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Assessing the repeatability, robustness to disturbance, and parent‐offspring colony resemblance of collective behavior
Fisher, David; Lichtenstein, James; Costa-Pereira, Raul; Yeager, Justin; Pruitt, Jonathan — 2019-12-16 Groups of animals possess phenotypes such as collective behaviour, which may determine the fitness of group members. However, the stability and robustness to perturbations of collective phenotypes in natural conditions is not established. Furthermore, whether group phenotypes are transmitted from parent to offspring groups with fidelity is required for understanding how selection on group phenotypes contributes to evolution, but parent-offspring resemblance at the group level is rarely estimated. We evaluated the repeatability, robustness to perturbation, and parent-offspring resemblance of collective foraging aggressiveness in colonies of the social spider Anelosimus eximius. Among-colony differences in foraging aggressiveness were consistent over time but changed if the colony was perturbed through the removal of individuals, or via individuals’ removal and subsequent return. Offspring and parent colony behaviour were correlated at the phenotypic level, but only once the offspring colony had settled after being translocated, and the correlation overlapped with zero at the among-colony level. The parent-offspring resemblance was not driven by a shared elevation but could be due to other environmental factors. The behaviour of offspring colonies in a common garden laboratory setting was not correlated with the behaviour of the parent colony nor the same colony’s behaviour once it was returned to the field. The phenotypes of groups represent a potentially important tier of biological organisation, and assessing the stability and heritability of such phenotypes helps us better understand their role in evolution.
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Territory acquisition mediates the influence of predators and climate on juvenile red squirrel survival
Hendrix, Jack G; Fisher, David; Martinig, April; Boutin, Stan; Dantzer, Ben; Lane, Jeffrey; McAdam, Andrew — 2021-03-06 <p>1) Juvenile survival to first breeding is a key life history stage for all taxa. Survival through this period can be particularly challenging when it can coincide with harsh environmental conditions such as a winter climate or food scarcity, leading to highly variable cohort survival. However, the small size and dispersive nature of juveniles generally makes studying their survival more difficult. 2) In territorial species, a key life history event is the acquisition of a territory. A territory is expected to enhance survival, but how it does so is not often identified. We tested how the timing of territory acquisition influenced the winter survival of juvenile North American red squirrels Tamiasciurus hudsonicus, hereafter red squirrels, and how the timing of this event mediated sources of mortality. We hypothesized that securing a territory prior to when food resources become available would reduce juvenile susceptibility to predation and climatic factors over winter. 3) Using 27 years of data on the survival of individually-marked juvenile red squirrels, we tested how the timing of territory acquisition influenced survival, whether the population density of red squirrel predators and mean temperature over winter were related to individual survival probability, and if territory ownership mediated these effects. 4) Juvenile red squirrel survival was lower in years of high predator abundance and in colder winters. Autumn territory owners were less susceptible to lynx Lynx canadensis, and possibly mustelid Mustela and Martes spp., predation. Autumn territory owners had lower survival in colder winters, but surprisingly non-owners had higher survival in cold winters. 5) Our results show how the timing of a life history event like territory acquisition can directly affect survival and also mediate the effects of biotic and abiotic factors later in life. This engenders a better understanding of the fitness consequences of the timing of key life history events.</p>

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(Author: Fisher, David)

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