A Model of Fire Selection for Serotiny in Lodgepole Pine

Self Cite

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. This content downloaded from 128.235.251.160 on Sun, Abstract. Mature Pinus contorta var. latifolia in the Bitterroot watershed of western Montana bear either predominantly serotinous cones (cone scales sealed by a resin bond and requiring a heat treatment for opening) or nonserotinous cones. This study investigated the extent to which amongstand variation in serotiny could be explained by environmental variables, estimated fire frequency, and the nature of the stand-initiating disturbance. The frequency distribution of serotiny at the stand level was bimodal, with peaks near 25 and 75% serotinous cones. Stand-level serotiny was not related to measured environmental variables and was only weakly related to estimated fire frequency. In contrast, much of the among-stand variation in serotiny could be explained by the nature of the standinitiating disturbance, with a predominance of serotinous trees in stands that had originated from stand-replacing burs and of nonserotinous trees in those that had originated from disturbances not related to fire. The disturbance regime is highly variable in time and space, and this variability, coupled with gene flow, is an important factor maintaining the polymorphism of cone type in stands.

Section: Maintenance Of Variability In Cone Typessupporting

confidence: 55%

Section: Correlations With Serotinymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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Disturbance History and Serotiny of Pinus contorta in Western Montana

Muir¹,

Lotan²

1985

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“…Most studies attempting to account for variation in the frequency of serotiny have focused on the frequency of stand-replacing fires, and high fire frequency is hypothesized to favor increased serotiny (Givnish 1981, Schoennagel et al 2003. Fire frequency is positively correlated with percentage serotiny in several species, and models and empirical work have suggested that increased fire frequency can select for serotiny (Perry and Lotan 1979, Muir and Lotan 1985, Lamont et al 1991, Gauthier et al 1996, Enright et al 1998, Schoennagel et al 2003, Radeloff et al 2004. Less attention has been given to the potential of biotic interactions to influence percentage serotiny, although population models suggest that any factor that depletes the canopy seed bank (e.g., pre-dispersal seed predation) can select against serotiny (Enright et al 1998).…”

Section: Introductionmentioning

confidence: 99%

Landscape‐scale eco‐evolutionary dynamics: Selection by seed predators and fire determine a major reproductive strategy

Talluto

2013

Recent work in model systems has demonstrated significant effects of rapid evolutionary change on ecological processes (eco-evolutionary dynamics). Fewer studies have addressed whether eco-evolutionary dynamics structure natural ecosystems. We investigated variation in the frequency of serotiny in lodgepole pine (Pinus contorta), a widespread species in which postfire seedling density and ecosystem structure are largely determined by serotiny. Serotiny, the retention of mature seeds in cones in a canopy seed bank, is thought to be an adaptation for stand-replacing fire, but less attention has been paid to the potential selective effects of seed predation on serotiny. We hypothesized that spatial variation in percentage serotiny in lodgepole pine forests results from an eco-evolutionary dynamic where the local level of serotiny depends on the relative strengths of conflicting directional selection from fire (favoring serotiny) and seed predation (favoring cones that open at maturity). We measured percentage serotiny, the abundance of American red squirrels (Tamiasciurus hudsonicus; the primary pre-dispersal seed predator of lodgepole pine), and several measures of forest structure in Yellowstone National Park, USA. Fire frequency strongly predicted the frequency of serotiny, a pattern that is well-supported in the literature. At sites with high fire frequency (return intervals of -135-185 years) where fire favors increased serotiny, squirrel abundance was negatively associated with serotiny, suggesting that selection from predation can overwhelm selection from fire when squirrels are abundant. At sites with low fire frequency (return intervals of -280-310 years), serotiny was nearly universally uncommon (< 10%). Finally, forest structure strongly predicted squirrel density independently of serotiny, and serotiny provided no additional explanatory power, suggesting that the correlation is caused by selection against serotiny exerted by squirrels, rather than squirrels responding to variation in percentage serotiny.

“…Moreover, why the frequency of serotiny is not higher in some pines (e.g., Pinus contorta ssp. latifolia) that frequently experience stand-replacing fires is unclear (Perry and Lotan 1979), especially when serotiny is favored over a wide range of fire frequencies (Enright et al 1998). This suggests that other factors are likely to affect the frequency of serotiny.…”

Section: Introductionmentioning

confidence: 99%

A Keystone Selective Agent? Pine Squirrels and the Frequency of Serotiny in Lodgepole Pine

Benkman

Siepielski

2004

Serotiny is a key life history trait in fire‐prone habitats that is favored in plants that experience stand‐replacing fires within their average life span. Although variation in fire frequency has been the focus of most studies attempting to understand variation in serotiny among populations and species of plants, other factors can select against serotiny. One agent in particular that can select against serotiny is an efficient pre‐dispersal seed predator that eats a large fraction of the seeds held in the canopy. To test whether selection by such a predator selects against serotiny, we compared levels of serotiny in fire‐adapted Rocky Mountain lodgepole pine (Pinus contorta ssp. latifolia) in five ranges lacking its dominant pre‐dispersal seed predator, the pine squirrel (Tamiasciurus hudsonicus) to 344 stands with pine squirrels. Where pine squirrels were absent, the frequency of serotiny was consistently near 100%, whereas where squirrels were present, the frequency was variable, rarely approached the high levels found in areas without squirrels, and averaged much less than 50%. This indicates that squirrels select against serotiny and that, in the absence of squirrels, the frequency of serotiny would probably be uniformly higher throughout much of the Rocky Mountains. Because serotiny levels also influence the density of seedlings following a fire, squirrels, by selecting strongly against serotiny, have the potential to alter the early stages and perhaps the course of succession and various community attributes.