Nancy G. Solomon - US grants

Factors in the social environment, such as psychosocial stimulation and stress from interactions with conspecifics, may influence the timing of sexual maturation. The degree of sociality of a species may affect the responsiveness of females to social signals or the mechanism by which social cues influence reproduction. The long-term goal of this research program is to examine the mechanisms that affect the timing of reproduction. Understanding the nature of the social cues that may influence reproduction and sexual development is central to uncovering the physiological and neural mechanisms, as well as the evolutionary basis, of reproductive timing in mammals. There are three specific goals of these experiments: (1) to determine whether or not social cues can suppress or delay reproduction in two species of rodents that differ in the degree of sociality, (2) if females in both species exhibit reproductive suppression, then to examine the cues involved in mediating suppression and, (3) to test the effects of suppressive cues under natural conditions. Two rodent species will be compared in these experiments: the pine vole, a cooperative breeder, and the meadow vole, which tends to be less social during the breeding season. In a number of cooperatively breeding species, only one female typically reproduces although non-reproductive group members also provide care to young. Delayed reproduction has also been reported in noncooperatively breeding females, at least during periods of high population density. Lack of or delayed reproduction seems extremely costly to individuals due to losses in direct fitness (Brown 1987). Initial experiments (Exp 1 and 2) will determine the source of suppression of younger females. The relative effectiveness of chemical versus behavioral cues in suppression of reproduction will be examined (Exp 1 and 2). Variations in the amount of contact with a potential mate and suppressive cues will be examined to determine the likelihood of suppression of reproduction versus lack of sufficient contact with males as an explanation of suppression in the wild (Exp 3). Finally, the frequency with which chemical cues need to be presented will be determined prior to tests in a natural setting (Exp 4). If suppression of reproduction occurs in response to chemical cues in the laboratory, field experiments will be conducted to assess the effectiveness of chemical cues on reproduction in semi-natural settings (Exp 5 and 6). Breeding females will be removed and then chemical cues presented to determine if chemical cues alone can suppress reproduction in a field situation. Finally, a similar study using chemical cues will be conducted in an orchard setting with pine voles (Exp 7). The results of these experiments will provide valuable insights into the mechanisms and selection pressures responsible for the evolution and/or maintenance of delayed reproduction in mammalian species that differ in the degree of sociality.

9700900 Solomon Both individuals and populations should be strongly influenced by habitat quality. In turn, habitat quality can be influenced by many factors, such as the abundance and distribution of food, cover, and the presence of potential mates or competitors. Individuals within a population usually do not utilized all available habitat. The portion of habitat that individuals use on a daily basis is referred to as their home range and if this space is defended, it is referred to as their territory. The objective of this study is to determine the influence of territory quality and resource distribution on movement and space use of meadow voles. Female meadow voles are territorial during the breeding season and occupy relatively small ranges. Male meadow voles are non-territorial throughout the year and occupy ranges several times larger than female ranges. It has been hypothesized that female territoriality should be more pronounced in high-quality habitat relative to low-quality habitat and should be more evident when resources are clumped rather than evenly distributed. We will test these hypotheses by examining patterns of overlap among female territories; low levels of overlap indicate territoriality whereas high levels indicate non-territorial behavior. If overlap is lower in high-quality habitat than in low-quality habitat and lower on clumped than evenly distributed resources these hypotheses will be supported. Offspring born on high-quality territories are more likely to remain in the natal area than offspring born on low-quality territories. Additionally, offspring that leave high-quality territories should be older than offspring that leave low-quality territories. We will test these hypotheses by examining the proportion of offspring that remain in the natal area as adults and the ages of individuals that leave the natal area. Understanding how meadow voles respond to territory quality and resource distribution is important since these animals can alter pla nt communities thus influencing ecological succession, are an important prey species for many predators, and are known to be an important agricultural pest. Determining how meadow voles respond to habitat quality and resource distribution could therefore lead to a better understanding of ecological succession, how predator assemblages respond to resource and prey abundance and distribution, and help design new agricultural practices that can help reduce vole damage.

Factors that influence reproductive success may act through their influence on dispersal and selection for audible territory. The social environment of mammals such as stress from interactions with same-sex conspecifics or stimulation by members of the opposite sex may affect the probability of success in there endeavors but the mechanisms involved are not well understood. Furthermore, the social environment may affect males and females in the same or in different ways. The aim of this study is to examine alternative hypotheses about whether or not there is a gender difference in the cues that influence emigration and immigration. The intra sexual competition hypothesis predicts that same-sexconspecifics will induce emigration but prevent immigration. In contrast, the inbreeding avoidance hypothesis predicts that opposite- sex conspecifics should induce emigration. The mate access hypothesis may work in conjunction with either of the two previous hypotheses and predicts that individuals will emigrate if there are no potential mates in the social group. Finally, the conspecific cuing hypothesis predicts that individuals will immigrate into territories containing same-sex conspecifics because their presence indicates that the territory is suitable. To test these hypotheses, I will examine preferences of young and mature female and male pine voles to different of olfactory and social cues in series of laboratory experiments. Lab experiments also will be conducted to examine responses of female and male residents to visitors of different sexes and age classes. Finally, I propose to examine the effects of group composition on intergroup transfer in lab and field experiments. I will test whether reproductive vacancies affect movement and whether the gender of remaining group members influences the timing and gender of immigrants. The long-term objectives of this research are to understand the factors involved in social control of behavior as well as to begin to understand the physiological mechanisms underlying these. Studies like the ones proposed here would allow me to examine the relationship between social interactions and dispersal, which ultimately affects the probability of reproduction. Interactions with conspecifics can also be important in the expression of gender-related behavior; this study will provide a model to access reproductive strategies in males and females.

Dissertation Research: Disentangeling the Effects of Female Choice, Contest Competition and Scamble Competition for Mates

Drs. Nancy G. Solomon & Douglas B. Meile; Mark D. Spritzer

Sexual selection is differential mating success caused by variation among members of one sex in a trait that influences acquisition of mates. Although sexual selection is one of the most intensively studied areas in the field of behavioral ecology, surprisingly little is known about the relative importance of the different mechanisms of sexual selection. The main goal of the proposed research is to determine the relative importance of female choice, contest competition, and scramble competition for mates in determining the mating success of males. Female choice involves females choosing to mate with a male based on conspicuous ornaments or behaviors. Contest competition involves direct aggressive interactions between males and scramble competition, in contrast, involves a male's ability to rapidly and accurately locate mates. Meadow voles were used as the study species because past studies suggest that all three of these mechanisms of sexual selection occur among these rodents. Male navigation ability was chosen as a trait believed to be favored by scramble competition, and male dominance rank was chosen as a trait believed to be favored by contest competition. In addition, the influence of female choice upon both of these traits will be tested. The specific objectives are to determine: (1) the relationship between male navigation ability and male mating success, (2) the relationship between dominance and navigation ability among male voles, (3) the relative influence of dominance and navigation ability upon male mating success, and (4) female mating preferences for males with varying levels of navigation ability and dominance. A series of lab and field experiments will be used to achieve these objectives. Navigation ability will be measured by scoring each male's ability to complete a maze test, and male dominance will be tested by scoring aggression between pairs of males in arena trials. Male reproductive success will be determined using genetic paternity analyses. The results of this project will be an important next step in understanding how sexual selection shapes the evolution of a species.

Project Summary
Little is known about the mechanisms of maternal investment that affect offspring fitness in
communal groups. This study is the first to evaluate specific mechanisms of investment that
affect the fitness of offspring in communal groups. My objectives are to: (1) evaluate dam-
offspring discrimination in a communal rodent, (2) determine if communal nesting improves
offspring growth even when food is restricted, (3) determine the relative importance of tactile
stimulation, warmth and dams milk provided in communal groups on offspring growth, and (4)
monitor the survival and reproduction of offspring reared by communal and solitary dams. I
found that prairie vole dams treat conspecific newborns but not conspecific weanlings as own.
Also, offspring in single-dam groups grow more than offspring reared by solitary dams when
food is provided ad-lib. I will test the effect of simulated tactile stimulation and warmth provided
by an additional female on offspring growth and dams milk (Expt. 3). I will monitor survival
and reproduction of offspring from single-dam groups and solitary dams in outdoor enclosures
(Expt. 4). By integrating proximate and ultimate levels of analysis, I will improve our
understanding of the evolution of communal nesting. Undergraduates have and will continue be
involved in this study.

Cooperative breeding, in which multiple adults share a nest and care for young born at that nest, is unusual among vertebrates. Delayed dispersal, a hallmark of cooperative breeding, can result from lack of vacant territories or benefits to offspring that remain at the nest where they were born. The investigators propose to test these alternatives in a cooperatively breeding mammal, the prairie vole. They will establish prairie vole populations at high and low densities in field enclosures. The prediction is that the proportion of juveniles that remain at home and the size of extended family groups will be greater at high density. In these same populations the investigators also will test predictions regarding potential benefits to offspring that remain at home. Throughout the field experiment, they will use genetic techniques to determine kinship of group members. This study will be the first to combine a field experiment manipulating population density with genetic data on kinship and should allow the investigators to examine previously mentioned ideas about delayed dispersal. The results of this study will contribute to our understanding of the ways in which demographic and social factors shape mammalian behavior.

This study will provide opportunities for students to gain first-hand experience in the application of the scientific method. The investigators also plan to introduce grade school and high school teachers to this research as part of a summer workshop.

DESCRIPTION (provided by applicant): Early views considered mating systems to be species-specific i.e., did not vary among different populations. As multiple populations of different species were studied, it became evident that interpopulation differences in mating systems were more common than previously imagined. In addition, use of term mating system without any modifiers was problematic since it confounded social and genetic mating systems of males and females. Therefore, I propose to conduct a comparative study to identify ecological correlates of social and genetic mating systems using prairie voles, Microtus ochrogaster. Populations of prairie voles in different parts of their range live in habitats that differ in climate, which affects the quality and distribution of vegetation. Characterization of the mating system of prairie voles has been based on a population from Illinois. If the mating system is influenced by climate and its effects on the distribution of resources, prairie voles in Kansas may display an alternative mating system. My objective is to determine whether social and genetic monogamy are seen under certain ecological conditions. The prairie vole is an interesting model system since it has been used as a model of monogamy and affiliative behavior. Understanding factors that affect variation in social mating systems (e.g. pair bonds) are key to understanding the biological basis of attachment. Eventually understanding the variability in behavioral processes involved in social mating relationships might also provide insight into the biological basis of variability in response to stressors. I will sample prairie vole populations in eastern Kansas and east-central Illinois to determine the ecological correlates of the social and genetic mating system of females and males. Animals will be live-trapped and radio tracked to determine the social mating system. Tissue samples will be collected for subsequent genetic analysis using microsatellite primers identified for prairie voles in my laboratory previously. This study will be the first to compare the social and genetic mating systems of multiple populations of a rodent thought to be monogamous, and will allow me to design experimental manipulations to determine the factors that influence mammalian mating systems.

Researchers have begun to identify specific genes that appear to influence social behavior in animals. While these studies have made a substantial contribution towards understanding the link between genes and behavior, they have been conducted almost exclusively on captive animals in the laboratory. Since laboratory settings can be highly artificial, these studies may not reflect what happens in the real world. Therefore, the next logical step in studying the relationship between genes and social behavior is to investigate how genetic differences among individuals effect social behavior in a species' natural environment.
Prairie voles (Microtus ochrogaster) are rodents that typically form behavioral attachments to one opposite-sex partner during their lifetime (social monogamy). Although the prairie vole is a popular laboratory model for studying monogamy, in nature this species varies in the degree of social monogamy exhibited among populations as well as within populations. A recent study suggests that variation in social bonding among prairie voles in nature might be due in part to genetic differences in a single gene that codes for a receptor localized in the brain that binds a specific chemical messenger called vasopressin. In laboratory tests, males with longer versions of this gene spent significantly more time in contact with their female partner compared to an unfamiliar female, relative to males with shorter forms of this gene. These data are intriguing because they suggest that size differences in the gene coding for the vasopressin receptor causally affect social attachment and possibly mate fidelity among male prairie voles. This study will be the first to examine the real world consequences on social attachment of genetic variation in the gene coding for the vasopressin receptor in male prairie voles. Detecting a significant relationship between size differences in the gene coding for the vasopressin receptor and social/genetic indices of monogamy would be strong evidence that this gene influences social behavior in male prairie voles under ecologically relevant conditions.
Vasopressin is known to be involved in the regulation of complex social behaviors in mammals such as social recognition, aggression and affiliation. Thus, prairie voles may be an excellent animal model for studying social attachment among other mammals, including humans. In particular, prairie voles can provide a tractable model to investigate how genetic changes may influence the activity of specific areas in the brain, which may impact the display of social behaviors, such as the formation of social attachments or bonds. The proposed research will also require extensive contributions from undergraduate and graduate students, providing opportunities for them to gain first-hand experience conducting scientific research.

Biological Sciences (61)
"Integrated Pedagogy to Promote Understanding of Nature of Science and Scientific Inquiry in a College Biology Laboratory" is creating learning materials and teaching strategies and conducting research on undergraduate STEM education via a multi-department, multi-institution collaboration. The project aims to increase student understanding of the nature of science (NOS) and scientific inquiry (SI) in response to findings that undergraduate science students do not understand NOS and SI and do not necessarily improve their understanding by performing science. Current research-based practice calls for incorporation of explicit reflection about NOS and SI as part of the science curriculum, and this project is employing a full factorial design to compare the efficacy of inquiry versus non-inquiry labs and reflective versus non-reflective practices on student learning of NOS and SI in introductory biology laboratories at both a 4-yr and a 2-yr institution. Project outcomes include: TA's better informed about NOS, SI, and innovative instructional techniques, a NOS / SI symposium, and a pilot lab manual.