The naturalization to invasion transition: Are there introduction‐history correlates of invasiveness in exotic plants of Australia?

Of the large number of exotic plant species that become naturalized in new geographic regions, only a subset make the transition to become invasive. Identifying the factors that underpin the transition from naturalization to invasion is important for our understanding of biological invasions. To determine introduction‐history correlates of invasiveness among naturalized plant species of Australia, we compared geographic origin, reason for introduction, minimum residence time and growth form between naturalized non‐invasive species and naturalized invasive plant species. We found that more invasive species than expected originated from South America and North America, while fewer invasive species than expected originated from Europe and Australasia. There was no significant difference between invasive and non‐invasive species with respect to reason for introduction to Australia. However, invasive species were significantly more likely to have been resident in Australia for a longer period of time than non‐invasive species. Residence times of invasive species were consistently and significantly higher than residence times of non‐invasive species even when each continent of origin was considered separately. Furthermore, residence times for both invasive and non‐invasive species varied significantly as a function of continent of origin, with species from South America having been introduced to Australia more recently on average than species from Europe, Australasia and North America. We also found that fewer invasive species than expected were herbs and more invasive species than expected were primarily climbers. Considered together, our results indicate a high propensity for invasiveness in Australia among exotic plant species from South America, given that they appear in general capable of more rapid shifts to invasiveness than aliens from other regions. Furthermore, our findings support an emerging global generality that introduction‐history traits must be statistically controlled for in comparative studies exploring life‐history and ecological correlates of invasion success.     

Using species distribution models to identify suitable areas for biofuel feedstock production

The 2007 Energy Independence and Security Act mandates a five‐fold increase in US biofuel production by 2022. Given this ambitious policy target, there is a need for spatially explicit estimates of landscape suitability for growing biofuel feedstocks. We developed a suitability modeling approach for two major US biofuel crops, corn (Zea mays) and switchgrass (Panicum virgatum), based upon the use of two presence‐only species distribution models (SDMs): maximum entropy (Maxent) and support vector machines (SVM). SDMs are commonly used for modeling animal and plant distributions in natural environments, but have rarely been used to develop landscape models for cultivated crops. AUC, Kappa, and correlation measures derived from test data indicate that SVM slightly outperformed Maxent in modeling US corn production, although both models produced significantly accurate results. When compared with results from a mechanistic switchgrass model recently developed by Oak Ridge National Laboratory (ORNL), SVM results showed higher correlation than Maxent results with models fit using county‐scale point inputs of switchgrass production derived from expert opinion estimates. However, Maxent results for an alternative switchgrass model developed with point inputs from research trial sites showed higher correlation to the ORNL model than the corresponding results obtained from SVM. Further analysis indicates that both modeling approaches were effective in predicting county‐scale increases in corn production from 2006 to 2007, a time period in which US corn production increased by 24%. We conclude that presence‐only methods are a powerful first‐cut tool for estimating relative land suitability across geographic regions in which candidate biofuel feedstocks can be grown, and may also provide important insight into potential land‐use change patterns likely to be associated with increased biofuel demand.     

Evaluating possible cap and trade legislation on cellulosic feedstock availability

An integrated, socioeconomic–biogeophysical model is used to analyze the interactions of cap‐and‐trade legislation and the Renewable Fuels Standard. Five alternative policy scenarios were considered with the purpose of identifying policies that act in a synergistic manner to reduce carbon emissions, increase economic returns to agriculture, and adequately meet ethanol mandates. We conclude that climate and energy policies can best be implemented together by offering carbon offset payments to conservation tillage, herbaceous grasses for biomass, and by constraining crop residue removal for ethanol feedstocks to carbon neutral level. When comparing this scenario to the Baseline scenario, the agricultural sector realizes an economic benefit of US$156 billion by 2030 and emissions are reduced by 135 Tg C‐equivalent (Eq) yr^?1. Results also indicate that geographic location of cellulosic feedstocks could shift significantly depending on the final policies implemented in cap and trade legislation. Placement of cellulosic ethanol facilities should consider these possible shifts when determining site location.     

Vulnerability of African mammals to anthropogenic climate change under conservative land transformation assumptions

Recent observations show that human‐induced climate change (CC) and land transformation (LT) are threatening wildlife globally. Thus, there is a need to assess the sensitivity of wildlife on large spatial scales and evaluate whether national parks (NPs), a key conservation tools used to protect species, will meet their mandate under future CC and LT conditions. Here, we assess the sensitivity of 277 mammals at African scale to CC at 10′ resolution, using static LT assumptions in a ‘first‐cut’ estimate, in the absence of credible future LT trends. We examine the relationship between species' current distribution and macroclimatic variables using generalized additive models, and include LT indirectly as a filter. Future projections are derived using two CC scenarios (for 2050 and 2080) to estimate the spatial patterns of loss and gain in species richness that might ultimately result. We then apply the IUCN Red List criteria A3(c) of potential range loss to evaluate species sensitivity. We finally estimate the sensitivity of 141 NPs in terms of both species richness and turnover. Assuming no spread of species, 10–15% of the species are projected to fall within the critically endangered or extinct categories by 2050 and between 25% and 40% by 2080. Assuming unlimited species spread, less extreme results show proportions dropping to approximately 10–20% by 2080. Spatial patterns of richness loss and gain show contrasting latitudinal patterns with a westward range shift of species around the species‐rich equatorial zone in central Africa, and an eastward shift in southern Africa, mainly because of latitudinal aridity gradients across these ecological transition zones. Xeric shrubland NPs may face significant richness losses not compensated by species influxes. Other NPs might expect substantial losses and influxes of species. On balance, the NPs might ultimately realize a substantial shift in the mammalian species composition of a magnitude unprecedented in recent geological time. To conclude, the effects of global CC and LT on wildlife communities may be most noticeable not as a loss of species from their current ranges, but instead as a fundamental change in community composition.     

Age‐ and sex‐related differences in the spatial ecology of a dichromatic tropical python (Morelia viridis)

Abstract: Despite outnumbering their temperate counterparts, tropical snake species have been poorly studied. Yet, the few tropical species that have been studied show a variety of behavioural traits beyond those described in temperate species. Here we reveal both age and sexual differences in the movements of tropical green pythons (Morelia viridis: Pythonidae). We radio‐tracked 27 individuals (17 females and 10 males) for up to 18 months, locating individuals during both the day and night. The home range size for adult females (mean ± SE of 6.21 ± 1.85 ha) was correlated with snout–vent length. Neither adult males nor juveniles had a stable home range. Adult females had stable home ranges that overlapped considerably with those of other females and yellow individuals. Multiple radio‐tracked adult males passed through the territory of radio‐tracked adult females during the study. Females of all sizes were more likely to change position each day than males. There were no differences between the sexes or size categories in the distances moved in most months, although the variation in movement distances was higher in the dry season than during the wet season. In the wet season (January–March) movement distances increased and these were size‐ and sex‐related. This increased activity may be associated with mate searching. Males of M. viridis may maximize their rate of encountering mature females by roaming rather than maintaining a home range. Juvenile green pythons moved distances equal to adult snakes in most months despite their comparatively small size.     

Black Point is associated with reduced levels of stress, disease- and defence-related proteins in wheat grain

Black Point in wheat is a dark discoloration at the embryo end of the grain, which causes substantial financial losses to wheat growers due to down-grading of otherwise high-grade wheat. There does not appear to be a single cause for Black Point, although evidence suggests that fungal infection is the main link to Black Point symptoms. We sought to identify grain proteins from Black Point-affected and Black Point-free wheat cultivar SUN239V, which is known to be very susceptible to Black Point. The proteomes of both the germ and endosperm-bran components of Black Point-affected and Black Point-free grain were compared using two-dimensional gel electrophoresis (2-DE) with six replicate gels run for each protein sample. Approximately 1478 discrete protein spots were found in 2-DE gels from the germ fraction of the grain, of which 354 were identified by mass spectrometry (MS). Similarly, 1360 discrete protein spots were found from the endosperm-bran fraction, of which 303 were identified by MS. No proteins of fungal or bacterial origin were positively identified, suggesting that, at least in some cases, Black Point is not associated with microbial activity. Of the germ proteins, 252 were differentially expressed in Black Point-affected tissue, with 67 of these proteins identified by MS. Of the endosperm-bran proteins, 317 were differentially expressed in Black Point-affected tissue, with 86 identified. The largest of 12 functional classes to which the differentially abundant proteins were assigned was the 'stress' class, i.e. products of genes associated with stress, disease and defence. Higher levels of these proteins were found in Black Point-free grain, suggesting that protection from the disease might be afforded by increased levels of the 'stress' proteins.     

Assessment of 17 new whiskered auklet (Aethia pygmaea) microsatellite loci in 42 seabirds identifies 5–15 polymorphic markers for each of nine Alcinae species

We isolated 17 microsatellite loci in the whiskered auklet (Aethia pygmaea) and tested them for amplification in 48 species from 13 seabird families (including 42 seabirds). Fifteen of these loci were also tested for polymorphism in 38 of the species, which included nine species of Alcinae (four auklets, Atlantic puffin, dovekie, razorbill and two murre species). On the average, nine loci were polymorphic per Alcinae species.     

Effect of season of burning and removal of herbaceous cover on seedling emergence in a eucalypt savanna of north‐eastern Australia

Abstract Seedling emergence in a eucalypt savanna of north‐eastern Australia was documented over a 12‐month period, between May 1999 and May 2000. Seedling emergence for grasses, forbs and subshrubs was found to mainly occur in a brief pulse at the start of the wet season following fire or the removal of grass biomass. Only a minor number of tree and shrub seedlings were detected overall. Burning, or cutting away the grass layer in unburnt savanna, in both the early (i.e. May) and the late (i.e. October) dry seasons significantly increased seedling emergence over undisturbed savanna that had been unburnt for 3 years. Removing the grass layer in unburnt savanna, during either the early or the late dry season, triggered similar seedling densities to savanna burnt in the early dry season. Late dry season fires promoted the greatest seedling density. We attribute this to the higher intensity, late dry season fires releasing a greater proportion of seed from dormancy, coupled with the higher density of soil seed reserves present in the late dry season.     

Microsatellite loci for the New Zealand trematode Maritrema novaezealandensis

Seven polymorphic microsatellite loci were isolated and characterized from the coastal New Zealand trematode Maritrema novaezealandensis, an important driving force in the population dynamics of its snail and crustacean intermediate hosts. Observed heterozygosities ranged from 0.33 to 0.82, and three to 17 alleles were detected in 22 trematode sporocysts. These loci will be integral for identifying parasite genetic clones within hosts and addressing a range of questions concerning the molecular ecology of this species.