Responses of 9 lepidopteran species to Bacillus thuringiensis: How useful is phylogenetic relatedness for selecting surrogate species for nontarget arthropod risk assessment?

To evaluate phylogenetic relatedness as a proxy for susceptibility to Bacillus thuringiensis (Bt) when selecting species to act as surrogates for others in prerelease testing, we examined the responses of 11 laboratory‐reared lepidopteran colonies, comprising members of 2 families, 5 genera, and 9 species, to a commercial Bt preparation. Survival, pupal mass, and timing of pupation and adult emergence of 2 noctuids (Spodoptera litura and Helicoverpa armigera) and 7 tortricids (Cnephasia jactatana, Ctenopseustis obliquana, Ctenopseustis herana,Planotortrix octo, Planotortrix notophaea,Planotortrix excessana [2 different laboratory colonies], and Epiphyas postvittana [2 colonies]) were examined after feeding first instar larvae with artificial diet containing 5 μL/100 mL Dipel® ES (Bt subsp. kurstaki). Bt caused significant larval mortality in all species except S. litura, in which only pupation was delayed compared with untreated controls. Neither of the noctuid species tested would act as a suitable surrogate for the other in tests of Bt impacts on survival. With the exception of the 2 colonies of E. postvittana, which differed from each other not only in their responses to Bt but also in their development times when not treated with Bt, species within each tortricid genus had similar responses to Bt and thus could act as surrogates for each other. Members of different genera within this family could represent each other only if relatively coarse measurement endpoints (e.g., toxic or not) were considered adequate for assessing risks to nontarget species in the field.     

Habitat enhancement and native fish conservation: can enhancement of channel complexity promote the coexistence of native and introduced fishes?

Native fishes worldwide have declined as a consequence of habitat loss and degradation and introduction of non-native species. In response to these declines, river restoration projects have been initiated to enhance habitat and remove introduced fishes; however, non-native fish removal is not always logistically feasible or socially acceptable. Consequently, managers often seek to enhance degraded habitat in such a way that native fishes can coexist with introduced species. We quantified dynamics of fish communities to three newly constructed side channels in the Provo River, Utah, USA, to determine if and how they promoted coexistence between native fishes (nine species) and non-native brown trout (Salmo trutta L.). Native and introduced fishes responded differently in each side channel as a function of the unique characteristics and histories of side channels. Beaver activity in two of the three side channels caused habitat differentiation or channel isolation that facilitated the establishment of native species. The third side channel had greater connectivity to and similar habitat as the main channel of the Provo River, resulting in a similar fish community to main channel habitats (i.e. dominated by brown trout with only a few native fish species). These results demonstrate the importance of understanding habitat preferences for each species in a community to guide habitat enhancement projects and the need to create refuge habitats for native fishes.     

Is the biomass of water hyacinth lost through herbivory in native areas important?

The lamina area damaged and biomass per leaves removed by invertebrate herbivores were measured across seasons on water hyacinth, Eichhornia crassipes (Mart.) Solms (Pontederiaceae). The amount of the leaf biomass per meter square lost through herbivory was also assessed in different sampling dates in the plant population. Ten leaves of water hyacinth were sampled in each of 18 site-habitat-date combinations. Sampling dates were chosen to follow the plant phenology. The lamina area damaged (surface abrasions and holes) was measured with the visual estimation method; biomass removed by herbivores (surface abrasions and holes) was calculated indirectly from the damaged lamina area. Significant differences in total damaged area and removed biomass per lamina were found between sampling dates at each site, with highest values in March (end of growth period). Total damaged area per lamina (surface abrasions + holes) varied between 11% in March and 6% in July (decay period). Total removed biomass (surface abrasions + holes) varied between 27% in March and 13% in July. Significant differences in biomass removed by herbivory were found between sampling dates at each site. Biomass of lamina removed by herbivores per m⁻² varied between 26 and 13% in different seasons. The herbivore damage of discrete samples and the indirect method to calculate the biomass removed is useful in sites with aquatic free floating plants, where experimental exclusion of insects may be difficult to carry out.     

Do Australian small mammals respond to native and introduced predator odours?

Abstract Coevolution is thought to have led to many small mammal species avoiding the scent marks of their main mammalian predators, as they provide a reliable cue to predation risk. Most support for this hypothesis comes from northern hemisphere predator/prey systems, however, it is unclear whether this avoidance of predator faecal odour occurs in Australia's mammalian fauna, which has evolved in relative isolation from the rest of the world, and is dominated by marsupials rather than placentals. We tested this theory for an Australian system with marsupial and placental predators and prey, that share a long‐term (>1 million years) or short‐term (<150 years) exposure to each other. The predators were the native marsupial tiger quoll Dasyurus maculatus and the introduced placental red fox Vulpes vulpes. The potential prey were three native rodent species, the bush rat Rattus fuscipes, the swamp rat Rattus lutreolus, the eastern chestnut mouse Pseudomys gracilicaudatus, and the marsupial brown antechinus Antechinus stuartii. Small mammals were captured in Elliott traps with 1/3 of traps treated with fox faeces, 1/3 treated with quoll faeces and the remainder left untreated. The native rodent species all showed avoidance of both tiger quoll and red fox odours whereas the marsupial antechinus showed no responses to either odour. Either predator odour avoidance has not evolved in this marsupial or their reaction to predator odours may be exhibited in ways which are not recognizable through trapping. The avoidance by the rodents of fox odour as well as quoll odour indicates this response may either be due to common components in fox and quoll odour, or it may be a recently evolved response.     

Is the “Difference index” useful for assessment of protein relatedness?

This paper assesses the usefulness of the Difference Index (Metzger, Shapiro, Mosimann &; Vinton, 1968) for predicting, from amino acid compositions, whether two proteins are related or unrelated. It is concluded that, with a 5 % probability of false identification, Difference Index values less than 10-0 indicate relatedness and values greater than 26·8 indicate unrelatedness. A large proportion of protein pairs have Difference Index values in the region 10·0–26·8 and cannot therefore be reliably identified as related or unrelated by this criterion.     

Effects of crayfish on leaf litter breakdown and shredder prey: are native and introduced species functionally redundant?

Recent increases in biological invasions frequency may have important consequences on native communities. However, functional redundancy between invasive and native species could reduce non-native species effects on native ecosystems. Despite this, even small differences in functional traits between these species may still have unpredictable effects on colonized ecosystems. Invasive crayfish, as ecosystem engineers, potentially have wide and complex effects on recipient ecosystems, even when replacing a native counterpart. We used laboratory microcosms to test whether native (Astacus astacus) and invasive crayfish species (Orconectes limosus, Pacifastacus leniusculus and Procambarus clarkii) are actually functionally redundant in their effects on prey/shredder density and leaf litter breakdown. Results show that crayfish strongly influenced macroinvertebrate numbers and leaf litter breakdown and indicate that differences in direct (prey and leaf litter consumption) and indirect (prey habitat use and leaf litter breakdown) effects between crayfish species do exist. While the replacement of A. astacus by O. limosus may have induced only minor changes in freshwater ecosystems, invasions by the larger and more aggressive P. clarkii and P. leniusculus will likely have strong effects on invaded ecosystem. Overall, there seems to be no functional redundancy between these four species and outcomes of crayfish invasion will likely be species specific.     

Response to soil biota by native, introduced non-pest, and pest grass species: is responsiveness a mechanism for invasion?

Soil biota have been credited with helping to maintain native plant diversity in multiple systems. Recent evidence suggests that introduced species may be less responsive to soil communities than most native species. If response to soil communities is correlated with invasive ability, we predict that introduced pest species should be less responsive to soil communities than introduced non-pest species or natives. In this study we test whether response to soil biota from two diverse grassland communities differs between four introduced pest, six introduced non-pest, and five native species in grasses in Yolo County, California. We found no variation in plant size or response to soil biota between introduced pest and introduced non-pest species, and these were combined in subsequent analyses. Overall, all introduced species grew significantly faster than native species. Native species showed greater variation in response to soil communities than both groups of introduced species, and native species’ response varied with soil community. Variation among native species’ response to soil nutrients and biota through processes like soil feedbacks may be key to maintaining diversity across landscapes in uninvaded environments. Introduced species appear less responsive to landscape variability in soil communities, which may allow them to establish and dominate plant communities in multiple habitats.     

What drives interspecies graft union success? Exploring the role of phylogenetic relatedness and stem anatomy

The underlying mechanisms that determine whether two species can form a successful graft union (graft compatibility) remain obscure. Two prominent hypotheses are (1) the more closely related species are, the higher the graft success and (2) the vascular anatomy at the graft junction influences graft success. In this paper these two hypotheses are examined in a systematic way using graft combinations selected from a range of (a) phylogenetically close and more distant legume species, (b) species displaying different germination patterns and (c) scions and rootstocks possessing contrasting stem tissues and vascular patterns. Relatedness of species was not a good predictor of graft compatibility, as vascular reconnection can occur between distantly related species and can fail to occur in some more closely related species. Similarly, neither the stem tissues present at the graft junction nor the vascular anatomy correlated with the success of vascular reconnection. Relatedness and stem anatomy therefore do not appear to be the determining factors in successful vascular reconnection after grafting in legumes. These results are discussed in conjunction with other hypotheses such as the role of auxin.     

Distribution of plants in a California serpentine grassland: are rocky hummocks spatial refuges for native species?

Invasions by non-native taxa can have severe consequences for native species. In the heavily invaded serpentine grasslands of central California, many native species appear to be restricted to isolated outcrops of shallow serpentine soil, or hummocks, although the extent to which these hummocks function as refuges for native vegetation has never been quantified. We tested whether native plant species were restricted to hummocks within a serpentine grassland at the University of California Sedgwick Reserve near Santa Barbara, California by sampling species along hummock-grassland gradients. We also examined the influence of soil parameters, hummock area, proximity to other hummocks, and spatial location on species composition across 16 hummocks at this site. Both the hummocks and the surrounding grassland had high Mg, low Ca, and low Ca to Mg ratios typical of serpentine systems. Hummocks appeared to be more stressful environments because of their shallower soils, lower cation exchange capacity, and greater percent sand. Of the 27 most common plant species sampled along hummock-grassland transects, we identified 8 hummock specialists, 7 edge specialists, 8 matrix specialists, and 4 generalists. Importantly, both the hummock and matrix specialist groups included native species. Plant community composition was correlated with spatial positioning of the hummocks and with soil Ca, Na, K, and N. The number of species increased and community composition changed with increasing hummock area. Species composition was most similar among hummocks in close proximity to each other, and decreased with increasing distance between hummocks. Our results suggest that the community structure of serpentine grasslands is spatially complex and an effective management or restoration plan must address this complexity.     

Is it possible to distinguish alien species of beetles (Coleoptera) from native ones?

Species established outside their native ranges are termed alien. Biological invasions of beetles are poorly studied. Distinguishing between alien and native species is necessary for conservation as well as for taxonomic, zoogeographic, and evolutionary studies. It constitutes a difficult problem, but the experience of botany and some branches of zoology gives reasons to believe that it is not unsolvable. The following criteria for distinguishing alien beetle species from native ones are proposed based on the criteria developed for plants, algae, mammals, and marine invertebrates: (1) detection of an established population of the species which has not been recorded earlier in the region; (2) disjunction of the range which cannot be explained by disjunction of suitable landscapes or host plant ranges; (3) expansion of a part of the range isolated from its main part; (4) highly localized distribution in an area adjacent to a known invasion pathway; (5) establishment in other regions; (6) dependency on another non-native species (feeding on an alien host plant or animal); (7) absence of specific parasites in the given region and their presence in some other region; (8) association with anthropogenic biotopes; (9) sharp fluctuations of abundance; (10) lack of taxonomically close species in the given region and their presence in other regions; (11) detection in the region of two or more taxonomically and/or ecologically close species typical of another region; (12) presence of known vectors of invasion; (13) low genetic diversity; (14) reproduction by parthenogenesis or inbreeding. These criteria are mere indirect evidences of the alien status of a species in the given territory, because numerous exceptions exist. Usually it is impossible to recognize an alien species by a single criterion, but matching several criteria characterizes the species as an alien one with high probability.     

Is orchid species richness and abundance related to the conservation status of oak forest?

The response of organisms to anthropogenic or natural modification of the environment is one of the most important questions in conservation biology and ecological theory. In spite of the fact that orchids are one of the most studied groups of plants, little information exists regarding their response to habitat alteration. The few existing studies are biased toward European orchid species and no consensus exists with regard to the response of orchids to human and natural disturbance. In this study, we sampled 30 transects (0.1 ha each) of oak forest located in Morelos, Central Mexico, and measured 13 variables related to forest aging and stump abundance, and six variables of orchid species richness and abundance. Neither abundance nor the richness and specific abundance of orchid genus or species were related to timber extraction. The abundance of dead standing trees in the forest, a surrogate variable of forest age, was positively related to abundance of orchids of the genus Malaxis, orchid richness and orchid abundance. This finding suggests that the conservation of all facets of the studied forest orchid community is dependent on natural processes (such as self-thinning) and the maintenance of older areas of the forest, and concurs with previous studies that suggest that natural disturbance is a key process for orchid survival.     

Is Mycobacterium bovis in the environment important for the persistence of bovine tuberculosis?

Mycobacterium bovis is the causative agent of bovine tuberculosis (bTB) in cattle and wildlife. Direct aerosol contact is thought to be the primary route of infection between conspecifics, whereas indirect transmission via an environmental reservoir of M. bovis is generally perceived not to be a significant source for infection. Here, we report on the application of molecular technology (PCR) to quantify the prevalence of M. bovis in the environment and to explore its epidemiological significance. We show that the detectability of viable M. bovis at badger setts and latrines is strongly linked to the frequency of M. bovis excretion by infected badgers, and that putative M. bovis in the environment is prevalent on a large proportion of endemic cattle farms in Britain. These results raise important questions about the role of an environmental reservoir in bTB persistence.     

Invasive species profiling? Exploring the characteristics of non‐native fishes across invasion stages in California

1. The global spread of non‐native species is a major concern for ecologists, particularly in regards to aquatic systems. Predicting the characteristics of successful invaders has been a goal of invasion biology for decades. Quantitative analysis of species characteristics may allow invasive species profiling and assist the development of risk assessment strategies. 2. In the current analysis we developed a data base on fish invasions in catchments throughout California that distinguishes among the establishment, spread and integration stages of the invasion process, and separates social and biological factors related to invasion success. 3. Using Akaike's information criteria (AIC), logistic and multiple regression models, we show suites of biological variables, which are important in predicting establishment (parental care and physiological tolerance), spread (life span, distance from nearest native source and trophic status) and abundance (maximum size, physiological tolerance and distance from nearest native source). Two variables indicating human interest in a species (propagule pressure and prior invasion success) are predictors of successful establishment and prior invasion success is a predictor of spread and integration. 4. Despite the idiosyncratic nature of the invasion process, our results suggest some assistance in the search for characteristics of fish species that successfully transition between invasion stages.     

Is regulation of aromatase expression in reptiles the key to understanding temperature-dependent sex determination?

A brief review of our current understanding (or lack of understanding) of the molecular basis of temperature-dependent sex determination (TSD) in reptiles is presented. Current theories are discussed: yolk steroids as sex determinants, the brain as the driver for TSD and the enzyme aromatase and estrogen production as the possible determinants of sex. There is little evidence to support the first two theories, but enough evidence to keep the third theory in play. As yet, however, we have no molecular understanding of how a two-degree difference in temperature during the temperature-sensitive phase of egg incubation can initiate the molecular cascade that determines whether the indifferent gonad develops as an ovary or a testis.     

Why is the choice of future climate scenarios for species distribution modelling important?

Species distribution models (SDMs) are common tools for assessing the potential impact of climate change on species ranges. Uncertainty in SDM output occurs due to differences among alternate models, species characteristics and scenarios of future climate. While considerable effort is being devoted to identifying and quantifying the first two sources of variation, a greater understanding of climate scenarios and how they affect SDM output is also needed. Climate models are complex tools: variability occurs among alternate simulations, and no single 'best' model exists. The selection of climate scenarios for impacts assessments should not be undertaken arbitrarily - strengths and weakness of different climate models should be considered. In this paper, we provide bioclimatic modellers with an overview of emissions scenarios and climate models, discuss uncertainty surrounding projections of future climate and suggest steps that can be taken to reduce and communicate climate scenario-related uncertainty in assessments of future species responses to climate change.     

Is the originality of a species measurable?

In this paper, we introduce the concept of 'originality of a species within a set' in order to indicate the average rarity of all the features belonging to this species. Using a phylogenetic tree of 70 species of New World terrestrial Carnivora, we suggest measuring the originality by a probability distribution. This maximizes the expected number of features shared by two species randomly drawn from the set. By using this new index, we take account of branch lengths whereas current indices of originality focus on tree topology. As a supplement to Nee and May's optimizing algorithm, we find that originality must be one of the criteria used in conservation planning.     

Origin of the widely and discontinuously distributed mitochondrial genotypes of Oryzias latipes: introduced or native genotypes?

Ichthyological Research - A mitochondrial cytochrome b genotype of Oryzias latipes, “mitotype B15”, is widely and discontinuously distributed in various localities in Japan. To...