Low host specificity of herbivorous insects in a tropical forest. Nature

Department of Biology and Ecology, University of Ostrava, Ostrava, Moravskoslezský, Czech Republic
Nature (Impact Factor: 41.46). 05/2002; 416(6883):841-4. DOI: 10.1038/416841a
Source: PubMed


Two decades of research have not established whether tropical insect herbivores are dominated by specialists or generalists. This impedes our understanding of species coexistence in diverse rainforest communities. Host specificity and species richness of tropical insects are also key parameters in mapping global patterns of biodiversity. Here we analyse data for over 900 herbivorous species feeding on 51 plant species in New Guinea and show that most herbivorous species feed on several closely related plant species. Because species-rich genera are dominant in tropical floras, monophagous herbivores are probably rare in tropical forests. Furthermore, even between phylogenetically distant hosts, herbivore communities typically shared a third of their species. These results do not support the classical view that the coexistence of herbivorous species in the tropics is a consequence of finely divided plant resources; non-equilibrium models of tropical diversity should instead be considered. Low host specificity of tropical herbivores reduces global estimates of arthropod diversity from 31 million (ref. 1) to 4 6 million species. This finding agrees with estimates based on taxonomic collections, reconciling an order of magnitude discrepancy between extrapolations of global diversity based on ecological samples of tropical communities with those based on sampling regional faunas.

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    • "Complementary insights into the role of environmental filtering in community assembly can be gleaned using analyses of functional composition (Cadotte, Carscadden & Mirotchnick 2011). Most studies examining insect diversity have focused on species richness or taxonomic composition (Erwin 1982; Novotny et al. 2002, 2007; May 2010; Basset et al. 2012). Yet the literature on assembly rules in plant communities has underlined contrasts between patterns of taxonomic and functional diversity and composition (Baraloto et al. 2012; Lavorel et al. 2013). "
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    • "Recently, indices of species diversity have been applied to calculate how similar the parasite faunas of host species are (Novotny et al. 2002; Weiblen et al. 2006; Vinarski et al. 2007; Davies and Pedersen 2008; Poulin 2010), driving a new interest in the understanding of community similarity of host species, also known as faunal similarity. The Jaccard index is widely used to assess community similarity across geography and phylogeny, and for the case of parasites, a number of studies have shown that the similarity in species composition decreases exponentially with phylogenetic and geographic distance among the host species (Poulin 2003, 2010; Fellis and Esch 2005; Krasnov et al. 2005; Oliva and Gonz alez 2005; Poulin et al. 2011). "
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    • "The lack of increase in specialism toward the poles matches the patterns reported for other interaction types, which we also show to form well-linked webs in our study region (Appendix 2). Comparisons between tropical and temperate latitudes offer no evidence of latitudinal differences in the specialism of antagonistic interactions of herbivores and plants (Beaver 1979; Fiedler 1998; Novotny et al. 2002, 2006; Lewinsohn and Roslin 2008), or suggest an increase in specialism toward the equator (Dyer et al. 2007). An increase in specialism toward the equator has been also found in mutualistic interactions of plants and pollinators (Olesen and Jordano 2002; Armbruster 2006; Dalsgaard et al. 2011; Trojelsgaard and Olesen 2013), but such latitudinal trends sometimes disappear once sampling bias (Ollerton and Cranmer 2002; V azquez and Stevens 2004) or differences in plant diversity (Ollerton et al. 2006) have been accounted for. "
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