The evolutionary ecology of vegetative dormancy in mature herbaceous perennial plants

Abstract

Summary1. I present an evolutionary ecology interpretation of vegetative dormancy in mature herbaceous perennials. This kind of vegetative dormancy has been noted for at least 40 years, but has only recently become a topic of study. 2. Vegetative dormancy may be considered in a life-history context. Both vegetative dormancy and mortality typically decrease with increasing size. Vegetative dormancy's relationship to reproduction is more complex, because some species increase flowering and fruiting after dormancy while others do the opposite. 3. If vegetative dormancy is adaptive, then it is most likely a bet-hedging trait. Dormancy-prone plants are often long-lived, and in such organisms, bet-hedging traits should counter the effects of environmental stochasticity on adult survival. This adaptive context may vary by life span, because in shorter-lived plants, fitness is most sensitive to changes in reproduction rather than survival. 4. Vegetative dormancy could evolve if the costs of sprouting ever outweigh the benefits. The benefits of sprouting include: (i) photosynthesis and (ii) the opportunity to flower and reproduce. The costs include: (i) greater chance of herbivory, (ii) greater need for limiting nutrients, and (iii) greater maintenance costs. The many losses of photosynthesis among plants suggest that these benefits may not always outweigh the costs. 5. Vegetative dormancy may be an evolutionary step towards the loss of photosynthesis. Many non-photosynthetic plants acquire carbon from their mycorrhizal fungi. Many autotrophic, dormancy-prone plants also acquire some carbon from their mycorrhizal fungi. Further, nonphotosynthetic plants often become dormant to an even greater extent than autotrophic, dormancy-prone plants. 6. Synthesis. Vegetative dormancy often occurs in clades with non-photosynthetic, myco-heterotrophic plants, with implications for the evolution of traits involved in carbon nutrition. The links between vegetative dormancy, other life-history traits, mycorrhizas and the loss of photosynthesis should provide exciting directions for further research in plant evolutionary ecology. Particularly needed is an assessment of the physiology of vegetative dormancy, including whether the mycorrhiza is a carbon source in all dormancy-prone plant species. Equally important is a better understanding of the genetic relationships among photosynthesis, myco-heterotrophy and dormancy.

Fast–slow continuum and reproductive strategies structure plant life-history variation worldwide

“…However, the plant kingdom encompasses a vast amount of lifehistory variation; plant longevity, for instance, ranges from weeks to millennia (12). Many plant species' life cycles include cryptic life stages such as seedbanks (13) or dormant adults (similar to animal hibernation) (14). Reproduction also can be highly variable among plants, with seed mass and per-capita seed production ranging across six orders of magnitude (15).…”

Linking vegetative dormancy to fitness in two long‐lived herbaceous perennials

“…Although the main benefits of vegetative dormancy have been suggested to be as a bet-hedging trait (Shefferson 2009), some have also suggested that no benefits may actually exist or that other ecological phenomena may conflate the observation of evolutionary impacts (Shefferson et al 2001, Gregg 2011. Vegetative dormancy likely functions differently in many species, and has likely evolved on many separate occasions (Shefferson 2009). Here, vegetative dormancy did not appear to function as a bethedging trait in the two long-lived perennial species that we studied.…”

“…Instead, flowering probability increases with size (Kull 1999(Kull , 2002. Further, plants may forego sprouting for several years via vegetative dormancy, and the tendency to become vegetatively dormant decreases with increasing plant size (Shefferson 2009). Fruiting results in dust seeds, which germinate and develop into protocorms, a non-photosynthetic, immature life stage in which the orchid consumes carbon and all other nutrition from its mycorrhizal fungus (Rasmussen 1995, Kull 1999.…”

“…Vegetative dormancy is a life history stage or phenomenon in which a perennial herbaceous plant lives for one or more growing season(s) without sprouting (Lesica and Steele 1994). It has been noted now in at least 10 families and 52 species of plants (Shefferson 2009), and in some species and populations represents the most common life stage from year to year (Shefferson et al 2011). During vegetative dormancy, the plant may mobilize stored energy reserves (Gremer et al 2010), or potentially even utilize energy from beneficial soil fungi (Gill 1989, Bidartondo et al 2004.…”

Liverworts (Marchantiophyta) of Mahogany Hammock, Everglades National Park, Florida

“…There are no completely achlorophyllous orchids known from EVER. Important here is that myco-heterotrophic orchids are known to go through periods of vegetative dormancy of one to 11 years (Shefferson 2009). It is thought that vegetative dormancy may allow orchids to recover from environmental stress, and if proper conditions are restored then flowering will re-occur.…”