Spatially inconsistent direct and indirect effects of herbivory on floral traits and pollination success in a tropical shrub

Abstract

Investigations on plant–animal interactions have traditionally focused on single interactions at a time (e.g. herbivory, pollination), yet plant fitness is generally influenced in complex ways by several interactions operating concurrently, and very little is known on the degree of spatial consistency of the direct and indirect effects that link different interactions. This paper evaluates experimentally whether direct and indirect effects of herbivory on male and female flower size and pollination success of the monoecious tropical shrub Cnidoscolus aconitifolius (Euphorbiaceae) remain consistent at three distant regions in Yucatan (southeastern Mexico). Plants were subjected to different levels of leaf defoliation, and treatment effects on floral traits (corolla area, corolla tube length, pollen production), and male and female components of pollination success (percent pollen removal, number of pollen tubes) were subsequently measured to evaluate the indirect effect of herbivory on plant reproductive success via pollination. Defoliation had significant direct effects on floral traits, but its indirect effects differed between the male and female components of pollination success. Moreover, the relationships between defoliation, floral traits and male and female pollination success varied spatially (i.e. between regions), although they were frequently more spatially‐consistent for male success than for female success. Results from this study stress the importance of explicitly testing for spatial variation in direct and indirect effects arising from plant‐animal interactions.

Pollination, Herbivory, and Habitat Fragmentation: Their Effects on the Reproductive Fitness of Angadenia berteroi, a Native Perennial Plant of the South Florida Pine Rocklands

“…This absence of effects is in contrast with several other studies demonstrating negative effects of herbivory on the same parameters we measured, such as decreased flower size (Mothershead and Marquis, 2000;Thompson et al, 2004, Parra-Tabla andHerrera, 2010), reduced nectar production (Irwin and Brody 2011), decreased pollen quality (Strauss et al, 1996;Parra-Tabla and Herrera, 2010), or altered floral sex ratios (Thompson et al, 2004;Avila-Sakar and Stephenson, 2006;Narbona and Dirzo, 2010; Parra-Tabla and Herrera, 2010). We did not measure every parameter (e.g., pollen number), however, so our conclusions must be regarded as provisional.…”

Pollen limitation, fruit abortion, and autonomous selfing in three populations of the perennial herbRuellia nudiflora

“…Hence, a multipopulation approach can provide a more robust understanding of how reproductive traits and extrinsic factors interact to affect plant fitness differentially across sites, as well as shed light on ecological factors responsible for spatial variation in the outcomes of selection (Moeller & Geber ; Vanhoenacker et al . ; Parra‐Tabla & Herrera ).…”

When resources don't rescue: flowering phenology and species interactions affect compensation to herbivory in Ipomopsis aggregata

“…Plants exhibit wide variation in their responses to herbivory. The challenge remains to understand the mechanisms driving that variation (Parra‐Tabla and Herrera 2010, Bagchi and Ritchie 2011). Compensatory response to damage can be predicated on stored nutrients (Wise and Abrahamson 2007) or more immediate availability of resources (Juenger and Bergelson 1997, Sharaf and Price 2004), pollen limitation (Mothershead and Marquis 2000), the timing of damage (Maschinski and Whitham 1989) and/or subsequent interactions with other floral enemies (Strauss and Irwin 2004).…”