Quantitative genetics of life-history traits in a long-lived wild mammal

Quantitative genetic studies of life-history traits in wild populations are very rare, yet variance/ covariance estimates of these traits are crucial to understanding the evolution of reproductive strategies. We estimated her itabilities (h(2)) of several life-history traits (longevity, age and mass at primiparity, and reproductive traits) in two bighorn sheep (Ovis canaden sis) populations, and both phenotypic (r(p)) and genetic (r(A)) correlation s between life-history traits in one population. We included adult mass in our analyses because it is related to several life-history traits. We used the mother-daughter regression method and resampling tests based on data fr om long-term monitoring of marked females. Contrary to the theoretical pred iction of low heritability for fitness-related traits, heritability estimat es in the Ram Mountain population ranged from 0.02 to 0.81 (mean of 0.52), and several were different from zero. Coefficients of variation tend to sup port the hypothesis of a higher environmental influence on life-history tra its. In contrast, at Sheep River we found low heritabilities of life-histor y traits. Phenotypic correlations Varied between -0.09 and 0.95. Several ge netic correlations were strong, particularly for different reproductive tra its that are functionally related, and ranged from -0.34 to 1.71. Overall, genetic and phenotypic correlations between the same variables were similar in magnitude and direction. We found no phenotypic or genetic correlations suggesting trade-offs among life-history traits. Bighorn sheep may not for m the large, outbred populations at equilibrium that are assumed by both Fi sher's fundamental theorem and by theories predicting antagonistic pleiotro py between life-history traits. Alternatively, the absence of negative gene tic correlations may result from genetic variation in ability to acquire re sources or from novel environmental conditions existing during the study pe riod.