Value of Riparian Vegetation Remnants for Leaf-Litter Ants (Hymenoptera: Formicidae) in a Human-Dominated Landscape in Central Veracruz, Mexico

Sweep Sampling Comparison of Terrestrial Insect Communities Associated with Herbaceous Stratum in the Riparian Zone of the Miho River, Korea

Simple Summary

Insect pests and their natural enemies can harbor in riparian zones. To determine the impact of insect communities on agriculture and ecology, we must quantitatively assess insect populations in riparian areas. To identify the appropriate methodology for effective insect sampling in riparian areas, we assessed sweep sampling within three plant communities using different numbers of subsampling units (50 sweeps carried out twice, or 10 sweeps over 10 times) over two years. The results reveal that effective insect sampling varies between different plant communities and insect orders. The similarities between terrestrial insect communities in the same plant community were relatively high, even in different years. The optimum sampling size to obtain approximately 80% of the total species was estimated for each survey site. Our results lay the foundations for providing techniques to assess insect populations within riparian areas to predict and prevent herbivorous insect pest invasions in the future.

Abstract

To investigate insect and plant community relationships in riparian zones, terrestrial insect communities were compared in plant communities in the riparian zone of the Miho River, Korea. The sweep netting method was used to sample insects in 50 m transects in three herbaceous plant communities. In 2020, each plant community—Chenopodium album, Beckmannia syzigachne, and Artemisia indica—was swept 100 times (50 sweeps × 2). In 2021, two communities had an additional 100 sweeps collected using 10 subsamples of 10 sweeps (excluding C. album communities). The surveyed dominant species or subdominant species of the insect community in each site preyed on the dominant plant species at the site. The Bray–Curtis similarity was significantly higher than the Sørensen similarity when comparing datasets across different years for the same plant species community. The predicted optimum sampling size to obtain approximately 80% of the total species estimated to be at each survey site, for effective quantitative collection of terrestrial insect herbivores in each plant community, was examined. Fifty sweeps were required for the A. indica community and 100 sweeps were required for the B. syzigachne community. The results of this study provide important data for riparian biodiversity conservation and future pest monitoring.

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

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.

Assessing Three Sampling Methods to Survey and Monitor Ground Beetles (Coleoptera: Carabidae) in Riparian Cloud Forests

Understanding how biodiversity is distributed across space and time is one of the main challenges of biological conservation. Moreover, the choice of an adequate sampling methodology is crucial since this must provide an efficient overview of species diversity. We assessed the effectiveness and complementarity of three sampling methods (hand collection [HC], pitfall trapping [PT], and light trapping [LT]) for collecting ground beetles, which are known as a robust ecological indicator sensitive to habitat modifications. Our results varied in the number of species and abundance thereof caught by each sampling method. Both HC and LT were the most efficient and showed the highest species complementarity. HC recorded the highest number of ground beetle individuals, whereas the largest number of species were recorded with LT, but most represented by few individuals. Furthermore, the results revealed that PT do not work efficiently to provide reliable inventories in the remnant riparian cloud forests, which are characterized to be a highly heterogeneous environment. Our results might provide guidelines to choose the most efficient standardized sampling protocol for future inventory and monitoring of ground beetle (Coleoptera: Carabidae) diversity as a tool for the conservation planning in this threatened ecosystem.

The surrounding landscape influences the diversity of leaf-litter ants in riparian cloud forest remnants

Riparian vegetation is a distinctive and ecologically important element of landscapes worldwide. However, the relative influence of the surrounding landscape on the conservation of the biodiversity of riparian remnants in human-modified tropical landscapes is poorly understood. We studied the surrounding landscape to evaluate its influence on leaf-litter-ant alpha and beta diversity in riparian remnants in the tropical montane cloud forest region of central Veracruz, Mexico. Sampling was carried out in 12 sites with riparian vegetation during both rainy (2011) and dry (2012) seasons. Ten leaf-litter samples were collected along a 100-m transect per site and processed with Berlese-Tullgren funnels and Winkler sacks. Using remotely-sensed and ground-collected data, we characterized the landscape around each site according to nine land cover types and computed metrics of landscape composition and configuration. We collected a total of 8,684 ant individuals belonging to 53 species, 22 genera, 11 tribes, and 7 subfamilies. Species richness and the diversity of Shannon and Simpson increased significantly in remnants immersed in landscapes with a high percentage of riparian land cover and a low percentage of land covers with areas reforested with Pinus, cattle pastures, and human settlements and infrastructure. The composition of ant assemblages was a function of the percentage of riparian land cover in the landscape. This study found evidence that leaf-litter ants, a highly specialized guild of arthropods, are mainly impacted by landscape composition and the configuration of the focal remnant. Maintaining or improving the surrounding landscape quality of riparian vegetation remnants can stimulate the movement of biodiversity among forest and riparian remnants and foster the provision of ecosystem services by these ecosystems. Effective outcomes may be achieved by considering scientific knowledge during the early stages of riparian policy formulation, in addition to integrating riparian management strategies with broader environmental planning instruments.