Spatio-temporal variation of Cerambycidae-host tree interaction networks

Wood trait preferences of Neotropical xylophagous beetles (Coleoptera: Cerambycidae)

Tree life history strategies are correlated with functional plant traits, such as wood density, moisture content, bark thickness, and nitrogen content; these traits affect the nutrients available to xylophagous insects. Cerambycid beetles feed on substrates that vary in these traits, but little is known about how they affect community composition. The goal of this project is to explore the community composition of two cerambycid subfamilies (Cerambycinae and Lamiinae) according to the wood traits in the wood they eat. In a salvage project conducted adjacent to the Panama Canal, trees were felled and exposed to Cerambycidae for oviposition. Disks from branches of differing thickness from the same plant individuals were used to calculate wood density, moisture content, and bark thickness in the field; nitrogen data were acquired offsite. Thick and thin branches tended to differ in wood trait values; therefore, data were analyzed separately in subsequent analyses. In thin branches, cerambycid abundance and species richness were higher in samples with less dense, moister wood, and thicker bark. Thick branches showed similar trends, but the wood traits accounted for little variability in beetle abundance or species richness. There were no significant regressions between beetle data and nitrogen. Cerambycines emerged more slowly, and from denser, drier wood, than lamiines. Cerambycines might be more drought-tolerant than lamiines, and therefore more resistant to the longer, more severe dry seasons that are predicted to occur due to climate change.

Interaction Networks Help to Infer the Vulnerability of the Saproxylic Beetle Communities That Inhabit Tree Hollows in Mediterranean Forests

Insect communities are facing contrasting responses due to global change. However, knowledge on impacts of communities' reorganizations is scarce. Network approaches could help to envision community changes in different environmental scenarios. Saproxylic beetles were selected to examine long-term variations in insect interaction/diversity patterns and their vulnerability to global change. We evaluated interannual differences in network patterns in the tree hollow-saproxylic beetle interaction using absolute samplings over an 11-year interval in three Mediterranean woodland types. We explored saproxylic communities' vulnerability to microhabitat loss via simulated extinctions and by recreating threat scenarios based on decreasing microhabitat suitability. Although temporal diversity patterns varied between woodland types, network descriptors showed an interaction decline. The temporal beta-diversity of interactions depended more on interaction than on species turnover. Interaction and diversity temporal shifts promoted less specialized and more vulnerable networks, which is particularly worrisome in the riparian woodland. Network procedures evidenced that saproxylic communities are more vulnerable today than 11 years ago irrespective of whether species richness increased or decreased, and the situation could worsen in the future depending on tree hollow suitability. Network approaches were useful for predicting saproxylic communities' vulnerability across temporal scenarios and, thus, for providing valuable information for management and conservation programs.

Cerambycid Beetle Communities in Caatinga Dry Forests Are Structured by Seasonal Species Turnover

Dry forests in the Caatinga biome of Brazil are seasonal ecosystems where diversity is driven by water availability. Understanding how the distribution of communities is driven by temporal climate changes has intrigued researchers for decades. However, temporal diversity patterns should be more evident in dry environments, since seasonality is characterized by being highly limiting to insect activities. Cerambycid beetles are considered good ecological indicators because they respond well to impacts of environmental changes. Thus, we asked two questions: (i) How do climatic changes affect the diversity of these insects across seasons? (ii) Are diversity components correlated with increasing air humidity, rainfall, and temperature? Our results showed a marked seasonality of cerambycid beetles, with higher abundance and richness in the wet season. The mean temperature and relative humidity were predictors of the composition of beetle assemblages. However, the variation of cerambycid assemblages between seasons is related mainly to species turnover. Our study demonstrates that the combined effect of temperature and humidity drives the temporal distribution of the cerambycids in dry forests. Although thermal sensitivity was low, the decrease in air moisture during the dry season was the limiting factor for these insects. Species turnover increased continuously with air moisture and temperature rise, creating temporal segregation among cerambycid species and maintaining the stability of the assemblage. Thus, our results are consistent with mechanisms invoking activity patterns, desiccation resistance, and physiologic constraints that predict a decrease in richness and abundance of the cerambycids from warmer and moister to colder and drier conditions.

Biodiversity and Spatiotemporal Variation of Longhorn Beetles (Coleoptera: Cerambycidae) in Tropical Forest of Thailand

Simple Summary

Longhorn beetles are a large family of beetles and have a wide-geographic distribution. Some of them are pests of many economic plants and invasive species. They also play roles in decomposition and nutrient cycling in forest ecosystems. They feed on living, dying, or dead woody plants in the larval stage. So far, 308 species of longhorn beetles have been reported from northern Thailand. However, the biodiversity and distribution of longhorn beetles in different elevation gradients and seasons, associated with environmental factors across six regions in the country, has not yet been investigated. In this study, longhorn beetle specimens were collected by malaise trap from 41 localities in 24 national parks across six regions in Thailand. A total of 199 morphospecies were identified from 1376 specimens. Seasonal species richness and abundance of longhorn beetles peaked during the hot and early rainy season in five regions, except for the southern region, which peaked in the rainy season. Our finding revealed that most species’ distribution was correlated with the region and forest type (at middle and low elevations). Quantitative data from this study can be useful to manage agricultural and forest plantations.

Abstract

Longhorn beetles are highly diversified and important for agriculture and health of the environment. However, the fauna and ecology of these beetles are not well known in Thailand. This study is the first to report the biodiversity, elevation, and seasonal distribution of longhorn beetles. Specimens were collected by malaise traps from 41 localities in 24 national parks throughout the country during 2006–2009. The traps were operated at each site for 12 consecutive months with a monthly service. A total of 199 morphotaxa in 36 tribes of 6 subfamilies were identified from 1376 specimens. Of these, 40.7% and 14.5% of total taxa were singletons and doubletons, respectively. The Shannon diversity index and observed species richness at Panernthung, Loei Forest Unit and Mae Fang Hotspring were high at 0.96 (30), 0.88 (50), and 0.86 (34), respectively. Local richness ranged between 3 and 50 species, while the species richness estimator showed between 6 and 1275 species. The most relatively abundant species, Nupserha lenita, Pterolophia sp.1, Oberea sp.3, Acalolepta pseudospeciosa, and Ac. rustricatrix represented 4.80%, 4.80%, 4.80%, 4.5%, and 4.43% of the species, respectively. The species with the widest distribution range of percentage of species occurrence (% SO) was Pt. sp.1 (63.4%), followed by Ac. rustricatrix (39%) and Moechotypa suffusa (39%). In a significantly negative relationship between species richness and elevation (p > 0.05, R² = 0.04), the species richness pattern showed a hump-shaped curve that peaked at the middle elevation (501–1000 m asl). Regarding seasonal variation, most of the species occurred during the hot season (March–April) and peaked in early rainy season (May), while a low number of species were found during the mid-rainy (June–October) and cold season (November–February). Ordination analysis indicated that the distribution of most species was associated with regions and forest type, and most of the species correlated with forest located at middle and low elevation. The results of this study indicated the very high biodiversity of longhorn beetles in Thailand, which suggests that an understanding of their seasonal and elevational distribution will be of value to agriculture management and conservation. They also indicated that malaise traps are appropriate for the evaluation of biodiversity.