On the adequacy of fruit removal as a proxy for fitness in studies of bird‐mediated phenotypic selection

PALACIO, FACUNDO X.; CATAUDELA, J. FRANCISCO; MONTALTI, D.; ORDANO, M.

AMERICAN JOURNAL OF BOTANY

BOTANICAL SOC AMER INC

Año: 2023

0002-9122

Premise: In fleshy‐fruited plants, fruit removal is widely used as a proxy for plantreproductive success. Nevertheless, this proxy may not accurately reflect the numberof seeds dispersed, an assumed better proxy for total fitness (fruit removal × meannumber of seeds dispersed per fruit).Methods: We examined under what circumstances fruit removal can be reliable as aproxy for total fitness when assessing bird‐mediated selection on fruit traits. In threepopulations of the Blue Passionflower (Passiflora caerulea), we used the number offruits pecked per plant as a surrogate for fruit removal to estimate phenotypicselection on fruit and seed traits, and simulations of the effect of the fruit‐seednumber trade‐off on the number of fruits removed.Results: Fruit removal was a good indicator of fitness, accounting for 55 to 68% of thevariability in total fitness, measured as total number of seeds removed. Moreover,multivariate selection analyses on fruit crop size, mean fruit diameter and mean seednumber using fruit removal as a fitness proxy yielded similar selection regimes tothose using total fitness. Simulations showed that producing more fruits, a lowernumber of seeds per fruit, and a higher variability in seed number can result in anegative relationship between fruit removal and total fitness.Conclusions: Our results suggest that fruit removal can be reliably used as a proxy fortotal fitness when (1) there is a weak fruit number‐seed number trade‐off, (2) fruitcrop size and fruit removal correlate positively, and (3) seed number variability doesnot largely exceed fruit number variability