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1.
Fire regimes shape plant communities but are shifting with changing climate. More frequent fires of increasing intensity are burning across a broader range of seasons. Despite this, impacts that changes in fire season have on plant populations, or how they interact with other fire regime elements, are still relatively understudied. We asked (a) how does the season of fire affect plant vigor, including vegetative growth and flowering after a fire event, and (b) do different functional resprouting groups respond differently to the effects of season of fire? We sampled a total of 887 plants across 36 sites using a space‐for‐time design to assess resprouting vigor and reproductive output for five plant species. Sites represented either a spring or autumn burn, aged one to three years old. Season of fire had the clearest impacts on flowering in Lambertia formosa with a 152% increase in the number of plants flowering and a 45% increase in number of flowers per plant after autumn compared with spring fires. There were also season × severity interactions for total flowers produced for Leptospermum polygalifolium and L. trinervium with both species producing greater flowering in autumn, but only after lower severity fires. Severity of fire was a more important driver in vegetative growth than fire season. Season of fire impacts have previously been seen as synonymous with the effects of fire severity; however, we found that fire season and severity can have clear and independent, as well as interacting, impacts on post‐fire vegetative growth and reproductive response of resprouting species. Overall, we observed that there were positive effects of autumn fires on reproductive traits, while vegetative growth was positively related to fire severity and pre‐fire plant size. 相似文献
2.
Herpetofauna are frequently cited as ideal indicators for environmental and restoration monitoring due to their importance to ecological functioning, dominance of vertebrate biomass, and sensitivity to environmental change. Despite this relevance, herpetofauna have yet to be fully integrated into comprehensive, community‐scale restoration monitoring methodologies. We tested the applicability of one such method, abundance–biomass comparisons (ABCs), to monitoring restoration success in a longleaf pine ecosystem currently undergoing restoration via prescribed burning. W statistics (a metric of environmental perturbation) for herpetofaunal assemblages in longleaf pine stands managed under varying fire intervals closely tracked forest succession from recently burned longleaf pine stands to those characterized by longer times since last burn and high levels of hardwood encroachment. Our results suggest that ABCs may be an applicable method for terrestrial restoration monitoring that encompasses entire faunal assemblages and allows for generality in restoration or disturbance response. We emphasize, however, that applications of this method and others need to take into account the specific ecological characteristics of study organisms and the natural history of study sites to avoid incorrect interpretations of disturbance response and inappropriate management recommendations. 相似文献
3.
Stephanie A. Blain Louise Chavarie Mackenzie H. Kinney Dolph Schluter 《Ecology and evolution》2022,12(4)
A solitary population of consumers frequently evolves to the middle of a resource gradient and an intermediate mean phenotype compared to a sympatric pair of competing species that diverge to either side via character displacement. The forces governing the distribution of phenotypes in these allopatric populations, however, are little investigated. Theory predicts that the intermediate mean phenotype of the generalist should be maintained by negative frequency‐dependent selection, whereby alternate extreme phenotypes are favored because they experience reduced competition for resources when rare. However, the theory makes assumptions that are not always met, and alternative explanations for an intermediate phenotype are possible. We provide a test of this prediction in a mesocosm experiment using threespine stickleback that are ecologically and phenotypically intermediate between the more specialized stickleback species that occur in pairs. We manipulated the frequency distribution of phenotypes in two treatments and then measured effects on a focal intermediate population. We found a slight frequency‐dependent effect on survival in the predicted direction but not on individual growth rates. This result suggests that frequency‐dependent selection might be a relatively weak force across the range of phenotypes within an intermediate population and we suggest several general reasons why this might be so. We propose that allopatric populations might often be maintained at an intermediate phenotype instead by stabilizing or fluctuating directional selection. 相似文献
4.
Christopher M. Murray Caleb D. McMahan Allison R. Litmer Jeffrey M. Goessling Dustin Siegel 《Ecology and evolution》2021,11(23):17519
Biological patterns across latitudinal gradients elucidate a number of striking natural clines from which numerous processes can be further explored. The trade‐off between reproduction and somatic maintenance and growth represents a suite of life‐history traits with variable energy allocation and potential latitudinal patterns. Specifically, male sexually dimorphic traits in female choice systems represent one such reproductive investment constrained by resource acquisition and subsequent allocation. Latitudinal variation in sexual dimorphism has been suggested although the relationship between dimorphic traits and latitude are conflicting. Here, we test alternative hypotheses regarding this pattern using two broadly distributed vertebrates exhibiting sexually dimorphic traits. We hypothesized that the exaggeration of dimorphic traits correlates with latitude, with males having exaggerated sexually dimorphic traits at either higher or lower latitudes. Results indicate that male sexually dimorphic traits are exaggerated at lower latitudes while relative gonopodium size in Poecilia latipinna was larger at higher latitudes. This pattern may be a result of lower latitude populations experiencing greater population densities and longer access to resources that could manifest in females more intensively selecting for higher quality males in lower latitudes. Experimental work should address this pattern and investigate mechanistic processes. 相似文献
5.
Sexually dimorphic ornamental traits are widely regarded as indicators of nutritional condition. However, variation of nutritional condition outside the reproductive and the ornament production seasons has rarely been considered, although it affects the generality of information content, especially for ornaments that may be used across the year. We measured several indicators of migratory and molt condition in male and female blackcaps (Sylvia atricapilla) during their autumn migration, and quantified their crown reflectance. We detected robust correlations between migratory and molt condition indices, and the correlation structure was similar in the two sexes. Furthermore, the across‐season measure of body condition was positively related to the darkness of the black crown in males, while being unrelated to reflectance traits of the reddish crown in females. Our results reinforce the possibility that some melanin‐based ornaments may be year‐round indicators of individual quality via their dependence on nutritional condition. 相似文献
6.
Disparate resource use originating from phenology of biotic resources, abiotic conditions, and life cycles of exploiting organisms underscores the importance of research across time and space to guide management practices. Our goal was to evaluate resource use of northern bobwhite (Colinus virginianus; bobwhite) at two spatial scales and across three age classes, from hatching through a period of the postjuvenile molt. Our study was conducted at Tall Timbers Research Station, Tallahassee, FL, USA—situated in a landscape subjected to small scale (<20 ha) prescribed fires on a 2‐year fire rotation. We predicted prescribed fire, disking, and supplemental feeding would dictate resource use, but effects would depend on time since fire, brood age, and time of day. We predicted vegetation and temperature would govern roost use by broods, but these effects would also depend on age. We radio‐tracked 62 broods 21–35 times / week during May–October 2018 and 2019. Broods were less likely to use areas with large proportions of hardwood drains but favored sites with greater proportions of burned uplands, regardless of the time of day. Broods were less likely to use areas at greater distances from supplemental feed; this relationship had no interaction with age but was stronger later in the nesting season (>July 15). Broods were more likely to use areas with greater proportions of fallow fields during the day than for roosting. Broods used roosts with more woody cover and visual obscurity than at available sites. Roosts consisted of less grass and bare ground. However, these effects interacted with age; broods used sparser cover at older ages. Neonate broods were more likely to use cooler roosts with greater thermal stability, but this effect was reversed for juveniles. Broods may alter resource use with changes in vulnerabilities to threats such as thermal risks and predation. 相似文献
7.
Silvana Piersanti Gianandrea Salerno Viviana Di Pietro Leonardo Giontella Manuela Rebora Albyn Jones Ola M. Fincke 《Ecology and evolution》2021,11(9):4399
Search image formation, a proximal mechanism to maintain genetic polymorphisms by negative frequency‐dependent selection, has rarely been tested under natural conditions. Females of many nonterritorial damselflies resemble either conspecific males or background vegetation. Mate‐searching males are assumed to form search images of the majority female type, sexually harassing it at rates higher than expected from its frequency, thus selectively favoring the less common morph. We tested this and how morph coloration and behavior influenced male perception and intersexual encounters by following marked Ischnura elegans and noting their reactions to conspecifics. Contrary to search image formation and associative learning hypotheses, although males encountered the minority, male‐like morph more often, sexual harassment and clutch size were similar for both morphs. Prior mating attempts or copula with morphs did not affect a male''s subsequent reaction to them; males rarely attempted matings with immature females or males. Females mated early in the day, reducing the opportunity for males to learn their identity beforehand. Once encountered, the male‐like morph was more readily noticed by males than the alternative morph, which once noticed was more likely to receive mating attempts. Flexible behavior gave morphs considerable control over their apparency to males, influencing intersexual encounters. Results suggested a more subtle proximal mechanism than male learning maintains these color polymorphisms and call for inferences of learning to be validated by behavior of wild receivers and their signalers. 相似文献
8.
The presence of shell bands is common in gastropods. Both the marine snails Littorina fabalis and Lttorina saxatilis are polymorphic for this trait. Such polymorphism would be expected to be lost by the action of genetic drift or directional selection, but it appears to be widespread at relatively constant frequencies. This suggests it is maintained by balancing selection on the trait or on a genetically linked trait. Using long time series of empirical data, we compared potential effects of genetic drift and negative frequency‐dependent selection (NFDS) in the two species. The contribution of genetic drift to changes in the frequency of bands in L. fabalis was estimated using the effective population size estimated from microsatellite data, while the effect of genetic drift in L. saxatilis was derived from previously published study. Frequency‐dependent selection was assessed by comparing the cross‐product estimator of fitness with the frequency of the polymorphism across years using a regression analysis. Both studied species showed patterns of NFDS. In addition, in L. fabalis, contributions from genetic drift could explain some of the changes in banding frequency. Overdominance and heterogeneous selection did not fit well to our data. The possible biological explanations resulting in the maintenance of the banding polymorphism are discussed. 相似文献
9.
Alexandra H. M. Jebb Daniel T. Blumstein Pierre Bize Julien G. A. Martin 《Ecology and evolution》2021,11(7):3435
Body mass is often viewed as a proxy of past access to resources and of future survival and reproductive success. Links between body mass and survival or reproduction are, however, likely to differ between age classes and sexes. Remarkably, this is rarely taken into account in selection analyses. Selection on body mass is likely to be the primary target accounting for juvenile survival until reproduction but may weaken after recruitment. Males and females also often differ in how they use resources for reproduction and survival. Using a long‐term study on body mass and annual survival in yellow‐bellied marmots (Marmota flaviventer), we show that body mass was under stabilizing viability selection in the first years of life, before recruitment, which changed to positive directional selection as age increased and animals matured. We found no evidence that viability selection across age classes on body mass differed between sexes. By investigating the link between running speed and body mass, we show that the capacity to escape predators was not consistent across age classes and followed a quadratic relationship at young ages only. Overall, our results indicate that mature age classes exhibit traditional patterns of positive viability selection on body mass, as expected in a hibernating mammal, but that mass in the first years of life is subjected to stabilizing selection which may come from additional predation pressures that negate the benefits of the largest body masses. Our study highlights the importance to disentangle selection pressures on traits across critical age (or life) classes. 相似文献
10.
Salome Lopez&#x;Serna Catalina Gonzalez&#x;Quevedo Hector Fabio Rivera&#x;Gutierrez 《Ecology and evolution》2021,11(24):18552
In animal communication, signals are expected to evolve to be honest, so that receivers avoid being manipulated by signalers. One way that signals can evolve to be honest is for them to be costly, with only high‐quality individuals being able to bear the costs of signal expression. It has been proposed that parasites can introduce costs that affect the expression of sexually selected traits, and there is evidence to support the role of parasitism in modulating animal behavior. If host infection status or intensity is found to relate to differences in signal expression, it may indicate a fitness cost that mediates honesty of signals. Birdsong is a good model for testing this, and physically challenging songs representing complex motor patterns provide a good example of sexually selected traits indicating individual condition. We performed a field study to evaluate the relationship between song performance and avian malaria infection in a common songbird. Previous work on this subject has almost always evaluated avian malaria in terms of binary infection status; however, parasitemia—infection intensity—is rarely assessed, even though differences in parasite load may have profound physiological consequences. We estimated parasitemia levels by using real‐time PCR. We found that birds with higher parasitemia displayed lower vocal performance, providing evidence that this song trait is an honest signal of parasitic load of haemosporidian parasites. To our knowledge, this study links parasite load and the expression of a sexually selected trait in a way that has not been addressed in the past. Studies using song performance traits and parasitemia offer an important perspective for understanding evolution of characters via sexual selection. 相似文献
11.
Lisa Crozier Reece Foy Brandon L Mouery Robert H Whitaker Andrea Corno Christos Spanos Tony Ly Jeanette Gowen Cook Adrian T Saurin 《The EMBO journal》2022,41(6)
CDK4/6 inhibitors arrest the cell cycle in G1‐phase. They are approved to treat breast cancer and are also undergoing clinical trials against a range of other tumour types. To facilitate these efforts, it is important to understand why a cytostatic arrest in G1 causes long‐lasting effects on tumour growth. Here, we demonstrate that a prolonged G1 arrest following CDK4/6 inhibition downregulates replisome components and impairs origin licencing. Upon release from that arrest, many cells fail to complete DNA replication and exit the cell cycle in a p53‐dependent manner. If cells fail to withdraw from the cell cycle following DNA replication problems, they enter mitosis and missegregate chromosomes causing excessive DNA damage, which further limits their proliferative potential. These effects are observed in a range of tumour types, including breast cancer, implying that genotoxic stress is a common outcome of CDK4/6 inhibition. This unanticipated ability of CDK4/6 inhibitors to induce DNA damage now provides a rationale to better predict responsive tumour types and effective combination therapies, as demonstrated by the fact that CDK4/6 inhibition induces sensitivity to chemotherapeutics that also cause replication stress. 相似文献
12.
Avian feathers need to be replaced periodically to fulfill their functions, with natural, social, and sexual selection presumably driving the evolution of molting strategies. In temperate birds, a common pattern is to molt feathers immediately after the breeding season, the pre‐basic molt. However, some species undergo another molt in winter‐spring, the pre‐alternate molt. Using a sample of 188 European passerine species, Bayesian phylogenetic mixed models, and correlated evolution analyses, we tested whether the occurrence of the pre‐alternate molt was positively associated with proxies for sexual selection (sexual selection hypothesis) and nonsexual social selection (social selection hypothesis), and with factors related to feather wear (feather wear hypothesis) and time constraints on the pre‐basic molt (time constraints hypothesis). We found that the pre‐alternate molt was more frequent in migratory and less gregarious species inhabiting open/xeric habitats and feeding on the wing, and marginally more frequent in species with strong sexual selection and those showing a winter territorial behavior. Moreover, an increase in migratory behavior and sexual selection intensity preceded the acquisition of the pre‐alternate molt. These results provide support for the feather wear hypothesis, partial support for the sexual selection and time constraints hypotheses, and no support for the social selection hypothesis. 相似文献
13.
Developmental plasticity can allow the exploitation of alternative diets. While such flexibility during early life is often adaptive, it can leave a legacy in later life that alters the overall health and fitness of an individual. Species of the spadefoot toad genus Spea are uniquely poised to address such carryover effects because their larvae can consume drastically different diets: their ancestral diet of detritus or a derived shrimp diet. Here, we use Spea bombifrons to assess the effects of developmental plasticity in response to larval diet type and nutritional stress on juvenile behaviors and stress axis reactivity. We find that, in an open‐field assay, juveniles fed shrimp as larvae have longer latencies to move, avoid prey items more often, and have poorer prey‐capture abilities. While juveniles fed shrimp as larvae are more exploratory, this effect disappears if they also experienced a temporary nutritional stressor during early life. The larval shrimp diet additionally impairs juvenile jumping performance. Finally, larvae that were fed shrimp under normal nutritional conditions produce juveniles with higher overall glucocorticoid levels, and larvae that were fed shrimp and experienced a temporary nutritional stressor produce juveniles with higher stress‐induced glucocorticoid levels. Thus, while it has been demonstrated that consuming the novel, alternative diet can be adaptive for larvae in nature, doing so has marked effects on juvenile phenotypes that may recalibrate an individual''s overall fitness. Given that organisms often utilize diverse diets in nature, our study underscores the importance of considering how diet type interacts with early‐life nutritional adversity to influence subsequent life stages. 相似文献
14.
Ella von Weissenberg Anna Jansson Kristiina A. Vuori Jonna Engstrm&#x;
st 《Ecology and evolution》2022,12(2)
The marine ecosystems are under severe climate change‐induced stress globally. The Baltic Sea is especially vulnerable to ongoing changes, such as warming. The aim of this study was to measure eco‐physiological responses of a key copepod species to elevated temperature in an experiment, and by collecting field samples in the western Gulf of Finland. The potential trade‐off between reproductive output and oxidative balance in copepods during thermal stress was studied by incubating female Acartia sp. for reproduction rate and oxidative stress measurements in ambient and elevated temperatures. Our field observations show that the glutathione cycle had a clear response in increasing stress and possibly had an important role in preventing oxidative damage: Lipid peroxidation and ratio of reduced and oxidized glutathione were negatively correlated throughout the study. Moreover, glutathione‐s‐transferase activated in late July when the sea water temperature was exceptionally high and Acartia sp. experienced high oxidative stress. The combined effect of a heatwave, increased cyanobacteria, and decreased dinoflagellate abundance may have caused larger variability in reproductive output in the field. An increase of 7°C had a negative effect on egg production rate in the experiment. However, the effect on reproduction was relatively small, implying that Acartia sp. can tolerate warming at least within the temperature range of 9–16°C. However, our data from the experiment suggest a link between reproductive success and oxidative stress during warming, shown as a significant combined effect of temperature and catalase on egg production rate. 相似文献
15.
Samantha E.S. Kreling Kaitlyn M. Gaynor Alex McInturff Kendall L. Calhoun Justin S. Brashares 《Ecology and evolution》2021,11(22):15683
With rapid global change, the frequency and severity of extreme disturbance events are increasing worldwide. The ability of animal populations to survive these stochastic events depends on how individual animals respond to their altered environments, yet our understanding of the immediate and short‐term behavioral responses of animals to acute disturbances remains poor. We focused on animal behavioral responses to the environmental disturbance created by megafire. Specifically, we explored the effects of the 2018 Mendocino Complex Fire in northern California, USA, on the behavior and body condition of black‐tailed deer (Odocoileus hemionus columbianus). We predicted that deer would be displaced by the disturbance or experience high mortality post‐fire if they stayed in the burn area. We used data from GPS collars on 18 individual deer to quantify patterns of home range use, movement, and habitat selection before and after the fire. We assessed changes in body condition using images from a camera trap grid. The fire burned through half of the study area, facilitating a comparison between deer in burned and unburned areas. Despite a dramatic reduction in vegetation in burned areas, deer showed high site fidelity to pre‐fire home ranges, returning within hours of the fire. However, mean home range size doubled after the fire and corresponded to increased daily activity in a severely resource‐depleted environment. Within their home ranges, deer also selected strongly for patches of surviving vegetation and woodland habitat, as these areas provided forage and cover in an otherwise desolate landscape. Deer body condition significantly decreased after the fire, likely as a result of a reduction in forage within their home ranges, but all collared deer survived for the duration of the study. Understanding the ways in which large mammals respond to disturbances such as wildfire is increasingly important as the extent and severity of such events increases across the world. While many animals are adapted to disturbance regimes, species that exhibit high site fidelity or otherwise fixed behavioral strategies may struggle to cope with increased climate instability and associated extreme disturbance events. 相似文献
16.
Elisabeth Yarwood Claudia Drees Jeremy E. Niven Marisa Gawel Wiebke Schuett 《Ecology and evolution》2021,11(15):9949
- Species’ ranges are dynamic, changing through range shifts, contractions, and expansions. Individuals at the edge of a species’ shifting range often possess morphological traits that increase movement capacity, that are not observed in individuals farther back within the species’ range. Although morphological traits that increase in proportion toward the range edge may differ between the sexes, such sex differences are rarely studied.
- Here, we test the hypotheses that body size and condition increase with proximity to an expanding range edge in the flightless ground beetle, Carabus hortensis, and that these trait changes differ between the sexes.
- Male, but not female, body size increased with proximity to the range edge. Body size was positively correlated with male front and mid tibia length and to female hind tibia length, indicating that body size is indicative of movement capacity in both sexes. Body condition (relative to body size) decreased with increasing population density in males but not females. Population density was lowest at the range edge.
- Our results indicate that sex is an important factor influencing patterns in trait distribution across species’ ranges, and future studies should investigate changes in morphological traits across expanding range margins separately for males and females. We discuss the implications for sex differences in resource allocation and reproductive rates for trait differentiation across species’ shifting ranges.
17.
Xuanxiao Xie Jennifer Shrimpton Gina M. Doody Philip G. Conaghan Frederique Ponchel 《Aging cell》2021,20(4)
BackgroundAge‐related immune deficiencies are thought to be responsible for increased susceptibility to infection in older adults, with alterations in lymphocyte populations becoming more prevalent over time. The loss of humoral immunity in ageing was attributed to the diminished numbers of B cells and the reduced ability to generate immunoglobulin.AimsTo compare the intrinsic B‐cell capacity for differentiation into mature plasma cells (PCs), between young and old donors, using in vitro assays, providing either effective T‐cell help or activation via TLR engagement.MethodsB cells were isolated from healthy individuals, in younger (30–38 years) and older (60–64 years) donors. An in vitro model system of B‐cell differentiation was used, analysing 5 differentiation markers by flow cytometry, under T‐dependent (TD: CD40/BCR stimulation) or T‐independent (TI: TLR7/BCR activation) conditions. Antibody secretion was measured by ELISA and gene expression using qPCR.ResultsTI and TD differentiation resulted in effective proliferation of B cells followed by their differentiation into PC. B‐cell‐executed TI differentiation was faster, all differentiation marker and genes being expressed earlier than under TD differentiation (day 6), although generating less viable cells and lower antibody levels (day 13). Age‐related differences in B‐cell capacity for differentiation were minimal in TD differentiation. In contrast, in TI differentiation age significantly affected proliferation, viability, differentiation, antibody secretion and gene expression, older donors being more efficient.ConclusionAltogether, B‐cell differentiation into PC appeared similar between age groups when provided with T‐cell help, in contrast to TI differentiation, where multiple age‐related changes suggest better capacities in older donors. These new findings may help explain the emergence of autoantibodies in ageing. 相似文献
18.
Prescribed burning is the primary method used to reduce wildfire risk in a range of ecosystems globally. Knowledge of how animal populations respond to prescribed burns is essential for designing fuel management plans that are sensitive to ecological values. We conducted a before–after, control-impact experiment in the temperate jarrah forest ecosystem of south-western Australia to examine how reptiles respond to season of burning (spring or autumn) and time since burning (0–5 years). Through pitfall trapping at 10 survey grids over 7 years, we captured 1808 reptiles from 22 species. Bayesian mixed effects models revealed that six of the eight species analysed showed either a decrease or increase in capture rate at burnt compared to unburnt sites, and most of these effects only occurred within the first 2 years post fire. Species richness showed a weak negative response to one autumn burn and no relationship with time since fire. Fire effects were more common in autumn compared to spring burns, which is likely a reflection of differing fire severities. These results suggest that prescribed burning can temporarily reduce habitat suitability and abundance for some species, particularly those that rely on leaf litter for shelter and foraging. Our findings emphasise the dynamic nature of reptile responses to prescribed burns and underscore the importance of considering both fire seasonality and recency of burning in wildlife management plans. 相似文献
19.
20.
David Lopez‐Idiaquez Pablo Vergara Juan Antonio Fargallo Jesús Martinez‐Padilla 《Ecology and evolution》2016,6(4):1224-1235
Secondary sexual traits displayed by males and females may have evolved as a signal of individual quality. However, both individual quality and investment on producing or maintaining enhanced sexual traits change as individuals age. At the same time, the costs associated to produce sexual traits might be attenuated or increased if environmental conditions are benign or worse respectively. Accordingly, environmental conditions are expected to shape the association between the expression of sexual traits and their reproductive outcome as individuals age. Nonetheless, little is known about the environmental influence on the co‐variation between sexual traits and reproductive outcome throughout the life of individuals. We studied the age‐dependency of the number and size of back spots, a melanin‐based and sexual trait in adults of common kestrels (Falco tinnunculus). We analysed the age‐dependence of reproductive traits and the environmental influence, defined as vole abundance, using a 10‐year individual‐based dataset. We broke down age‐related changes of reproductive traits into within‐ and between‐individual variation to assess their contribution to population‐level patterns. Our results showed a within‐individual decrease in the number, but not the size, of back spots in males. The size of back spots was positively correlated with food availability in males. Reproductive performance of males increased as they aged, in agreement with the life‐history theory but depending of vole abundance. Remarkably, we found that having fewer back spots was positively associated with clutch size only for old individuals under low‐food conditions. We suggest that environmental variation may shape the association between the expression of a sexual signal and reproductive outcome. We speculate that the reliability of sexual traits is higher when environmental conditions are poor only for old individuals. Within an evolutionary context, we suggest that the expression of sexual traits might be constrained by environmental conditions at later stages of life. 相似文献