Award Date

5-15-2026

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Life Sciences

First Committee Member

Daniel Thompson

Second Committee Member

Elizabeth Stacy

Third Committee Member

Sean Neiswenter

Fourth Committee Member

Haroon Stephen

Number of Pages

96

Abstract

The Nevada endemic dune beetle Pseudocotalpa giulianii is currently known only from two dune systems in Amargosa Valley, Nevada, yet much of its life cycle occurs below the sand surface and remains poorly documented. This thesis addresses key gaps in adult-stage biology and egg-stage development that are relevant to understanding reproduction, vulnerability, and habitat requirements in this dunerestricted species.

To characterize adult sexual dimorphism and life history, I quantified morphological differences between males and females and measured sex-specific adult survival under laboratory conditions relative to the aboveground flight season. Males and females overlapped broadly in external body size, but tarsal claw morphology provided a reliable, size-independent diagnostic trait, as males possessed markedly longer tarsal claws than females. Adult lifespan differed strongly between sexes, with males surviving an average of 20.23 ± 0.72 days (mean ± SE), approximately the duration of the brief aboveground flight season, whereas females persisted substantially longer, surviving 47.95 ± 1.70 days under laboratory conditions. To evaluate whether sex differences in survival were associated with differences in energetic reserves, I quantified whole-body triglyceride and protein content. These measures scaled with body size but did not show clear sex-specific differences after accounting for size, suggesting that longevity differences may be driven more by allocation and/or behavior than by larger initial size-adjusted lipid stores.

To characterize egg-stage ecology, I quantified female egg production and oviposition patterns, estimated incubation duration under controlled laboratory conditions, and tested egg hatch success across sand moisture treatments. Eggs required approximately five to six weeks to hatch under laboratory conditions, with an estimated mean incubation period of 37.7 days. Hatch success was strongly moisture dependent: eggs failed to hatch in dry sand (0% gravimetric H₂O), but hatched readily in moist sand, with no clear differences among the moisture treatments tested (3%, 5%, and 10% gravimetric H₂O).

Together, these results extend the effective reproductive timeline well beyond the visible flight season, indicate that sex differences in adult lifespan are not explained by differences in size-adjusted adult triglyceride or protein storage, and identify subsurface moisture as an important habitat feature for successful hatching. This work provides baseline life-history information for P. giulianii and highlights priority directions for future research on underground stages that likely govern recruitment and population persistence.

Keywords

desiccation; female longevity; maternal investment; non-feeding adults; Rutelinae; Scarabaeidae

Disciplines

Ecology and Evolutionary Biology | Entomology | Environmental Sciences | Natural Resources and Conservation | Terrestrial and Aquatic Ecology

File Format

PDF

File Size

2500 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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