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Direct and indirect effects in host-parasitoid interactions: ecological and evolutionary consequences
Get PDFhttps://www.ester.ee/record=b1547854*es
Phenological responses to climate warming in temperate moths and butterflies: species traits predict future changes in voltinism
No full textChanges in the number of generations per year (voltinism) have been among the most common phenological responses to climate warming in insects inhabiting seasonal environments. Nevertheless, numerous species have maintained univoltine (one generation per year) phenology with increasing temperatures, indicating the involvement of phylogenetic, ecological or some other constraints on phenological change. I examined geographic variation in voltinism in moths and butterflies of Northern Europe to identify species traits that might predispose species to univoltine/multivoltine phenology. I focused on species with a wide latitudinal distribution range (15 degrees as a minimum) which makes it unlikely that constraints imposed by season length could preclude multivoltinism across their distribution. Almost half of the 731 moth and butterfly species considered appear to have a single generation throughout their entire European range. A univoltine life-cycle across a wide latitudinal gradient suggests the presence of some constraint that makes additional generations either impossible or at least strongly disadvantageous, which will unlikely change with future climate warming. The scattered distribution of univoltine and multivoltine species across the lepidopteran phylogeny indicates that phylogenetic constraints are not strongly limiting changes in voltinism, and the trait is open to ecologically-driven adaptive evolution. My data show that species with one generation per year are generally larger than multivoltine species, but size forms no absolute constraint to having multiple generations per year. Obligately univoltine species dominate among egg and adult overwinterers (life-histories typical of so-called spring-feeders), whereas species with capacity for multiple generations prevail among pupal overwinterers. Multivoltinism is also infrequent among species feeding on grasses, particularly in endophagous grass-feeders. Larval diet breadth has no discernible effect on voltinism. Given the diverse ecological consequences of voltinism and its changes, accounting for the species' capacity for multivoltinism may be a key to address future challenges in biodiversity conservation and pest management.Explanations for the data set. size = adult wing span, overwintering stage: E = egg, L = larva, P = pupa, A = adult, AP = adult within pupal case (classified as adult overwinterers in the analysis); host type: W = woody plants (species feeding exclusively on coniferous trees are indicated by W(c)), F = forbs, G = grasses (endophagous grass-feeders are indicated by G(i)), WH = woody + herbaceous plants, L = lichens; larval diet breadth: M = monophagous, O = oligophagous, P = polyphagous; voltinism: U = univoltine, M = multivoltine.
Funding provided by: Estonian Research Council / Eesti Teadusagentuur*Crossref Funder Registry ID: Award Number: PRG741Funding provided by: Internal Grant Agency of the Faculty of Environmental Sciences, Czech University of Life Sciences Prague*Crossref Funder Registry ID: Award Number: 42900/1312/3166Funding provided by: Estonian Research Council / Eesti TeadusagentuurCrossref Funder Registry ID: Award Number: PRG741The data set used in this study is mostly literature-derived. Details regarding the collection, sources and processing of the data are described in full in the paper
Early-life food stress hits females harder than males in insects: a meta-analysis of sex differences in environmental sensitivity
No full textFitness consequences of early-life environmental conditions are often sex-specific, but corresponding evidence for invertebrates remains inconclusive. Here we use meta-analysis to evaluate sex-specific sensitivity to early-life nutritional conditions in insects. Using literature-derived data for 85 species with broad phylogenetic and ecological coverage, we show that females are generally more sensitive to food stress than males. Stressful nutritional conditions during development typically lead to female-biased mortality and thus increasingly male-biased sex ratios of emerging adults. We further demonstrate that the general trend of higher sensitivity to food stress in females can primarily be attributed to their typically larger body size in insects and hence higher energy needs during development. By contrast, there is no consistent evidence of sex-biased sensitivity in sexually size-monomorphic species. Drawing conclusions regarding sex-biased sensitivity in species with male-biased size dimorphism remains to wait for the accumulation of relevant data. Our results suggest that environmental conditions leading to elevated juvenile mortality may potentially affect the performance of insect populations further by reducing the proportion of females among individuals reaching reproductive age. Accounting for sex-biased mortality is therefore essential to understanding the dynamics and demography of insect populations, not least importantly in the context of ongoing insect declines.Data are provided as .xlsx files, and R scripts are provided for analyses. We encourage researchers interested in the re-use of this data set and code to contact the authors of the data set.Funding provided by: Eesti TeadusagentuurCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100002301Award Number: PRG741Funding provided by: Internal Grant Agency of the Faculty of Environmental Sciences*Crossref Funder Registry ID: Award Number: 42900/1312/3141Data collection
These data were collected for a meta-analysis to assess sex-specific sensitivity to early-life nutritional conditions in insects. We made use of experimental case studies reporting sex ratios at adult emergence in conspecifics reared under two or more diet treatments (food quality or availability). We collated primary studies in two complementary ways. The majority of primary data sets for this synthesis were collected systematically by the lead author (T. Teder) from an extensive list of journals in the field of entomology, ecology and evolutionary biology, partly as a result of one-time retrospective screening (articles published before 2003) and partly as a result of continuous screening (articles published between 2004 and 2021) of journals' tables of contents. Our systematic screening meant that the journals' tables of contents were routinely examined, and all papers identified as potentially containing relevant data on the basis of article titles were subjected to full-text review. As data of this type are typically reported in tables and figures, their identification within articles was straightforward.
To increase the amount of primary data, additional studies were identified by a thorough search in major literature databases (Google Scholar, Web of Science, Scopus, published until 2021). These complementary searches in the literature databases were undertaken to find relevant data in journals that remained uncovered by our main data collection method. Accordingly, while exploring the search results, we primarily focused on studies published in journals that were not subjected to systematic screening. The basic procedure for identifying relevant primary papers among search results was basically identical to that used when screening journals' contents: papers identified as potentially containing relevant data based on article titles were retrieved for full-text review. To minimize any search-related biases, we used only search queries that were strictly neutral concerning the focal questions of our study (i.e. sex-specific sensitivity to nutritional stress). Accordingly, our search queries included only combinations of very generic search terms: one of several synonyms of sex ratio ('sex ratio', 'proportion/percentage/fraction of males/females'), 'mortality' and one of particular insect order names ('Diptera', 'Hemiptera', 'Lepidoptera', 'Coleoptera', 'Orthoptera', etc., or 'insect*'). No restriction was set on the language or publication year of primary studies.
As a major exception, we systematically ignored studies focusing on Hymenoptera and Thysanoptera during the process of data collection. These groups of insects have haplodiploid sex determination (males develop from unfertilized and females from fertilized eggs) which provides mothers with an efficient mechanism for manipulating offspring sex ratio. We also did not consider taxa regularly exhibiting asexual reproduction, such as aphids.
Data extraction and criteria for eligibility
For a study to be considered, it had to provide two types of information: i) sex ratios at adult emergence for multiple (two or more) diet treatments together with sample sizes, and ii) corresponding juvenile mortality rates. Typically, sex ratios in primary studies were reported as the proportion/percentage of males/females or the ratio of the two sexes at adult emergence (or, in a few cases, at the pupal stage). As sample sizes for sex ratio estimates were not always explicitly indicated, we applied various indirect approaches to derive them, most often combining information on sample sizes at the start of the experiment with data on mortality throughout juvenile stages.
The combined juvenile mortality rate of the two sexes was used as a proxy for nutritional stress. Accordingly, our research relies on the premise that, within each primary study, food stress was most severe in treatments with the highest mortality rates and least pronounced in treatments with the lowest mortality rates. Both egg-to-adult and larval mortality rates (often reported as survival rates) were considered equally acceptable measures of juvenile mortality. In a few cases, we also accepted mortality rates estimated over a particular fixed part of the larval stage (two primary studies) or the pupal stage (three studies).
We limited our inclusion criteria to studies where major external mortality agents – predators and parasitoids – were explicitly excluded. In all studies included, experimental treatments were applied to the F1 generation only, whereas their parents were maintained under identical conditions, excluding in this way any parental effect on sex ratios. Among-treatment differences in nutritional stress were solely due to variations in food quality (e.g., different host plants, different prey species, also different artificial diets) or food availability. Otherwise, the conditions were uniform within the experiments. Data from multifactorial experiments (e.g. those manipulating both diet and temperature) were divided into different data sets so that the environmental factor of our interest was allowed to vary while other factors were held constant. In some primary studies, food quality and amount were manipulated indistinguishably within the same experimental setup. Data extracted from different studies were always treated as different data sets. However, data from a single study could also be split into multiple primary data sets if obtained from different experiments or using different species/populations/genotypes. We deliberately did not consider studies in which diet treatments applied contained pesticides or their residues. WebPlotDigitizer 4.3 (A. Rohatgi; https://automeris.io/WebPlotDigitizer) was used to extract graphically presented data.
One should note that the overwhelming majority of primary studies were conducted in contexts other than the focus of our synthesis: sex differences in stress responses per se were rarely addressed in these papers. Therefore, a considerable share of primary studies found, between-treatment differences in juvenile mortality were relatively small, indicating low variation in environmental stress levels. Naturally, in order to meaningfully evaluate sex-specific responses to food stress, there must be some variation in food stress across treatments. We therefore arbitrarily limited our main database to a subset of primary studies in which mortality rates across treatments had at least a 10 % difference (calculated as the difference between the maximum and minimum mortality rates across treatments). This way we ensured that growth conditions within studies were not "too similar" across treatments. Applying this threshold retained us altogether 125 primary data sets which formed the backbone of our analyses
Early-life food stress hits females harder than males in insects: a meta-analysis of sex differences in environmental sensitivity
No full textFitness consequences of early-life environmental conditions are often sex-specific, but corresponding evidence for invertebrates remains inconclusive. Here we use meta-analysis to evaluate sex-specific sensitivity to early-life nutritional conditions in insects. Using literature-derived data for 85 species with broad phylogenetic and ecological coverage, we show that females are generally more sensitive to food stress than males. Stressful nutritional conditions during development typically lead to female-biased mortality and thus increasingly male-biased sex ratios of emerging adults. We further demonstrate that the general trend of higher sensitivity to food stress in females can primarily be attributed to their typically larger body size in insects and hence higher energy needs during development. By contrast, there is no consistent evidence of sex-biased sensitivity in sexually size-monomorphic species. Drawing conclusions regarding sex-biased sensitivity in species with male-biased size dimorphism remains to wait for the accumulation of relevant data. Our results suggest that environmental conditions leading to elevated juvenile mortality may potentially affect the performance of insect populations further by reducing the proportion of females among individuals reaching reproductive age. Accounting for sex-biased mortality is therefore essential to understanding the dynamics and demography of insect populations, not least importantly in the context of ongoing insect declines.Data are provided as .xlsx files, and R scripts are provided for analyses. We encourage researchers interested in the re-use of this data set and code to contact the authors of the data set.Funding provided by: Eesti TeadusagentuurCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100002301Award Number: PRG741Funding provided by: Internal Grant Agency of the Faculty of Environmental Sciences*Crossref Funder Registry ID: Award Number: 42900/1312/3141Data collection
These data were collected for a meta-analysis to assess sex-specific sensitivity to early-life nutritional conditions in insects. We made use of experimental case studies reporting sex ratios at adult emergence in conspecifics reared under two or more diet treatments (food quality or availability). We collated primary studies in two complementary ways. The majority of primary data sets for this synthesis were collected systematically by the lead author (T. Teder) from an extensive list of journals in the field of entomology, ecology and evolutionary biology, partly as a result of one-time retrospective screening (articles published before 2003) and partly as a result of continuous screening (articles published between 2004 and 2021) of journals' tables of contents. Our systematic screening meant that the journals' tables of contents were routinely examined, and all papers identified as potentially containing relevant data on the basis of article titles were subjected to full-text review. As data of this type are typically reported in tables and figures, their identification within articles was straightforward.
To increase the amount of primary data, additional studies were identified by a thorough search in major literature databases (Google Scholar, Web of Science, Scopus, published until 2021). These complementary searches in the literature databases were undertaken to find relevant data in journals that remained uncovered by our main data collection method. Accordingly, while exploring the search results, we primarily focused on studies published in journals that were not subjected to systematic screening. The basic procedure for identifying relevant primary papers among search results was basically identical to that used when screening journals' contents: papers identified as potentially containing relevant data based on article titles were retrieved for full-text review. To minimize any search-related biases, we used only search queries that were strictly neutral concerning the focal questions of our study (i.e. sex-specific sensitivity to nutritional stress). Accordingly, our search queries included only combinations of very generic search terms: one of several synonyms of sex ratio ('sex ratio', 'proportion/percentage/fraction of males/females'), 'mortality' and one of particular insect order names ('Diptera', 'Hemiptera', 'Lepidoptera', 'Coleoptera', 'Orthoptera', etc., or 'insect*'). No restriction was set on the language or publication year of primary studies.
As a major exception, we systematically ignored studies focusing on Hymenoptera and Thysanoptera during the process of data collection. These groups of insects have haplodiploid sex determination (males develop from unfertilized and females from fertilized eggs) which provides mothers with an efficient mechanism for manipulating offspring sex ratio. We also did not consider taxa regularly exhibiting asexual reproduction, such as aphids.
Data extraction and criteria for eligibility
For a study to be considered, it had to provide two types of information: i) sex ratios at adult emergence for multiple (two or more) diet treatments together with sample sizes, and ii) corresponding juvenile mortality rates. Typically, sex ratios in primary studies were reported as the proportion/percentage of males/females or the ratio of the two sexes at adult emergence (or, in a few cases, at the pupal stage). As sample sizes for sex ratio estimates were not always explicitly indicated, we applied various indirect approaches to derive them, most often combining information on sample sizes at the start of the experiment with data on mortality throughout juvenile stages.
The combined juvenile mortality rate of the two sexes was used as a proxy for nutritional stress. Accordingly, our research relies on the premise that, within each primary study, food stress was most severe in treatments with the highest mortality rates and least pronounced in treatments with the lowest mortality rates. Both egg-to-adult and larval mortality rates (often reported as survival rates) were considered equally acceptable measures of juvenile mortality. In a few cases, we also accepted mortality rates estimated over a particular fixed part of the larval stage (two primary studies) or the pupal stage (three studies).
We limited our inclusion criteria to studies where major external mortality agents – predators and parasitoids – were explicitly excluded. In all studies included, experimental treatments were applied to the F1 generation only, whereas their parents were maintained under identical conditions, excluding in this way any parental effect on sex ratios. Among-treatment differences in nutritional stress were solely due to variations in food quality (e.g., different host plants, different prey species, also different artificial diets) or food availability. Otherwise, the conditions were uniform within the experiments. Data from multifactorial experiments (e.g. those manipulating both diet and temperature) were divided into different data sets so that the environmental factor of our interest was allowed to vary while other factors were held constant. In some primary studies, food quality and amount were manipulated indistinguishably within the same experimental setup. Data extracted from different studies were always treated as different data sets. However, data from a single study could also be split into multiple primary data sets if obtained from different experiments or using different species/populations/genotypes. We deliberately did not consider studies in which diet treatments applied contained pesticides or their residues. WebPlotDigitizer 4.3 (A. Rohatgi; https://automeris.io/WebPlotDigitizer) was used to extract graphically presented data.
One should note that the overwhelming majority of primary studies were conducted in contexts other than the focus of our synthesis: sex differences in stress responses per se were rarely addressed in these papers. Therefore, a considerable share of primary studies found, between-treatment differences in juvenile mortality were relatively small, indicating low variation in environmental stress levels. Naturally, in order to meaningfully evaluate sex-specific responses to food stress, there must be some variation in food stress across treatments. We therefore arbitrarily limited our main database to a subset of primary studies in which mortality rates across treatments had at least a 10 % difference (calculated as the difference between the maximum and minimum mortality rates across treatments). This way we ensured that growth conditions within studies were not "too similar" across treatments. Applying this threshold retained us altogether 125 primary data sets which formed the backbone of our analyses
Going 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
Jälkeläisten elinkierto-ominaisuuksien vuodenaikaisvaihtelu hirvikärpäsellä
No full textAbstractThe life histories of ectoparasites are shaped by both host and off-host environment. A suitable host is primarily needed during reproduction, whereas juvenile stages outside the host are directly exposed to environmental variability. Viviparity, i.e. the development of an embryo inside the body of the mother resulting in large offspring size, increases offspring survival. The production of large offspring has its consequences in terms of high variation in offspring age and in the environment that each young individual will face. I used a viviparous ectoparasite, the deer ked (Lipoptena cervi), to investigate the consequences of long reproductive lifespan and varying offspring environment on offspring life-histories and seasonal adaptations.Offspring life-histories varied seasonally. I showed that the resources provided by the deer ked females determine offspring performance throughout its off-host period. Offspring size increased towards the spring and the end of the reproductive period, and simultaneously offspring survival and cold tolerance increased. Seasonal variation in offspring size did not reflect the resources that would guarantee offspring survival during the longest diapause or the highest cold tolerance during the harshest winter period. Diapause intensity varies with birth time according to the expected length of the winter ahead. However, the deer ked pupae, regardless of their age, overwinter at an opportunistic diapause, which may be terminated rapidly only by an exposure to high temperature. Contrary to general observations, photoperiod has no role in regulating the seasonal shifts of the deer ked. Neither is high cold tolerance associated only with diapause, but it remains high through four seasons, also in the active developmental and adult stages. I also evaluated the effects of life-history variation on the invasion potential of the deer ked. I conducted a large-scale transplant experiment to test the survival and pupal development at and beyond the current range. I found that the lower spring and summer temperatures and the shorter growth season in the north cause a deterioration in pupal performance and shorten the flight period. However, the colder climate may not totally prevent further spread. A more important factor that will affect deer ked invasion is host availability, and especially in Finland, the density of the moose population.Seasonal variation in offspring life histories in viviparous ectoparasites differs from the variation patterns reported in most invertebrates. This may be due to the extremely large offspring size and to the fact that maternally derived resources determine offspring performance through the entire off-host period. Variation in offspring performance is thus determined by maternal resources and seasonal variation in the condition of the moose.TiivistelmäUseimpien ulkoloisten elinkierto on riippuvainen isännästä ja isännän ulkopuolella kasvavien jälkeläisten kohtaamista ympäristöoloista. Viviparia eli jälkeläisen kehitys naaraan sisällä ja siitä usein seuraava suuri jälkeläiskoko parantavat jälkeläisten selviytymistä. Suurten jälkeläisten tuottaminen pitkällä aikavälillä johtaa siihen, että eri-ikäiset jälkeläiset kohtaavat vuodenajasta riippuen hyvin erilaiset olosuhteet. Väitöstyössäni tarkastelin Suomessa nopeasti yleistyneen hirvieläinten ulkoloisen, hirvikärpäsen (Lipoptena cervi), avulla, mitä seurauksia viviparialla, pitkällä lisääntymiskaudella ja ympäristön vuodenaikaisvaihtelulla on jälkeläisten elinkierto-ominaisuuksiin.Väitöskirjatyössäni havaitsin, että hirvikärpäsjälkeläisten elinkiertopiirteet vaihtelevat jälkeläisen syntymäajan mukaan. Osoitin myös, että hirvikärpäsnaaraan jälkeläisilleen tarjoamat ravintovarat määrittelevät jälkeläisten isännästä riippumattoman elinkierron aikaisen menestyksen. Jälkeläisten keskimääräinen koko kasvoi lisääntymiskauden edetessä talvesta kohti kevättä, jolloin myös selviytyminen ja kylmänsietokyky paranivat. Jälkeläiskoon vuodenaikaisvaihtelu ei näin ollen vastaa jälkeläisten tarvitsemia resursseja suhteessa talvehtimisen pituuteen eikä korreloi koville talvipakkasille altistumisen todennäköisyyden kanssa. Lepotilan keston määrittelevä diapaussin syvyys vaihteli syntymävuodenaikaa vastaavasti. Diapaussin havaitsin kuitenkin olevan ensisijaisesti opportunistinen, jolloin pelkästään korkea lämpötila voi nopeasti päättää lepotilan kaikenikäisillä yksilöillä. Vastoin yleisiä käsityksiä valorytmi ei vaikuta diapaussin säätelyyn. Vastoin ennakko-odotuksia kylmänsietokyky säilyy korkeana vuoden ympäri ja kaikissa tutkituissa elinkierron vaiheissa. Sovelsin tutkimieni elinkiertopiirteiden vaikutusta myös lajin invaasiokykyyn, ja tutkin istutuskokeen avulla koteloiden selviytymistä ja kehitystä nykyisellä esiintymisalueella ja sen pohjoispuolella. Alhaisemmat kevät- ja kesälämpötilat sekä lyhyempi kasvukausi vähentävät aikuiseksi selviytymistä ja lyhentävät lentoaikaa syksyllä. Ilmastotekijöiden suhteen hirvikärpänen voisi esiintyä nykyistä pohjoisempana. Tärkein tekijä hirvikärpäsen leviämistä tarkasteltaessa on kuitenkin sopivien isäntäeläimien saatavuus ja Suomen oloissa erityisesti hirven eli hirvikärpäsen pääisännän kannan tiheys.Tutkimukseni perusteella ulkoloisten vivipariasta seuraava jälkeläisten elinkiertopiirteiden ajallinen vaihtelu eroaa muiden selkärangattomien vastaavasta vaihtelusta. Yhtenä syynä eroihin lienee se, että hirvikärpäsnaaras tuottaa erityisen suuria jälkeläisiä ja että jälkeläiset puolestaan ovat täysin riippuvaisia emon antamista resursseista. Emon lisääntymisresurssit ja hirven kunnon vuodenaikaisvaihtelu vaikuttavat mahdollisesti siihen, minkälaisia jälkeläisiä hirvikärpänen milloinkin kykenee tuottamaan.Academic dissertation to be presented with the assent of the Doctoral Training Committee of Technology and Natural Sciences of the University of Oulu for public defence in Kuusamonsali (Auditorium YB210), Linnanmaa, on 25 August 2012, at 12 noonAbstract
The life histories of ectoparasites are shaped by both host and off-host environment. A suitable host is primarily needed during reproduction, whereas juvenile stages outside the host are directly exposed to environmental variability. Viviparity, i.e. the development of an embryo inside the body of the mother resulting in large offspring size, increases offspring survival. The production of large offspring has its consequences in terms of high variation in offspring age and in the environment that each young individual will face. I used a viviparous ectoparasite, the deer ked (Lipoptena cervi), to investigate the consequences of long reproductive lifespan and varying offspring environment on offspring life-histories and seasonal adaptations.
Offspring life-histories varied seasonally. I showed that the resources provided by the deer ked females determine offspring performance throughout its off-host period. Offspring size increased towards the spring and the end of the reproductive period, and simultaneously offspring survival and cold tolerance increased. Seasonal variation in offspring size did not reflect the resources that would guarantee offspring survival during the longest diapause or the highest cold tolerance during the harshest winter period. Diapause intensity varies with birth time according to the expected length of the winter ahead. However, the deer ked pupae, regardless of their age, overwinter at an opportunistic diapause, which may be terminated rapidly only by an exposure to high temperature. Contrary to general observations, photoperiod has no role in regulating the seasonal shifts of the deer ked. Neither is high cold tolerance associated only with diapause, but it remains high through four seasons, also in the active developmental and adult stages. I also evaluated the effects of life-history variation on the invasion potential of the deer ked. I conducted a large-scale transplant experiment to test the survival and pupal development at and beyond the current range. I found that the lower spring and summer temperatures and the shorter growth season in the north cause a deterioration in pupal performance and shorten the flight period. However, the colder climate may not totally prevent further spread. A more important factor that will affect deer ked invasion is host availability, and especially in Finland, the density of the moose population.
Seasonal variation in offspring life histories in viviparous ectoparasites differs from the variation patterns reported in most invertebrates. This may be due to the extremely large offspring size and to the fact that maternally derived resources determine offspring performance through the entire off-host period. Variation in offspring performance is thus determined by maternal resources and seasonal variation in the condition of the moose.Tiivistelmä
Useimpien ulkoloisten elinkierto on riippuvainen isännästä ja isännän ulkopuolella kasvavien jälkeläisten kohtaamista ympäristöoloista. Viviparia eli jälkeläisen kehitys naaraan sisällä ja siitä usein seuraava suuri jälkeläiskoko parantavat jälkeläisten selviytymistä. Suurten jälkeläisten tuottaminen pitkällä aikavälillä johtaa siihen, että eri-ikäiset jälkeläiset kohtaavat vuodenajasta riippuen hyvin erilaiset olosuhteet. Väitöstyössäni tarkastelin Suomessa nopeasti yleistyneen hirvieläinten ulkoloisen, hirvikärpäsen (Lipoptena cervi), avulla, mitä seurauksia viviparialla, pitkällä lisääntymiskaudella ja ympäristön vuodenaikaisvaihtelulla on jälkeläisten elinkierto-ominaisuuksiin.
Väitöskirjatyössäni havaitsin, että hirvikärpäsjälkeläisten elinkiertopiirteet vaihtelevat jälkeläisen syntymäajan mukaan. Osoitin myös, että hirvikärpäsnaaraan jälkeläisilleen tarjoamat ravintovarat määrittelevät jälkeläisten isännästä riippumattoman elinkierron aikaisen menestyksen. Jälkeläisten keskimääräinen koko kasvoi lisääntymiskauden edetessä talvesta kohti kevättä, jolloin myös selviytyminen ja kylmänsietokyky paranivat. Jälkeläiskoon vuodenaikaisvaihtelu ei näin ollen vastaa jälkeläisten tarvitsemia resursseja suhteessa talvehtimisen pituuteen eikä korreloi koville talvipakkasille altistumisen todennäköisyyden kanssa. Lepotilan keston määrittelevä diapaussin syvyys vaihteli syntymävuodenaikaa vastaavasti. Diapaussin havaitsin kuitenkin olevan ensisijaisesti opportunistinen, jolloin pelkästään korkea lämpötila voi nopeasti päättää lepotilan kaikenikäisillä yksilöillä. Vastoin yleisiä käsityksiä valorytmi ei vaikuta diapaussin säätelyyn. Vastoin ennakko-odotuksia kylmänsietokyky säilyy korkeana vuoden ympäri ja kaikissa tutkituissa elinkierron vaiheissa. Sovelsin tutkimieni elinkiertopiirteiden vaikutusta myös lajin invaasiokykyyn, ja tutkin istutuskokeen avulla koteloiden selviytymistä ja kehitystä nykyisellä esiintymisalueella ja sen pohjoispuolella. Alhaisemmat kevät- ja kesälämpötilat sekä lyhyempi kasvukausi vähentävät aikuiseksi selviytymistä ja lyhentävät lentoaikaa syksyllä. Ilmastotekijöiden suhteen hirvikärpänen voisi esiintyä nykyistä pohjoisempana. Tärkein tekijä hirvikärpäsen leviämistä tarkasteltaessa on kuitenkin sopivien isäntäeläimien saatavuus ja Suomen oloissa erityisesti hirven eli hirvikärpäsen pääisännän kannan tiheys.
Tutkimukseni perusteella ulkoloisten vivipariasta seuraava jälkeläisten elinkiertopiirteiden ajallinen vaihtelu eroaa muiden selkärangattomien vastaavasta vaihtelusta. Yhtenä syynä eroihin lienee se, että hirvikärpäsnaaras tuottaa erityisen suuria jälkeläisiä ja että jälkeläiset puolestaan ovat täysin riippuvaisia emon antamista resursseista. Emon lisääntymisresurssit ja hirven kunnon vuodenaikaisvaihtelu vaikuttavat mahdollisesti siihen, minkälaisia jälkeläisiä hirvikärpänen milloinkin kykenee tuottamaan
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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