Serotiny and life history of Pinus contorta var. latifolia

Abstract

Mature serotinous and nonserotinous trees of Pinus contorta Dougl. var. latifolia Engelm. in the Bitterroot Watershed of western Montana do not differ in most life-history characteristics (reproductive or vegetative). No differences between trees of the two cone types were found in height, basal area, basal area growth rates over the lives of the trees, or crown ratio. Cone number, weights of individual cones and seeds, and estimates of reproductive effort were similar in serotinous and non-serotinous trees. Reproductive characteristics were either independent of tree age, or related similarly in trees of the two cone types. Nonserotinous trees may, however, have more seeds per cone than serotinous trees. This difference in seed numbers may be adaptive if serotinous trees invest relatively heavily in cone materials to protect seeds (which are retained in cones for many years), while nonserotinous trees (which shed seeds each year) invest relatively heavily in seeds. Trees of the two cone types differ mainly in the particular types of disturbance favoring their regeneration, but they often grow in the same stands where there are similar selective pressures on most aspects of their biology. Gene flow between them probably homogenizes all but those differences maintained by strong selective pressures.

Disturbance History and Serotiny of Pinus contorta in Western Montana

“…The four indices of fire frequency that were constructed (Muir 1984) were: 1) simple unweighted summation of standardized variables, not weighted by inverse of summed squared correlations; 2) summation of standardized variables after each was scaled to unit weighting to accommodate the correlation structure; 3) as in (2), but before summing, variables were multiplied by factors as follows: aspect and location relative to intermountain valley, 3x; elevation, 2.5 x; topographic position and Bitterroots/Sapphires, 2 x; local fire breaks, 1.5 x; and slope, 1 x. The four indices of fire frequency that were constructed (Muir 1984) were: 1) simple unweighted summation of standardized variables, not weighted by inverse of summed squared correlations; 2) summation of standardized variables after each was scaled to unit weighting to accommodate the correlation structure; 3) as in (2), but before summing, variables were multiplied by factors as follows: aspect and location relative to intermountain valley, 3x; elevation, 2.5 x; topographic position and Bitterroots/Sapphires, 2 x; local fire breaks, 1.5 x; and slope, 1 x.…”

“…However, a variety of analyses indicated that cone phenotype is not subject to such modification (Muir 1984). However, a variety of analyses indicated that cone phenotype is not subject to such modification (Muir 1984).…”

The Influence of a Competitor on the Geographic Mosaic of Coevolution Between Crossbills and Lodgepole Pine

“…Although these analyses are based on crude estimates of drought, no relationship was found between individual seed mass and precipitation during June and July (r ϭ 0.00, df ϭ 14, P ϭ 0.87). We do not have measures of competition experienced by seedlings, although when most of the trees in a stand have serotinous cones (most trees from all sites had serotinous cones and only serotinous cones were sampled) seeds generally germinate after a stand-replacing fire (Muir and Lotan 1985). In the absence of a relationship between measures of precipitation and seed mass, and given that the seedlings generally develop in full sun following a fire, we have no evidence that conditions during early growth have differentially favored large seeds in the absence of Tamiasciurus.…”

Fruit‐seed relations in Hakea: serotinous species invest more dry matter in predispersal seed protection

“…It is expected that serotinous seeds will be protected from granivores by the surrounding structures. This is achieved through larger and tougher fruits or cone scales (Elliott 1974), or fruit or cone aggregation (Smith 1970;Muir & Lotan 1985;Judd & Ashton 1991). However, strongly serotinous species do not *Present address: Department of Environmental Management, Edith Cowan University, 100 Joondalup Drive, Joondalup, WA 6027, Australia.…”