Study Area
This study was conducted in the spring of 2017 at the Phillips 66 Oil Refinery (35.0388889, -120.5894444) in San Luis Obispo County, California (Fig. 2). The region is characterized by a Mediterranean-type climate with cool, wet winters and hot, dry summers, while also receiving occasional inputs of water from coastal fog (Baguskas et al. , 2016). San Luis Obispo County receives an average precipitation of 33.1 cm annually and an average wind speed of 10.83 km/hr (November – May) with average low and high temperatures range from 5.92°C - 18.9°C during the growing season (Western Regional Climate Center 2020).
In our study area, Phillips 66 was required to mitigate for their oil development by establishing protected areas where extant populations are regularly monitored and restrict management actions that could negatively affect L. nipomensis populations (USFWS, 2009).The protected area in which we conducted our study is a coastal back dune ecosystem and the oldest part of a dune complex. These less disturbed areas often have later successional plants with increased soil stability as well as higher plant and insect diversity (Buckler, 1979; Miller, Gornish and Buckley, 2010; Ferrier et al. , 2012). The study site is dominated by non-native, invasive perennial veldt grass (Ehrharta calycina ) with scattered native annual forbs and perennial shrubs. The area is actively grazed by cattle during L. nipomensis dormant season (June-November) to suppress the invasive veldt grass.
The entire population of L. nipomensis is restricted to seven colonies within the Phillips 66 protected area. Two of the colonies were excluded due to their wide and sparse distribution, making these areas ineffective for targeted sampling. One colony was newly rediscovered from historic occurrence data not found until partway through the course of the study. A fourth population was located along a roadside with different ambient disturbance characteristics compared to other areas. We conducted plant visitor observations and vegetation monitoring at the remaining three colonies within the protected area in accordance to our California Fish and Wildlife permit (Permit No. 2081(a)-16-010) (Fig. 2).