Abstract
Despite its high ecological importance, the commensal interactions at community level are poorly studied. In tropical dry forests (TDF) there is a great diversity of species adapted to the high seasonality that characterizes them; however, little is known regarding how the spatial and temporal availability of resources generates changes in the pattern of commensal interactions. We experimentally studied changes in the diversity, composition, and pattern of interactions in spatio-temporal associations between the saproxylophagous beetles and their host trees in a TDF in Morelos, Mexico. A total of 65 host tree species were selected, from which 16 wood sections were obtained per species. These sections were exposed in the field to allow oviposition by the cerambycids under four different (spatio-temporal) treatments. We analyzed the network structure and generated indices at species level (i.e., specialization, species strength, and effective partners) and those related to physical characteristics of the wood (hardness and degradation rate) and the cerambycids (body size). In total, 1,323 individuals of 57 species of cerambycids emerged. Our results showed that, independently of the space and time, the network presented a nested and modular structure, with a high specialization degree and a high turnover of cerambycid species and their interactions. In general, we found that the cerambycids are mostly associated with softwood species with a lower decomposition rate of wood, as well as with the most abundant host species. The commensalistic interactions between the cerambycids and their host trees are highly specialized but are not spatio-temporally static. The high turnover in the interactions is caused by the emergence patterns of cerambycids, which seem to restrict their use to certain species. The knowledge of the spatio-temporal variation in Cerambycidae-host tree interactions allows us to predict how environmental and structural changes in the habitat can modify the species ensemble, and therefore its interactions.
Highlights
The tropical dry forest (TDF) is an ecosystem with high biodiversity [1] and the species that inhabit it are adapted to survive under seasonal conditions of scarce rain [2]
Regarding 0D, no differences were found among treatments (Fig 1), while 1D was greater in both dry season treatments (Dc, Dry ground (Dg)), with no differences presented between these two treatments
The volume and decomposition rate of the woods was related to their species strength and the body size index (BSI) of the cerambycids to specialization at species level
Summary
The tropical dry forest (TDF) is an ecosystem with high biodiversity [1] and the species that inhabit it are adapted to survive under seasonal conditions of scarce rain [2]. In recent years some studies have analyzed the Cerambycidae-host tree commensalistic interactions through the network’s method, finding that, as with mutualistic and antagonistic interactions, these present a defined structure that is mainly nested They present lower values of nestedness than other networks of commensalistic interactions (e.g., epiphyte-phorophyte NODF = 59.44 ± 20; [41]), showing high specialization level in the early stages of wood decomposition Despite the progress in the detection of patterns and characterization of the Cerambycidae-host tree commensalistic interactions, it is not known how these interactions vary spatio-temporally and how the physical characteristics of the wood and of the cerambycids will be related to the network parameters, in highly seasonal habitats such as the TDF. The importance of host species will be inversely related to the hardness and decomposition rate of the wood because softer woods decompose faster and can be used in an environment where the rainy season is short
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