Seed dispersers shape the pulp nutrients of fleshy-fruited plants

Abstract

The dispersal-syndrome hypothesis posits that fruit traits are a product of selection by frugivores. Although criticized as adaptationist, recent studies have suggested that traits such as fruit or seed size, colour and odour exhibit signatures that imply selection by animal mutualists. These traits imply nutritional rewards (e.g. lipid, carbohydrate), attracting frugivores; however, this remains incompletely resolved. Here, we investigated whether fruit nutrients (lipid, sugar, protein, vitamin C, water content) moderate the co-adaptation of key disperser-group mutualisms. Multivariate techniques revealed that fruit nutrients assembled non-randomly and grouped according to key dispersal modes. Bird-dispersed fruits were richer in lipids than mammal-dispersed fruits. Mixed-dispersed fruits had significantly higher vitamin C than did mammal- or bird-dispersed fruits separately. Sugar and water content were consistently high irrespective of dispersal modes, suggesting that these traits appeal to both avian and mammalian frugivores to match high-energy requirements. Similarly, protein content was low irrespective of dispersal modes, corroborating that birds and mammals avoid protein-rich fruits, which are often associated with toxic levels of nitrogenous secondary compounds. Our results provide substantial over-arching evidence that seed disperser assemblages co-exert fundamental selection pressures on fruit nutrient trait adaptation, with broad implications for structuring fruit–frugivore mutualism and maintaining fruit trait diversity.

How Does Changing Environment Influence Plant Seed Movements as Populations of Dispersal Vectors Decline?

“…Seed dispersal responses to changing environmental conditions can be influenced by plant traits, specifically fruit and seed morphological and biochemical characteristics. Studies have suggested that traits such as fruit or seed size, color and odor influence the way dispersers choose them as food [ 16 ], thereby shaping plant distribution. Here, results revealed a large proportion of studies that mentioned achene, capsule, drupe, fleshy, and nuts as fruit/seed types of many endozoochorous and ornithochorous plant species.…”

Multiple intrinsic and extrinsic drivers influence the quantity and quality components of seed dispersal effectiveness in the rare shrub Lindera subcoriacea

“…The single-seeded drupes of L. subcoriacea mature simultaneously in late July and early August (S1 Fig) , and although not documented in the species, are most likely avian-dispersed based on fruit traits [53][54][55] and observations for congeners [34,56]. Although L. subcoriacea has fruits/seeds of similar size to L. benzoin (ovate seeds are 7.02 ± 0.29 mm, n = 101 [37] and 7.02 ± 0.11 mm, n = 50 [57] long, respectively), L. subcoriacea individuals produce fewer fruits than L. benzoin (80 ± 178, n = 290 [37] and 164 ± 104, n = 11 [58], respectively).…”

Conflicting selection pressures on seed size and germination caused by carnivorous seed dispersers

“…gut passage effects) (Torres et al 2020), post-feeding movements (Tucker et al 2021), environmental conditions of deposition sites (Tochigi et al 2022), fruit morphology, abundance, and seed traits (e.g. size) (Lei et al 2021).…”

“…Variations in propagule traits that affect seed dispersal in plants have been attributed to selection exerted by dispersal vectors (Zhou et al 2013;Lei et al 2021). Seed size is a key trait for seed dispersal, and is pinpointed as one key attribute in the function of these dispersal agents (Ong et al 2022).…”