Sites dominated by common fiddleneck (Amsinckia menziesii var. intermedia) support diverse plant-pollinator interactions

Biodiversity is declining at unprecedented rates worldwide due largely to
land use change and abnormal disturbance events. The high species
diversity and endemicity found in California’s coastal sage scrub (CSS)
are especially at risk from urban development and ongoing disturbance.
However, several CSS plant species have disturbance adaptations which may
allow them to serve as vital resources for insect pollinators when native
plant diversity is threatened. Common fiddleneck (Amsinckia menziesii var.
intermedia) is one of the first annual forbs to germinate in CSS and as a
result, it occurs in high density patches in early spring which
temporarily creates a near monoculture. Although fiddleneck is a prominent
CSS plant, particularly in areas that have experienced a disturbance
event, its larger ecological role is not well explored. Therefore, we
monitored ten sites across a disturbance gradient for two spring seasons
to assess the composition of plant-pollinator networks in
fiddleneck-dominated plots. We found fiddleneck supported a diverse
pollinator community with 68% of recorded taxa visiting fiddleneck. The
plants most frequently visited included two native annual forbs (common
fiddleneck and Phacelia distans) and two invasive annual forbs (Erodium
cicutarium and Brassica tournefortii). Plant and pollinator abundances
increased with increased mean precipitation. Additionally,
plant-pollinator networks changed over time; the number of links per
species increased throughout the season but did not differ amongst
disturbance types. Despite the numerical dominance of fiddleneck, CSS
supported a diversity of pollinator taxa and exhibited complex
plant-pollinator networks across the disturbance gradient.