R. David Maclaren, Ph.D.
Associate Professor of Biology
B.A. Biology, University of Maine at Farmington, 1998
Ph.D. Ecology and Evolutionary Biology, Indiana University, 2004
Office: Mendel 270
Evolution, Animal Behavior, Marine Biology and Sustainability, Comparative Animal Anatomy and Physiology I: Neurobiology and Endocrinology, Principles of Biology II and Senior Thesis Research in Biology.
Dr. MacLaren is President of the Marine Studies Consortium and Program Coordinator for Merrimack College.
I have two research foci: (1) The role of sexual selection in fish evolution, and (2) Behavior, ecology, and conservation of marine mammals in the Gulf of Maine.
Sexual selection in fish evolution: Our research combines ethological, evolutionary, ecological, and phylogenetic approaches to investigate animal behavior. Using experimental and observational methods, our interests focus on the elicitation, control, function, and evolution of behavior in fishes. Current projects investigate visual signals and the mechanisms by which they control and mediate courtship, aggression, and other social behaviors. Much of my research to date involves experimental studies on mate choice, sexual selection and aggression in Poeciliid fishes.
Through studies of mate choice in Poeciliid fishes, students learn first hand about the powerful roles sexual selection plays in guiding the process of evolution by natural selection. Recent projects include an on-going series of experiments examining the evolutionary basis of preference for male fin elaborations in the family of live-bearing fishes known as the Poecilidae (e.g. mollies, swordtails, platy fish, & guppies). Female preference for sexually dimorphic male fin elaborations in this family may be driven by a preexisting perceptual bias for increased overall size or lateral projection area (LPA) that has existed since the lineages diverged from a common ancestor. The LPA bias hypothesis suggests that a male with greater LPA (i.e. larger body and/or fin size) projects a larger image onto the female’s retina at a given viewing distance, eliciting a greater sensory and thus behavioral response to the stimulus. Support for the preexisting bias hypothesis requires phylogenetic evidence that the female preference evolved within the lineage before the male trait. Our research takes a comparative phylogenetic approach using dummy males to examine female preferences for dorsal fin size, body size and fin:body size ratio in multiple species of poeciliid fishes, including species whose males naturally possess an LPA-enhancing enlarged dorsal fin, species whose males possess alternative forms of LPA-enhancing fin elaboration (fantails and swordtails), as well as species whose males possess no fin elaborations.
Morphological and behavioral characterization of two Girardinus metallicus color morphs: Investigating ethologically-based reproductive isolation and possible new fish species identification: Most recently, my students and I have begun a long term study of G. metallicus, a relatively unstudied species of live-bearing Poeciliid fish native to Cuba. Very little is known about its basic ecology, behavior and life history. Three varieties of this species exist in nature, one in which the males possess a varying amount of black pigmentation, a second with yellow body coloration in similar anatomical locations, and a third colorless morph. Females of the first 2 varieties have very different pigmentation patterns than males, but vary extensively in coloration, body size and shape.
We (myself and currently eight undergraduates working in my fish laboratory at Merrimack) are quantifying the variation in male and female morphology for the black and yellow morphs as a first step towards describing this species. We are also in the midst of describing, quantifying and comparing the reproductive and aggressive behavior of the two morphs through both observation and controlled behavior experiments in the laboratory. Specifically, we are looking for quantifiable differences in the reproductive and aggressive behavior of the two morphs and examining the mating preferences of females of both morphs for males varying in “variety”-specific traits such as yellow vs. black pigmentation. These data, in collaboration with Dr. Gita R. Kolluru, Assistant Professor at California Polytechnic State University who is studying male preference for female traits in G. metallicus, should provide us with the information necessary to evaluate the degree of reproductive isolation (if any) between the two varieties. Depending on the degree to which the two varieties are isolated, we may be in a unique position to provide either: 1) rare empirical evidence in support of the maintenance of a polymorphism via “reinforcement”- a result of natural selection favoring assortative mating or 2) the characterization/description of a new species. Complete pre-mating, ethologically-based reproductive isolation according to the widely accepted biological species concept, might change the fish’s taxonomic designation from “polymorphic varieties of single species G. metallicus” to separate species. Thus, upon the project’s completion we could be on the verge of naming/describing a new species.
Behavior, ecology, and conservation of marine mammals in the Gulf of Maine: I also hold a strong interest in marine mammal behavior, ecology, and conservation. In Spring 2009 I established a partnership in research and education with the Blue Ocean Society for Marine Conservation (http://www.blueoceansociety.org/), a non-profit organization dedicated to marine mammal research, conservation, and education centered in Portsmouth, NH. During the summer months I serve as “Naturalist” aboard whale watch vessels, collecting behavioral and physical data on the whale, dolphin, and sea bird populations in the Jeffreys Ledge region of the Gulf of Maine while educating the public on marine mammal ecology and conservation. This work involves mentoring undergraduate students conducting summer research atMerrimack and/or interning withBlueOcean. All the data collected are added toBlueOcean’s data base, which we then analyze during the off season. As part of this collaboration,BlueOcean provides competitive internship/research opportunities toMerrimack students interested in marine mammal ecology, behavior & conservation.
My students and I are currently working on several research projects, including the following:
The Girardinus metallicus project described above.
An investigation into the possible role of sexual imprinting on mate preferences in Poeciliid fishes.
Additionally, my students and I are collaborating with Blue Ocean scientists in the analysis of 14+ years of marine mammal data from the Jeffreys Ledge region of the Gulf of Maine. Data mining efforts cover a wide range of study questions primarily addressing humpback (Megaptera novaeangliae) and fin whale (Balenoptera physalus) behavior, ecology and conservation.
* denotes undergraduate researcher
MacLaren, R.D. and *Fontaine, A. 2012. Incongruence between the sexes in preferences for body and dorsal fin size in Xiphophorus variatus. Behavioural Processes. DOI: 10.1016/j.beproc.2012.10.013
MacLaren, R.D., Schulte, D. and Kennedy, J. 2012. Field research studying whales in an undergraduate animal behavior laboratory. Bioscene Journal of College Biology Teaching.
MacLaren, R.D. and *Fontaine, A. 2012. Female bias for male lateral projection area in Poecilia reticulata. Environmental Biology of Fishes. Vol. 93, Issue 1, 105-119.
MacLaren, R.D., *He, R., and *Gagnon, J. 2011. Bias for enlarged male body and dorsal fins in female Xiphophorus variatus. Behavioural Processes 87, 197-202.
MacLaren, R.D. and *Daniska, D. 2008. Female preferences for dorsal fin and body size in Xiphophorus helleri : further investigation of the LPA bias in Poeciliid fishes. Behaviour. 145, 897-913.
MacLaren, R.D. 2007. Female preference in Xiphophorus helleri: Further investigation of the LPA bias in Poeciliid fishes. 2007 Annual Animal Behavior Society Conference Abstracts.
MacLaren, R.D. 2006. The effects of male proximity, apparent size, and absolute size on female preference in the sailfin molly, Poecilia latipinna. Behaviour. 143, 1457-1472
MacLaren, R.D. and Rowland, W.J. 2006a. Female preference for male lateral projection area in the shortfin molly Poecilia mexicana; evidence for a preexisting bias. Ethology. 112, 678-690.
MacLaren, R.D. and Rowland, W.J. 2006b. Differences in female preferences for male body size in Poecilia latipinna using simultaneous vs. sequential stimulus presentation designs. Behaviour. 143, 273-292.
MacLaren, R.D., Rowland, W.J., and *Morgan, N. 2004. Female preferences for sailfin and body size in the sailfin molly, Poecilia latipinna. Ethology.110, 363-379.
Rowland, W.J., *Grindle, N., MacLaren, R.D., and Granquist, R. 2002. Male preference for a subtle posture cue that signals spawning readiness in female sticklebacks. Animal Behaviour. 63.