Kin effects on energy allocation in group-living ground squirrels.
Journal of Animal Ecology 85(5):1361 (2016)
The social environment has potent effects on individual phenotype and fitness in group-living species. We asked whether the presence of kin might act on energy allocation, a central aspect of life-history variation. Using a 22-year data set on reproductive and somatic allocations in Columbian gr...
Color ornaments and territory position in king penguins.
Behavioural Processes 119:32 (2015)
King penguins exhibit mutual color ornamentation of feathers and beak color. They breed in dense colonies and produce a single chick every 2 years. Thus, males and females must choose partners carefully to be reproductively successful, and auricular patches of males and UV coloration of beak spo...
Ectoparasites and fitness of female Columbian ground squirrels.
Philosophical Transactions of the Royal Society... 370(1669) (2015)
Parasites play an important role in the evolution of host traits via natural selection, coevolution and sexually selected ornaments used in mate choice. These evolutionary scenarios assume fitness costs for hosts. To test this assumption, we conducted an ectoparasite removal experiment in free-l...
How life history influences population dynamics in fluctuating environments.
American Naturalist 182(6):743 (2013)
A major question in ecology is how age-specific variation in demographic parameters influences population dynamics. Based on long-term studies of growing populations of birds and mammals, we analyze population dynamics by using fluctuations in the total reproductive value of the population. This...
Live fast, die young, and win the sperm competition.
PNAS 110(44):17610 (2013)
The role of microhabitat in predation on females with alternative dorsal patterns in a small Costa Rican anole (Squamata: Dactyloidae).
Revista de Biologia Tropical 61(2):887 (2013)
Predation is one of the major selective agents influencing evolution of color patterns. Cryptic color patterns decrease detection probability by predators, but their concealing function depends on the background against which patterns are seen; therefore, habitat use and color patterns are tight...
Delayed phenology and reduced fitness associated with climate change in a wild hibernator.
Nature 489(7417):554 (2012)
The most commonly reported ecological effects of climate change are shifts in phenologies, in particular of warmer spring temperatures leading to earlier timing of key events. Among animals, however, these reports have been heavily biased towards avian phenologies, whereas we still know comparat...
Lifestyles and phylogeny explain bird life histories.
PNAS 109(27):10747 (2012)
Philopatry and within-colony movements in Columbian ground squirrels.
Molecular Ecology 21(3):493 (2012)
Philopatry and dispersal result in selection of habitat locations that may differ in resources and social environment and thus should influence fitness components like survival and reproduction. We examined short-distance movements of young and adult females from natal or previous nesting sites ...
Kin selection in Columbian ground squirrels: direct and indirect fitness benefits.
Molecular Ecology 21(3):524 (2012)
Empirical and theoretical studies have supported kin selection by demonstrating nepotism or modelling its conditions and consequences. As an alternative, we previously found that female Columbian ground squirrels had greater direct fitness when more close kin were present. Extending those result...
Demography of squirrel monkeys (Saimiri sciureus) in captive environments and its effect on population growth.
American Journal of Primatology 73(10):1041 (2011)
Understanding which life-history variables have the greatest influence on population growth rate has great ecological and conservation importance. Applying models of population regulation and demographic mechanisms can aid management and conservation of both wild and captive populations. By comp...
Kin selection in Columbian ground squirrels (Urocitellus columbianus): littermate kin provide individual fitness benefits.
Proceedings of the Royal Society B: Biological ... 277(1684):989 (2010)
Since W. D. Hamilton's seminal work on the evolution of sociality, a large body of research has accumulated on how kin selection might explain the evolution of cooperation in many group-living species. Our study examined the evolutionary basis of philopatry and cooperation; specifically, whether...
Reproductive value and the stochastic demography of age-structured populations.
American Naturalist 174(6):795 (2009)
The dynamics of an age-structured population in a fluctuating environment is determined by the stochastic individual contributions from annual survival and fecundity to the total reproductive value of the population the next year. All parameters required to describe the population dynamics are s...
Senescence rates are determined by ranking on the fast-slow life-history continuum.
Ecology Letters 11(7):664 (2008)
Comparative analyses of survival senescence by using life tables have identified generalizations including the observation that mammals senesce faster than similar-sized birds. These generalizations have been challenged because of limitations of life-table approaches and the growing appreciation...
A lifestyle view of life-history evolution.
PNAS 104(45):17565 (2007)
Variation in litter size: a test of hypotheses in Richardson's ground squirrels.
Ecology 88(2):306 (2007)
We studied litter size variation in a population of Richardson's ground squirrels (Spermophilus richardsonii) in Alberta, Canada, from 1987 to 2004. Litter size at first emergence of juveniles from the natal burrow ranged from 1 to 14; the most common litter sizes, collectively accounting for 41...
Threats to avifauna on oceanic islands.
Conservation Biology 21(1):125 (2007)
Results of the study by Blackburn et al. (2004a) of avifauna on oceanic islands suggest that distance from the mainland and time since European colonization have major influences on species extinctions and that island area is a significant but secondary contributing factor. After augmenting the ...
How slow breeding can be selected in seabirds: testing Lack's hypothesis.
Proceedings of the Royal Society B: Biological ... 274(1607):275 (2007)
The historical debate of the 1960s between group and individual selection hinged on how the slow breeding of seabirds could be explained. While this debate was settled by the ascendance of individual selection, championed by David Lack, explanations for slow breeding in seabirds remain to be tes...
The relative importance of life-history variables to population growth rate in mammals: Cole's prediction revisited.
American Naturalist 161(3):422 (2003)
The relative importance of life-history variables to population growth rate (lambda) has substantial consequences for the study of life-history evolution and for the dynamics of biological populations. Using life-history data for 142 natural populations of mammals, we estimated the elasticity of...
Why breed every other year? The case of albatrosses.
Proceedings of the Royal Society B: Biological ... 269(1503):1955 (2002)
Albatrosses exhibit extremely low reproductive rates, each pair brooding only one egg and subsequent chick at a time. Furthermore, in several of the species, the majority of successful pairs breed only once every second year (termed 'biennial' breeding). Thus, on average, these latter species ha...