Drivers of intraspecific variation in seed dispersal can differ across two species of fleshy-fruited savanna plants

Abstract

Various factors may mediate the visitation of frugivores to fruiting plants, which can dictate the quantum of seeds removed (dispersed) away from the parent plant. Past studies have laid emphasis on species-specific factors and environmental contexts that frugivores may use as cues to make foraging decisions and differentially visit various plant species. However, differences in plant traits (intrinsic factors) and local environmental contexts (extrinsic factors) can influence the diversity and abundance of frugivores that visit individual plants of the same species, resulting in intraspecific variation in seed dispersal. We observed individuals of two co-fruiting plant species with morphologically similar fruits—Naringi crenulata and Ziziphus oenopolia—for 134 h and examined the influence of fruit crop size, plant height, and fruiting neighborhood on the diversity of visiting avian frugivores and quantum of fruit removal for individual plants. We found that despite their similarity in fruits and sharing of a similar set of frugivore species, the two plant species differed in how they attracted frugivores, with consequences for fruit removal rates. Fruit crop size was an important determinant of fruit removal for N. crenulata¸ while plant height led to greater visitation and fruit removal for Z. oenopolia. We discuss potential reasons for the difference in frugivore visitation and fruit removal for the two plant species. Our results support a growing body of evidence that intraspecific variation in seed dispersal is pervasive and highly context-dependent, and describe frugivore interactions of two plant species from an understudied tropical savanna.