Cell cycle regulation during development and dormancy in embryos of the annual killifish Austrofundulus limnaeus

Embryos of the annual killifish Austrofundulus limnaeus can enter into a state of metabolic dormancy, termed diapause, as a normal part of their development. In addition, these embryos can also survive for prolonged sojourns in the complete absence of oxygen. Dormant embryos support their metabolism using anaerobic metabolic pathways, regardless of oxygen availability. Dormancy in diapause is associated with high ATP and a positive cellular energy status, while anoxia causes a severe reduction in ATP content and large reductions in adenylate energy charge and ATP/ADP ratios. Most cells are arrested in the G₁/G₀ phase of the cell cycle during diapause and in response to oxygen deprivation. In this paper, we review what is known about the physiological and biochemical mechanisms that support metabolic dormancy in this species. We also highlight the great potential that this model holds for identifying novel therapies for human diseases such as heart attack, stroke and cancer.     

Cell cycle regulation during development and dormancy in embryos of the annual killifish Austrofundulus limnaeus

Embryos of the annual killifish Austrofundulus limnaeus can enter into a state of metabolic dormancy, termed diapause, as a normal part of their development. In addition, these embryos can also survive for prolonged sojourns in the complete absence of oxygen. Dormant embryos support their metabolism using anaerobic metabolic pathways, regardless of oxygen availability. Dormancy in diapause is associated with high ATP and a positive cellular energy status, while anoxia causes a severe reduction in ATP content and large reductions in adenylate energy charge and ATP/ADP ratios. Most cells are arrested in the G₁/G₀ phase of the cell cycle during diapause and in response to oxygen deprivation. In this paper, we review what is known about the physiological and biochemical mechanisms that support metabolic dormancy in this species. We also highlight the great potential that this model holds for identifying novel therapies for human diseases such as heart attack, stroke and cancer.     

Long life cycles in insects

Long life cycles covering more than one year are known for all orders of insects. There are different mechanisms of prolongation of the life cycle: (1) slow larval development; (2) prolongation of the adult stage with several reproduction periods; (3) prolongation of diapause; (4) combination of these mechanisms in one life cycle. Lasting suboptimal conditions (such as low temperature, low quality of food or instability of food resources, natural enemies, etc.) tend to prolong life cycles of all individuals in a population. In this case, the larvae feed and develop for longer than a year, and the active periods are interrupted by dormancy periods. The nature of this dormancy is unknown: in some cases it appears to be simple quiescence, in others it has been experimentally shown to be a true diapause. Induction and termination of these repeated dormancy states are controlled by different environmental cues, the day-length being the principal one as in the case of the annual diapause. The long life cycles resulting from prolonged adult lifespan were experimentally studied mainly in beetles and true bugs. The possibility of repeated diapause and several periods of reproductive activity is related to the fact that the adults remain sensitive to day length, which is the main environmental cue controlling their alternative physiological states (reproduction vs. diapause). Habitats with unpredictable environmental changes stimulate some individuals in a population to extend their life cycles by prolonged diapause. The properties of this diapause are poorly understood, but results of studies of a few species suggest that this physiological state differs from the true annual diapause in deeper suppression of metabolism. Induction and intensity of prolonged diapause in some species appear to be genetically controlled, so that the duration of prolonged diapause varies among individuals in a group, even that of sibles reared under identical conditions. Thus, long life cycles are realized due to the ability of insects to interrupt activity repeatedly and enter dormancy. This provides high resistance to various environmental factors. Regardless of the nature of this dormancy (quiescence, annual or prolonged diapause, or other forms) and the life cycle duration, the adults always appear synchronously after dormancy in the nature. The only feasible explanation of this is the presence of a special synchronizing mechanism, most likely both exo- and endogenous, since the adults appear not only synchronously but also in the period best suited for reproduction. As a whole, the long life cycles resulting from various structural modifications of the annual life cycle, are typical of the species living under stable suboptimal conditions when the pressure of individual environmental factors is close to the tolerance limits of the species, even though it represents its norm of existence. Such life cycles are also typical of the insects living in unstable environments with unpredictable variability of conditions, those developing in cones and galls, feeding on flowers, seeds, or fruits with limited periods of availability, those associated with the plant species with irregular patterns of blossoming and fruiting, and those consuming low-quality food or depending on unpredictable food sources (e.g., predators or parasites). Long cycles are more common in: (1) insect species at high latitudes and mountain landscapes where the vegetation season is short and unstable; (2) species living in deserts or arid areas where precipitation is unstable and often insufficient for survival of food plants; (3) inhabitants of cold and temporary water bodies that are not filled with water every year. At the same time, long life cycles sometimes occur in insects from other climatic zones as well. It is also important to note that while there is a large body of literature dealing with the long life cycles in insects, it mostly focuses on external aspects of the phenomenon. Experimental studies are needed to understand this phenomenon, first of all the nature of dormancy and mechanisms of synchronization of adult emergence.     

缓步动物休眠现象研究进展

本文对缓步动物休眠现象的研究历史和现状作了简要的回顾和总结。休眠现象是一个集合名词,指的是缓步动物为克服不利的环境条件而出现的新陈代谢活动减弱甚至暂停的生命状态。最新的观点将其划分为两类,即隐生和滞育。根据导致隐生的环境因子的不同,又可分为低湿隐生、低温隐生、高压隐生、低氧隐生四种形式。滞育包括包囊和休眠卵两种形式。缓步动物的三种休眠状态（桶状、包囊和休眠卵）在其一生中任何一个阶段都能够出现,以度过极端不利的环境,并以此延长生物个体的寿命。总之,休眠现象存缓步动物的生态和进化方面具有不可估量的作用。     

New aspects in investigations of diapause and non-diapause dormancy types in insects and other arthropods

The paper resumes consideration of the problem posed by the Russian ecologist A.M. Emme (1953) on the need for a comparative study of diapause and quiescence (a non-diapause type of dormancy) in insects and other arthropods. The problem has recently become important due to the scarcity of eco-physiological studies of non-diapause dormancy, whose role in life cycle regulation remains unclear, and to the fact that most attention is now paid to diapause (as the leading adaptation in the control of seasonal development of arthropods). Analysis of data available for insects and acariform mites revealed the prospects of a comprehensive study of non-diapause forms of dormancy known presently (the common stage-independent quiescence, modified stage-specific quiescence, and post-diapause quiescence). The combination of post-diapause quiescence and diapause proper, revealed in many recent insects and acariform mites (mainly Prostigmata), may correspond to the initial ancestral state of dormancy in arthropods, representing a universal adaptation to both predictable and unpredictable environmental changes. This hypothesis gives a reasonable explanation of the possible dual nature of winter dormancy in oribatid mites (in contrast to the existing contradictory interpretations of their hibernal dormancy as only quiescence or only diapause).     

Temporal Population Genetics of Time Travelling Insects: A Long Term Study in a Seed-Specialized Wasp

Many animal species experiencing spatial or interannual fluctuations of their environment are capable of prolonged diapause, a kind of dormancy that extends over more than one year. Such a prolonged diapause is commonly perceived as a temporal demographic refuge in stochastic environments, but empirical evidence is still lacking of its consequences on temporal population genetic structures. In this long-term study, we investigated how a particular pattern of prolonged diapause may influence the temporal population genetics of the invasive seed-specialized wasp Megastigmus schimitscheki (Hymenoptera: Torymidae) in southeastern France. We characterized the diapause strategy of M. schimitscheki using records of emergence from diapause in 97 larval cohorts, and we conducted a temporal population genetic study on a natural invasive wasp population sampled during ten consecutive years (1999–2008) using polymorphic microsatellite markers. We found that M. schimitscheki can undergo a prolonged diapause of up to five years and displays two main adult emergence peaks after two and four years of diapause. Such a bimodal and atypical pattern did not disrupt temporal gene flow between cohorts produced in even and in odd years during the period of the study. Unexpectedly, we found that this wasp population consisted of two distinct genetic sub-populations that strongly diverged in their diapause strategies, with very few admixed individuals. One of the sub-populations displayed both short and prolonged diapause (2 and 4 years respectively) in equal proportions, whereas the other sub-population displayed mainly short diapause. This study provided empirical evidence that prolonged diapause phenotypes can substantially contribute to reproduction and impact temporal genetic structures. Prolonged diapause is likely to act as both demographic and genetic refuges for insect populations living in fluctuating environments.     

Regulation of summer dormancy by water deficit and ABA in Poa bulbosa ecotypes

BACKGROUND AND AIMS: Survival of many herbaceous species in Mediterranean habitats during the dry, hot summer depends on the induction of summer dormancy by changes in environmental conditions during the transition between the winter (growth) season to the summer (resting) season, i.e. longer days, increasing temperature and drought. In Poa bulbosa, a perennial geophytic grass, summer dormancy is induced by long days, and the induction is enhanced by high temperature. Here the induction of summer dormancy in a Mediterranean perennial grass by water deficit under non-inductive photoperiodic conditions is reported for the first time. METHODS: Plants grown under 22/16 degrees C and non-inductive short-day (9 h, SD) were subjected to water deficit (WD), applied as cycles of reduced irrigation, or sprayed with ABA solutions. They were compared with plants in which dormancy was induced by transfer from SD to inductive long-day (16 h, LD). Responses of two contrasting ecotypes, from arid and mesic habitats were compared. Dormancy relaxation in bulbs from these ecotypes and treatments was studied by comparing sprouting capacity in a wet substrate at 10 degrees C of freshly harvested bulbs to that of dry-stored bulbs at 40 degrees C. Endogenous ABA in the bulbs was determined by monoclonal immunoassay analysis. KEY RESULTS: Dormancy was induced by WD and by ABA application in plants growing under non-inductive SD. Dormancy induction by WD was associated with increased levels of ABA. Bulbs were initially deeply dormant and their sprouting capacity was very low, as in plants in which dormancy was induced by LD. Dormancy was released after 2 months dry storage at 40 degrees C in all treatments. ABA levels were not affected by dormancy relaxation. CONCLUSIONS: Summer dormancy in P. bulbosa can be induced by two alternative and probably additive pathways: (1) photoperiodic induction by long-days, and (2) water deficit. Increased levels of endogenous ABA are involved in both pathways.     

First evidence for photoperiodic regulation of the life cycle in a millipede species, Polydesmus angustus (Diplopoda: Polydesmidae)

The hypothesis that the periods of dormancy previously described in the millipede Polydesmus angustus may be photoperiodically induced diapauses was tested experimentally. In this species, biennial individuals exhibit two successive periods of dormancy: aestivation in the penultimate stadium (stadium VII) and reproductive dormancy in the adults, which emerge in autumn. It was first established that the reproductive dormancy is not a thermally controlled state of quiescence. When adults emerging in autumn were kept at 16 °C under natural photoperiod, their reproduction was delayed for several months in comparison with adults emerging in spring at similar temperatures. This indicates that the reproductive dormancy begins with a period of diapause. Further experiments provided evidence of a photoperiodic induction of the adult diapause. When millipedes were reared under short day length (L:D 12:12 h) throughout their development, they required more time to reproduce than millipedes reared under long day length (L:D 16:8 h) at the same temperatures. Photoperiod influenced reproduction in females, but no significant effects were detected in adult males. On the other hand, stadium VII was markedly longer at L:D 16:8 h than at L:D 12:12 h in both sexes, which strongly suggests that aestivation is also induced by photoperiod. However, the effects on the duration of stadium VII varied among individuals, some of which showed no response to long days. This study is the first to document photoperiodic regulation of the life cycle in the class Diplopoda, a trait common in other classes of terrestrial arthropods.     

Negligible Senescence during Reproductive Dormancy in Drosophila melanogaster

Some endemic Drosophila overwinter in a state of adult reproductive diapause where egg maturation is arrested in previtellogenic stages. When maintained at cool temperatures, adult Drosophila melanogaster enter reproductive dormancy, that is, diapause or diapause-like quiescence. The ability to survive for extended periods is a typical feature of diapause syndromes. In adults this somatic persistence may involve reduced or slowed senescence. Here we assess whether reproductively dormant D. melanogaster age at slow rates. Adults were exposed to dormancy-inducing conditions for 3, 6, or 9 wk. After this period, demographic parameters were measured under normal conditions and compared to the demography of newly eclosed cohorts. The age-specific mortality rates of postdormancy adults were essentially identical to the mortality rates of newly eclosed, young flies. Postdormancy reproduction, in contrast, declined with the duration of the treatment; somatic survival during dormancy may tradeoff with later reproduction. Adults in reproductive dormancy were highly resistant to heat and to oxidative stress. Suppressed synthesis of juvenile hormone is known to regulate reproductive diapause of many insects. Treatment of dormant D. melanogaster with a juvenile hormone analog restored vitellogenesis, suppressed stress resistance, and increased demographic senescence. We conclude that D. melanogaster age at slow rates as part of their reproductive dormancy syndrome; the data do not agree with an alternative hypothesis based on heat-dependent "rate of living." We suggest that low temperature reduces neuroendocrine function, which in turn slows senescence as a function of altered stress response, nutrient reallocation, and metabolism.     

Rapid evolution of sex frequency and dormancy as hydroperiod adaptations

Dormancy can serve as an adaptation to persist in variable habitats and often is coupled with sex. In cyclically parthenogenetic rotifers, an asexual phase enables rapid population growth, whereas sex results in diapausing embryos capable of tolerating desiccation. Few studies have experimentally tested whether sex–dormancy associations in temporary waters reflect evolution in response to the short hydroperiod selecting for diapause ability. Here, we demonstrate evolution of higher propensity for sex and dormancy in ephemeral rotifer cultures mimicking temporary ponds, and lower propensity in permanent cultures. Results are consistent with rapid evolution, with evolutionary changes occurring in a short timeframe (385 days, ≤ 84 generations). We also provide insight into mechanisms for rapid evolution in basal metazoans, discussing potential roles of new mutations, recombination and clonal selection.     

Obligate annual and successive facultative diapause establish a bet‐hedging strategy of Rhagoletis cerasi (Diptera: Tephritidae) in seasonally unpredictable environments

To cope with temporal and spatial heterogeneity of habitats, herbivorous insects in the temperate zone usually enter diapause that facilitates synchronization of their life cycle with specific stages of host plants, such as fruit ripening. In the present study, we address those factors regulating dormancy responses as part of a ‘longer strategy’ to persist and thrive in temperate environments, focusing on Rhagoletis cerasi, a univoltine, oligophagous species, which overwinters as pupae and emerges when host fruits are available for oviposition at local scale. To ensure population survival and reproduction at habitats with ecological heterogeneity, R. cerasi has evolved a sophisticated diapause strategy based on a combination of local adaptation and diversified bet‐hedging strategies. Diapause duration is determined both by (i) the adaptive response to local host fruit phenology patterns (annual diapause) and (ii) the plastic responses to unpredictable inter‐annual (temporal) climatic variability that drives a proportion of the populations to extend dormancy by entering a second, successive, facultative cycle of prolonged diapause as part of a bet‐hedging strategy. Besides the dormant periods, post‐diapause development (which varies among populations) exerts ‘fine tune’ adjustments that assure synchronization and may correct possible errors. Adults emerging from pupae with prolonged diapause are larger in body size compared with counterparts emerging during the first year of diapause. However, female fecundity rates are reduced, followed by an extended post‐oviposition period, whereas adult longevity remains unaffected. Overall, it appears that R. cerasi populations are adapted to ecological conditions of local habitats and respond plastically to unpredictable environmental (climatic) conditions.     

Differentiation in sex investment by clones and populations of Daphnia

Dormancy is an ecological strategy by which organisms avoid stressful environments, but it also can have genetic consequences. Many facultative parthenogens shift from asexual to sexual reproduction to enter dormancy. Hence, conditions that favour dormancy are predicted to select for more sex, which should increase clonal diversity. We examined lake populations of Daphnia that face different ecological risks to remaining active year‐round, and quantified the extent to which they have differentiated in their investment in dormancy and sex. There was substantial genetic variation among populations and clones for sex induction and production of dormant eggs, and striking evidence of gender specialization. We also observed a positive association between the magnitudes of population‐level investment in dormancy and of variance among clones in sex induction. These results document an ecological gradient in dormancy that is manifest as a genetic gradient in clonal variation for the propensity to engage in sex.     

Reproductive diapause and quiescence in a tropical rice buh,Leptocorisa oratorius

Experiments were carried out to analyze the effects of food supply and photoperiod on the induction of dormancy inLeptocorisa oratorius Fabricius (Heteroptera: Alydidae) adults in Alor Setar (latitude 6.1^o N), West Malaysia. When the adults were deprived of food, they ceased oviposition, became tolerant to starvation, and their oxygen consumption rate decreased, but they did not accumulate lipid. Their oxygen consumption rate again increased when they were allowed to resume feeding. Therefore, food limitation induced quiescence in the adult. On the other hand, diapause was induced by short daylength (critical photoperiod was 12L:12D), leading to immature ovaries, hypertrophied fat bodies, lipid accumulation and low oxygen consumption rate even when food was available. However, in the study area most of the bugs probably did not enter diapause at any time of the year, because the shortest outdoor daylength including civil twilight was longer than the critical daylength for diapause induction.     

Diapause and overwintering of two spruce bark beetle species

Diapause, a strategy to endure unfavourable conditions (e.g. cold winters) is commonly found in ectothermic organisms and is characterized by an arrest of development and reproduction, a reduction of metabolic rate, and an increased resistance to adversity. Diapause, in addition to adaptations for surviving low winter temperatures, significantly influences phenology, voltinism and ultimately population growth. We review the literature on diapause and overwintering behaviour of two bark beetle species that affect spruce‐dominated forests in the northern hemisphere, and describe and compare how these strategies can influence population dynamics. The European spruce bark beetle Ips typographus (L.) (Coleoptera, Curculionidae) is the most important forest pest of Norway spruce in Europe. It enters an adult reproductive diapause that might be either facultative or obligate. Obligate diapausing beetles are considered strictly univoltine, entering this dormancy type regardless of environmental cues. Facultative diapausing individuals enter diapause induced by photoperiod, modified by temperature, thus being potentially multivoltine. The spruce beetle Dendroctonus rufipennis (Kirby) (Coleoptera: Curculionidae) infests all spruce species in its natural range in North America. A facultative prepupal diapause is averted by relatively warm temperatures, resulting in a univoltine life cycle, whereas cool temperatures induce prepupal diapause leading to a semivoltine cycle. An adult obligate diapause in D. rufipennis could limit bi‐ or multivoltinism. We discuss and compare the influence of diapause and overwinter survival on voltinism and population dynamics of these two species in a changing climate and provide an outlook on future research.     

Prolonged pupal dormancy is associated with significant fitness cost for adults of Rhagoletis cerasi (Diptera: Tephritidae)

In temperate areas, dormancy (diapause and/or quiescence) enables herbivorous insect species to persist and thrive by synchronizing growth and reproduction with the seasonal phenology of their host plants. Within-population variability in dormancy increases survival chances under unpredictable environmental changes. However, prolonged dormancy may be costly, incurring trade-offs in important adult fitness traits such as life span and reproduction. We used the European cherry fruit fly, Rhagoletis cerasi, a stenophagous, univoltine species that overwinters in the pupal stage for usually one or more years to test the hypotheses that prolonged dormancy of pupae has trade-offs with body size, survival and reproduction of the resulting adults. We used two geographically isolated populations of R. cerasi to compare the demographic traits of adults obtained from pupae subjected to one or two cycles of warm-cold periods (annual and prolonged dormancy respectively). Regardless of population, adults from pupae that experienced prolonged dormancy were larger than counterparts emerging within 1year. Prolonged dormancy did not affect adult longevity but both lifetime fecundity and oviposition were significantly decreased. Extension of the life cycle of some individuals in R. cerasi populations in association with prolonged dormancy is likely a bet-hedging strategy.     

Metabolic rate in diapause and nondiapause brown locust eggs correlated with embryonic development

Insects use dormancy to survive adverse conditions. Brown locust Locustana pardalina (Walk.) eggs offer a convenient model to study dormancy (diapause and quiescence), which contributes to their survival under arid conditions. The metabolic rates of developing nondiapause, diapause and quiescent eggs are compared in the present study using closed‐system respirometry. The embryo becomes committed to continue development and hatch or to enter diapause 6 days after the eggs are placed on moist soil. The metabolic rate of nondiapause eggs increases exponentially until hatching, whereas that of diapause eggs is low and stable. The metabolic rate of diapause laboratory eggs (1.9 ± 0.6 µL CO₂ mg^?1 h^?1) is significantly higher than that of field eggs (0.5 ± 0.3 µL CO₂ mg^?1 h^?1), although the ranges of metabolic rate overlap and the embryos are all in late anatrepsis. The metabolic rate of quiescent eggs is similar to that of diapause eggs but decreases with time. Low metabolic rates during arrested development allow eggs to persist over long periods before hatching.     

One phase of the dormancy developmental pathway is critical for the evolution of insect seasonality

Evolutionary change in the timing of dormancy enables animals and plants to adapt to changing seasonal environments and can result in ecological speciation. Despite its clear biological importance, the mechanisms underlying the evolution of dormancy timing in animals remain poorly understood because of a lack of anatomical landmarks to discern which phase of dormancy an individual is experiencing. Taking advantage of the nearly universal characteristic of metabolic suppression during insect dormancy (diapause), we use patterns of respiratory metabolism to document physiological landmarks of dormancy and test which of the distinct phases of the dormancy developmental pathway contribute to a month‐long shift in diapause timing between a pair of incipient moth species. Here, we show that divergence in life cycle between the earlier‐emerging E‐strain and the later‐emerging Z‐strain of European corn borer (ECB) is clearly explained by a delay in the timing of the developmental transition from the diapause maintenance phase to the termination phase. Along with recent findings indicating that life‐cycle differences between ECB strains stem from allelic variation at a single sex‐linked locus, our results demonstrate how dramatic shifts in animal seasonality can result from simple developmental and genetic changes. Although characterizing the multiple phases of the diapause developmental programme in other locally adapted populations and species will undoubtedly yield surprises about the nature of animal dormancy, results in the ECB moth suggest that focusing on genetic variation in the timing of the dormancy termination phase may help explain how (or whether) organisms rapidly respond to global climate change, expand their ranges after accidental or managed introductions, undergo seasonal adaptation, or evolve into distinct species through allochronic isolation.     

Cell cycle arrest associated with anoxia-induced quiescence, anoxic preconditioning, and embryonic diapause in embryos of the annual killifish Austrofundulus limnaeus

Embryos of the annual killifish Austrofundulus limnaeus can enter into dormancy associated with diapause and anoxia-induced quiescence. Dormant embryos are composed primarily of cells arrested in the G(1)/G(0) phase of the cell cycle based on flow cytometry analysis of DNA content. In fact, most cells in developing embryos contain only a diploid complement of DNA, with very few cells found in the S, G(2), or M phases of the cell cycle. Diapause II embryos appear to be in a G(0)-like state with low levels of cyclin D1 and p53. However, the active form of pAKT is high during diapause II. Exposure to anoxia causes an increase in cyclin D1 and p53 expression in diapause II embryos, suggesting a possible re-entry into the cell cycle. Post-diapause II embryos exposed to anoxia or anoxic preconditioning have stable levels of cyclin D1 and stable or reduced levels of p53. The amount of pAKT is severely reduced in 12?dpd embryos exposed to anoxia or anoxic preconditioning. This study is the first to evaluate cell cycle control in embryos of A. limnaeus during embryonic diapause and in response to anoxia and builds a foundation for future research on the role of cell cycle arrest in supporting vertebrate dormancy.     

Dormancy release, ABA and pre-harvest sprouting

Seed dormancy is an adaptive trait that enables the seeds of many species to remain quiescent until conditions become favorable for germination. Dormancy is normally initiated during seed maturation and maintained to seed maturity. In mature seeds, the loss of dormancy may be gradual (after-ripening) or can be terminated by chilling and other environmental triggers. Dormancy is an important trait for many important crop species: it inhibits pre-harvest spouting or vivipary, a widespread problem in many regions of the world. Too much dormancy, however, can lead to non-uniform germination in the field. Recent progress has been made in understanding the role of abscisic acid metabolism and dormancy release in both model plants and crop species. Advances in our understanding of the molecular mechanisms that are involved in dormancy, along with approaches using quantitative genetics, will provide new strategies through which the desired level of dormancy can be introduced into crop species.     

Distribution of seed dormancy classes across a fire-prone continent: effects of rainfall seasonality and temperature

Background and AimsDifferent seed dormancy classes control the timing of germination via different cues. The ecological dissimilarities between classes therefore suggest that they are likely to be subject to different selective pressures, and that species within each class will have diverse functional responses. We aimed to investigate this by assessing how variation in the distribution of dormancy classes is correlated with regional environmental factors, in particular rainfall seasonality and temperature. Additionally, we compare the relative proportions of species with physiological (PD) or physical (PY) dormancy to assess whether dormancy class influences their ability to persist under different rainfall seasonality regimes.MethodsDormancy class was assigned for 3990 species from 281 genera occurring across two climate regions, with either winter or aseasonal rainfall, across temperate fire-prone Australia. All regions have similar vegetation and fire regimes. Using a Bayesian framework, we compared the distribution of dormancy classes across temperature and rainfall climate gradients, for threatened and common species.Key ResultsA high dormant:non-dormant species ratio highlighted the critical role of dormancy across our study regions. Critically, species showing PD were more likely to be threatened in aseasonal rainfall climate regions.ConclusionsOur results support the assumption that dormancy is favoured in environments with stochastic disturbance