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.

Fruit scent has evolved as a communication channel between plants and primates that disperse their seeds.

The decomposition of dead mammalian tissue involves a complex temporal succession of epinecrotic bacteria. Microbial activity may release different cadaveric volatile organic compounds which in turn attract other key players of carcass decomposition such as scavenger insects. To elucidate the dynamics and potential functions of epinecrotic bacteria on carcasses, we monitored bacterial communities developing on still-born piglets incubated in different forest ecosystems by combining high-throughput Illumina 16S rRNA sequencing with gas chromatography-mass spectrometry of volatiles. Our results show that the community structure of epinecrotic bacteria and the types of cadaveric volatile compounds released over the time course of decomposition are driven by deterministic rather than stochastic processes. Individual cadaveric volatile organic compounds were correlated with specific taxa during the first stages of decomposition which are dominated by bacteria. Through best-fitting multiple linear regression models, the synthesis of acetic acid, indole and phenol could be linked to the activity of Enterobacteriaceae, Tissierellaceae and Xanthomonadaceae, respectively. These conclusions are also commensurate with the metabolism described for the dominant taxa identified for these families. The predictable nature of in situ synthesis of cadaveric volatile organic compounds by epinecrotic bacteria provides a new basis for future chemical ecology and forensic studies.

The adaptive significance of fruit colour has been investigated for over a century. While colour can fulfil various functions, the most commonly tested hypothesis is that it has evolved to increase fruit visual conspicuousness and thus promote detection and consumption by seed dispersing animals. However, fruit colour is a complex trait which is subjected to various constraints and selection pressures. As a result, the effect of animal selection on fruit colour are often difficult to identify, and several studies have failed to detect it. Here, we employ an integrative approach to examine what drives variation in fruit colour. We quantified the colour of ripe fruit and mature leaves of 97 tropical plant species from three study sites in Madagascar and Uganda. We used phylogenetically controlled models to estimate the roles of phylogeny, abiotic factors, and dispersal mode on fruit colour variation. Our results show that, independent of phylogeny and leaf coloration, mammal dispersed fruits are greener than bird dispersed fruits, while the latter are redder than the former. In addition, fruit colour does not correlate with leaf colour in the visible spectrum, but fruit reflection in the ultraviolet area of the spectrum is strongly correlated with leaf reflectance, emphasizing the role of abiotic factors in determining fruit colour. These results demonstrate that fruit colour is affected by both animal sensory ecology and abiotic factors and highlight the importance of an integrative approach which controls for the relevant confounding factors.

Olfaction, the sense of smell, was a latecomer to the systematic investigation of primate sensory ecology after long years in which it was considered to be of minor importance.1 This view shifted with the growing understanding of its role in social behavior2 and the accumulation of physiological studies demonstrating that the olfactory abilities of some primates are on a par with those of olfactory-dependent mammals such as dogs and rodents.3,4 Recent years have seen a proliferation of physiological, behavioral, anatomical, and genetic investigations of primate olfaction. These investigations have begun to shed light on the importance of olfaction in the process of food acquisition. However, integration of these works has been limited. It is therefore still difficult to pinpoint large-scale evolutionary scenarios, namely the functions that the sense of smell fulfills in primates’ feeding ecology and the ecological niches that favor heavier reliance on olfaction. Here, we review available behavioral and physiological studies of primates in the field or captivity and try to elucidate how and when the sense of smell can help them acquire food.

The senses play critical roles in helping animals evaluate foods, including fruits that can change both in colour and scent during ripening to attract frugivores. Although numerous studies have assessed the impact of colour on fruit selection, comparatively little is known about fruit scent and how olfactory and visual data are integrated during foraging. We combine 25 months of behavioural data on 75 wild, white-faced capuchins ( Cebus imitator ) with measurements of fruit colours and scents from 18 dietary plant species. We show that frequency of fruit-directed olfactory behaviour is positively correlated with increases in the volume of fruit odours produced during ripening. Monkeys with red–green colour blindness sniffed fruits more often, indicating that increased reliance on olfaction is a behavioural strategy that mitigates decreased capacity to detect red–green colour contrast. These results demonstrate a complex interaction among fruit traits, sensory capacities and foraging strategies, which help explain variation in primate behaviour.

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The ecological function of fruit colour has been the focus of many studies. The most commonly tested hypothesis is that fruit colour has evolved to facilitate detection by seed-dispersing animals. We tested whether distributions of fruit colours are consistent with the hypothesis that colour is an evolved signal to seed dispersers using a comparative community approach. We compared the contrast between ripe fruits and leaf backgrounds at two sites, one in Madagascar where seed dispersers are primarily night-active, red–green colour-blind lemurs, and the other in Uganda, where most vertebrate seed dispersers are day-active primates and birds with greater capacity for colour vision. We show that fruits in Uganda have higher contrast against leaf background in the red–green and luminance channels whereas fruits in Madagascar contrast more in the yellow–blue channel. These results indicate that fruit colour has evolved to contrast against background leaves in response to the visual capabilities of local seed disperser communities.