Beyond Venom and Constriction: Bite Performance and Trophic Ecology in the Genus Drymarchon

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  Beyond Venom and Constriction: Bite Performance and Trophic Ecology in the Genus Drymarchon Abstract Snakes exhibit extreme cranial kinesis that facilitates ingestion of prey with large cross-sectional area, but this ability is widely predicted to reduce bite performance due to decreased structural rigidity. Consequently, most large-bodied snakes rely on envenomation or constriction to subdue prey prior to ingestion. Species within the genus Drymarchon represent a notable exception: these large, non-venomous, non-constricting snakes routinely consume a wide range of prey, including large and potentially dangerous vertebrates, using only simple seizing and pinioning behaviors. Here, we quantify bite performance in three species of Drymarchon ( D. corais, D. couperi, and D. melanurus ), examine morphological predictors of biting performance, compare biting pressure to constriction pressure in similarly sized snakes, and synthesize dietary records across the genus. Our results sh...

Small stream floodplains have high conservation value for riparian carabid beetles but less for ground-dwelling spiders

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Small stream floodplains have high conservation value for riparian carabid beetles but less for ground-dwelling spiders

Abstract

  1. Floodplains along rivers and streams are characterised by a high habitat heterogeneity and a large biodiversity. However, floodplains are highly threatened by anthropogenic activities such as channelisation and bank enforcement of watercourses. While floodplains along rivers are well known for their importance for riparian biodiversity, the conservation value of floodplains along small streams is less understood.
  2. We studied carabid beetles (Coleoptera: Carabidae) and ground-dwelling spiders (Arachnida: Aranea) along forested small streams (~ up to 5 m width) in Rhineland-Palatinate (Germany). We investigated 16 pairs of floodplains (natural stream sites with shallow bank and regular flooding events) and controls (deeply cut stream sites without regular flooding), where we sampled carabid beetles and spiders at different distances to the stream bank (0, 5 and 10 m).
  3. We found that floodplains along small streams had contrasting value for carabid beetles and ground-dwelling spiders. For carabid beetles, we observed several typical floodplain species and distinct species assemblages and 2.7 times more individuals across species of conservation concern in floodplain sites. Moreover, species richness and total number of individuals of carabid beetles were highest directly at the stream bank (0 m distance) of floodplains compared with the more distant locations, while the opposite was found for the control stream sites. The spider composition also differed between floodplains and control steam sites, but only one typical floodplain species was detected. Species richness and number of individuals in ground-dwelling spiders were lower in floodplains than in control stream sites.
  4. We conclude that the conservation value of floodplains of small streams is taxa-dependent and that they appear less relevant for ground-dwelling spiders but provide important habitats for riparian carabid beetles.
Bauspiess, P., Kolb, S., Joschko, T. J., Schulz, R., & Schirmel, J. Small stream floodplains have high conservation value for riparian carabid beetles but less for ground-dwelling spiders. Insect Conservation and Diversity. https://doi.org/10.1111/icad.12759