Effects of herbivore identity on plant fecundity

Abstract

Herbivores are pervasive, yet their effects on plant fecundity are often variable. One potential source of variation in herbivore impacts results from differing feeding modes of herbivores. We examined the relative importance of inflorescence-feeding insects versus large ungulates in affecting the fecundity of Balsamorhiza sagittata (Asteraceae), a dominant native perennial forb in western Montana, USA. We quantified these effects across four sites that varied in elevation to determine how consistent herbivore impacts were across these divergent sites. Insect herbivores were present in flower heads at all sites but they significantly depressed plant fecundity at two of the four sites. At the two sites where herbivore suppression had significant effects, this treatment let to 1.6 and 3.4-fold increases in seed production, respectively. In contrast, across all sites ungulates had minimal impacts on balsamroot flower and seed production. Seed addition experiments revealed that at some sites and in some years B. sagittata is seedlimited, as there was a positive relationship between seed input and seedling recruitment. Thus, reductions in seed production from heavy insect herbivory may limit balsamroot recruitment in some locations.Overall, results show that inconspicuous insects have stronger effects on balsamroot fecundity than do mammalian herbivores, but the magnitude of negative impacts at both the individual and populationlevel vary by site.

Rodent seed predators and a dominant grass competitor affect coexistence of co‐occurring forb species that vary in seed size

“…Fecundity was measured on adult plants that had no visible evidence of herbivory. For three target species ( Balsamorhiza sagittata , Lithospermum ruderale , and Lupinus sericeus ), we utilized fecundity estimates (in the absence of herbivory) from our previous work (Amsberry & Maron, ; Bricker & Maron, ; Bricker, Pearson, & Maron, ), and for Artemisia ludoviciana , we obtained fecundity estimates from the literature, which were also made in F. campestris grasslands in western Montana (Harvey, ). For the rest of our target species, we quantified average per capita seed production in June and July 2016.…”

Non‐target effects of broadleaf herbicide on a native perennial forb: a demographic framework for assessing and minimizing impacts

“…Arrowleaf balsamroot grows in deep sandy soil in open areas, ranging from grasslands to sagebrush steppe to open Ponderosa pine Pinus ponderosa forests, sometimes forming spectacular stands (Taylor 1992). It is an ecologically important species because its relatively large, nutritious seeds are predated by a number of vertebrate and invertebrate species (Amsberry and Maron 2006).…”

Indirect positive effects ameliorate strong negative effects of Euphorbia esula on a native plant

“…Balsamorhiza sagittata is a large dominant native forb whose shoots, flowers and seeds are commonly eaten by native generalist herbivores, such as pronghorn, bighorn sheep, mule deer and deer mice Pitt 1979, 1991;Burell 1982;USDA 1988). Seeds of B. sagittata are also consumed by specialist insects (Amsberry and Maron 2006) that live in the seed head (capitulum) and feed as larvae.…”