The insect‐focused classification of fruit syndromes in tropical rain forests: An inter‐continental comparison

Abstract

We propose a new classification of rain forest plants into eight fruit syndromes, based on fruit morphology and other traits relevant to fruit‐feeding insects. This classification is compared with other systems based on plant morphology or traits relevant to vertebrate fruit dispersers. Our syndromes are based on fruits sampled from 1,192 plant species at three Forest Global Earth Observatory plots: Barro Colorado Island (Panama), Khao Chong (Thailand), and Wanang (Papua New Guinea). The three plots differed widely in fruit syndrome composition. Plant species with fleshy, indehiscent fruits containing multiple seeds were important at all three sites. However, in Panama, a high proportion of species had dry fruits, while in New Guinea and Thailand, species with fleshy drupes and thin mesocarps were dominant. Species with dry, winged seeds that do not develop as capsules were important in Thailand, reflecting the local importance of Dipterocarpaceae. These differences can also determine differences among frugivorous insect communities. Fruit syndromes and colors were phylogenetically flexible traits at the scale studied, as only three of the eight seed syndromes, and one of the 10 colors, showed significant phylogenetic clustering at either genus or family levels. Plant phylogeny was, however, the most important factor explaining differences in overall fruit syndrome composition among individual plant families or genera across the three study sites. Abstract in Melanesian is available with online material.

Factors that shape large‐scale gradients in clonality

“…Our findings for clonality are aligned with previous evidence showing that seed size is more closely related to growth form than with environmental variables including latitude, NPP and vegetation type (Moles et al, 2007). Similarly, fruit syndromes are better explained by species' phylogenetic relations than by sites of species (Dahl et al, 2019). In short, evidence is accumulating that we may need to consider species' traits as a coordinated suite that respond to environmental variables, rather than studying them one at a time in the future.…”

Host specificity and interaction networks of insects feeding on seeds and fruits in tropical rainforests

“…Plant assemblages at different rainforests may be phylogenetically different or may possess different traits, or both. Tree assemblages are phylogenetically distinct in many rainforests (Webb 2000) and there are important differences in seed functional traits between our rainforest sites (Supporting information; Dahl et al 2019). Plant phylogenetic distance had an important effect on subnetwork structure (e.g.…”

“…Host specificity is likely to differ among insect guilds associated with fruit pulp versus seeds, as seeds are better chemically protected than pulp (Janzen 1971). Plant traits may also influence seed predator load and host specificity (Janzen 1971, 1980, Basset et al 2018, Dahl et al 2019). Low plant richness may favor high insect host specificity, as suggested by comparisons of insect herbivores in temperate and tropical forests (Novotny et al 2002).…”