No abstract

Limited information exists on the extent of genetic variability for freezing tolerance among perennial biotypes of annual bluegrass (Poa annua L.) that evolved under golf greens management. We characterized the freezing tolerance of 42 ecotypes collected across the United States and in Québec using plants hardened to low temperatures during fall and winter. We subsequently analyzed cold‐induced biochemical changes in a subset of ecotypes with varied levels of tolerance. There was a large variability among ecotypes for freezing tolerance expressed as the lethal temperature for 50% of the plants (LT50) with values ranging from <−27.0 to −17.0°C. Variation was observed between ecotypes originating from the same region and even the same golf course. Ecotypes from Québec—better insulated from extreme subfreezing temperatures by reliable and abundant snow cover—developed less freezing tolerance than those evolving under milder winter climates. Significant differences in the concentrations of specific amino acids and carbohydrates were observed among ecotypes. Only fructans of high molecular weight, however, were significantly correlated with freezing tolerance and accounted for as much as 50% of the LT50 variance. A 26‐kDa polypeptide that markedly accumulated in cold acclimated crowns was more abundant in plants from Québec. Extensive genetic variability for freezing tolerance among perennial biotypes of annual bluegrass can thus be exploited to mitigate winter damage to golf greens.

Green roofs have recently gained recognition for their potential contribution to urban ecosystems by providing, among other services, habitat for plants and animals, and stepping stones for mobile organisms, thereby enhancing permeability among habitat patches across densely built cities. In Switzerland, investigations over the past 20 years on more than one hundred distinct green roofs across six cities have provided an unprecedented dataset on ground beetles, albeit with information that is scattered across unpublished reports and local databases. We present here for the first time a synthesis of the state of knowledge of ground beetle communities from green roofs in Switzerland. We describe 91 ground beetles species (19,428 individuals) and highlight patterns of species occurrence and composition across green roofs and cities. Most of the roofs host ground beetle communities dominated by five common mobile species with quite diversified ecological requirements. In addition, we observed nine species (10% of all species collected) that are conservation concerns in Switzerland and Central Europe as well as numerous stenotopic species (from grasslands and pioneer vegetation). This indicates that, besides sustaining local populations of common species, green roofs can also offer suitable ecological conditions of high conservation interest. We suggest both improving the design of green roofs (composition and configuration of vegetation, as well as soil depth and substrate composition) to increase their ecological value for species with the most different ecological needs, and to integrate green roofs into urban planning to make them more efficient as biodiversity supports.Keywords Biodiversity . Urban ecology . Urban green . Vertical green . Endangered species . Carabid beetles . Green infrastructures . Red list species * Gaël Pétremand

1 The effect of tannins and monoterpenes on the development, mortality and food utilization of spruce budworm Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae) was investigated under laboratory conditions using an artificial diet. Tannins were extracted from balsam fir foliage of thinned and unthinned stands to reproduce stand thinning related variations in tannins. A mixture of synthetic monoterpenes was utilized to simulate the concentration found in young and old balsam fir trees. 2 Longer development time and lower pupal weight were observed for insects fed on diets with a lower nitrogen concentration and a higher tannin concentration (unthinned treatment). Tannins induced higher insect mortality at a low nitrogen concentration compared with the diet with a higher nitrogen concentration. 3 Approximate digestibility was higher for larvae fed on diets with high concentrations of nitrogen at both low and high concentrations of tannins. Efficiency of conversion of digested food (ECD) decreased with an increase in tannin concentration. Tannins reduced both the relative consumption and growth rate (RCR and RGR). 4 Monoterpenes increased spruce budworm mortality and this mortality reached almost 50% under concentrations of monoterpene typical of the young trees compared with 20% under monoterpene concentrations found in old trees. 5 A higher digestibility was observed for larvae fed on diet with a higher concentration of monoterpenes, whereas efficiency of conversion of ingested food (ECI), ECD, RCR, and RGR decreased with an increase in monoterpenes in the diet. 6 The results obtained in the present study are consistent with the defensive role of secondary compounds such as tannins and monoterpenes in the spruce budworm-balsam fir system.

One of the most damaging insect pests in deciduous forests of North America is the forest tent caterpillar, Malacosoma disstria Hübner. It can feed on a variety of plants, but trembling aspen (Populus tremuloides Michaux) is its preferred host and sugar maple (Acer saccharum Marshall) serves as a secondary one in the northern part of its distribution. Because host plant characteristics influence insect performance and survival, we evaluated the impact of trembling aspen and sugar maple foliage on M. disstria performance. Host effects on insect cold hardiness and overwintering survival of offspring were also studied. Forest tent caterpillar reared on aspen leaves had a shorter development time, higher pupal weights and fecundity, and superior egg parameters (length and weight) compared with those reared on sugar maple leaves. Larvae from the two food treatments had low glucose levels during diapause, whereas glycerol content of insects reared on maple was significantly higher during diapause than larvae fed on aspen. Lower glycerol content may explain the higher overwinter mortality of pharate larvae from aspen-reared parents even though their supercooling points were as low as -36 degrees C. This study shows the influence of host plant on insect life history and the need to consider overwintering success and offspring performance in studies to understand and predict population growth and cycling.