Temporal and spatial variation in soil moisture is known to drive phenotypic differentiation within and among plant populations. Here we investigate trait variation and plasticity along a fine-scaled soil moisture gradient between two sympatric monkeyflowers: Erythranthe guttata and a close relative, Erythranthe serpentinicola D.J. Keil (Phrymaceae). E. serpentinicola is endemic to the central coast of California in ephemerally wet serpentine rock outcrops that are adjacent to perennially wet seeps where Erythranthe guttata typically occurs. Morphological, physiological, phenological and soil moisture data data was collected along an environmental gradient from rock outcrop to seep habitats. We collected seed from rock outcrops and seeps to grow under common conditions, then collected morphological, physiological, and phenological data to determine whether the trait divergence in the field was maintained. 

Field research took place in the USA, San Luis Obispo County, CA in the City Open Spaces of San Luis Obispo in two different sites near perennial serpentine seeps with surrounding rock outcrops: Laguna Lake Park (33.9036 °N, 117.9398 °W) and South Hills (35.2635 °N,-120.66300 °W). Another site: Irish Hills (35.2522 °N,-120.7031 °W) was excluded from analyses. GPS coordinates provide general locations of each open space, not any rare or threatened species. Lab research took place at California Polytechnic State University, San Luis Obispo, Biological Sciences Department, 1 Grand Ave., San Luis Obispo, CA 93407. Morphological and phenological data was primarily collected using a Survey123 survey form in the field or the greenhouse. Physiological data, stomatal density and specific leaf area (SLA), were collected in the lab at Cal Poly, SLO, and manually added to the data downloaded from Survey123. Raw data was processed and analyzed with R statistical software (v4.1.2; R Core Team 2021).

Windows Excel to open csv files and R statistical software (v4.1.2; R Core Team 2021) for the R markdown and R script files.