The dispersal syndrome hypothesis: How animals shaped fruit traits, and how they did not

Abstract

1. Fleshy fruits have evolved multiple times and display a tremendous diversity of colours, shapes, aromas and textures. For over a century this was attributed, at least in part, to frugivore-driven selection. The dispersal syndrome hypothesis posits that fruits and frugivores co-evolved, each exerting sufficient selective pressure on one another, and resulting to in suites of fruit traits that match frugivore behaviour, morphology and sensory capacities.2. In the last two decades of the past century, the dispersal syndrome hypothesis has been deemed overly adaptationist. Challenges are based on a variety of arguments, primarily that previous studies did not sufficiently incorporate a phylogenetic framework, and that non-adaptive factors can explain a great deal of extant fruit trait variation.3. In recent years, many studies have addressed these issues and found support for the dispersal syndrome hypothesis. As empirical evidence mounts, it's become increasingly clear that many fruit traits-primarily size, colour and scent-are strongly affected by frugivore trait preference. 4. At the same time, many studies do not sufficiently consider the many confounding factors involved in fruit trait evolution. 5. We review the evidence supporting the dispersal syndrome hypothesis and highlight the existing gaps in knowledge and the factors that are currently still not fully incorporated into the study of the evolution of fruit traits. K E Y W O R D S dispersal syndrome hypothesis, frugivory, fruit syndrome hypothesis, mutualism, plant-animal co-evolution, seed dispersal | 1159 Functional Ecology VALENTA ANd NEVO S U PP O RTI N G I N FO R M ATI O N Additional supporting information may be found online in the Supporting Information section.

What we talk about when we talk about color

“…4d). The morphological characteristics of fruit, including color, are known to be adapted to the sensory systems of frugivores that act as their seed dispersers, for vertebrates in general [45–47] and primates in particular [48–50]. And so our results support the hypothesis that communicative need in human cultures emphasize the colors of salient objects that stand out or attract attention in our shared visual system across a typical range of environments ‡ .…”

Yak Dung Seed Bank on the Qinghai-Tibetan Plateau: Effects of Grazing Season, Seed Characteristics and Forage Preferences

“…Therefore, we recommend further investigation in the following areas: (i) studies of dung seedling growth and development to more clearly de ne the contributions of the dung seed bank to grassland vegetation renewal; (ii) observation of livestock grazing behaviors (e.g., spatial patterns and frequency of defecation, distances traveled, etc.) on the QTP grassland, followed by the determination of the directed dispersal of speci c plant species through endozoochory, and nally examination of ongoing co-evolution between plants and animals, i.e., simultaneous evolution between interacting species (Maron et al 2019, Valenta andNevo 2020). Figure 4 Density, richness, and diversity of both dung seedlings (left) and the aboveground vegetation (right) during the warm and cold grazing seasons.…”

No Effect of Selective Maturation on Fruit Traits for a Bird-Dispersed Species, Sambucus racemosa

“…However, larger fruits may not always be preferred by some bird dispersers. Some frugivorous birds have a limit to the size of fruits they can ingest [ 37 ] with gape width limiting the ability of frugivores to process large fruits [ 38 ]. Therefore, the effects of selective maturation on fruit traits may also depend on what species of birds disperse the fruit.…”

“…Therefore, bird-dispersed plant species would selectively mature larger, but not seedier, fruits. On the other hand, some frugivorous birds are known to be limited in the size of fruits they can ingest [ 37 ], and several studies suggest that gape width limits the ability of frugivores to process large fruits [ 38 ]. Therefore, larger fruits may not always be preferred by bird dispersers.…”