Four ways towards tropical herbivore megadiversity

Abstract

Most multicellular species alive are tropical arthropods associated with plants. Hence, the host-specificity of these species, and their diversity at different scales, are keys to understanding the assembly structure of global biodiversity. We present a comprehensive scheme in which tropical herbivore megadiversity can be partitioned into the following components: (A) more host plant species per se, (B) more arthropod species per plant species, (C) higher host specificity of herbivores, or (D) higher species turnover (beta diversity) in the tropics than in the temperate zone. We scrutinize recent studies addressing each component and identify methodological differences among them. We find substantial support for the importance of component A, more tropical host species. A meta-analysis of published results reveals intermediate to high correlations between plant and herbivore diversity, accounting for up to 60% of the variation in insect species richness. Support for other factors is mixed, with studies too scarce and approaches too uneven to allow for quantitative summaries. More research on individual components is unlikely to resolve their relative contribution to overall herbivore diversity. Instead, we call for the adoption of more coherent methods that avoid pitfalls for larger-scale comparisons, for studies assessing different components together rather than singly, and for studies that investigate herbivore beta-diversity (component D) in a more comprehensive perspective.

Influence of plant resistance traits in selectiveness and species strength in a tropical plant‐herbivore network

“…Th e increased precipitation during the wet season is likely to promote greater quality and quantity of host plants ( Reich et al, 1997 ;Asner et al, 2009 ;Janecke and Smith, 2011 ;López-Carretero et al, 2014 ), providing a fair variety of microhabitats and resources favoring richness and abundance of herbivores ( Janzen, 1993 ;Fernandes et al, 2004 ;Yarnes and Boecklen, 2005 ;López-Carretero, 2010 ;López-Carretero et al, 2014 ), and a homogeneous distribution of food resources for all herbivore species ( Lewinsohn et al, 2005 ;Lewinsohn and Roslin, 2008 ). Th ese factors are likely to be translated into increased plant species strength and herbivore selectiveness (or specialization) in the network.…”

Vertical canopy gradient shaping the stratification of leaf‐chewer–parasitoid interactions in a temperate forest

“…Herbivores and their parasitoids represent a major component of global insect diversity (Lewinsohn & Roslin, 2008; Price, 2002). Being one of the fundamental forces determining population dynamics and community structure in terrestrial ecosystems, parasitoids regulate herbivorous insect populations influencing host–plant use and promoting species diversification (Lill, Marquis, & Ricklefs, 2002; Stireman & Singer, 2003).…”

Functional traits reveal the expansion and packing of ecological niche space underlying an elevational diversity gradient in passerine birds

“…Despite the generality of these patterns, the underlying mechanisms are poorly understood [3][4][5]. Geographical gradients in richness may to some extent be explained by historical factors, particularly variation in the rate or time available for species diversification, yet they are also likely to reflect deterministic differences in the ecological capacity of environments to support diversity [3].…”

“…Accordingly, several analyses have confirmed that the richness of consumers is often tightly correlated with the richness or ecological diversity at lower trophic levels [4,11,12]. In contrast, the extent to which niche packing changes along diversity gradients is more contentious, not least because the underlying relationships are complex and difficult to measure [4,5]. One approach to addressing this question is to classify species into functional groups (e.g.…”

“…These models of niche packing and expansion are not mutually exclusive and both may occur in tandem ( figure 1c,d). However, the relative extent to which major gradients in richness are associated with an increased volume or packing of niche space remains disputed [4,5,10].…”