Morphological matching and phenological overlap promote niche partitioning and shape a mutualistic plant–hawkmoth network

Abstract

1. Species interact with one another in communities forming complex interaction networks which are shaped by multiple non-exclusive processes. Although plant-hawkmoth interactions have been studied for over a century, how processes underlying species' specialisation influence community-level patterns of niche partitioning and contribute to the emergence of network structures remains poorly investigated. 2. This study described a mutualistic plant-hawkmoth network sampled for 18 consecutive months in Southern Brazil and tested (i) whether it presents modular and/or nested structures and (ii) what drivers (morphologies, phenologies, or abundances) are more important in defining interaction intensities. 3. Network structure was modular, presenting three distinct modules, and had a nestedness value lower than null model expectations. Interaction frequencies were primarily defined by morphological matching and phenological overlap but were not importantly influenced by species' relative abundances. Module composition reinforced the importance of morphological matching, as well as barriers imposed by morphology, and also suggested that modularity may be a consequence of other factors, such as timing between hawkmoth flight period and plants' anthesis. 4. This study's data contribute to filling the shortage of plant-centred interaction networks involving hawkmoths and plants and reveal that modularity emerges likely as a consequence of processes thought to shape niche partitioning in this system, as well as in other pollination networks. The findings of this study are in agreement with the neutral-niche continuum model, which predicts that, in systems with high trait functional variation (morphologies and phenologies in this case), niche-based processes such as trait matching must be relatively more important than abundances as drivers of interspecific interactions.

Short flowers for long tongues: Functional specialization in a nocturnal pollination network of an asclepiad in long‐tongued hawkmoths

“…grandiflora relies exclusively on long‐tongued hawkmoths, similarly to the phenotypically specialized sphingophilous plants. Morphological match and phenology are some of the main determinants of hawkmoth‐plant interaction networks (Lautenschleger et al, 2020; Sazatornil et al, 2016). Nevertheless, plants belonging to the module reflecting the long‐tongued hawkmoth pollinator niche are not blooming simultaneously in the study area.…”

Evolutionary history and ecological traits shape a mutualistic plant-hawkmoth interaction network

“…In fact, interactions between organisms that coexist in communities connect species forming interaction networks whose structures can be shaped by multiple ecological, evolutionary, neutral and historical processes (Lewinsohn et al, 2006;. In plant-hawkmoth interaction networks, recent studies indicate that ecological processes, such as morphological matching between proboscis length and floral tube length and phenological overlap, are primary mechanisms structuring interactions (Sazatornil et al, 2016;Johnson et al, 2017;Lautenschleger et al, 2020). This importance results from the tendency of hawkmoths to visit flowers with corolla tubes of similar length to their proboscis, and the impossibility of interaction between partners that have non-overlapping flowering and foraging times.…”

“…This importance results from the tendency of hawkmoths to visit flowers with corolla tubes of similar length to their proboscis, and the impossibility of interaction between partners that have non-overlapping flowering and foraging times. Thus, mechanisms associated with niche partitioning tend to be more important than 'neutrality', which postulates that partners interact in proportion to their relative abundances, resulting in abundant species interacting more frequently than rarer species (Lautenschleger et al, 2020).…”

“…In biological communities, niche partitioning based on trophic specialization may be associated with multispecies reciprocal selection, i.e., diffuse coevolution, resulting in modular network structure (Olesen et al, 2007). Modularity is known to emerge in plant-hawkmoth networks possibly owing to behavioral differences in the foraging times of some hawkmoth species and the time of flower anthesis, in addition to morphological and phenological constraints (Amorim, 2020;Lautenschleger et al, 2020). Modules may reflect variations in pollinator traits and their efficiency in obtaining resources, which is reinforced by the influence of functional traits playing a key role on the structure of hawkmoth communities (Johnson et al, 2017).…”

“…Specifically, we (i) tested the relative importance of species phylogenetic relationships in comparison to niche-based and neutral processes in defining interaction frequencies; (ii) evaluated the phylogenetic signal of ecological traits; and (iii) tested whether module composition was associated with hawkmoths phylogenetic relationships and functional traits. Given the importance of niche-based processes (morphological matching and temporal overlap) in structuring this interaction network (Lautenschleger et al, 2020) and the tendency of phylogenetically close species interact with similar partners (Thompson, 2005), we hypothesized that the evolutionary history of hawkmoths is associated with interaction frequencies and that traits related to morphology and temporal distribution of this group present phylogenetic signal. Due to the ability to predict hawkmoth visitors based on converging floral traits (Oliveira et al, 2014), we expected that plants' phylogenetic relationship have little or no association with their interactions with hawkmoths.…”