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This study addresses the spatial distribution of spiders (Araneae) in relation to their environment along multiple ecological and biogeographical gradients. Two study regions representing considerable variation in the alpine climate were sampled for epigeal spiders using pitfall traps: one in the oceanic region and one in the continental region of Norway. We aimed to identify the driving forces for spider species annidation in an alpine tundra ecosystem using a multi-scale approach. During the snow-free season in 2009, we sampled 6,628 adult specimens at 73 sampling locations. These data and additional information from previous studies on spider habitat preferences were used to examine the features of the species' spatial distribution. We analysed our data set using ordination space partitioning (Isopam), which relies on hierarchical partitioning of the ordination space. This method is based on a hierarchical classification of the sampling locations according to their species composition and results in classes that can be distinguished by indicator species. The aggregated classes and their spatial patterns could be linked to snow cover. Local climatic conditions had a stronger influence on spider biogeography than did broad-scale climatic conditions. We identified various indicator species for typical alpine tundra habitats that could be described as either 'chionophobous' or 'chionophilous', depending on the topography-related snow cover at the sites where they occurred. Through this multi-scale approach, this study is the first to demonstrate the importance of snow-cover patterns on the ecology and biogeography of spiders in alpine tundra ecosystems. Zusammenfassung: Diese Studie untersucht Webspinnen (Araneae) und ihre räumlichen Verteilungsmuster in Bezug zu ihrer Umwelt entlang verschiedener ökologischer und biogeographischer Gradienten. Die epigäische Webspinnenfauna zweier alpiner Untersuchungsgebiete, die sich aufgrund ihrer klimatischen Bedingungen erheblich voneinander unterscheiden, wurde mit Hilfe von Bodenfallen untersucht. Eines der Untersuchungsgebiete befand sich im westlichen, ozeanisch geprägten Teil Norwegens, ein weiteres im östlichen, kontinental geprägten Teil Norwegens. Unser Ziel war es, die Kontrollfaktoren für die Einnischung einzelner Webspinnenarten in alpinen Tundraökosystemen unter Verwendung eines multiskaligen Ansatzes zu identifizieren. Während der schneefreien Periode im Jahr 2009 wurden insgesamt 6,628 adulte Individuen an 73 Standorten gefangen. Diese Daten sowie Erkenntnisse früherer Studien wurden verwendet, um Charakteristika der räumlichen Verteilung der vorhandenen Webspinnenarten zu untersuchen. Zur Analyse des Datensatzes wurde der Ordinationsraum der Standorte mit Hilfe des Isopam-Algorithmus unterteilt. Diese Methode basiert auf einer hierarchischen Einteilung der Standorte anhand ihrer Artenzusammensetzung und ergibt Klassen, die über Indikatorarten abgegrenzt werden können. Die aggregierten Klassen und ihre räumliche Verteilung konnten als direkte Folge der Schneebed...

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Differentiations in reproductive traits along climatic gradients can be substantial for a species to spread along a wide spatial range. We compared the reproductive effort allocated to first egg sacs of five species of the genus Pardosa: P. palustris (Linnaeus 1758), P. amentata (Clerck 1757), P. lugubris (Walckenaer 1802), P. hyperborea (Thorell 1872), and P. riparia (C. L. Koch 1833) along three elevation transects in central Norway. We tested whether population differences are consistent among the three transects, respectively along the elevational gradient. We assumed that the harsh environments of alpine areas would lead to adaptations in reproductive traits resulting in larger eggs but smaller clutches at higher elevations. The results show that female size and egg number were positively correlated among all species. However, no clear elevation-related trend was found. Other traits did not change consistently between species and along the elevational gradient. We assume that local microclimatic impacts on spider fitness are a crucial but poorly understood factor. Without further knowledge about adaptation and phenotypic plasticity in ectotherms, modeling of possible future reproduction biology might remain flawed.