Diversity and deadwood-based interaction networks of saproxylic beetles in remnants of riparian cloud forest

Abstract

We studied the saproxylic beetle community inhabiting deadwood in remnants of riparian cloud forests in “La Antigua” basin, in central Veracruz (Mexico). We assessed the influence of deadwood features (tree species, trunk position, trunk diameter, trunk volume and decomposition stages) on saproxylic beetle diversity. In order to assess the stability of beetle species-deadwood interactions, we also analyzed the ecological networks structure. A total of 63 deadwood trunks, belonging to four tree species, were sampled by standardized hand-collection throughout well-preserved remnants of riparian cloud forest. We found that tree species and deadwood decay stage are the main drivers that determine the diversity and stability of saproxylic beetle species interactions. Our results indicate that Quercus corrugata is the main tree species in terms of maintaining the significantly highest saproxylic beetle diversity, but with no stable interactions (saproxylic beetle-deadwood). A nested network structure was detected for Clethra mexicana and Liquidambar styraciflua , with a pool of core (generalist) saproxylic beetle species. We observed that beetle diversity from the early and late deadwood stages comprises distinct assemblages and the four stages of decomposition showed a nested network structure. During deadwood succession, community composition and guilds changed among networks; the early successional stage had more specialized xylophagous beetles, while other guilds (mycophagous, saprophagous and zoophagous) arrive later and become the core species in the advanced stages of decomposition networks. Heliscus tropicus (Passalidae) is a key species constituting the core of all of the networks and could be considered an ecosystem engineer in cloud forests. By exploring links between saproxylic beetles and deadwood characteristics, we can further our understanding of species interaction in order to develop management strategies oriented towards the protection of species and their habitats in this threatened ecosystem.

Spatio-temporal variation of Cerambycidae-host tree interaction networks

“…Other studies have reported similar nestedness values in different habitat types (e.g., WNODF = 15, 12.12 and 8.36, [39]). Unlike other studies ( [40] but see [38]), our results show a significantly modular structure; the modular network pattern is positively related with the specialization degree and suggests that groups of species co-evolved among themselves [57]. It is possible that the differences in the detection of the modular pattern among this and other studies (e.g., [40]), are due to the fact that previous studies use presence/absence metrics and in this study, we use quantitative analysis, which consider the intensity of the interaction (e.g., species abundance).…”

“…Unlike other studies ( [40] but see [38]), our results show a significantly modular structure; the modular network pattern is positively related with the specialization degree and suggests that groups of species co-evolved among themselves [57]. It is possible that the differences in the detection of the modular pattern among this and other studies (e.g., [40]), are due to the fact that previous studies use presence/absence metrics and in this study, we use quantitative analysis, which consider the intensity of the interaction (e.g., species abundance). However, the absence of modularity is to be expected in commensalistic interactions, where interactions are asymmetrical and coevolution is lax, because at least for a group (e.g., trees) there are no direct benefits/costs associated with the use of its dead wood by cerambycids; while for the other group (i.e., cerambycids), a part of their life cycle depends on the availability of dead wood.…”

“…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 (e.g., [38][39][40]. However, 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 ( [25,40]. Wende et al [25] showed that these levels of specialization are related to the characteristics of the plants (i.e., their chemical compounds) and animals (i.e., body size).…”

“…Wende et al [25] showed that these levels of specialization are related to the characteristics of the plants (i.e., their chemical compounds) and animals (i.e., body size). So, although it is possible to hypothesize that the relationships between cerambycids and their trees are generalists, few studies suggest that the generality in the use of wood is restricted by the characteristics of the wood and the body size of the insects [25,40]. 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, particularly in highly seasonal habitats such as the TDF.…”

The bess beetles (Coleoptera, Passalidae) of three subregions of the Department of Sucre, Caribbean region of Colombia

“…Saproxylic beetles are easily inventoried and their diversity has been well documented, especially for conservation purposes (Grove and Stork 1999;Grove 2002). Beetles belonging to the families Scarabaeidae, Passalidae, and Cerambycidae have been considered useful biological indicators of habitat modification due to their high vulnerability to habitat degradation (Skotland et al 2012;Ramírez-Hernández et al 2019). Passalidae are among those saproxylic beetles that live and feed in decomposing wood, accelerating the physical degradation of wood and thus the recycling of organic matter (Castillo and Reyes-Castillo 2003).…”