Topic
Pine squirrel
About: Pine squirrel is a research topic. Over the lifetime, 10 publications have been published within this topic receiving 294 citations. The topic is also known as: Tamiasciurus.
Papers
TL;DR: A critical aspect of this study centers around the idea that, if the degree of variation in the cones and seed characters is great enough to allow a squirrel to discriminate among cones, then an effective selective agent exists for determining cone and seed characteristics.
Abstract: Recent papers by Smith (1970) and Janzen (1969, 1971) have emphasized different strategies by plants in their evolutionary responses to seed predators. Janzen, while working with insect seed predators, concluded that seed predators may select primarily for smaller seed size by killing a higher per cent o,f the seed crop of trees with fewer but larger seeds. Smith, on the other hand, studying squirrels, proposed that predators discriminate between tre,es on the basis of which tree will give them the highest feeding rate. The basis for this discriminatory behavior could be factors other than s,eed size, such as the production of chemical deterrents or protective tissue with the seed size remaining constant. The close correlation between se,ed size and the physical environment (Salisbury, 1942; Baker, 1972) and the evidence that seed size is one of the least variable of plant characters (Harper, 1961) indicates that selection for seed size is not likely to be one of the "lines o,f least resistance" (Stebbins, 1967) for seed predator selection to follow. Assuming, as Baker (1972) has shown, that certain plant communities exhibit an optimum seed size, it appears that if both seed size and effectiveness of seed protection are variable, selective pressure from seed predators will select for greater energy expenditures in se,ed protection with the seed size remaining constant (Smith, 1970). This selective trend would result in an individual plant producing fewer seeds due to the increased production of protective devices. It is quite possible that the differing theo,ries of Smith and Janzen are, to a large degree, reflective of the different predatorprey systems with which each worked. Likewise, it is possible that each prediction is correct in describing its respective system, and that neither can be expanded to a generalized theory. However, before such conclusions can b,e made, more information is needed in regard to identifying which plant characters most closely resemble predator independent factors, primarily controlled by the physical environment, and which characters are more likely to be predator dependent. The evolutionary responses of plants, to seed predators can be determined only by identifying the criteria by which predators discriminate, if they do, between varying prey items. This research is an effort at such a determination. The pine squirrel (Tamiasciurus hudsonicus) shows discrimination in its feeding behavior among the cones of lodgepole pines (Pinus contorta). This discrimination is based primarily on the number of seeds per cone (Hatt, 1929; Smith, 1968, 1970), which has been shown to vary by a factor of eight (Smith, 1968). Variation between trees has also been shown to, exist in the hardness of cones, the size of cones, and the symmetry or shape of cones (Critchfield, 1957), all of which have been observed to influence the feeding efficiency of Tamiasciurus (Smith, 1970). However, the degree of variation in seed size and its relationship to the effects of seed predators have not been previously studied. Thus, a critical aspect of this study centers around the idea that, if the degree of variation in the cone and seed characters is great enough to allow a squirrel to discriminate among cones, then an effective selective agent exists for determining cone and seed characteristics. Personal observations of squirrel feeding behavior during the summer of 1971 and
81 citations
TL;DR: Compared levels of serotiny in fire-adapted Rocky Mountain lodgepole pine in five ranges lacking its dominant pre-dispersal seed predator, the pine squirrel, to 344 stands with pine squirrels indicates that squirrels select against serot Tiny and that, in the absence of squirrels, the frequency would probably be uniformly higher throughout much of the Rocky Mountains.
Abstract: 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
67 citations
1 Jan 2008
TL;DR: This paper provides a general overview of the natural histories of the most influential species involved with whitebark pine seed fate: Clark’s nutcracker and the pine squirrel.
Abstract: Whitebark pine is a critical component of subalpine ecosystems in western North America, where it contributes to biodiversity and ecosystem function and in some communities is considered a keystone species. Whitebark pine is undergoing rangewide population declines attributed to the combined effects of mountain pine beetle, white pine blister rust, and fire suppression. The restoration and maintenance of whitebark pine populations require an understanding of all aspects of seed fate. In this paper, we review the literature on seed dispersal in whitebark pine. Clark’s nutcracker, pine squirrels, and scatter-hoarding rodents are all known to influence whitebark pine seed fate and ultimately affect the ability of whitebark pine populations to regenerate. We also provide a general overview of the natural histories of the most influential species involved with whitebark pine seed fate: Clark’s nutcracker and the pine squirrel.
42 citations
30 citations
29 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2009 | 1 |
| 2008 | 1 |
| 2004 | 1 |
| 1974 | 1 |
| 1964 | 1 |
| 1960 | 2 |