Searching for keystone plant resources in fruit‐frugivore interaction networks across the Neotropics

Loss of endangered frugivores from seed dispersal networks generates severe mutualism disruption

Many tropical seed-dispersing frugivores are facing extinction, but the consequences of the loss of endangered frugivores for seed dispersal is not well understood. We investigated the role of frugivore endangerment status via robustness-to-coextinction simulations (in this context, more accurately described as robustness-to-partner-loss simulations) using data from the Brazilian Atlantic Forest biodiversity hotspot. By simulating the extinction of endangered frugivores, we found a rapid and disproportionate loss of tree species with dispersal partners in the network, and this surprisingly surpassed any other frugivore extinction scenario, including the loss of the most generalist frugivores first. A key driver of this pattern is that many specialist plants rely on at-risk frugivores as seed-dispersal partners. Moreover, interaction compensation in the absence of endangered frugivores may be unlikely because frugivores with growing populations forage on fewer plant species than frugivores with declining populations. Therefore, protecting endangered frugivores could be critical for maintaining tropical forest seed dispersal, and their loss may have higher-than-expected functional consequences for tropical forests, their regeneration processes, and the maintenance of tropical plant diversity.

Melastomataceae of the Parque Natural Municipal de São Lourenço, Espírito Santo, Brazil

Abstract The Atlantic Forest is one of the diversity centers of Melastomataceae in the world, and studies have been showing the great richness of its species in Espírito Santo, a state that once was entirely covered by this phytogeographic domain. We present here a floristic survey of the species of Melastomataceae in a protected area in this state, the Municipal Natural Park of São Lourenço, located at the municipality of Santa Teresa. We also present an identification key for the species, detailed descriptions, comments on distribution, habitat and phenology, photographs and illustrations. A thorough sampling was based on several expeditions during 2019 and 2020; in addition, we analyzed all specimens collected in the area and deposited in the herbaria FLOR, HUEFS, MBM, MBML, NY, RB, UPCB, US and VIES. The family has 10 genera and 56 species in the area, with Miconia having 42 species, Pleroma six and the genera Aciotis, Acisanthera, Bertolonia, Chaetogastra, Henriettea, Meriania, Microlicia and Mouriri represented by only one species each.

Frugivory and seed dispersal in a hyperdiverse plant clade and its role as a keystone resource for the Neotropical fauna

BACKGROUND AND AIMS

Much of our understanding of the ecology and evolution of seed dispersal in the Neotropics is founded on studies involving the animal-dispersed, hyperdiverse plant clade Miconia (Melastomataceae). Nonetheless, no formal attempt has been made to establish its relevance as a model system or indeed provide evidence of the role of frugivores as Miconia seed dispersers.

METHODS

We built three Miconia databases (fruit phenology/diaspore traits, fruit-frugivore interactions and effects on seed germination after gut passage) to determine how Miconia fruiting phenology and fruit traits for >350 species interact with and shape patterns of frugivore selection. In addition, we conducted a meta-analysis evaluating the effects of animal gut passage/seed handling on Miconia germination.

KEY RESULTS

Miconia produce numerous small berries that enclose numerous tiny seeds within water- and sugar-rich pulps. In addition, coexisting species provide sequential, year long availability of fruits within communities, with many species producing fruits in periods of resource scarcity. From 2396 pairwise interactions, we identified 646 animal frugivore species in five classes, 22 orders and 60 families, including birds, mammals, reptiles, fish and ants that consume Miconia fruits. Endozoochory is the main dispersal mechanism, but gut passage effects on germination were specific to animal clades; birds, monkeys and ants reduced seed germination percentages, while opossums increased it.

CONCLUSIONS

The sequential fruiting phenologies and wide taxonomic and functional diversity of animal vectors associated with Miconia fruits underscore the likely keystone role that this plant clade plays in the Neotropics. By producing fruits morphologically and chemically accessible to a variety of animals, Miconia species ensure short- and long-distance seed dispersal and constitute reliable resources that sustain entire frugivore assemblages.