Population variation in the intensity of fruit infestation and pre-dispersal seed predation in Yucca schidigera (Asparagaceae) by its obligate pollinator

Abstract

Variation in the occurrence and the intensity of pre-dispersal seed predation can help understand ecological and evolutionary dynamics of plant populations. Pre-dispersal seed predation can vary in intensity, resulting in costs that differ in magnitude among populations. We examined variation in the cost of pre-dispersal seed predation across nine Yucca schidigera populations, by quantifying yucca moth infestation, damage on fertile seeds and seed mass in 650 fruits sampled from 73 Yucca plants. We recorded Tegeticula mojavella larvae on 100% of the Y. schidigera plants. Across populations, mean infestation rates ranged from 2.9 to 6.11 larvae per fruit. Despite slight variation in the level of fruit infestation, predation on mature seeds differed among the nine populations, ranging from 10 to 26%. Mean seed mass and germination rate differed among populations, but the effect of larvae infestation on these traits was not significant. Altogether, our results demonstrate that infestation and pre-dispersal seed predation by yucca moths differ significantly across populations of Y. schidigera. Variable ratios of seed predation result in different costs across plant populations, despite experiencing similar infestation ratios. It seems that, regardless of its spatial distribution, the interaction between Y. schidigera and T. mojavella is dependent on local ecological factors that regulate oviposition and seed predation.