Relating Red Squirrel Body Size to Different Conifer Cone Morphologies within the Same Geographic Location

Wheatley, Matthew

doi:10.1644/06-mamm-a-106r1.1

Cited by 6 publications

(3 citation statements)

References 26 publications

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“…To understand whether gene flow across the study transect is sufficient to homogenize variation in neutral morphological traits, we estimated gene flow rates and directionality using IMA2 (Hey, 2010). IMA2 uses a coalescent-based model of isolation-with-migration under a Bayesian framework to co-estimate the multilocus effective population sizes (present and ancestral), divergence times, and migration rates (Nielsen & Wakeley, 2001;Hey & Nielsen, 2004, 2007. To improve computational efficiency of our multilocus genotype dataset consisting of 18 microsatellite loci, we analyzed a subset of the 60 collected individuals.…”

Section: Interior Populationsmentioning

confidence: 99%

“…A possible selective factor that could lead to phenotypic variation in biting ability is the transition within forests of the Pacific Northwest in the hardness (serotiny) of coniferous tree cones, which vary from softer cone species in the west to harder cone species in the east (Lindsay, 1986;Schoennagel, Turner & Romme, 2003). Wheatley (2007) also found a lack of association between body size and cone hardness within T. hudsonicus in mixed forests in Canada (Wheatley, 2007). By contrast to these negative intraspecific findings, significant interspecific differences do exist in skull morphology between T. douglasii and T. hudsonicus across their hybrid zone in an ecologically similar forest system in the northern Cascade Mountains of British Columbia and Washington (Smith, 1981;Chavez et al, 2011).…”

Section: Lack Of Clinal Variation In Skull Morphologymentioning

confidence: 99%

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Clinal colour variation within a panmictic population of tree squirrels,Tamiasciurus douglasii(Rodentia: Sciuridae), across an ecological gradient

Chavez

Kenagy

2014

Biol J Linn Soc Lond

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Local adaptation occurs when a population in a heterogeneous environment experiences divergent ecological selection but only if selection is stronger than the homogenizing effects of gene flow. The forest environments of Oregon vary along a physical and biotic gradient from a wet, closed‐canopy forest near the coast to a drier open‐canopy forest eastward across the Cascade Mountains. The present study explores patterns of local adaptation in Douglas squirrels (Tamiasciurus douglasii) in relation to these transitions in forest structure and ecology. We test for the presence of morphological clines in relation to gene flow and, more specifically, whether any such character clines correspond with environmental clines. We sampled animals at six locations (10 specimens each) and evaluated environmental parameters across a 240‐km west‐to‐east transect. Population structure analysis of 18 microsatellite loci indicates a single, panmictic squirrel population across the entire transect. Coalescent‐based estimates show bidirectional gene flow at similar west–east intensities between squirrels in coastal and interior forests. Of the four skull traits examined, none shows a significant clinal transition. By contrast, ventral fur colour shows a strong clinal transition, from deep‐orange in coastal forest to whitish–yellow in the interior forest. This pattern of phenotypic divergence coincides with the gradient in tree‐canopy cover. Ventral fur colour of T. douglasii exemplifies a gradation of continuous phenotypic variation maintained despite ongoing gene flow in a panmictic population. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 536–546.

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Section: Interior Populationsmentioning

confidence: 99%

Section: Lack Of Clinal Variation In Skull Morphologymentioning

confidence: 99%

Clinal colour variation within a panmictic population of tree squirrels,Tamiasciurus douglasii(Rodentia: Sciuridae), across an ecological gradient

Chavez

Kenagy

2014

Biol J Linn Soc Lond

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“…High seed years in limber pine have been reported to occur intermittently every two to four years (ASRD and ACA ); however, no scientific studies have investigated their geographic synchrony or the degree of cone failure following large crops. A long‐term coevolution has occurred between conifer cone traits and red squirrels ( Tamiasciurus hudsonicus ), Erxleben (Benkman , Wheatley ). Limber pine seed dispersal adaptations, which include large seed size and gravity‐assisted dispersal, represent a compromise between avoiding red squirrels and facilitating dispersal by limber pine's primary seed disperser, Clark's nutcracker ( Nucifraga columbiana ), Wilson (Linhart and Tomback , Siepielski and Benkman ).…”

Section: Introductionmentioning

confidence: 99%

Resiliency in masting systems: Do evolved seed escape strategies benefit an endangered pine?

2017

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Abstract. Satiation of predispersal seed predators by mast years has been demonstrated in many intact ecosystems. When disease causes mortality of seed-bearing trees in an ecosystem, the abundance of food sources may alter seed predator behavior and abundance, and the ecosystem services derived from mutualistic seed dispersers. We used the endangered limber pine (Pinus flexilis) to examine whether the benefits of interannual variation in cone production vary depending on the severity of white pine blister rust (Cronartium ribicola) infections, the abundance of seed predator populations, and stand characteristics. We compared infection level, cone production, cone predation, and abundance of red squirrels (Tamiasciurus hudsonicus) in 17 stands over two mast years and two nonmast years. Stands were selected from a southern and northern ecosystem within Alberta's montane ecoregion, with varying forest composition and history of blister rust infection. Considerable variability in interannual cone production, and proportionately greater cone escape (those remaining in stands) in the 2010 mast year led to 10 times greater cone escape overall in the mast year than in nonmast years. Model selection using Akaike's information criterion (AIC) suggests that both cone escape and proportion cone escape from seed predators depended primarily on temporal variability in cone production among mast vs. nonmast years, basal area of canopy trees within stands, squirrel abundance, and ecosystem differences. Several two-way and three-way interactions between masting, ecosystems, and predator abundance were selected by AIC for inclusion into the best model of the a priori candidate set for both the cone escape model and proportion cone escape model. Our study suggests that masting confers temporal resiliency in seed escape in declining limber pine ecosystems, even under varying disease and seed predator threats. These findings also suggest that evolved seed escape strategies may be resilient to a variety of ecological conditions, including low reproductive capacity. Nonetheless, proximate ecological conditions may determine the fate of declining species, as predator behavior differed between ecosystems, and greater net cone escape in favorable stands may be necessary to attract mutualistic seed dispersers.

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Domains of scale in forest-landscape metrics: Implications for species-habitat modeling

Wheatley

2010

Acta Oecologica

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Relating Red Squirrel Body Size to Different Conifer Cone Morphologies within the Same Geographic Location

Cited by 6 publications

References 26 publications

Clinal colour variation within a panmictic population of tree squirrels,Tamiasciurus douglasii(Rodentia: Sciuridae), across an ecological gradient

Clinal colour variation within a panmictic population of tree squirrels,Tamiasciurus douglasii(Rodentia: Sciuridae), across an ecological gradient

Resiliency in masting systems: Do evolved seed escape strategies benefit an endangered pine?

Domains of scale in forest-landscape metrics: Implications for species-habitat modeling

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