five of these diagnostic SNPs were employed in a high-throughput assay that genotyped 635 trees of different age classes, sampled from 15 sites with various degrees of anthropogenic disturbance. The degree of admixture within sampled trees was then assessed through Bayesian clustering of genotypes. Hybrids were present in seven of the populations, with 2.4% of all sampled trees showing spontaneous admixture. Sites with hybrids were significantly more disturbed than pure stands, while hybrids comprised both immature juveniles and trees of reproductive age. All three possible F1s were detected. Advanced-generation hybrids were consistently biased towards P. balsamifera regardless of whether hybridization had occurred with P. deltoides or P. nigra. Gene exchange between P. deltoides and P. nigra was not detected beyond the F1 generation; however, detection of a trihybrid demonstrates that even this apparent reproductive isolation does not necessarily result in an evolutionary dead end. Collectively, results demonstrate the natural fertility of hybrid poplars and suggest that introduced genes could potentially affect the genetic integrity of native trees, similar to that arising from introgression between natives.     

Vicars,tramps and assembly of the New Zealand avifauna: a review of molecular phylogenetic evidence

The avifauna of New Zealand is taxonomically and ecologically distinctive, as is typical of island biotas. However, the potential for an old geological age of New Zealand has encouraged a popular notion of a ‘Moa’s ark’ based on the idea that much of the fauna was isolated when Zealandia broke from Gondwana c. 83 million years ago. Molecular phylogenetics has proved useful for exploring the relative importance of different biogeographical processes, revealing for example that ‘tramp’ species (widely dispersing taxa) have arrived in New Zealand even in the last few hundred years, and that some avian taxa have close phylogenetic relatives overseas (predominantly Australian), indicating their recent ancestors were tramps, too. Distinctive taxa with deep phylogenetic ancestry might be ‘vicars’ that owe their presence to vicariance, but lack of close morphological, taxonomic and phylogenetic affinity provides only tenuous evidence for this. Disproving the alternative possibility that apparent vicars are descended from tramps that dispersed in earlier times remains challenging, but molecular analyses have yielded startling insights. Among New Zealand’s iconic taxa, the world’s largest eagle shared a Pleistocene ancestor with a small Australian eagle, and giant, flightless moa are phylogenetic sisters of the much smaller, flying tinamous of South America. The New Zealand avifauna is neither isolated nor stable, but demonstrative of prolonged and ongoing colonization, speciation and extinction.     

Effects of planting method on the recovery of arboreal ant activity on revegetated farmland

Ecological restoration aims to re‐establish both biodiversity and ecological function in damaged ecosystems. Ants are important drivers of ecological functions and are early colonizers of restored ecosystems. Rates at which ants perform functions are thought to be fuelled by access to plant sugars. In revegetated farmland in south‐eastern Australia, I tested if ant activity on trees, which reflects use of arboreal sugars, follows a predictable trajectory of recovery towards a remnant‐like state. Additionally, I examined whether planting method alters this trajectory by comparing tube stock (TS), which results in low Eucalyptus densities, with direct seeding (DS), which results in high Eucalyptus densities. Replicate sites (n = 5) of young (planted between 1998 and 2001) and old (planted between 1989 and 1994) TS and DS revegetation, pastures and remnants were compared. Activity on trunks was significantly positively correlated with ant tending of Hemiptera in young and old revegetation. In DS plantings, activity and estimated liquid loads on Eucalyptus trees were low and rapidly approached that in remnants, while TS sites remained similar to high values observed in pastures with trees. Patterns for Acacia were less clear, reflecting consistent densities for this species between TS and DS. At the whole‐of‐field scale, planting methods did not differ. Importantly, although trajectories differed, neither TS nor DS sites approached the low activity or estimated liquid loads observed in remnants. Rates of ant use of arboreal sugars and associated sugar‐fuelled processes may thus take considerably longer to recover than the period covered by this study. This finding suggests planting method may affect the trajectory and outcome of revegetation for plant health, as well as sugar‐fuelled ecosystem functions performed by ants.     

A review of Killer Whale interactions with other marine mammals: predation to co-existence

Killer Whales are well-known as predators of other marine mammals, including the large Sperm and baleen whales. Members of all marine mammal families, except the river dolphins and manatees, have been recorded as prey of Killer Whales; attacks have been observed on 20 species of cetaceans, 14 species of pinnipeds, the Sea Otter, and the Dugong. Ecological interactions have not been systematically studied and further work may indicate that the Killer Whale is a more important predator for some populations than previously believed. Not all behavioural interactions between Killer Whales and other marine mammal species result in predation, however. Some involve 'harassment' by the Killer Whales, feeding by both species in the same area, porpoises playing around Killer Whales, both species apparently 'ignoring' each other, and even apparently unprovoked attacks on Killer Whales by sea lions. These non-predatory interactions are relatively common. We conclude that interactions between Killer Whales and marine mammals are complex, involving many different factors that we are just beginning to understand.     

Variation in abundance across a species' range predicts climate change responses in the range interior will exceed those at the edge: a case study with North American beaver

The absence of information about how abundance varies across species' ranges restricts most modeling and monitoring of climate change responses to the range edge. We examine spatial variation in abundance across the northeastern range of North American beaver ( Castor canadensis ), evaluate the extent to which climate and nonclimate variables explain this variation, and use a species–climate envelope model that includes spatial variation in abundance to predict beaver abundance responses to projected climate change. The density of beaver colonies across Québec follows a roughly logistic pattern, with high but variable density across the southern portion of the province, a sharp decline in density at about 49°N, and a long tail of low density extending as far as 58°N. Several climate and nonclimate variables were strong predictors of variation in beaver density, but 97% of the variation explained by nonclimate variables could be accounted for by climate variables. Because of the peak and tail density pattern, beaver climate sensitivity (change in density per unit change in climate) was greatest in the interior and lowest at the edge of the range. Combining our best density–climate models with projections from general circulation models (GCM) predicts a relatively modest expansion of the species' northern range limit by 2055, but density increases in the range interior that far exceed those at the range edge. Thus, some of the most dramatic responses to climate change may be occurring in the core of species' ranges, far away from the edge-of-the-range focus of most current modeling and monitoring efforts.     

Non-propagative translocation of velvet tobacco mottle virus in the mirid, Cyrtopeltis nicotianae

Nymphs of the mirid, Cyrtopeltis nicotianae became infective when injected with velvet tobacco mottle virus (VTMoV). Injections of amounts between 1 and 154 ng into the haemocoele induced 2/60 to infect test plants and these two nymphs contained 50 and 63 ng of virus respectively. Injection of amounts between 15 and 2400 ng rendered 11/47 nymphs infective. This observation is characteristic of a circulative association. However, there is no evidence that the salivary glands are involved in transmission and the virus is therefore defined as translocating, rather than circulating, in the mirid vector. Mirids which acquired infectivity by feeding lost it between 5 and 9 days after completion of acquisition, and the most rapid loss of infectivity occurred within 2 days. Nine days after acquisition none contained antigen detectable by ELISA, but detectable antigen decreased less rapidly than infectivity, and at all times more mirids contained antigen than were able to transmit. Mirids containing antigen carried between 150 and 3340 ng each. Thus, although VTMoV can be transmitted by its mirid vector following introduction of virus into the body cavity by injection, VTMoV is not propagative. Nor does the presence of virus within the mirid guarantee an ability to transmit.