Translator Disclaimer
1 July 2003 VARIATION IN VIABILITY SELECTION AMONG COHORTS OF JUVENILE RED SQUIRRELS (TAMIASCIURUS HUDSONICUS)
Andrew G. McAdam, Stan Boutin
Author Affiliations +
Abstract

Selection will result in observable changes in traits only if it acts consistently in space and time, but few estimates of selection in natural populations have been temporally replicated. Here we estimate viability selection on nestling growth rates for 13 cohorts (1989–2001) of red squirrels (Tamiasciurus hudsonicus) from a natural population located in southwestern Yukon, Canada. Directional selection on nestling growth rates varied in magnitude and direction from one cohort to the next. The magnitude of directional selection was relatively weak in most years (median β′ = 0.24), but there were episodes of very strong viability selection (β′ > 0.5) in some cohorts. We found no evidence of significant stabilizing or disruptive selection on this trait. Examination of viability selection episodes over shorter time periods suggested that the strength of selection on juveniles in this population was positively related to the time scale over which selection was measured. Viability selection from birth to emergence from the natal nest (50 days of age) and from emergence to successful recruitment (100 days of age) were positively correlated, but were both independent of selection on nestling growth rates from recruitment to potential breeding age (one year). The strength of directional selection on growth rates prior to recruitment was negatively correlated with spring temperature whereas selection from recruitment to breeding was positively correlated with the abundance of spruce cones produced in the previous fall. Episodes of strong directional selection from birth to breeding age appear to be due to potentially rare combinations of environmental conditions. As a result, predicting the occurrence of very strong episodes of selection will be extremely difficult, but predicting the microevolutionary responses to observed selection on individual cohorts remains feasible.

Andrew G. McAdam and Stan Boutin "VARIATION IN VIABILITY SELECTION AMONG COHORTS OF JUVENILE RED SQUIRRELS (TAMIASCIURUS HUDSONICUS)," Evolution 57(7), 1689-1697, (1 July 2003). https://doi.org/10.1554/02-393
Received: 2 July 2002; Accepted: 14 February 2003; Published: 1 July 2003
JOURNAL ARTICLE
9 PAGES

This article is only available to subscribers.
It is not available for individual sale.
+ SAVE TO MY LIBRARY

Share
SHARE
KEYWORDS
Directional selection
growth rate
litter size
maternal selection
parturition date
selection gradients
RIGHTS & PERMISSIONS
Get copyright permission
Back to Top