scholarly journals Phenological variation in annual timing of hibernation and breeding in nearby populations of Arctic ground squirrels

2010 ◽  
Vol 278 (1716) ◽  
pp. 2369-2375 ◽  
Author(s):  
Michael J. Sheriff ◽  
G. Jim Kenagy ◽  
Melanie Richter ◽  
Trixie Lee ◽  
Øivind Tøien ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Ground Squirrels ◽  
Ecological Communities ◽  
Physiological Mechanisms ◽  
Interacting Species ◽  
Trade Offs ◽  
Phenological Shifts ◽  
Arctic Ground Squirrels ◽  
Northern Alaska

Ecologists need an empirical understanding of physiological and behavioural adjustments that animals can make in response to seasonal and long-term variations in environmental conditions. Because many species experience trade-offs between timing and duration of one seasonal event versus another and because interacting species may also shift phenologies at different rates, it is possible that, in aggregate, phenological shifts could result in mismatches that disrupt ecological communities. We investigated the timing of seasonal events over 14 years in two Arctic ground squirrel populations living 20 km apart in Northern Alaska. At Atigun River, snow melt occurred 27 days earlier and snow cover began 17 days later than at Toolik Lake. This spatial differential was reflected in significant variation in the timing of most seasonal events in ground squirrels living at the two sites. Although reproductive males ended seasonal torpor on the same date at both sites, Atigun males emerged from hibernation 9 days earlier and entered hibernation 5 days later than Toolik males. Atigun females emerged and bred 13 days earlier and entered hibernation 9 days earlier than those at Toolik. We propose that this variation in phenology over a small spatial scale is likely generated by plasticity of physiological mechanisms that may also provide individuals the ability to respond to variation in environmental conditions over time.

scholarly journals Changing seasonality and phenological responses of free-living male arctic ground squirrels: the importance of sex

2013 ◽  
Vol 368 (1624) ◽  
pp. 20120480 ◽  
Author(s):  
Michael J. Sheriff ◽  
Melanie M. Richter ◽  
C. Loren Buck ◽  
Brian M. Barnes
Keyword(s):  
Snow Cover ◽  
Ground Squirrels ◽  
Free Living ◽  
Male And Female ◽  
Reproductive Maturation ◽  
Changing Patterns ◽  
Arctic Ground Squirrels ◽  
Northern Alaska ◽  
The Impact

Many studies have addressed the effects of climate change on species as a whole; however, few have examined the possibility of sex-specific differences. To understand better the impact that changing patterns of snow-cover have on an important resident Arctic mammal, we investigated the long-term (13 years) phenology of hibernating male arctic ground squirrels living at two nearby sites in northern Alaska that experience significantly different snow-cover regimes. Previously, we demonstrated that snow-cover influences the timing of phenological events in females. Our results here suggest that the end of heterothermy in males is influenced by soil temperature and an endogenous circannual clock, but timing of male emergence from hibernation is influenced by the timing of female emergence. Males at both sites, Atigun and Toolik, end heterothermy on the same date in spring, but remain in their burrows while undergoing reproductive maturation. However, at Atigun, where snowmelt and female emergence occur relatively early, males emerge 8 days earlier than those at Toolik, maintaining a 12-day period between male and female emergence found at each site, but reducing the pre-emergence euthermic period that is critical for reproductive maturation. This sensitivity in timing of male emergence to female emergence will need to be matched by phase shifts in the circannual clock and responsiveness to environmental factors that time the end of heterothermy, if synchrony in reproductive readiness between the sexes is to be preserved in a rapidly changing climate.

scholarly journals Risks and benefits of catching pretty good yield in multispecies mixed fisheries

2017 ◽  
Vol 74 (8) ◽  
pp. 2097-2106 ◽  
Author(s):  
Robert B. Thorpe ◽  
Simon Jennings ◽  
Paul J. Dolder
Keyword(s):  
Good Yield ◽  
Maximum Sustainable Yield ◽  
Fishing Mortality ◽  
Interacting Species ◽  
Risks And Benefits ◽  
The North ◽  
Trade Offs ◽  
The North Sea ◽  
Stock Collapse

Abstract Multispecies mixed fisheries catch ecologically interacting species with the same gears at the same time. We used an ensemble of size-based multispecies models to investigate the effects of different rates of fishing mortality (F) and fleet configurations on yield, biomass, risk of collapse and community structure. Maximum sustainable yield (MSY) and FMSY for 21 modelled species’ populations in the North Sea were defined at the Nash equilibrium, where any independent change in F for any species would not increase that species’ MSY. Fishing mortality ranges leading to “Pretty Good Yield” (F-PGY), by species, were defined as ranges yielding ≥0.95 × MSY. Weight and value of yield from the entire fishery increased marginally when all species were fished at the upper end of F-PGY ranges rather than at FMSY, but risk of species’ collapse and missing community targets also increased substantially. All risks fell markedly when fishing at the lower end of F-PGY ranges, but with small impacts on total fishery yield or value. While fishing anywhere within F-PGY ranges gives managers flexibility to manage trade-offs in multispecies mixed fisheries, our results suggest high long-term yields and disproportionately lower risks of stock collapse are achieved when F ≤ FMSY for all component stocks.

scholarly journals Do Early-Life Conditions Drive Variation in Senescence of Female Bighorn Sheep?

2021 ◽  
Vol 9 ◽  
Author(s):  
Gabriel Pigeon ◽  
Julie Landes ◽  
Marco Festa-Bianchet ◽  
Fanie Pelletier
Keyword(s):  
Reproductive Success ◽  
Environmental Conditions ◽  
Early Life ◽  
Life Histories ◽  
Bighorn Sheep ◽  
Long Term Effects ◽  
Trade Offs ◽  
Early Life Conditions ◽  
Specific Variation

The rate of senescence may vary among individuals of a species according to individual life histories and environmental conditions. According to the principle of allocation, changes in mortality driven by environmental conditions influence how organisms allocate resources among costly functions. In several vertebrates, environmental conditions during early life impose trade-offs in allocation between early reproduction and maintenance. The effects of conditions experienced during early life on senescence, however, remain poorly documented in wild populations. We examined how several early-life environmental conditions affected reproductive and survival senescence in wild bighorn sheep. We found long-term effects of high population density at birth, precipitations during the winter before birth, and temperature during the winter following birth that decreased survival after 7 years of age. High temperature during the first summer and autumn of life and high Pacific decadal oscillation decreased reproductive success at old ages. However, harsh early-life environment did not influence the rate of senescence in either survival or reproduction. Contrary to our expectation, we found no trade-off between reproductive allocation prior to senescence and senescence. Our results do show that early-life environmental conditions are important drivers of later survival and reproductive success and contribute to intra-specific variation in late-life fitness, but not aging patterns. These conditions should therefore be considered when studying the mechanisms of senescence and the determinants of variation in both survival and reproductive senescence at older ages.

scholarly journals Phenological shifts of native and invasive species under climate change: insights from the Boechera–Lythrum model

2017 ◽  
Vol 372 (1712) ◽  
pp. 20160032 ◽  
Author(s):  
Robert I. Colautti ◽  
Jon Ågren ◽  
Jill T. Anderson
Keyword(s):  
Climate Change ◽  
Environmental Conditions ◽  
Rocky Mountain ◽  
Flowering Phenology ◽  
Lythrum Salicaria ◽  
Genetic Constraints ◽  
Floral Phenology ◽  
Phenological Shifts ◽  
Delayed Flowering

Warmer and drier climates have shifted phenologies of many species. However, the magnitude and direction of phenological shifts vary widely among taxa, and it is often unclear when shifts are adaptive or how they affect long-term viability. Here, we model evolution of flowering phenology based on our long-term research of two species exhibiting opposite shifts in floral phenology: Lythrum salicaria , which is invasive in North America, and the sparse Rocky Mountain native Boechera stricta . Genetic constraints are similar in both species, but differences in the timing of environmental conditions that favour growth lead to opposite phenological shifts under climate change. As temperatures increase, selection is predicted to favour earlier flowering in native B. stricta while reducing population viability, even if populations adapt rapidly to changing environmental conditions. By contrast, warming is predicted to favour delayed flowering in both native and introduced L. salicaria populations while increasing long-term viability. Relaxed selection from natural enemies in invasive L. salicaria is predicted to have little effect on flowering time but a large effect on reproductive fitness. Our approach highlights the importance of understanding ecological and genetic constraints to predict the ecological consequences of evolutionary responses to climate change on contemporary timescales. This article is part of the themed issue ‘Human influences on evolution, and the ecological and societal consequences’.

scholarly journals Unravelling Darwin's entangled bank: architecture and robustness of mutualistic networks with multiple interaction types

2016 ◽  
Vol 283 (1843) ◽  
pp. 20161564 ◽  
Author(s):  
Wesley Dáttilo ◽  
Nubia Lara-Rodríguez ◽  
Pedro Jordano ◽  
Paulo R. Guimarães ◽  
John N. Thompson ◽  
...  
Keyword(s):  
Evolutionary Dynamics ◽  
Plant Protection ◽  
Interaction Network ◽  
Ecological Communities ◽  
Multiple Forms ◽  
Interacting Species ◽  
Interactive Species ◽  
Mutualistic Networks ◽  
Multiple Interaction

Trying to unravel Darwin's entangled bank further, we describe the architecture of a network involving multiple forms of mutualism (pollination by animals, seed dispersal by birds and plant protection by ants) and evaluate whether this multi-network shows evidence of a structure that promotes robustness. We found that species differed strongly in their contributions to the organization of the multi-interaction network, and that only a few species contributed to the structuring of these patterns. Moreover, we observed that the multi-interaction networks did not enhance community robustness compared with each of the three independent mutualistic networks when analysed across a range of simulated scenarios of species extinction. By simulating the removal of highly interacting species, we observed that, overall, these species enhance network nestedness and robustness, but decrease modularity. We discuss how the organization of interlinked mutualistic networks may be essential for the maintenance of ecological communities, and therefore the long-term ecological and evolutionary dynamics of interactive, species-rich communities. We suggest that conserving these keystone mutualists and their interactions is crucial to the persistence of species-rich mutualistic assemblages, mainly because they support other species and shape the network organization.

scholarly journals A heterothermic spectrum in hummingbirds

2022 ◽  
Author(s):  
Anusha Shankar ◽  
Isabelle N. H. Cisneros ◽  
Sarah Thompson ◽  
Catherine H. Graham ◽  
Donald R. Powers
Keyword(s):  
Energy Savings ◽  
Genetic Regulation ◽  
Bird Species ◽  
Ground Squirrels ◽  
Fine Scale ◽  
Body Temperatures ◽  
Trade Offs ◽  
Natural Temperature ◽  
Balance Energy ◽  
Arctic Ground Squirrels

Many endotherms use torpor, saving energy by a controlled reduction of their body temperature and metabolic rate. Some species (e.g., arctic ground squirrels, hummingbirds) enter deep torpor, dropping their body temperatures by 23-37°C, while others can only enter shallow torpor (e.g., pigeons, 3-10°C reductions). However, deep torpor in mammals can increase predation risk (unless animals are in burrows or caves), inhibit immune function, and result in sleep deprivation, so even for species that can enter deep torpor, facultative shallow torpor might help balance energy savings with these potential costs. Deep torpor occurs in three avian orders, but the trade-offs of deep torpor in birds are unknown. Although the literature hints that some bird species (mousebirds and perhaps hummingbirds) can use both shallow and deep torpor, little empirical evidence of such an avian heterothermy spectrum within species exists. We infrared imaged three hummingbird species that are known to use deep torpor, under natural temperature and light cycles, to test if they were also capable of shallow torpor. All three species used both deep and shallow torpor, often on the same night. Depending on the species, they used shallow torpor for 5-35% of the night. The presence of a heterothermic spectrum in these bird species indicates a capacity for fine-scale physiological and genetic regulation of avian torpid metabolism.

scholarly journals Managing anabolic steroids in pre-hibernating Arctic ground squirrels: obtaining their benefits and avoiding their costs

2014 ◽  
Vol 10 (11) ◽  
pp. 20140734 ◽  
Author(s):  
Rudy Boonstra ◽  
Kaiguo Mo ◽  
Douglas Ashley Monks
Keyword(s):  
Ground Squirrel ◽  
Anabolic Steroids ◽  
Muscle Growth ◽  
Ground Squirrels ◽  
Arctic Ground Squirrel ◽  
Androgen Action ◽  
Trade Offs ◽  
Arctic Ground Squirrels ◽  
Columbian Ground Squirrels ◽  
Southern Species

Androgens have benefits, such as promoting muscle growth, but also significant costs, including suppression of immune function. In many species, these trade-offs in androgen action are reflected in regulated androgen production, which is typically highest only in reproductive males. However, all non-reproductive Arctic ground squirrels, irrespective of age and sex, have high levels of androgens prior to hibernating at sub-zero temperatures. Androgens appear to be required to make muscle in summer, which, together with lipid, is then catabolized during overwinter. By contrast, most hibernating mammals catabolize only lipid. We tested the hypothesis that androgen action is selectively enhanced in Arctic ground squirrel muscle because of an upregulation of androgen receptors (ARs). Using Western blot analysis, we found that Arctic ground squirrels have AR in skeletal muscle more than four times that of Columbian ground squirrels, a related southern species that overwinters at approximately 0°C and has low pre-hibernation androgen levels. By contrast, AR in lymph nodes was equivalent in both species. Brain AR was also modestly but significantly increased in Arctic ground squirrel relative to Columbian ground squirrel. These results are consistent with the hypothesis that tissue-specific AR regulation prior to hibernation provides a mechanism whereby Arctic ground squirrels obtain the life-history benefits and mitigate the costs associated with high androgen production.

scholarly journals Disorder or a new order: how climate change affects phenological variability

2021 ◽  
Author(s):  
Michael Stemkovski ◽  
James R. Bell ◽  
Elizabeth R. Ellwood ◽  
Brian D. Inouye ◽  
Hiromi Kobori ◽  
...  
Keyword(s):  
Climate Change ◽  
Biotic Interactions ◽  
New Order ◽  
Spring Phenology ◽  
Interacting Species ◽  
First Occurrence ◽  
Phenological Shifts ◽  
Flower Phenology ◽  
Over Time

Advancing spring phenology is a well-documented consequence of anthropogenic climate change, but it is not well understood how climate change will affect the variability of phenology year-to-year. Species' phenological timings reflect adaptation to a broad suite of abiotic needs (e.g. thermal energy) and biotic interactions (e.g. predation and pollination), and changes in patterns of variability may disrupt those adaptations and interactions. Here, we present a geographically and taxonomically broad analysis of phenological shifts, temperature sensitivity, and changes in inter-annual variance encompassing nearly 10,000 long-term phenology time-series representing over 1,000 species across much of the northern hemisphere. We show that early-season species in colder and less seasonal regions were the most sensitive to temperature change and had the least variable phenologies. The timings of leaf-out, flowering, insect first-occurrence, and bird arrival have all shifted earlier and tend to be less variable in warmer years. This has led leaf-out and flower phenology to become moderately but significantly less variable over time. These simultaneous changes in phenological averages and the variation around them have the potential to influence mismatches among interacting species that are difficult to anticipate if shifts in average are studied in isolation.

scholarly journals Long-Term Experimental Evolution in Escherichia coli. IV. Targets of Selection and the Specificity of Adaptation

Genetics ◽  
1996 ◽  
Vol 143 (1) ◽  
pp. 15-26 ◽  
Author(s):  
Michael Travisano ◽  
Richard E Lenski
Keyword(s):  
Escherichia Coli ◽  
Experimental Evolution ◽  
Common Ancestor ◽  
The Novel ◽  
Physiological Mechanisms ◽  
Outer Membranes ◽  
Limiting Nutrient ◽  
Novel Environments ◽  
Uptake Mechanisms

Abstract This study investigates the physiological manifestation of adaptive evolutionary change in 12 replicate populations of Escherichia coli that were propagated for 2000 generations in a glucose-limited environment. Representative genotypes from each population were assayed for fitness relative to their common ancestor in the experimental glucose environment and in 11 novel single-nutrient environments. After 2000 generations, the 12 derived genotypes had diverged into at least six distinct phenotypic classes. The nutrients were classified into four groups based upon their uptake physiology. All 12 derived genotypes improved in fitness by similar amounts in the glucose environment, and this pattern of parallel fitness gains was also seen in those novel environments where the limiting nutrient shared uptake mechanisms with glucose. Fitness showed little or no consistent improvement, but much greater genetic variation, in novel environments where the limiting nutrient differed from glucose in its uptake mechanisms. This pattern of fitness variation in the novel nutrient environments suggests that the independently derived genotypes adapted to the glucose environment by similar, but not identical, changes in the physiological mechanisms for moving glucose across both the inner and outer membranes.

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