David Jacobs

My research focuses on the evolution of small mammals. In particular I study how small mammals are adapted to their environment in attempt to understand the interaction between morphology, behaviour, ecology and geography. This research is done within the context of two broad evolutionary questions.

How are animals adapted to their environment?

What are the historical processes that have lead to such adaptation.

I study the evolution of morphological and sensory adaptations to understand the constraints that mammals face as a result of the trade offs associated with becoming increasingly adapted to a particular niche e.g. adaptations for being an aerial insectivore in open habitat precludes foraging within vegetation even though there might be more prey within vegetation. I have chosen insectivorous bats as the system to work on because their evolution of flight and echolocation allows one to understand the interaction between a sensory system that provides information about space and time and a morphological system that allows the negotiation of that space. The morphology (and nervous system) associated with flight and echolocation should be under extreme selection pressure because of the stringent conditions under which they have to operate as a result of acoustics and aerodynamics. A trait has to be well adapted to work in one situation but such adaptation might make it less suited to another situation. This makes bats ideal for understanding the evolutionary constraints faced by mammals as they become adapted to a particular habitat.

I have extended this interest into predator/prey arms races. Echolocation might be the primary constraint on bat diet, allowing some bats to overcome insect hearing and include many eared insects such as moths in their diet, while others might be prevented from taking eared insects because they are unable to capture them. This has lead to an investigation of the co-evolution of bat echolocation with moth hearing using a variety of approaches from laboratory based molecular studies to field based ecological studies at the level of the individual, the community and the region. The results of this work have lead to investigations into a number of related fields e.g. community structure. One of the principle questions in community ecology is whether communities have 'limited membership' (Elton 1927) or are mere assemblages of species that happen to co-occur (Roughgarden 1989).

More specifically, why does any regional species pool constitute only a subset of all species on earth? For that matter, why does the set of species coexisting at any point in space and time constitute only a subset of the regional species pool? The causes of limited membership include: lack of adaptations that permit a species to function under the physical conditions of the environment, limitations on dispersal, and interactions among species (Roughgarden and Diamond 1986). This research includes investigation into the factors responsible for current and past distibutions of animals (biogeography) and the historical processes that have shaped these distributions (phylogeography).