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Timing of eclosion affects diapause development, fat body consumption and longevity in Osmia lignaria, a univoltine, adult-wintering solitary bee
No full textMost insects from temperate areas enter diapause ahead of winter. Species diapausing in a feeding stage
and accumulating metabolic reserves during permissive pre-wintering conditions are expected to enter
diapause shortly before the onset of winter. In contrast, species diapausing in a non-feeding stage are
expected to lower their metabolism as soon as possible to avoid excessive consumption of metabolic
reserves. The solitary beeOsmia lignariawinters as a non-feeding adult within its cocoon, but previous
studies show important weight losses and increased winter mortality in populations pre-wintered for
extended periods. We measured respiration rates to assess diapause initiation and maintenance during
pre-wintering, and tested whether timing of adult eclosion affected fitness by measuring fat body
depletion, winter mortality and post-winter longevity. We worked with different cohorts of a population
reared under natural conditions, and manipulated pre-wintering duration in a population reared under
artificial conditions. In agreement with our expectation,O. lignarialower their metabolic rates within a
few days of adult eclosion, but nonetheless suffer strong weight loss during pre-wintering. Early
developing individuals suffer greater weight loss and fat body depletion, and have short post-winter
longevity. Although, we found no differences in winter mortality among treatments, our results indicate
that increased mortality may occur in years with late winter arrivals. We discuss fundamental
ecophysiological differences between adult and prepupal diapause within the Megachilidae, and
hypothesize that species wintering as adults will be more negatively affected by a situation of extended
summers under a scenario of global warmin
Foraging and nesting behavior of Osmia lignaria (Hymenoptera: Megachilidae) in the presence of fungicides: cage studies
No full textEffetto potenziale del “global warming” sul ciclo biologico e la sopravvivenza di un apoideo solitario
No full text
Effect of temperature regime on diapause intensity in an adult-wintering Hymenopteran with obligate diapause.
No full textOsmia lignaria is a solitary bee that over-winters as a fully eclosed, cocooned, unfed adult. Our objective is to understand the effect of wintering temperature on diapause maintenance and termination in this species. We measure respiration rates and weight loss in individuals exposed to various wintering temperatures (0, 4, 7, 22 °C, outdoors) and durations (28, 84, 140, 196, 252 days). We use time to emerge and respiration response (respiration rate measured at 22 °C) as indicators of diapause intensity. Adults spontaneously lower their respiration rates to 0.1 ml/g h within 1 month after adult eclosion, indicating obligatory diapause. Non-wintered individuals maintain low respiration rates, but lose weight rapidly and die by mid-winter. In wintered adults, two phases can be distinguished. First, respiration response undergoes a rapid increase and then reaches a plateau. This phase is similar in bees wintered at 0, 4 and 7 °C. In the second phase, respiration response undergoes an exponential increase, which is more pronounced at the warmer temperatures. Composite exponential functions provide a good fit to the observed respiration patterns. Adults whose respiration response has reached 0.45 ml/g h emerge promptly when exposed to 20 °C, indicating diapause completion. Individuals wintered for short periods do not reach such respiration levels. When exposed to 20 °C these individuals lower their metabolic rate, and their emergence time is extended. The relationship between respiration rates and emergence time follows a negative exponential function. We propose two alternative models of diapause termination to interpret these result
The long summer: Pre-wintering temperatures affect metabolic expenditure and winter survival in a solitary bee. 57: 1651-1659.
No full texthe impact of climate change on insect populations depends on specific life cycle traits and physiological adaptations. The solitary bee Osmia lignaria winters as a pre-emergent adult, and requires a period of cold temperature for winter diapause completion. It is a univoltine species, and diapause induction does not depend on photoperiod. To understand the potential effects of longer summers on O. lignaria populations, we exposed individuals to three treatments simulating early, mid and late winter arrivals, and measured respiration rates, metabolic expenditure, weight loss, fat body depletion, lipid levels and winter mortality. The early-winter treatment disrupted diapause development, but had no apparent negative effects on fitness. In contrast, late-winter bees had a greater energetic expenditure (1.5-fold), weight (1.4-fold) and lipid (2-fold) loss, greater fat body depletion, and a 19% increase in mortality compared to mid-winter bees. We also monitored adult eclosion and arrival of winter temperatures under natural conditions in four years. We found a positive correlation between mean degree-day accumulation during pre-wintering (a measure of asynchrony between adult eclosion and winter arrival) and yearly winter mortality. Individually, bees experiencing greater degree-day accumulations exhibited reduced post-winter longevity. Timing of adult eclosion in O. lignaria is dependent on the duration of the prepupal period, which occurs in mid-summer, is also diapause-mediated, and is longer in populations from southerly latitudes. In a global warming scenario, we expect long summer diapause phenotypes to replace short summer diapause phenotypes, effectively maintaining short pre-wintering periods in spite of delayed winter arrivals
Ecofisiologia del pre-svernamento nell’ape solitaria Osmia lignaria Say (Hymenoptera Megachilidae)
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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