Weiss Lab Research Projects

Many egg-laying animals lack parental care and instead leave eggs unattended and exposed to environmental pathogens that can cause egg mortality. We are interested in mechanisms that animals use to prevent egg loss in the absence of parental care, and propose a novel source of protection: protective microbes that passively transfer from the reproductive system of the mother to eggshell surfaces during egg-laying.

In collaboration with Dr. Mark Martin and& Dr. Betsy Arnold at the University of Arizona, we study the maternal and eggshell microbiome and their interactions with soil pathogens utilizing lizards as a model system.

Preliminary data from the striped plateau lizard (Sceloporus virgatus) suggest that mature eggs have more bacteria, less fungal growth, and higher hatch success when oviposited than when surgically removed without cloacal contact (Science News published a brief story about these data). With support from NSF, we will:

1. quantify temporal variation in cloacal microbiomes of S. virgatus to test whether females’ microbiota change in preparation for egg-laying;
2. use both experiments and observational study to characterize vertical transmission and the role of transmitted microbes in reducing egg infections;
3. relate cloacal microbiota to female reproductive success, signals/cues of reproductive value (such as the female ornament and skin lipid chemical cues), and behavioral interactions; and
4. conduct comparative studies across Sceloporus spp. to examine the relationship of reproductive mode (oviparous vs. viviparous) and infection risk on antifungal capacity of cloacal microbiota. Vertical transmission during oviposition is expected to be a general phenomenon, so results should be broadly applicable to other oviparous taxa.

This work involves next-generation sequencing and bioinformatics analyses, culture-based techniques, in vitro analyses, and field study. We hope our research will be foundational to the integration of microbiology and behavioral ecology, contributing to long-standing theoretical questions about costs and benefits of parental care (or lack thereof) and sexual signaling, expanding knowledge of microbial diversity and composition in an understudied host lineage, and potentially identifying new antifungal agents.

A major question in evolutionary biology concerns the manner with which sexual selection pressures, such as mate choice and intrasexual competition, result in the origination and maintenance of elaborate ornamental traits. The selective forces influencing the evolution of female ornaments have been relatively ignored even though the occurrence of such traits is not as uncommon as traditionally assumed. Among lizards, for example, females of over 30 species express bright coloration that is absent in conspecific males.

My students and I examine the function and regulation of female ornaments, focusing on the striped plateau lizard (Sceloporus virgatus). Female striped plateau lizards develop orange color on their throats during the reproductive season. My working hypothesis is that males invest more resources into the courtship of more-ornamented females because these females are of higher quality and thus produce higher quality offspring. Females are expected to benefit from “indirect mate choice” – attracting males to them, inciting competition, and mating with higher quality winners, all while remaining sedentary during the energetically expensive period of egg development. To address this hypothesis, some of my research questions have included:

• How does the female ornament affect male behavior?
• Is the female ornament an honest signal of female phenotypic quality?
• Can the female ornament be used to predict characteristics of her offspring?
• What mechanisms (genetic or nongenetic) underlie the positive relationship between maternal ornamentation and offspring quality?
• How is female ornament expression regulated?

My students and I have recently expanded our work on female signals to include chemical signals. We have characterized the chemical make-up of female skin lipids cues, related individual variation in chemical cue composition to aspects of female reproductive state and condition, and examined male response to female cues (both whole cues and chemical standards of specific cue components).

In the long run, we want to address many of the same 5 questions bulleted above. In addition, we are examining whether the visual and chemical signals are redundant (i.e., provide the same information) or are instead providing distinct information to receivers.

I am part of a cross-institution study led by Dr. Sehoya Cotner (University of Minnesota) and Dr. Cissy Ballen (Auburn University, Montgomery) investigating the effect of gender and minority status on attitudes, participation, and performance in introductory science classrooms. A key finding to date is that small class sizes, like those at Puget Sound, reduce gender gaps in STEM class performance and participation (recently published in BioScience).

Some of the other projects that my students and I have dabbled in include:

• Chemical ecology of lizards. We have compared the response rate of sit-and-wait and active foraging lizards to chemical cues of prey.
• Population response to fire. In 2011, a fire burned through my study site.
  
  

  We compared lizard and prey populations on the burned site to those on a nearby unburned site. We now have a large data of demographic information available for future analyses.

• Factors that influence sprint speed in lizards. Some variables that have been examined include acute vs chronic elevations of corticosterone, incline of the race track, tail loss, and heritability.
• Role of corticosterone in stimulating hatching of late-term lizard embryos.
• Effect of developmental stress on larval development of tobacco hornworms.