Evolution of pollination by frugivorous birds in Neotropical Myrtaceae

Fleshy fruit traits and seed dispersers: which traits define syndromes?

BACKGROUND AND AIMS

Fruit traits and their inter-relationships can affect foraging choices by frugivores, and hence the probability of mutualistic interactions. Certain combinations of fruit traits that determine the interaction with specific seed dispersers are known as dispersal syndromes. The dispersal syndrome hypothesis (DSH) states that seed dispersers influence the combination of fruit traits found in fruits. Therefore, fruit traits can predict the type of dispersers with which plant species interact. Here, we analysed whether relationships of fruit traits can be explained by the DSH. To do so, we estimated the inter-relationships between morphological, chemical and display groups of fruit traits. In addition, we tested the importance of each trait group defining seed dispersal syndromes.

METHODS

Using phylogenetically corrected fruit trait data and fruit-seed disperser networks, we tested the relationships among morphological, chemical and display fruit traits with Pearson's correlations and phenotypic integration indices. Then, we used perMANOVA to test if the fruit traits involved in the analysis supported the functional types of seed dispersers.

KEY RESULTS

Morphological traits showed strong intragroup relationships, in contrast to chemical and display traits whose intragroup trait relationships were weak or null. Accordingly, only the morphological group of traits supported three broad seed disperser functional types (birds, terrestrial mammals and bats), consistent with the DSH.

CONCLUSIONS

Altogether, our results give some support to the DSH. Here, the three groups of traits interacted in different ways with seed disperser biology. Broad functional types of seed dispersers would adjust fruit consumption to anatomical limitations imposed by fruit morphology. Once this anatomical filter is sovercome, seed dispersers use almost all the range of variation in chemical and display fruit traits. This suggests that the effect of seed dispersers on fruit traits is modulated by hierarchical decisions. First, morphological constraints define which interactions can actually occur; subsequently, display and composition determine fruit preferences.

The Taming of Psidium guajava: Natural and Cultural History of a Neotropical Fruit

Guava (Psidium guajava L., Myrtaceae) is a Neotropical fruit that is widely consumed around the world. However, its evolutionary history and domestication process are unknown. Here we examine available ecological, taxonomic, genetic, archeological, and historical evidence about guava. Guava needs full sunlight, warm temperatures, and well-distributed rainfall throughout the year to grow, but tolerates drought. Zoochory and anthropochory are the main forms of dispersal. Guava's phylogenetic relationships with other species of the genus Psidium are unclear. A group of six species that share several morphological characteristics are tentatively accepted as the Psidium guajava complex. DNA analyses are limited to the characterization of crop genetic diversity within localities and do not account for possible evolutionary and domestication scenarios. A significant amount of archeological information exists, with a greater number and older records in South America than in Mesoamerica, where there are also numerous historical records. From this information, we propose that: (1) the guava ancestor may have originated during the Middle or Late Miocene, and the savannas and semi-deciduous forests of South America formed during the Late Pleistocene would have been the most appropriate ecosystems for its growth, (2) the megafauna were important dispersers for guava, (3) dispersal by humans during the Holocene expanded guava's geographic range, including to the southwestern Amazonian lowlands, (4) where its domestication may have started, and (5) with the European conquest of the Neotropics, accompanied by their domestic animals, new contact routes between previously remote guava populations were established. These proposals could direct future research on the evolutionary and domestication process of guava.