A synthesis of animal‐mediated seed dispersal of palms reveals distinct biogeographical differences in species interactions

Abstract

Aim:To synthesize published knowledge on palm-frugivore seed dispersal observations and to test whether broad-scale differences in geographic coverage, diversity, composition and functional structure of plant-animal interactions emerge between biogeographical regions.Location: Neotropics and Afrotropics. Methods:We constructed a meta-network for both regions by aggregating observations of pairwise palm-frugivore interactions from the primary literature. We assessed sampling completeness with accumulation curves and estimated knowledge gaps for individual palm species and geographic units within biogeographical regions. We compared the taxonomic composition as well as structural indices of regional interaction networks and tested whether functional trait matching (i.e., the relationship between palm fruit size and frugivore body size) differs between regions. Results:A total of 750 unique pairwise interaction records were retrieved from the primary literature covering 340 frugivores and 126 palms. Sampling completeness of frugivore interactions within biogeographical regions and for individual palm species was low (often <50%), geographic coverage limited, and relative knowledge gaps were largest in areas with high palm species richness.Interaction diversity and network modularity was larger in the Neotropics than the Afrotropics. A positive fruit size-body mass relationship (i.e., functional trait matching) was statistically significant in the Afrotropics, but not in the Neotropics. Main conclusions:Available data on palm-frugivore interactions suggest major biogeographical differences in ecological networks among regions, even when taking differences in palm species richness into account. The Neotropics showed a larger interaction diversity and more modular network structure than the Afrotropics.Broad-scale morphological trait matching among plants and frugivores was only observed in the Afrotropics. The lack of a Neotropical trait matching relationship might be driven by the late Quaternary extinctions of mammalian megafauna in this region. Although our work has increased the digital availability of palm-frugivore -

Associated evolution of fruit size, fruit colour and spines in Neotropical palms

“…The palms are a characteristic element of tropical habitats (Couvreur & Baker, 2013; Kissling et al, 2012) and their fruits are a keystone resource for the tropical fauna (Fleming & Kress, 2013). The great morphological diversity in palm fruits and seeds (Figure 1a‐c) (Henderson et al, 1995) allows seed dispersal by a wide range of frugivores, from small songbirds to elephants and tapirs (Muñoz, Trøjelsgaard, & Kissling, 2019; Zona & Henderson, 1989). This variety of morphological characteristics and interactions can be roughly mapped into two main seed‐dispersal syndromes: small‐colourful fruits dispersed mainly by birds and large‐dull‐coloured fruits dispersed mainly by mammals.…”

Multiple External Seed Dispersers Challenge the Megafaunal Syndrome Anachronism and the Surrogate Ecological Function of Livestock

“…In summary, our results agree with Howe's (1985) critical view that the megafaunal syndrome hypothesis suffers from a general lack of knowledge on the natural history of seed dispersal of many large-fruited plants. A knowledge gap in the number of interactions between Neotropical palms and vertebrates has been recently highlighted (Muñoz et al, 2019). For instance, Donatti et al (2007) expressed their surprise about the survival of some plant species, exemplified by the apparent lack of contemporary dispersers and dispersal mechanisms in A. speciosa, and only three interactions with frugivorous species have been recorded for this palm in a recent review (Muñoz et al, 2019).…”

“…A knowledge gap in the number of interactions between Neotropical palms and vertebrates has been recently highlighted (Muñoz et al, 2019). For instance, Donatti et al (2007) expressed their surprise about the survival of some plant species, exemplified by the apparent lack of contemporary dispersers and dispersal mechanisms in A. speciosa, and only three interactions with frugivorous species have been recorded for this palm in a recent review (Muñoz et al, 2019). However, we found that this palm is extensively dispersed primarily by a large macaw (Ara ararauna) and at least by seven secondary ground-and tree-dwelling dispersers, including rodents (see b Despite no fruit consumption, feces evaluated for the presence of seeds of other palm species confirmed the lack of seed dispersal.…”

“…Among large-fruited plants providing abundant food for multiple organisms, including human populations, palms (Arecaceae) have been highlighted as a keystone group of generally poor conservation status (Henderson, 2002;Smith, 2015). Information on the seed dispersal of large-fruited palms is limited (Zona and Henderson, 1989;Eiserhardt et al, 2011;Muñoz et al, 2019). In fact, previous studies attributed to extinct megafauna the dispersal of palm species because of the lack of essential natural history observations on the identity of current seed dispersers.…”

“…In fact, previous studies attributed to extinct megafauna the dispersal of palm species because of the lack of essential natural history observations on the identity of current seed dispersers. Moreover, one of the main conclusions of a synthesis of palm-frugivore interactions published very recently is that "massive knowledge gaps of interaction diversity remain in the tropics" (Muñoz et al, 2019), which may be partially due to the recent regional and global declines and extinctions of many of their main primary dispersers (de Andrade et al, 2015;Lanes et al, 2016;Baños-Villalba et al, 2017).…”