Available at: https://digitalcommons.calpoly.edu/theses/3187
Date of Award
12-2025
Degree Name
MS in Biological Sciences
Department/Program
Biological Sciences
College
College of Science and Mathematics
Advisor
Dena Grossenbacher
Advisor Department
Biological Sciences
Advisor College
College of Science and Mathematics
Abstract
Environmental heterogeneity can impose fluctuating selection pressures on species across space and time. If variations of a trait provide fitness benefits in certain environmental conditions but not others, these fitness tradeoffs under fluctuating selection could be a means of maintaining intraspecific variation. A common type of intraspecific variation is the production of anthocyanins, pigments responsible for red, pink, and blue colors in plants and that can also provide protection from abiotic stressors, such as water limitation and heavy metals. Leptosiphon parviflorus Benth. (Polemoniaceae, variable linanthus) is an annual wildflower whose individuals produce either pink or white flowers, and both flower color morphs often co-occur within populations. To assess potential fitness differences under a combination of abiotic stressors, pink- and white-flowered morphs from a population originating on serpentine soil were subjected to a 2 × 2 factorial greenhouse experiment of high and low magnesium and benign and limited watering conditions. Fitness was measured and modeled in terms of germination, survival to flowering, flower count, and lifetime fitness. Pink- and white-flowered morphs did not differ in probability of germinating nor in survival to flowering, regardless of magnesium conditions. White-flowered morphs had greater flower production than pink-flowered morphs overall. White-flowered morphs also had greater lifetime fitness under all treatments compared to pink-flowered morphs, suggesting a cost to floral anthocyanin production. The absence of observed fitness tradeoffs suggests that other stressors, such as nutrient limitation, heavy metal stress, or other combinations with water and magnesium stress, may be responsible for maintaining this flower color polymorphism.