Parasitism of Ground Beetles (Coleoptera: Carabidae) by a New Species of Hairworm (Nematomorpha: Gordiida) in Arctic Canada.

The host-parasite associations between ground beetles (Coleoptera: Carabidae) and hairworms (Nematomorpha: Gordiida) collected from the Arctic (an understudied and ecologically important region) is described. Carabids and their parasites were collected from 12 sites spanning the 3 northernmost ecoclimatic zones of Canada (north boreal, subarctic, and high Arctic) using standardized methods. The beetles and hairworms were identified using traditional morphological approaches. Seven beetle species are recorded as hosts: Amara alpina, Pterostichus caribou, Pterostichus brevicornis, Pterostichus tareumiut, Pterostichus haematopus, Patrobus septentrionis, and Notiophilus borealis. All represent new host records (increasing the known North American host list from 14 to 21), and this is the first record of hairworm infection in the genus Notiophilus. Beetles from Banks Island, Northwest Territory, were infected in high numbers (11-19% per sampling period) and were used as an ecological case study. There was no significant relationship between infection status and host species, body size, or sex. Beetles collected in yellow pan traps and in wet habitats were more likely to be infected, likely due to water-seeking behavior induced by the parasites. Morphological examinations indicate that the hairworms collected from all locations represent a single, new species of Gordionus, making it only the sixth hairworm species and the third species of that genus found in Canada. Hosts are unknown for all other Canadian (and 1 Alaskan) Gordionus species.

Drivers and Patterns of Ground-Dwelling Beetle Biodiversity across Northern Canada.

Many macroecological patterns of biodiversity, including the relationship between latitude and species richness, are well-described. Data collected in a repeatable, standardized manner can advance the discipline beyond the description of patterns and be used to elucidate underlying mechanisms. Using standardized field methods and a hyper-diverse focal taxon, viz. Coleoptera, we aim to (1) describe large-scale latitudinal patterns of taxonomic diversity, functional diversity, and assemblage structure across northern Canada, and (2) determine which climatic, spatial, and habitat variables best explain these patterns. We collected terrestrial beetles at twelve locations in the three northernmost ecoclimatic zones in North America: north boreal, subarctic, and high arctic (51-81°N, 60-138°W). After identifying beetles and assigning them to a functional group, we assessed latitudinal trends for multiple diversity indices using linear regression and visualized spatial patterns of assemblage structure with multivariate ordinations. We used path analysis to test causal hypotheses for species and functional group richness, and we used a permutational approach to assess relationships between assemblage structure and 20 possible climatic and environmental mechanisms. More than 9,000 beetles were collected, representing 464 species and 18 functional groups. Species and functional diversity have significant negative relationships with latitude, which are likely explained by the mediating effects of temperature, precipitation, and plant height. Assemblages within the same ecoclimatic zone are similar, and there is a significant relationship between assemblage structure and latitude. Species and functional assemblage structure are significantly correlated with many of the same climatic factors, particularly temperature maxima and minima. At a large spatial extent, the diversity and assemblage structure of northern beetles show strong latitudinal gradients due to the mediating effects of climate, particularly temperature. Northern arthropod assemblages present significant opportunities for biodiversity research and conservation efforts, and their sensitivity to climate make them ideal targets for long-term terrestrial diversity monitoring.