Effect of temperature and host tree on cold hardiness of hemlock looper eggs along a latitudinal gradient

The hemlock looper, Lambdina fiscellaria, is an economically important insect pest of Canadian forests which overwinters as eggs. Although the hemlock looper causes extensive damages, no information on the mechanisms related to its cold tolerance is known. The objective of this study was to determine the effect of temperature and exposure duration on hemlock looper winter survival but also to identify seasonal supercooling capacity and cryoprotectant levels of three populations along a latitudinal gradient. As host plant may contribute to offspring overwintering success, cold tolerance of hemlock looper eggs from parents whose larvae were fed on three different tree species was also measured. Mean supercooling point (SCP) of hemlock looper eggs was lower than −30 °C from October through the following spring with values being as low as −47 °C in February. Trehalose was the most abundant sugar found in hemlock looper eggs with a peak concentration of 0.3 μg mg⁻¹ DW⁻¹. Glycerol, a polyol, was more often absent in eggs of the different populations and tree species tested in the study. When exposed to different temperature regimes for various periods of time, significant mortality of hemlock looper eggs occurred at higher temperatures than the mean SCP. Thus, hemlock looper could be considered as a chill tolerant species. No clear pattern of population and host plant effects on SCP and cryoprotectants was detected in this study. However, when exposed to different winter temperatures and exposure duration, hemlock looper from higher latitudes survived better (survival rates ranging between 0 and 89% at −20 °C) than those from lower latitudes (survival rates ranging between 0 and 56% at −20 °C). Our results may contribute to a better understanding of hemlock looper winter biology and thus facilitate predictions of outbreaks and range expansion.     

Divergent mechanisms of frost-hardiness in two populations of the gall fly, Eurosta solidaginsis

Two populations of the gall fly Eurosta solidaginsis utilize different strategies to endure seasonal exposure to temperatures below freezing. Both populations are freezing tolerant. In north temperate populations, supercooling points rise from ?10.2°C to ?6.2°C following exposures to temperatures below freezing. This level is maintained throughout winter and ensures frequent and prolonged periods of tissue freezing. South temperate populations depress the supercooling point to ?14.2°C during autumn and early winter, and this depression precludes extracellular ice formation during periods of supra-optimal temperature fluctuations. During mid-winter, supercooling points rise to the same level as in northern groups.Both populations accumulate three principal cryoprotective agents following first frost exposures (glycerol, sorbitol and trehalose). Cryoprotectants levels do not peak in northern populations until 4–6 weeks after first frost. In southern populations the accumulation profile is characterized by a high initial rate of synthesis, a protective overshoot and pronounced seasonal fluctuations. The relative survival advantages of each strategy are discussed.     

Oviposition traps to survey eggs of Lambdina fiscellaria (Lepidoptera: Geometridae)

Outbreaks of the hemlock looper, Lambdina fiscellaria (Gueneé), are characterized by rapid increase and patchy distribution over widespread areas, which make it difficult to detect impending outbreaks. This is a major problem with this insect. Population forecasting is based on tedious and expensive egg surveys in which eggs are extracted from 1-m branches; careful observation is needed to avoid counting old unhatched eggs of previous year populations. The efficacy of artificial substrates as oviposition traps to sample hemlock looper eggs was tested as a means of improving outbreak detection and population forecasting. A white polyurethane foam substrate (1,095 lb/ft3) used with the Luminoc insect trap, a portable light trap, was highly efficient in sampling eggs of the hemlock looper. Foam strips placed on tree trunks at breast height were less efficient but easier and less expensive to use for the establishment of extensive survey networks. Estimates based on oviposition traps were highly correlated with those obtained from the 1-m branch extraction method. The oviposition trap is a standard, inexpensive, easy, and robust method that can be used by nonspecialists. This technique makes it possible to sample higher numbers of plots in widespread monitoring networks, which is crucial for improving the management of hemlock looper populations.     

Linking weather conditions and winter tick abundance in moose

Climate change may modify species distribution to higher latitudes, resulting in potential changes of parasite diversity and transmission dynamics in areas where animals might not be locally adapted to these new parasite species. In addition, climate change may increase the frequency and severity of infestations of parasites that are already present in a region, by promoting the development and survival of infectious stages. Over the last decades, the number of moose (Alces americanus) infested by winter ticks (Dermacentor albipictus) has increased in eastern Canada, possibly because milder climatic conditions are increasing winter tick survival. Our main objective was to determine which meteorological variables are more likely to influence winter tick load on moose. We compiled several weather variables that may limit winter tick survival and explored which weather variables, or their interactions, influenced the winter tick load of 4,100 hunted moose from 2013 to 2019 in Québec, Canada along a latitudinal gradient. Winter tick load in fall decreased with the maximum number of consecutive days in spring with average daily temperatures below −15°C and with the number of consecutive days in summer with a relative humidity <80% when snowmelt in spring was earlier. These results suggest that cold temperatures and prolonged periods of low humidity, amplified by early snowmelt, limit the survival of adult female ticks and eggs, thus limiting their subsequent load on moose during the following fall. With climate change, precipitation increases and warm temperatures occur earlier in spring and are more frequent in summer. Our results suggest that climate change may have a positive long-term influence on winter tick abundance in the environment and thereby increase winter tick load on moose, which could lead to a significant decrease in moose body condition and survival.     

Moderate disturbances accelerate forest transition dynamics under climate change in the temperate–boreal ecotone of eastern North America

Several temperate tree species are expected to migrate northward and colonize boreal forests in response to climate change. Tree migrations could lead to transitions in forest types, but these could be influenced by several non‐climatic factors, such as disturbances and soil conditions. We analysed over 10,000 forest inventory plots, sampled from 1970 to 2018 in meridional Québec, Canada, to identify what environmental conditions promote or prevent regional‐scale forest transitions. We used a continuous‐time multi‐state Markov model to quantify the probabilities of transitions between forest states (temperate, boreal, mixed, pioneer) as a function of climate (mean temperature and climate moisture index during the growing season), soil conditions (pH and drainage) and disturbances (severity levels of natural disturbances and logging). We further investigate how different disturbance types and severities impact forests' short‐term transient dynamics and long‐term equilibrium using properties of Markov transition matrices. The most common transitions observed during the study period were from mixed to temperate states, as well as from pioneer to boreal forests. In our study, transitions were mainly driven by natural and anthropogenic disturbances and secondarily by climate, whereas soil characteristics exerted relatively minor constraints. While major disturbances only promoted transitions to the pioneer state, moderate disturbances increased the probability of transition from mixed to temperate states. Long‐term projections of our model under the current environmental conditions indicate that moderate disturbances would promote a northward shift of the temperate forest. Moreover, disturbances reduced turnover and convergence time for all transitions, thereby accelerating forest dynamics. Contrary to our expectation, mixed to temperate transitions were not driven by temperate tree recruitment but by mortality and growth. Overall, our results suggest that moderate disturbances could catalyse rapid forest transitions and accelerate broad‐scale biome shifts.     

Influence of northern limit range on genetic diversity and structure in a widespread North American tree,sugar maple (Acer saccharum Marshall)

Due to climate change, the ranges of many North American tree species are expected to shift northward. Sugar maple (Acer saccharum Marshall) reaches its northern continuous distributional limit in northeastern North America at the transition between boreal mixed‐wood and temperate deciduous forests. We hypothesized that marginal fragmented northern populations from the boreal mixed wood would have a distinct pattern of genetic structure and diversity. We analyzed variation at 18 microsatellite loci from 23 populations distributed along three latitudinal transects (west, central, and east) that encompass the continuous–discontinuous species range. Each transect was divided into two zones, continuous (temperate deciduous) and discontinuous (boreal mixed wood), based on sugar maple stand abundance. Respective positive and negative relationships were found between the distance of each population to the northern limit (D_north), and allelic richness (A_R) and population differentiation (F_ST). These relations were tested for each transect separately; the pattern (discontinuous–continuous) remained significant only for the western transect. structure analysis revealed the presence of four clusters. The most northern populations of each transect were assigned to a distinct group. Asymmetrical gene flow occurred from the southern into the four northernmost populations. Southern populations in Québec may have originated from two different postglacial migration routes. No evidence was found to validate the hypothesis that northern populations were remnants of a larger population that had migrated further north of the species range after the retreat of the ice sheet. The northernmost sugar maple populations possibly originated from long‐distance dispersal.     

极端生理耐受性导致果蝇Zaprionus indianus 在温带地区广泛分布（英文）

在过去的十年中, Zaprionus indianus这一温带适应性果蝇已经入侵印度次大陆, 并扩大了其在该地区的分布。Z. indianus能成功入侵是由于它具有很强的适应性和对极端生理条件的耐受性。对Z. indianus (温带狭域分布种类) 和黑腹果蝇Drosophila melanogaster (全球广域分布种类)在极端温度下未成熟期和成虫期发育阈值的比较研究表明, 两者的死亡率和发育起点温度存在显著差异。为了检测越冬期间未成熟期和成虫期抗逆性和存活率的变化, 以采自印度温带和热带不同地点的Z. indianus种群进行饲养实验。在温带地区的田间养虫笼中以及恒定的实验室条件下监测这些种群的卵孵化率和成虫存活率, 直至全部成虫死亡。结果表明, 由于温带地区卵孵化率和存活率高, 导致总的孵化率和存活率在不同纬度间存在显著差异。卵至成虫发育实验结果表明, 低温条件下产下的卵在温度适中时成功发育成成虫。由此可见, 这种昆虫在未成熟期具有的气候适应性以及在成虫期具有的抗逆性可为该物种提供季节性保护。考虑到气候变暖情况, 即温度增加0.6℃, 温度的少许改变都可能导致种群存活能力的显著增强和发育历期缩短。这些结果可解释Z. indianus为什么能够轻易突破障碍并适应新的环境。     

Biodiversity bottleneck: seedling establishment under changing climatic conditions at the boreal–temperate ecotone

Climate change is increasing global temperatures, severe rainfall events, and the occurrence and severity of drought. Changes in global climate may have negative consequences for particular plant species and for biodiversity overall. In the short term, altered temperature and precipitation regimes may have the most severe effects on plant species near their range limits and in the earliest stages of plant development. To address these issues, we assessed seedling emergence, early survival, and growth of 18 boreal, temperate, and exotic woody species at the boreal–temperate forest ecotone in central Minnesota. We experimentally warmed forest plots to mimic projected warming by the end of the twenty-first century (+ 1.7 °C and + 3.4 °C). We also experimentally removed summer rainfall (~?42% reduction) to simulate drought conditions in this region. We found that emergence and survival of boreal and exotic species was lower in experimentally warmed plots. This was exacerbated by drought. Temperate species emergence and survival was largely unaffected by climate manipulations (on average). Conversely, temperate seedling growth was greater in warmer conditions, but only when paired with drought. We found that overall seedling species richness was reduced by warming, mostly due to lower boreal and exotic species emergence and survival (conifers were also strongly negatively affected across species-range groups). If temperate seedling emergence and survival does not compensate for loss of boreal species, these forests may experience loss of biodiversity (and associated ecosystem functions) in the future.     

Geographic biotype and host-associated local adaptation in a polyphagous species, Lambdina fiscellaria (Lepidoptera: Geometridae) feeding on balsam fir on Anticosti Island, Canada

The debate about mechanisms underlying the evolution of host specialization by herbivorous insects remains open. Natural selection may act locally and lead to different patterns of geographic variation in life history traits of polyphagous herbivores. The hypothesis of genetically-based trade-offs in offspring performance on different hosts has been proposed but this has rarely been demonstrated. Under laboratory conditions, the biological performance of two populations of the hemlock looper Lambdina fiscellaria (Guenée), a highly polyphagous lepidopteran, was compared when reared on three different tree host species: balsam fir, eastern hemlock and sugar maple. One population originated from Anticosti Island, Québec, Canada, where the insect has evolved without having access to two of the three tree species tested, the other being from the mainland where all tree species are present. When reared on balsam fir foliage, which was naturally available to each population, larvae from Anticosti Island underwent four instars compared with five for the mainland population, indicating the existence of geographic biotypes in L. fiscellaria. When reared on the foliage of non-naturally available host trees, larvae from Anticosti Island had a higher incidence of supernumerary instars. This is a unique example where local adaptation to environmental conditions of an insect herbivore is expressed through a differential number of larval instars. Moreover, the Anticosti Island population showed a higher growth related index on the host available to both populations indicating that a fitness trade-off was the evolutionary process underlying the local adaptation of this population on balsam fir.     

Overwintering Strategy and Mechanisms of Cold Tolerance in the Codling Moth (Cydia pomonella)

Background

The codling moth (Cydia pomonella) is a major insect pest of apples worldwide. Fully grown last instar larvae overwinter in diapause state. Their overwintering strategies and physiological principles of cold tolerance have been insufficiently studied. No elaborate analysis of overwintering physiology is available for European populations.

Principal Findings

We observed that codling moth larvae of a Central European population prefer to overwinter in the microhabitat of litter layer near the base of trees. Reliance on extensive supercooling, or freeze-avoidance, appears as their major strategy for survival of the winter cold. The supercooling point decreases from approximately −15.3°C during summer to −26.3°C during winter. Seasonal extension of supercooling capacity is assisted by partial dehydration, increasing osmolality of body fluids, and the accumulation of a complex mixture of winter specific metabolites. Glycogen and glutamine reserves are depleted, while fructose, alanine and some other sugars, polyols and free amino acids are accumulated during winter. The concentrations of trehalose and proline remain high and relatively constant throughout the season, and may contribute to the stabilization of proteins and membranes at subzero temperatures. In addition to supercooling, overwintering larvae acquire considerable capacity to survive at subzero temperatures, down to −15°C, even in partially frozen state.

Conclusion

Our detailed laboratory analysis of cold tolerance, and whole-winter survival assays in semi-natural conditions, suggest that the average winter cold does not represent a major threat for codling moth populations. More than 83% of larvae survived over winter in the field and pupated in spring irrespective of the overwintering microhabitat (cold-exposed tree trunk or temperature-buffered litter layer).     

Embryonic stage of obligatory diapause and effects of abiotic conditions on egg hatching in the balsam twig aphid,Mindarus abietinus

Diapause‐mediated dormancy in overwintering insect eggs has rarely been studied with regard to the ecological factors controlling postdiapause development. In insects of temperate latitudes, water availability at the end of winter, in interaction with temperature, could control the resumption of development for insect stages in postdiapause quiescence. The balsam twig aphid, Mindarus abietinus Koch (Hemiptera: Aphididae), overwinters as eggs in southern Québec, Canada, on balsam fir, Abies balsamea (L.) Miller (Pinaceae), in Christmas tree plantations, where it is known as a pest. Previous work has shown that eggs of this aphid maintain low water content during winter, presumably to survive sub‐zero temperatures. Conversely, in late winter and early spring, they passively or actively absorb surrounding moisture, which is accompanied by notable changes in size, shape, and fresh mass. The primary objective here was to determine the embryonic stage at which winter diapause starts and is maintained in M. abietinus, a relatively primitive aphid. Secondly, we tested the hypothesis that free water availability to postdiapause eggs, in combination with temperatures above developmental threshold, is essential for embryonic development and hatching, by experimentally soaking field‐collected eggs in water at controlled frequencies. We observed that embryogenesis starts at the time of egg laying and stops after a few days, before the anatrepsis stage of blastokinesis is complete, when the germ band has not yet entirely immersed itself into the yolk. We also found that water surrounding overwintered eggs on fir shoots, in interaction with temperature regime, significantly increases M. abietinus egg hatching rates. Potential impacts of environmental factors such as precipitation are discussed in relation to M. abietinus egg hatching rates and potential for population growth in spring.     

Winter warming effects on overwinter survival,energy use,and spring emergence of Cerotoma trifurcata (Coleoptera: Chrysomelidae)

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Study on the physiology of diapause, cold hardiness and supercooling point of overwintering pupae of the pistachio fruit hull borer, Arimania comaroffi

The pistachio fruit hull borer, Arimania comaroffi (Ragonot) (Lepidoptera: Pyralidae), is a key pest of pistachio orchards in Iran. This pest passes the winter as diapausing pupae. In this study, some physiological changes in relation to environmental temperature were investigated in field collected pupae. The relationship between supercooling point, cold hardiness and physiological changes of a wild population of this pest was also investigated. The glycogen content decreased with decrease in environmental temperature. Decrease in glycogen content was proportional to increase in total body sugar, trehalose, myo-inositol and sorbitol contents. In January with mean ambient temperature of 5.4°C, glycogen (5 mg/g fresh body weight) content was at the lowest level whereas total body sugar (10.3 mg/g fresh body weight), trehalose (8.6 mg/g fresh body weight), myo-inositol (5.3 mg/g fresh body weight) and sorbitol (2.6 mg/g fresh body weight) were at the highest levels. Total body sugar, trehalose, myo-inositol and sorbitol contents increased as mean temperature decreased from 22.7°C in October to 5.4°C in January. Total body lipid decreased during overwintering and reached to the lowest level at the end of March. Supercooling points were decreased from October to January and reached to the lowest level (-16°C) in January with minimum ambient temperature of -10°C. Survival at low temperature after 24 h was also greatest in January with 72% survival at -10°C, 39% survival at -15°C and 0% survival at -20°C. Increase in temperature from February onward, was proportional with increase in supercooling points and decrease in survival rate. Regardless of sampling date, all pupae died after 24 h at -20°C, whereas none pupae died after 24 h at -5°C. This indicates that this insect is freeze-intolerant.     

Geographic differences on accumulation of sugars and polyols in locust eggs in response to cold acclimation

The accumulation of low molecular weight sugars and polyols is one of major mechanisms hypothesized to increase cold tolerance in overwintering insects. But little is known about whether these sugars and polyols are involved in geographic variation of cold tolerance. In this study, we investigated accumulation patterns of eight low molecular weight sugars and polyols of eggs in tropical and temperate populations of the migratory locust, which exhibits between-population variation in cold tolerance, in response to cold acclimation (5, 0 and −5 °C). Excluding erythritol, the other seven carbohydrates were identified as possible cryoprotectants in locust eggs. Basal maximal and minimal concentrations were 45 μg/g wet weight for trehalose and 0.59 μg/g wet weight for glycerol. Most sugars and polyols were elevated after a −5 °C exposure. In a tropical population, fructose, glucose, sorbitol and myo-inositol were significantly accumulated by low temperature treatments, but glycerol was not. In the temperate population, glycerol, glucose, mannitol, sorbitol, myo-inositol were significantly accumulated but trehalose did not increase. Our results suggest different accumulation patterns of these carbohydrates of locust eggs between tropical and temperate populations and highlighted possible roles for them in geographic variation of cold tolerance in the migratory locust.     

Postponed reproduction as an adaptation to winter conditions in Drosophila melanogaster: evidence for clinal variation under semi-natural conditions

Patterns of climatic adaptation in drosophila and other insects have largely been inferred from laboratory comparisons of traits that vary clinally. Here, we extend this research to comparisons under semi-natural conditions. To test for clinal variation in reproductive patterns and survival over winter, Drosophila melanogaster populations were initiated from seven collection sites along the eastern coast of Australia, ranging from tropical to temperate regions. The fecundity and survival of these populations were monitored in field cages at a temperate location until all adults had died more than 5 months later. Total fecundity showed a curvilinear relationship with latitude, due to higher egg production by high- and low-latitude populations. Adults from temperate locations survived winter conditions better than those from subtropical populations but not tropical ones. There was a linear cline in the timing of egg production: temperate populations produced eggs later than populations from lower latitudes. This cline is likely to be adaptive because egg-to-adult viability experiments indicated that only eggs laid in spring developed successfully to the adult stage. There was no evidence for climatic adaptation in the immature stages. The adult mortality rate increased gradually over winter, and in some populations was also correlated with the minimum ambient temperature. These results indicate that adaptation to winter conditions in D. melanogaster has involved shifts in reproductive patterns.     

Factors affecting low temperature survival ofCinara pilicornis eggs on Sitka spruce

OviparousC. pilicornis deposited eggs in October and early November, the dry weight, but not the fresh weight, decreasing during winter. Diapause terminated in early March, eggs hatched in early May. Mean egg supercooling points varied during the winter, the variation being related to the temperature in the period preceding sample collection. Both glycerol and mannitol were isolated from the eggs. Mannitol levels decreased to zero by mid-winter, levels increasing after diapause termination. Glycerol levels increased up to diapause termination and thereafter decreased, none being present just prior to egg hatch. Neither glycerol nor mannitol were related to supercoolingability, the variation being related to low temperatures which possibly induced changes in the levels of an unknown factor.     

Streams in Quebec boreal and mixed-wood forests reveal a new aquatic hyphomycete species, Dwayaangam colodena sp. nov

Foam from eight streams in boreal and mixed-wood forests in Québec were sampled in early and late fall 2002 to evaluate the biodiversity of their aquatic hyphomycete communities. Two regions were studied: 53-54 degrees N and 46-49 degrees N. A total of 54 species were identified. Twenty taxa were found only in the northern region, and four were unique to the southern region. A new aquatic hyphomycete, Dwayaangam colodena sp. nov., was found mostly in northern streams. It is described along with its taxonomic position.     

Trophic cascades,invasive species and body-size hierarchies interactively modulate climate change responses of ecotonal temperate–boreal forest

As the climate warms, boreal tree species are expected to be gradually replaced by temperate species within the southern boreal forest. Warming will be accompanied by changes in above- and below-ground consumers: large moose (Alces alces) replaced by smaller deer (Odocoileus virginianus) above-ground, and small detritivores replaced by larger exotic earthworms below-ground. These shifts may induce a cascade of ecological impacts across trophic levels that could alter the boreal to temperate forest transition. Deer are more likely to browse saplings of temperate tree species, and European earthworms favour seedlings of boreal tree species more than temperate species, potentially hindering the ability of temperate tree species to expand northwards. We hypothesize that warming-induced changes in consumers will lead to novel plant communities by changing the filter on plant species success, and that above- and below-ground cascades of trophic interactions will allow boreal tree species to persist during early phases of warming, leading to an abrupt change at a later time. The synthesis of evidence suggests that consumers can modify the climate change-induced transition of ecosystems.     

The responses of microbial temperature relationships to seasonal change and winter warming in a temperate grassland

Microorganisms dominate the decomposition of organic matter and their activities are strongly influenced by temperature. As the carbon (C) flux from soil to the atmosphere due to microbial activity is substantial, understanding temperature relationships of microbial processes is critical. It has been shown that microbial temperature relationships in soil correlate with the climate, and microorganisms in field experiments become more warm‐tolerant in response to chronic warming. It is also known that microbial temperature relationships reflect the seasons in aquatic ecosystems, but to date this has not been investigated in soil. Although climate change predictions suggest that temperatures will be mostly affected during winter in temperate ecosystems, no assessments exist of the responses of microbial temperature relationships to winter warming. We investigated the responses of the temperature relationships of bacterial growth, fungal growth, and respiration in a temperate grassland to seasonal change, and to 2 years’ winter warming. The warming treatments increased winter soil temperatures by 5–6°C, corresponding to 3°C warming of the mean annual temperature. Microbial temperature relationships and temperature sensitivities (Q₁₀) could be accurately established, but did not respond to winter warming or to seasonal temperature change, despite significant shifts in the microbial community structure. The lack of response to winter warming that we demonstrate, and the strong response to chronic warming treatments previously shown, together suggest that it is the peak annual soil temperature that influences the microbial temperature relationships, and that temperatures during colder seasons will have little impact. Thus, mean annual temperatures are poor predictors for microbial temperature relationships. Instead, the intensity of summer heat‐spells in temperate systems is likely to shape the microbial temperature relationships that govern the soil‐atmosphere C exchange.     

Seasonal weather patterns drive population vital rates and persistence in a stream fish

Climate change affects seasonal weather patterns, but little is known about the relative importance of seasonal weather patterns on animal population vital rates. Even when such information exists, data are typically only available from intensive fieldwork (e.g., mark–recapture studies) at a limited spatial extent. Here, we investigated effects of seasonal air temperature and precipitation (fall, winter, and spring) on survival and recruitment of brook trout (Salvelinus fontinalis) at a broad spatial scale using a novel stage‐structured population model. The data were a 15‐year record of brook trout abundance from 72 sites distributed across a 170‐km‐long mountain range in Shenandoah National Park, Virginia, USA. Population vital rates responded differently to weather and site‐specific conditions. Specifically, young‐of‐year survival was most strongly affected by spring temperature, adult survival by elevation and per‐capita recruitment by winter precipitation. Low fall precipitation and high winter precipitation, the latter of which is predicted to increase under climate change for the study region, had the strongest negative effects on trout populations. Simulations show that trout abundance could be greatly reduced under constant high winter precipitation, consistent with the expected effects of gravel‐scouring flows on eggs and newly hatched individuals. However, high‐elevation sites would be less vulnerable to local extinction because they supported higher adult survival. Furthermore, the majority of brook trout populations are projected to persist if high winter precipitation occurs only intermittently (≤3 of 5 years) due to density‐dependent recruitment. Variable drivers of vital rates should be commonly found in animal populations characterized by ontogenetic changes in habitat, and such stage‐structured effects may increase population persistence to changing climate by not affecting all life stages simultaneously. Yet, our results also demonstrate that weather patterns during seemingly less consequential seasons (e.g., winter precipitation) can have major impacts on animal population dynamics.