Effects of method of straw disposal and depth of cultivation on populations of Fusarium spp. in soil and on brown foot rot in continuous winter wheat

Soil samples (0–10 cm depth) taken from plots of continuous winter wheat at intervals between January 1993 and July 1996 were dilution-plated on PCNB agar to identify and enumerate colony-forming units (cfus) of Fusarium spp. Cfus of the main wheat pathogen, F. culmorum, were more numerous in soil from plots that were shallow-cultivated to 10 cm after each harvest than in those that were ploughed. They were also usually more numerous in plots in which straw had been chopped and incorporated (by shallow cultivation or ploughing) than in those in which straw had been burnt. Increasing amounts of straw tended to increase the number of cfus. Deeper sampling (15–25 cm) showed that ploughing resulted in a more even, but diluted, distribution of cfus down the soil profile. Populations of some commonly found species that are not pathogenic on wheat {F. oxysporum, F. equiseti, F. flocciferum and F. merismoides) were sometimes also affected by straw disposal or cultivation treatments. Alternative methods of estimating population densities (baiting soil with wheat kernels or wheat seedlings, or plating-out straw fragments) showed generally similar effects of treatments on populations of F. culmorum; the relative merits of the methods are considered. Large differences in population densities of all species occurred within and between seasons. The smallest populations were found in January 1995 but, in the case of F. culmorum, they increased to relatively large numbers in July 1995. The summer of 1995 was warm and dry and especially favourable for development of fusarium foot rot. Severe disease occurred only in this year and was less frequent after ploughing than after tine-cultivation but more frequent after straw burning than after straw incorporation. The implications of these observations for understanding the role of propagules of F. culmorum in soil as inoculum for foot rot are discussed.     

Survival of Colonizing Wolves in the Northern Rocky Mountains of the United States, 1982–2004

Abstract: After roughly a 60-year absence, wolves (Canis lupus) immigrated (1979) and were reintroduced (1995-1996) into the northern Rocky Mountains (NRM), USA, where wolves are protected under the Endangered Species Act. The wolf recovery goal is to restore an equitably distributed metapopulation of ≥30 breeding pairs and 300 wolves in Montana, Idaho, and Wyoming, while minimizing damage to livestock; ultimately, the objective is to establish state-managed conservation programs for wolf populations in NRM. Previously, wolves were eradicated from the NRM because of excessive human killing. We used Andersen–Gill hazard models to assess biological, habitat, and anthropogenic factors contributing to current wolf mortality risk and whether federal protection was adequate to provide acceptably low hazards. We radiocollared 711 wolves in Idaho, Montana, and Wyoming (e.g., NRM region of the United States) from 1982 to 2004 and recorded 363 mortalities. Overall, annual survival rate of wolves in the recovery areas was 0.750 (95% CI = 0.728-0.772), which is generally considered adequate for wolf population sustainability and thereby allowed the NRM wolf population to increase. Contrary to our prediction, wolf mortality risk was higher in the northwest Montana (NWMT) recovery area, likely due to less abundant public land being secure wolf habitat compared to other recovery areas. In contrast, lower hazards in the Greater Yellowstone Area (GYA) and central Idaho (CID) likely were due to larger core areas that offered stronger wolf protection. We also found that wolves collared for damage management purposes (targeted sample) had substantially lower survival than those collared for monitoring purposes (representative sample) because most mortality was due to human factors (e.g., illegal take, control). This difference in survival underscores the importance of human-caused mortality in this recovering NRM population. Other factors contributing to increased mortality risk were pup and yearling age class, or dispersing status, which was related to younger age cohorts. When we included habitat variables in our analysis, we found that wolves having abundant agricultural and private land as well as livestock in their territory had higher mortality risk. Wolf survival was higher in areas with increased wolf density, implying that secure core habitat, particularly in GYA and CID, is important for wolf protection. We failed to detect changes in wolf hazards according to either gender or season. Maintaining wolves in NWMT will require greater attention to human harvest, conflict resolution, and illegal mortality than in either CID or GYA; however, if human access increases in the future in either of the latter 2 areas hazards to wolves also may increase. Indeed, because overall suitable habitat is more fragmented and the NRM has higher human access than many places where wolves roam freely and are subject to harvest (e.g., Canada and AK), monitoring of wolf vital rates, along with concomitant conservation and management strategies directed at wolves, their habitat, and humans, will be important for ensuring long-term viability of wolves in the region.     

Determination of traits associated with leafhopper (Empoasca fabae and Empoasca kraemeri) resistance and dissection of leafhopper damage symptoms in the common bean (Phaseolus vulgaris)

The typical presentation of potato leafhopper injury in beans includes necrosis at the leaf margins (leaf burn or hopperburn), and downward curling or “cupping” of the leaves. To evaluate potato leafhopper damage a visual score that combines the overall severity of leaf burn, leaf curling and stunting symptoms is usually used. Nonetheless, it may be useful to evaluate these symptoms separately since they may be the result of separate mechanisms of damage, controlled by separate genes. A population of 108 recombinant inbred lines (RILs), derived from a cross between a leafhopper‐susceptible Ontario cultivar (Berna) and a resistant line (EMP 419) were scored for injury after natural infestation with Empoasca fabae in Canada and Empoasca kraemeri in Colombia. Leaf burn and leaf curl were significantly rank‐correlated (0.37–0.74, P<0.001) in all environments. However, several RILs consistently exhibited high scores for leaf curl but low values for leaf burn, which suggests that genetic dissection of these characters may be possible. Indeterminate growth habit was associated with slightly lower damage scores in Colombia and Ontario, Canada (P<0.05) while white‐seeded lines had lower damage scores in Colombia (P<0.05). The resistant parental line had significantly lower nymph counts than did the susceptible parent. A positive relationship between damage scores and nymph counts was also observed in the F₃ families and the F_5:6 RILs.     

The fossil record and biogeography of the Ciehlidae (Actinopterygii: Labroidei)

The family Ciehlidae is a large group of tropical fishes in the order Perciformes, with an estimated number of living species exceeding 1400. The modern distribution of the family Ciehlidae is predominantly in fresh waters of Central and South America, Africa, Madagascar, India and the Middle East, with fossil members known from Africa, Saudi Arabia, the Levant, Europe, South America and Haiti. Many authors have referred to the distribution as being Gondwanan and have postulated that cichlids originated over 130 million years ago, in the Early Cretaceous. However, the suggested evidence for an Early Cretaceous origin of cichlids is equally or more compatible with a much younger age of origin. Based on the biology and distribution of modern and fossil cichlids, it is more probable that they arose less than 65 million years ago, in the Early Tertiary, and crossed marine waters to attain their current distribution.     

Evaluation of Potential Factors Predisposing Livestock to Predation by Jaguars

ABSTRACT Depredation of livestock by large carnivores is an important but poorly understood source of human-carnivore conflict. We examined patterns of livestock depredation by jaguars (Panthera onca) and pumas (Puma concolor) on a ranch-wildlife reserve in western Brazil to assess factors contributing to prey mortality. We predicted jaguars would kill a greater proportion of calves than yearling and adult cattle and that proximity to suitable habitat would increase mortality risk. We further speculated that exposure to predation risk would promote livestock grouping and increased movement distance. We recorded 169 cattle mortality incidents during 2003–2004, of which 19% were due to predation by jaguars and pumas. This level of mortality represented 0.2–0.3% of the total livestock holdings on the ranch. Jaguars caused most (69%) cattle predation events, and survival in allotments was lower for calves than for other age classes. Forest proximity was the only variable we found to explain patterns of livestock mortality, with predation risk increasing as distance to forest cover declined. Due to low predation risk, cattle movement patterns and grouping behavior did not vary relative to level of spatial overlap with radiocollared jaguars. The overall effect of predation on cattle was low and livestock likely constituted an alternative prey for large cats in our study area. However, selection of calves over other age cohorts and higher predation risk among cattle in proximity to forest cover is suggestive of selection of substandard individuals. Cattle ranchers in the Pantanal region may reduce cattle mortality rates by concentrating on losses due to nonpredation causes that could be more easily controlled.     

The role of forest maturation in causing the decline of Black Grouse Tetrao tetrix

Black Grouse Tetrao tetrix in Britain have declined through the 20th century, and most birds are now in Scotland. Many causes for this decline have been suggested, notably agricultural intensification, increased grazing levels and moorland afforestation. We examine habitat correlates of Black Grouse distribution and population change from a 700-km² area in the core of the Scottish range, where the numbers of lekking male Black Grouse declined by an estimated 70% to 270 between 1990 and 2002. Habitat data were derived from satellite imagery, in combination with map and field-collected data. Lek occurrence, lek size and changes in lek size were all correlated with forest structure, either positively with the amount of pre-thicket forest cover, or negatively with closed canopy cover. Additional effects of the cover of grass moor and dry heath suggest that Black Grouse are most likely to occur where moorland comprises Heather Calluna vulgaris and grass mosaics. Analysis of the change in Black Grouse abundance within 1.5 km of discrete forest blocks suggests that forest maturation, which has been the dominant habitat change during the course of the study, alone accounts for 58–78% of the decline. Given the close association of Black Grouse and the occurrence of woodland (and particularly conifer plantation) throughout much of their British range, these findings can be used to inform the design of management schemes for the recovery of Black Grouse.     

Non-random distribution among a guild of parasitoids: implications for community structure and host survival

Abstract 1. Immature stages of the gall midge, Asphondylia borrichiae, are attacked by four species of parasitoids, which vary in size and relative abundance within patches of the gall midge’s primary host plant, sea oxeye daisy (Borrichia frutescens). 2. In the current study, a bagging experiment found that the smallest wasp, Galeopsomyia haemon, was most abundant in galls exposed to natural enemies early in the experiment, when gall diameter is smallest, while the wasp with the longest ovipositor, Torymus umbilicatus, dominated the parasitoid community in galls that were not exposed until the 5th and 6th weeks when gall diameter is maximal. 3. Moreover, the mean number of parasitoids captured using large artificial galls were 70% and 150% higher compared with medium and small galls respectively, while stem height of artificial galls significantly affected parasitoid distribution. Galls that were level with the top of the sea oxeye canopy captured 60% more parasitoids compared with those below the canopy and 50% more than galls higher than the plant canopy. 4. These non‐random patterns were driven primarily by the differential distribution of the largest parasitoid, T. umbilicatus, which was found significantly more often than expected on large galls and the smallest parasitoid of the guild, G. haemon, which tended to be more common on stems level with the top of the plant canopy. 5. Large Asphondylia galls, especially those located near the top of the Borrichia canopy, were more likely to be discovered by searching parasitoids. Results using artificial galls were consistent with rates of parasitism of Asphondylia galls in native patches of sea oxeye daisy. Gall diameter was 19% greater and the rate of parasitism was reduced by almost 50% on short stems; as a result, gall abundance was 24% higher on short stems compared with ones located near the top of the plant canopy. 6. These results suggest that parasitoid community composition within galls is regulated by both interspecific differences in ovipositor length and preferences for specific gall size and/or stem length classes.     

An artificial intergeneric hybrid derived from sexual hybridization between the distantly related Arabidopsis thaliana and Pachycladon cheesemanii (Brassicaceae)

An artificial intergeneric hybrid derived from sexual hybridization between Arabidopsis thaliana (female) and Pachycladon cheesemanii (male) is characterized and formally named as ×Pachydopsis hortorum. A hybrid origin for ×Pachydopsis is supported by a chromosome number of 2n = 15, with this comprising haploid gametes from A. thaliana (n = 5) and P. cheesemanii (n = 10). DNA fingerprinting using amplified fragment length polymorphism data also confirmed the parentage of the hybrid, as it comprised the additive total of all of the fragments scored for P. cheesemanii and most of those scored for A. thaliana. ×Pachydopsis is a robust perennial herb with numerous leafy rosettes and long inflorescences like P. cheesemanii, and floral parts that are intermediate between the parents. ×Pachydopsis produces sterile pollen. Female function of ×Pachydopsis is partially normal, with the pollen of A. thaliana and several species of Pachycladon readily germinating on the stigma, and pollen tubes growing down the style and transmission tissue into the ovary. No seed was formed from these pollinations, although one embryo developed but subsequently aborted at the torpedo stage. Colchicine was used to induce polyploid inflorescences, and these were confirmed by the size and density of the stomata and pollen diameter. Flowers from the polyploid inflorescences of ×Pachydopsis were backcrossed with A. thaliana Landsberg erecta and 11 seeds were produced. Four backcross hybrid plants were raised and two of these had a chromosome number of 2n = 20, consistent with a haploid gamete (n = 15) from polyploid × Pachydopsis being fertilized by a haploid pollen gamete (n = 5) from A. thaliana Landsberg erecta. Polyploid × Pachydopsis flowers backcrossed with P. cheesemanii and crossed with P. novae‐zelandiae did not produce any seeds. The partially fertile intergeneric hybrid described here between Arabidopsis and Pachycladon is remarkable in that, although the two genera occur in an Arabidopsoid clade, they are separated by a reasonable phylogenetic distance. This relationship suggests that Pachycladon and ×Pachydopsis have the potential to be employed in the study of evolutionary and ecological processes using the wide array of Arabidopsis resources. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157 , 533–544.