Lefebvre L., Marino L., Sol D., Lemieux-Lefebvre S., Arshad S. (2006) Erratum: Large brains and lengthened life history periods in odontocetes (Brain, Behavior and Evolution (2006) 68, (218-228)). Brain, Behavior and Evolution. 68: 228-0.LinkDoi: 10.1159/000096902
[No abstract available]
Lefebvre L., Marino L., Sol D., Lemieux-Lefebvre S., Arshad S. (2006) Large brains and lengthened life history periods in odontocetes. Brain, Behavior and Evolution. 68: 218-228.LinkDoi: 10.1159/000094359
Previous work on primates and birds suggests that large brains require longer periods of juvenile growth, leading to reproductive constraints due to delayed maturation. However, longevity is often extended in large-brained species, possibly compensating for delayed maturation. We examined the relationship between brain size and life history periods in cetaceans, a large-brained mammalian order that has been largely ignored. We looked at males and females of twenty-five species of Odontocetes, using independent contrasts and multiple regressions to disentangle possible phylogenetic effects and inter-correlations among life history traits. We corrected all variables for body size allometry and separated life span into adult and juvenile periods. For females and both sexes combined, gestation, time to sexual maturity, time as an adult and life span were all positively associated with residual brain size in simple regressions; in multiple regressions, maximum life span and time as an adult were the best predictors of brain size. Males showed few significant trends. Our results suggest that brain size has co-evolved with extended life history periods in Odontocetes, as it has in primates and birds, and that a lengthened adult period could have been an important component of encephalization in cetaceans. Copyright © 2006 S. Karger AG.
Marino L., Sol D., Toren K., Lefebvre L. (2006) Does diving limit brain size in cetaceans?. Marine Mammal Science. 22: 413-425.LinkDoi: 10.1111/j.1748-7692.2006.00042.x
We test the longstanding hypothesis, known as the dive constraint hypothesis, that the oxygenation demands of diving pose a constraint on aquatic mammal brain size. Using a sample of 23 cetacean species we examine the relationship among six different measures of relative brain size, body size, and maximum diving duration. Unlike previous tests we include body size as a covariate and perform independent contrast analyses to control for phylogeny. We show that diving does not limit brain size in cetaceans and therefore provide no support for the dive constraint hypothesis. Instead, body size is the main predictor of maximum diving duration in cetaceans. Furthermore, our findings show that it is important to conduct robust tests of evolutionary hypotheses by employing a variety of measures of the dependent variable, in this case, relative brain size. © 2006 by the Society for Marine Mammalogy.
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