The mechanistic basis of slow-fast phenotypic diversity and its functional and evolutionary significance in social groups

Why some animals are fast as hares and others as slow as tortoises is a question that has not only intrigued biologists but also philosophers and the public at large. Sometimes referred to as the pace of life, these slow-fast differences in physiology, behavior and life history, integrated into a set of contrasting characteristics, can distinguish different species or different individuals within a species along a slow-fast axis.

Since the rate of energy use, or metabolic rate, can have a large impact in defining the overall lifestyle of an animal, this project will take advantage of two genetic lines of honeybees that have been bred for their low and high metabolic rates, to understand the fundamental basis of slow-fast differences. Even more importantly, since honeybee colonies are superorganisms, they allow one to ask how a collective slow-fast phenotype can emerge from the diversity among colony members and define performance at the group level.

Slow-fast differences are also seen among the different species of honeybees such that the ones which nest in cavities have a faster tempo than the ones which nest in the open. This project will also undertake a comparative study of the four different species to understand how ecology shapes slow-fast diversity. The results of this study will add to our understanding of slow-fast differences and how it contributes to the evolution of social behavior.

With the current concern about anthropogenic changes, understanding these differences in behavior and life history has implications for honeybee health and management. This project will also contribute to modules for use in the Science for School program which supports K-5 science curriculum and establish a student mentorship program for undergraduates with interests in animal behavior.

It will also provide students with opportunities to travel and participate in research internationally.

Slow-fast differences in physiology, behavior and life history is a classic and fundamental concept in behavioral and evolutionary ecology, owing its history to r- and k-selection. More recently, metabolic rate (MR) and cognitive style have been cited as the primary drivers of these phenotypic differences, modeled as a set of correlated traits under the pace-of-life framework.

Such slow-fast diversity is especially interesting in the context of a social group where the phenotypic expression at the group level is an emergent outcome of the phenotypic diversity of its members, which also makes it possible for the group to potentially override some of the constraints that might be imposed by the covariance among the different traits at the individual level. Using the experimental leverage of the genetic lines of Slow (low MR) and Fast (high MR) honeybees (Apis mellifera) that were bred, this project will take an integrative approach modeled on Tinbergen’s four questions to understand (1) the mechanistic and developmental bases of slow-fast differences, (2) the functional consequences of slow-fast phenotypic diversity at the group level, and (3) the evolutionary basis of slow-fast phenotypic differences and its ecological drivers using a comparative approach integrating the work with A. mellifera with that in the other three honeybee species, A. cerana, A. dorsata and A. florea, the first two being cavity-nesters and the latter two being open-nesters.

Together, these studies will provide a comprehensive understanding of the significance of slow-fast phenotypic diversity that characterizes different levels of biological organization.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.