SOURCE 2019

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Bikesh Shrestha (Graduate Student) - Effects of Dihydrotestosterone on Mouse Gut Microbiome – A Study of Sex Differences and Hormonal Effects on Gut Microbiome
Type 1 Diabetes (T1D) is a polygenic and multifactorial disease, traditionally attributed to genetic susceptibility and diet. Over the past decade, novel studies have placed a higher significance on the role of gut microbiome in T1D pathogenesis. Furthermore, diabetic mice models have shown higher incidence of T1D in females compared to males, attributed to the differences in gut microbial community structure. Interestingly, female mice models elicited male- like protection when transplanted with the male gut microbiome. In a previous study, we observed that female Non-obese diabetic (NOD) mice implanted with slow release 5-dihydrotestosterone (DHT) for 90 days showed improved glucose tolerance when compared to untreated females. We hypothesize that DHT treatment alters female gut microbial profile to resemble a male-like microbiome that induces improved glucose tolerance, a determinant of T1D protection. By comparing the gut microbiome composition of DHT treated female mice with untreated females and age matched males, we aim to identify the microbial changes and understand the relationship between gut microbiome and disease protection. Bacterial DNA was extracted from the gut microbiome and was sequenced. The sequence data will be used to identify organisms present, calculate microbial community diversity indices and identify predominant metabolic profiles in each sample. Our study will help to better understand the effects of androgens on gut microbiome composition and its protective effects against T1D.

Kenya Byrnes - Woodpecker Paradise: Territory Size of Melanerpes chrysogenys in Western Mexico
The Tropical Dry Forest shows intense seasonality, with distinct dry and rainy seasons and a high proportion of endemic species found nowhere else. One such endemic species is Melanerpes chrysogenys, the golden-cheeked woodpecker. Very little is known regarding the life history or behavior of this important cavity-nesting bird. This study was conducted from June to August 2019 at Estación de Biología Chamela, a tropical dry forest biological reserve in coastal Jalisco, Mexico. Our goal was to determine territory size of golden-cheeked woodpeckers in two habitats: 1) the dense foliage of its native tropical dry forest, and 2) domestic palm tree orchards in nearby towns. Territories were located by walking transects in both habitats (26 hectors in the forest and 15.4 in the palms) and, playing woodpecker vocalizations to locate individuals. Locations were pinpointed with GPS and a range finder and then mapped. Territory size was determined from the woodpecker’s reaction to the recorded vocalizations; locations defended in response to vocalizations were considered to be within territory boundaries. Territory size in both habitats was similar, around 0.5 hectors. The palm orchards showed greater territory densities (1.7/ha) compared to the forest (1.2/ha). This difference is likely due to the opportunistic nature of golden-cheeked woodpeckers who take advantage of available resources, such as fruit trees in a yard. Woodpeckers were also observed using tops of cut trees and telephone poles as temporary food storage receptacles even though it’s not common for species to store food in tropical habitats.

Cortnea Austin - Mapping Trail Networks of Turtle Ants in a Tropical Dry Forest of Western Mexico
Arboreal ants are important in the trophic ecology of tropical forests. They function as “ecosystem engineers”, yet their behavior remains largely a mystery. In the tropical dry forest of western Mexico, colonies of the arboreal turtle ants Cephalotes goniodontus nest and forage. They work as a collective colony to develop and maintain a network using pheromones to establish and reinforce foraging trails. These trails are constrained by the current network of surrounding vegetation such as tree branches, shrubs, and vines. During June-August 2019, I investigated how turtle ant trail networks change over time at Estación de Biología Chamela. I worked with Stanford professor Deborah Gordon to map three separate colonies in the surrounding forest. Each main trail was evident from heavy traffic of ants. Nodes on the main trail were labeled with fine wire and tape to easily track the network from day to day. Distance (cm) was measured from node to node and the repeatability, or likelihood of the exact path being reinforced, was determined. Surrounding nodes were also measured and recorded, extending at least 5 nodes away from the main trail. Over ten days, we recorded how each colony network was maintained or adjusted, and developed maps to represent the change over time. Though drastic changes occurred from day to day, the network ultimately remained stable.

Thomas McIntyre (Graduate Student) - Are Highways Stressful for Pikas? Analysis of Stress Hormones of Ochotona princeps Living Adjacent to Interstate 90
Human-modified landscapes disrupt ecosystem connectivity, harming wildlife populations. Some wildlife species live in modified habitats along roads, but their fitness in these stressful environments is poorly understood. Chronic stress alters behavior, reduces reproduction rates, and has been linked to reduced survival. In the Cascade Range of central Washington, American pikas (Ochotona princeps) have colonized anthropogenic rock embankment used for stabilization along Interstate 90 (I-90), but no research to date has determined the fitness or success of this population. To measure basal stress levels of this population, we extracted fecal glucocorticoid metabolites (GCM) from fresh fecal samples. We compared chronic stress levels in pikas adjacent to I-90 with those living in similar rock embankment in a rails-to-trails state park, and in natural talus patches. We also assessed the correlation between fecal GCM concentrations and potential stressors at a subset of sites by measuring environmental temperatures, elevation, and noise levels. A generalized linear mixed model was used to determine differences in GCM concentrations among habitats and assess the potential effects of these environmental variables on stress. Fecal GCM concentrations varied among the 3 habitats. Animals in the I90 habitat had the lowest fecal GCM levels, potentially indicating a suppressed stress response due to their chronic exposure to stressors.

Jessica Luna - Effect of Hurricane Patricia on Habitat Use by the Mexican Spotted Wood Turtle in a Tropical Dry Forest
Rinochlemmys rubida, more commonly known as the Mexican spotted wood turtle, is a small, terrestrial turtle endemic to the tropical dry forests of western Mexico. In October 2015, the devasting winds of Hurricane Patricia swept through the Tropical Dry Forest at the Biological Station in Chamela, Mexico where research on Rhinoclemmys was already underway. The strong winds broke branches, toppled trees, and deposited considerable woody debris onto the forest floor. In this study, we investigated how Mexican spotted wood turtles have responded to this disturbance. We focused on whether turtles have shown changes in patterns of movement, and habitat/shelter use after Hurricane Patricia. We radiotracked movements of 12 turtles (6 males and 6 females) during summers of 2017 and 2018 to quantify potential changes in home range size, microhabitat use, and activity patterns after the hurricane. We also measured the composition (leaf litter, vegetation, woody debris, bare soil) of microhabitats in the forest understory, and locations used by turtles, within 1x1 meter plots before the hurricane (2015) and recorded changes in the same plots after the hurricane (2017, 2018). Woody debris increased significantly in the forest understory after Hurricane Patricia, whereas vegetation