Physical dormancy in a changing climate

Abstract

Species with physically dormant (PY) seeds make up over 25% of plant species in a number of ecologically important ecosystems around the globe, such as savannah and Mediterranean shrublands. Many of these ecosystems are subject to temporally stochastic events, such as fire and drought; but are in areas projected to experience some of the most extreme climatic changes in the future. Given the importance of PY in controlling germination timing for successful recruitment, we ask how plastic the PY trait is, and if changes to the maternal environment from climate change could alter recruitment. This review focuses on: (1) the evidence for inter-and intraspecific variation in PY; (2) the genetic, maternal and environmental controls involved; and (3) the ecological consequences of (1) and (2) above. Evidence for (within-community) interspecific variation in conditions required to break PY is strong, but for intraspecific variation evidence is contradictory and limited by a paucity of studies. Identifying controllers of variation in PY is complex, there is some suggestion that conditions of the maternal environment may be important, but no consensus on the nature of effects. The implications of PY plasticity for the persistence of seed banks, species and communities under climate change are discussed. We highlight a number of key knowledge gaps, such as a lack of research estimating the components of variation in non-agricultural species, and identify a suite of seed attributes relevant to understanding the potential impacts of climate change on the population dynamics of PY species in the future. Mediterranean shrublands. Many of these ecosystems are subject to temporally stochastic events, such as fire and drought; but are in areas projected to experience some of the most extreme climatic changes in the future. Given the importance of PY in controlling germination timing for successful recruitment, we ask how plastic is the PY trait, and if changes to the maternal environment from climate change could alter recruitment. This review focuses on, 1) the evidence for inter-and intra-specific variation in PY; 2) the genetic, maternal and environmental controls involved; and 3) the ecological consequences of above (1) and (2).Evidence for (within community) inter-specific variation in conditions required to break PY is strong, but for intra-specific variation evidence is contradictory and limited by a paucity of studies. Identifying controllers of variation in PY is complex, there is some suggestion conditions of the maternal environment may be important, but no consensus on the nature of effects. The implications of PY plasticity for the persistence of seed banks, species and communities under climate change are discussed. We highlight a number of key knowledge gaps, such as a lack of research estimating the components of variation in non-agricultural species, and identify a suite of seed attributes relevant to understanding the potential impacts of climate change on the population dynamics of PY species in the f...

Inter- and intra-population variability in physical dormancy along a precipitation gradient

“…Nonetheless, a recent study focussing on five Fabaceae woody species found significant intra-population differences in initial dormancy only in one of the species (Liyanage & Ooi 2015). Intra-population variability could be a strategy that buffers species against local unpredictable events such as fire and drought (Hudson et al 2015;Liyanage & Ooi 2015) allowing a staggered seed germination.…”

“…Furthermore, some studies have suggested that PY variability allows seeds to persist in variable environments (Ooi et al 2012;Fernández-Pascual et al 2013). However, there is scarce knowledge about the degree of PY variability, both among and within populations, especially in natural ecosystems (Cochrane et al 2015;Hudson et al 2015).…”

“…Some authors agree that PY has evolved to enable plants to survive in temporally stochastic and harsh environments Hudson et al 2015). Consequently, in the context of climate change, it has been suggested that PY would prosper under warmer, more variable and unpredictable climates (Hudson et al 2015).…”

“…Consequently, in the context of climate change, it has been suggested that PY would prosper under warmer, more variable and unpredictable climates (Hudson et al 2015). Natural gradients (e.g., precipitation, temperature, altitude) offer great opportunities for evaluating inter-population variability and might provide information about how species may cope with environmental variability (Ooi et al 2012;Fernández-Pascual et al 2013).…”

“…Variation along precipitation gradients might be highly important for seed traits such as dormancy, because changes in humidity during seed development are related to the degree of seed dormancy (Jaganathan 2016). Within species, a review of studies comparing populations in sites with different precipitations found that low rainfall during seed development favours the occurrence of PY (Hudson et al 2015 and reference therein). In addition, some degree of intra-population variability has been observed in regeneration traits (Moreira et al 2012;.…”