| Spiders (Arachnida: Araneae) are one of the most diverse and abundant taxa in the Arctic and are affected by fine scale changes in their environment, including temperature, precipitation, and habitat structure. This thesis describes research that occurred across the boreal forest tundra transition zone in the Yukon Territory, Canada. This study system provides an opportunity to test hypotheses about biogeographic patterns and determinants of diversity and life history of spiders in the north. There were four objectives of this research: first, to determine which environmental factors most influence spider assemblage structure (i.e., composition, richness, abundance) at a regional scale in the Arctic; second, to understand patterns of spider assemblages across latitudinal and elevational gradients; third, to understand relationships of life history traits (i.e., body size, body condition, fecundity, reproductive effort) and some of the factors (i.e., density, parasitism, developmental timing) that might influence these traits; and fourth, to determine the effects of elevation on life history traits (i.e., body size, fecundity) in the region. I employed the use of pitfall traps and visual surveys to collect ground-dwelling spiders across latitude and elevation at a regional scale spanning the boreal forest tundra transition zone. My results show that, at a regional extent, spatially structured changes in vegetation best explain the patterns of spider assemblage structure. Elevation has significant effects on spider composition, species richness and overall abundance, but species-specific responses differed along the gradient. For wolf spiders (Lycosidae), female body size best explained variation in fecundity and body condition was the best predictor for relative reproductive effort. I found evidence for egg size-number tradeoffs and very high incidence of parasitism in some populations (e.g., 52% of individual egg sacs) of the species studied. I found that body size (which is correlated with fecundity) varies with elevation, between the sexes and among species. This thesis provides quantitative data about the regional biogeography of arctic spider assemblages, as well as relationships between life history traits for northern wolf spiders. These data can also serve as a foundation upon which to develop and test hypotheses in the contexts of biodiversity, biogeography, life history and climate change in the Arctic. |
