Drosophila larvae are attracted to a wide variety of chemical stimuli. The olfactory response to ethyl acetate, a powerful attractant, was found to be surprisingly well conserved across a variety of different wild-type strains. Strain differences are documented, however, both in attraction to ethyl acetate and in another chemosensory behavior: avoidance of an aversive stimulus. As a means of analyzing the extent of genetic heterogeneity within strains, one wild-type population, Canton-S, was screened for variant X chromosomes. An enrichment procedure was characterized and used to make the screening more efficient. Lines homozygous for individual X chromosomes were established, and all were found to exhibit a strong olfactory response, although evidence was found for variation among them. The olfactory response was found to be conserved through an extended period of larval development, including the final period during which larvae leave the culture medium in preparation for metamorphosis. The results are discussed in terms of the genetic basis of the response and the use of single-gene mutations as a means of dissecting olfactory system function.

Communicated by Alan Garen, July 10, 1989 ABSTRACT Although the Drosophila visual system has been described extensively, little is known about its olfactory system. A major reason for this discrepancy has been the lack of simple, reliable means of measuring response to airborne chemicals. This paper describes a jump response elicited by exposing Drosophila to chemical vapors. This behavior provides the basis for a single-fly chemosensory assay. The behavior exhibits dose dependence and chemical specificity: it is stimulated by exposure to ethyl acetate, benzaldehyde, and propionic acid but not ethanol. Animals can respond repeatedly at short intervals to ethyl acetate and propionic acid. The response relies on the third antennal segments. To illustrate the use of this behavior in genetic analysis of chemosensory response, nine acj mutants defective in response are isolated (acj = abnormal chemosensory jump), and their responses to two chemicals are characterized. All of the acj mutants are normal in giant fiber system physiology, and two exhibit defects in visual system physiology.

Understanding the effects of traditional livestock grazing abandonment on the ability of mountain grasslands to sustain multiple ecosystem functions (ecosystem multifunctionality; EMF) is crucial for implementing policies that promote grasslands conservation and the delivery of multiple ecosystem services. In this study, we evaluated the effect of short- and long-term transhumant sheep abandonment on EMF through a grazing exclusion experiment in a grassland of the Cantabrian Mountains range (NW Spain), where transhumant sheep flocks graze in summer. We considered four key ecosystem functions, derived from vegetation and soil functional indicators measured in the field: (A) biodiversity function, evaluated from total plant species evenness, diversity and richness indicators; (B) forage production function, evaluated from cover and richness of perennial and annual herbaceous species indicators; (C) carbon sequestration function, evaluated from woody species cover and soil organic carbon indicators; and (D) soil fertility function, evaluated from NH4+-N, NO3–-N, P and K content in the soil. The EMF index was calculated by integrating the four standardized ecosystem functions through an averaging approach. Based on linear mixed modeling we found that grazing exclusion induced significant shifts in the considered individual ecosystem functions and also on EMF. Long-term livestock exclusion significantly hindered biodiversity and forage production functions, but enhanced the carbon sequestration function. Conversely, the soil fertility function was negatively affected by both short- and long-term grazing exclusion. Altogether, grazing exclusion significantly decreased overall EMF, especially in long-term livestock exclusion areas, while the decline in EMF in short-term exclusions with respect to grazed areas was marginally significant. The results of this study support the sustainability of traditional transhumance livestock grazing for promoting the conservation of grasslands and their ecosystem function in mountain regions.

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The main objective of this study was to analyse the effect of recurrence and burn severity on ecosystem multifunctionality in Pinus pinaster forests. We selected a large wildfire that occurred in the Sierra del Teleno in 2012 (NW Spain), where we differentiated two recurrences and two burn severity situations. As a result, four scenarios were identified: low recurrence plus low severity, low recurrence plus high severity, high recurrence plus low severity, high recurrence plus high severity. In each one, a number of 1 m x 1 m plots proportional to the burned area were established. Three years after the wildfire we evaluated in each plot: (1) percentage of covered soil, (2) total percentage cover of herbaceous species, (3) percentage cover of each woody species, (4) total plant species richness. Also, a composite soil sample was collected from each plot. Chemical (total organic carbon, total nitrogen and available phosphorus) and microbiological (microbial biomass carbon) properties were analysed in each soil sample. The following variables were used as indicators of ecosystem functions: percentage of covered soil, total cover of herbaceous species, Pinus pinaster cover, total plant richness, total organic carbon, total soil nitrogen, available phosphorus and microbial biomass carbon. Another indicator of ecosystem functions was calculated: floral colours of shrub species diversity using the Shannon index. The values of each ecosystem function indicator were standardized. The indicators/functions of regulating ecosystem services were: Climate regulation (indicator: total % of organic soil carbon) and Erosion protection (indicator: covered soil %). The functions/ indicators of supporting ecosystem services were: soil fertility (indicator: total nitrogen and available phosphorous) and soil quality (indicator: microbial biomass C). The indicators/functions of cultural ecosystem services were: species diversity (indicator: plant species richness) and aesthetic value (indicator: the Shannon index of floral colours). The functions/indicators of provisioning ecosystem services were: grass for livestock (indicator: % cover of herbaceous species) and timber production (indicator: % cover of Pinus pinaster). The results indicated that all scenarios apart from low recurrence plus low severity negatively affected the multifunctionality of the ecosystems.