Introgression explains incongruence between nuclear and chloroplast DNA-based phylogenies in Allium section Cepa

Phylogenetic relationships between species of Allium section Cepa and A. rqylei (section Rhizirideum) have been inferred from nuclear DNA variation (RAPDs; nDNA dataset) and from morphological, pollen epidermis texture, chromosomal and chemical variation (supranuclear dataset). These sets were complemented with data, taken from the literature, on cpDNA variation and crossability. The trees produced with the supranuclear, nDNA and cpDNA datasets were compared by using the topology of the most parsimonious tree of one dataset as the constraint for the construction of a most parsimonious tree of another dataset. The accuracy of the trees were evaluated by calculating several Consistency and Incongruence Indices. The constrained tree of supranuclear-nDNA datasets showed the highest index values. The tree topologies of the supranuclear and cpDNA datasets were the least similar. The cpDNA tree and crossability dendrograms were identical. The most important difference between the nDNA-supranuclear trees and the cpDNA-crossability trees pertains to the position of Allium roylei , which is much closer to the clade A. cepa/A. vavilovii in the cpDNA tree than in the nDNA tree. This difference is considered to be the result of chloroplast capture from one species to another after an introgression event. A shorter distance between species inferred from a cpDNA tree than from a nDNA or comparable tree might be indicative for the level of crossability.     

A sublethal effect on native Anthocoris nemoralis through competitive interactions with invasive Harmonia axyridis

1. The invasive ladybird Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is implicated in declines of native ladybirds with intraguild predation identified as an underlying mechanism, however, less studied are the effects on non‐coccinellid predators. Intraguild predation between Anthocoris nemoralis Fabricius (Heteroptera: Anthocoridae) and H. axyridis and the relative effects of inter‐ and intraspecific competition on predators on potted Tilia cordata Mill. was investigated, at two aphid densities. 2. Intraguild predation was unidirectional in favour of H. axyridis in Petri dishes although a low level of ladybird egg predation by A. nemoralis occurred. However, on trees intraguild predation was rare. 3. A positive effect of aphid density on H. axyridis weight gain, and increased survival when reared with A. nemoralis on potted trees indicated stronger effects of intraspecific competition on H. axyridis. Consistent suppression of aphids by ladybirds revealed their superior competition for aphids. 4. Anthocoris nemoralis weight gain was reduced when reared with H. axyridis on potted trees, indicating a potential for a sublethal effect through interspecific competition. Survivorship of A. nemoralis did not differ between con‐ and heterospecific treatments, but high aphid density enhanced A. nemoralis survival. Overall, high mortality among nymphs across treatments suggested effects related to both inter‐ and intraspecific competition for resources. 5. Results provide evidence of a sublethal effect by invasive H. axyridis through resource competition, suggesting that where these predators co‐occur, competitive interactions for shared prey are more likely to affect A. nemoralis populations than intraguild predation by H. axyridis.     

Phylogeny and classification of whirligig beetles (Coleoptera: Gyrinidae): relaxed‐clock model outperforms parsimony and time‐free Bayesian analyses

Phylogenetic relationships among members of the family Gyrinidae (Coleoptera: Adephaga) were inferred from analysis of 42 morphological characters and DNA sequence data from the genes 12S rRNA, cytochrome c oxidase I and II, elongation factor 1 alpha (2 different copies) and histone III. Eighty‐nine species of Gyrinidae were included representing all known subfamilies, tribes and genera. Outgroups include species from Noteridae, Paelobiidae and Dytiscidae. Analyses include parsimony analysis, and partitioned time‐free and relaxed‐clock Bayesian analyses of the combined data using reversible‐jump MCMC to simultaneously integrate over all possible 4 × 4 nucleotide substitution models. Analyses resulted in conflicting topologies between the combined parsimony and Bayesian analyses on the one hand, and the relaxed‐clock analysis on the other. The marginal likelihoods of competing models were calculated with stepping‐stone sampling and used in a Bayes factor test, which, along with arguments from morphology, supported the topology generated by the relaxed‐clock analysis. This phylogenetic hypothesis is adopted to revise the higher classification of Gyrinidae. Major taxonomic conclusions include: (i) monophyletic Gyrinidae, (ii) the Nearctic Spanglerogyrinae Folkerts (with one species, Spanglerogyrus albiventris Folkerts) sister to all other Gyrinidae, (iii) the Madagascar endemic Heterogyrinae Brinck stat. n. (with one species, Heterogyrus milloti Legros) sister to all Gyrinidae except Spanglerogyrinae, (iv) monophyletic Gyrininae Latreille including three monophyletic tribes with the following relationship: Orectochilini Régimbart + (Gyrinini Latreille + Enhydrini Régimbart), (v) monophyletic Orectochilini comprising four monophyletic genera with the following relationships: (Gyretes Brullé + Patrus Aubé stat. n. ) + (Orectogyrus Régimbart + Orectochilus Dejean), (vi) monophyletic Gyrinini comprising three genera with the following relationships: Gyrinus Geoffroy + (Metagyrinus Brinck + Aulonogyrus Motschulsky), each monophyletic except Metagyrinus with only one included species and not tested for monophyly, and (vii) monophyletic Enhydrini comprising five genera with the following relationships: (Porrorhynchus Laporte + Dineutus MacLeay) + (Enhydrus Laporte + (Andogyrus Ochs + Macrogyrus Régimbart)), each monophyletic except Porrorhynchus, Enhydrus and Andogyrus each with one included species and untested for monophyly. Each subfamily, tribe and genus is diagnosed and discussed. The female reproductive tract of each group is presented, illustrated and discussed with respect to the phylogenetic conclusions.     

The impact of co‐occurring tree and grassland species on carbon sequestration and potential biofuel production

We evaluated how three co‐occurring tree and four grassland species influence potentially harvestable biofuel stocks and above‐ and belowground carbon pools. After 5 years, the tree Pinus strobus had 6.5 times the amount of aboveground harvestable biomass as another tree Quercus ellipsoidalis and 10 times that of the grassland species. P. strobus accrued the largest total plant carbon pool (1375 g C m^?2 or 394 g C m^?2 yr), while Schizachyrium scoparium accrued the largest total plant carbon pool among the grassland species (421 g C m^?2 or 137 g C m^?2 yr). Quercus ellipsoidalis accrued 850 g C m^?2, Q. macrocarpa 370 g C m^?2, Poa pratensis 390 g C m^?2, Solidago canadensis 132 g C m^?2, and Lespedeza capitata 283 g C m^?2. Only P. strobus and Q. ellipsoidalis significantly sequestered carbon during the experiment. Species differed in total ecosystem carbon accumulation from ?21.3 to +169.8 g C m^?2 yr compared with the original soil carbon pool. Plant carbon gains with P. strobus were paralleled by a decrease of 16% in soil carbon and a nonsignificant decline of 9% for Q. ellipsoidalis. However, carbon allocation differed among species, with P. strobus allocating most aboveground in a disturbance prone aboveground pool, whereas Q. ellipsoidalis, allocated most carbon in less disturbance sensitive belowground biomass. These differences have strong implications for terrestrial carbon sequestration and potential biofuel production. For P. strobus, aboveground plant carbon harvest for biofuel would result in no net carbon sequestration as declines in soil carbon offset plant carbon gains. Conversely the harvest of Q. ellipsoidalis aboveground biomass would result in net sequestration of carbon belowground due to its high allocation belowground, but would yield lower amounts of aboveground biomass. Our results demonstrate that plant species can differentially impact ecosystem carbon pools and the distribution of carbon above and belowground.     

Temperature adaptation of soil bacterial communities along an Antarctic climate gradient: predicting responses to climate warming

Soil microorganisms, the central drivers of terrestrial Antarctic ecosystems, are being confronted with increasing temperatures as parts of the continent experience considerable warming. Here we determined short‐term temperature dependencies of Antarctic soil bacterial community growth rates, using the leucine incorporation technique, in order to predict future changes in temperature sensitivity of resident soil bacterial communities. Soil samples were collected along a climate gradient consisting of locations on the Antarctic Peninsula (Anchorage Island, 67 °34′S, 68 °08′W), Signy Island (60 °43′S, 45 °38′W) and the Falkland Islands (51 °76′S 59 °03′W). At each location, experimental plots were subjected to warming by open top chambers (OTCs) and paired with control plots on vegetated and fell‐field habitats. The bacterial communities were adapted to the mean annual temperature of their environment, as shown by a significant correlation between the mean annual soil temperature and the minimum temperature for bacterial growth (T_min). Every 1 °C rise in soil temperature was estimated to increase T_min by 0.24–0.38 °C. The optimum temperature for bacterial growth varied less and did not have as clear a relationship with soil temperature. Temperature sensitivity, indicated by Q₁₀ values, increased with mean annual soil temperature, suggesting that bacterial communities from colder regions were less temperature sensitive than those from the warmer regions. The OTC warming (generally <1 °C temperature increases) over 3 years had no effects on temperature relationship of the soil bacterial community. We estimate that the predicted temperature increase of 2.6 °C for the Antarctic Peninsula would increase T_min by 0.6–1 °C and Q₁₀ (0–10 °C) by 0.5 units.     

Ecosystem feedbacks and cascade processes: understanding their role in the responses of Arctic and alpine ecosystems to environmental change

Global environmental change, related to climate change and the deposition of airborne N‐containing contaminants, has already resulted in shifts in plant community composition among plant functional types in Arctic and temperate alpine regions. In this paper, we review how key ecosystem processes will be altered by these transformations, the complex biological cascades and feedbacks that might result, and some of the potential broader consequences for the earth system. Firstly, we consider how patterns of growth and allocation, and nutrient uptake, will be altered by the shifts in plant dominance. The ways in which these changes may disproportionately affect the consumer communities, and rates of decomposition, are then discussed. We show that the occurrence of a broad spectrum of plant growth forms in these regions (from cryptogams to deciduous and evergreen dwarf shrubs, graminoids and forbs), together with hypothesized low functional redundancy, will mean that shifts in plant dominance result in a complex series of biotic cascades, couplings and feedbacks which are supplemental to the direct responses of ecosystem components to the primary global change drivers. The nature of these complex interactions is highlighted using the example of the climate‐driven increase in shrub cover in low‐Arctic tundra, and the contrasting transformations in plant functional composition in mid‐latitude alpine systems. Finally, the potential effects of the transformations on ecosystem properties and processes that link with the earth system are reviewed. We conclude that the effects of global change on these ecosystems, and potential climate‐change feedbacks, cannot be predicted from simple empirical relationships between processes and driving variables. Rather, the effects of changes in species distributions and dominances on key ecosystem processes and properties must also be considered, based upon best estimates of the trajectories of key transformations, their magnitude and rates of change.     

Post-Soviet steppe management causes pronounced synanthropy in the globally threatened Sociable Lapwing Vanellus gregarius

Habitat associations and distribution of breeding Sociable Lapwings were examined in 2004–2008 in central Kazakhstan to develop and assess hypotheses relating to the species' decline and high conservation threat status. At a landscape scale, breeding colonies were strongly positively associated with villages and rivers. Habitat suitability models had very high predictive power and suggested that only 6.6–8.0% of the 30 000-km² study area was potentially suitable for Sociable Lapwings. Models developed to describe the spatial distribution of nests in one region of Kazakhstan in one year predicted well the distribution of nests in another region, suggesting good generality. At a colony scale, nests were most likely to be found in the most heavily grazed areas, with a high cover of animal dung and bare ground. Despite the low density of human settlements in the study area, most Sociable Lapwing nests were < 2 km from a village. Patterns of grazing were assessed by fitting GPS loggers to cattle. There was a strong positive correlation around villages between grazing intensity and the density of Sociable Lapwing nests, with clear evidence of a threshold of grazing density that needs to be reached before birds will breed. This high degree of synanthropy, perhaps unique in a critically endangered bird, is likely to result from post-Soviet changes in steppe management and offers both threats and opportunities to the species' conservation.     

FACTORS INFLUENCING THE EFFICIENCY OF INCOMPLETE BLOCK DESIGNS IN SENSORY EVALUATION EXPERIMENTS

The efficiencies of incomplete block designs were investigated by comparing two hundred and twenty eight analyses from eleven trials using hedonic scales with corresponding randomized complete block analyses. Of the ten explanatory factors examined, only the panelist, the product type, the number of samples per session and the average score of the data had an effect on the efficiency of incomplete block designs. The effect of product type was attributed to influences of produce consumed outside the trial, and the effect of the data mean reflected decreased conscientiousness with products the panelists disliked. With three and four samples per session, incomplete block designs were 31 % and 2 % more efficient, respectively, than randomized complete block designs. When five or more samples were tested, the incomplete block designs were markedly less efficient. The practical implications of all these effects on experimental design are discussed.