Compartments in insect–plant associations and their consequences for community structure

Abstract

Summary 1.Compartmentation has been less explored than other forms of community structure. We assessed compartmentation of associations between insects and plants on a regional scale, and analysed some of its causes and consequences. The data set used was the host records of fruit flies (Diptera; Tephritidae) that breed in flowerheads of plants of the tribe Vernonieae (Asteraceae) in the Espinhaço Mountain range, Minas Gerais, Brazil. This data set was obtained with a consistent sampling protocol and is taxonomically fully resolved. 2. The binary association matrix had a total of 35 insect and 81 plant species. Most of the insects were specialized on plants of a single subtribe, genus or species group. Correspondence analysis showed that the association matrix is divided in six well-delimited compartments of insects specialized on subtribes or genera of plants. 3. Host dissimilarity among insects and insect dissimilarity among plants were expressed as Jaccard distances. Tests with a multi-response permutation procedure (MRPP) showed that both kinds of dissimilarities were higher among compartments than within them. 4. Monte Carlo randomizations were used to compare matrix parameters with values expected in the absence of compartments. In 4000 runs, the number of insect species that shared at least one host plant (ecological neighbours) was smaller than expected. Nevertheless, mean host similarity among insects, and the proportion of exclusive host plants used by each insect species did not differ from null model predictions. Host similarity of insects with their nearest neighbours in niche space was higher than expected by the null model. On the other hand, host similarity with farthest neighbours was lower than expected. 6. The observed compartmentation of insect/plant associations can be ascribed to the marked specialization of flowerhead tephritids, and allows the reduction of diffuse competition among insects. However, compartmentation did not decrease overall niche overlap among insects because reduction in number of neighbours is offset by increased overlap with species in the same compartment. Therefore, the pattern in this system cannot be derived from resource partitioning alone.

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

“…In these cases, regardless of their taxonomic identity, the most common species tend to interact at higher frequencies with greater number of species. Th is discrepancy could be the result of diff erences in the degree of generalization between these types of networks; whereas networks of mutualistic interactions tend toward generalization ( Bascompte et al, 2006 ), plant-herbivore networks are highly specialized ( Prado and Lewinsohn, 2004 ;Cagnolo et al, 2011 ;López-Carretero et al, 2014 ). Th is specialization has developed from a complex set of ecological, biochemical and historical factors ( Ehrlich and Raven, 1964 ;Novotny et al, 2002 ;Novotny and Basset, 2005 ;Ødegaard et al, 2005 ;Weiblen et al, 2006 ;Gómez-Zurita et al, 2007 ) that, in general, have promoted interactions within subgroups of available plant species regardless of their coverage or density.…”

“…Understanding the diff erent processes that infl uence the structuring of the antagonistic networks between plants and their herbivores is therefore an important challenge to understand the patterns of terrestrial biodiversity ( Lewinsohn et al, 2005 ). Plant-herbivore antagonistic networks are characterized by highly specialized interactions ( Cagnolo et al, 2011 ;López-Carretero et al, 2014 ) and a modular structure (i.e., nonrandom, compartmentalized pattern of interactions) ( Prado and Lewinsohn, 2004 ). However, relatively little is known about the ecological and phylogenetic mechanisms that promote particular patterns of these networks ( Vázquez et al, 2009 ).…”

“…Traditionally, the coevolutionary processes involved in the continuous defense and counterdefense of plants and herbivores has been invoked to explain the high specialization in their interactions ( Prado and Lewinsohn, 2004 ;Th ompson, 2005 ;Agrawal, 2007 ). Chemical and physical resistance traits of plants aff ect the foraging behavior and performance of herbivores, infl uencing the magnitude of their interaction with diff erent host plants ( Coley and Barone, 1996 ;Pilson, 2000 ;Poelman et al, 2008 ;Fatouros et al, 2014 ).…”

Network topology of stable isotope interactions in a sub-arctic raptor guild

“…Modular structures have previously been linked to an increased stability of the ecosystem process of concern, because any effects of perturbations likely will be restricted within isolated modules (Prado and Lewinsohn 2004;Stouffer and Bascompte 2011). However, the lack of nested patterns suggests little redundancy across modules.…”

“…In nested patterns of resource use, there is thus a large redundancy that may improve the stability of ecosystem dynamics (Holling 1973). A modular pattern is characterized by delimited sub-communities of consumers and resources, with more frequent and stronger interactions between organisms within than between sub-communities (May 1973;Prado and Lewinsohn 2004). Modular patterns may be ecologically important by delimiting the impacts of perturbations to specific modules, so that they may not permeate through the entire ecosystem (Stouffer and Bascompte 2011).…”