Summary: Numerical studies of the relationship between birds and their habitat are important because they provide understanding of the impacts of natural and human factors on avian diversity. However, collinearity between explanatory variables and spatial autocorrelation can hamper the detection of key environmental factors underlying bird–environment relationships identified by traditional regression approaches. This study utilized two alternative statistical methods to address these difficulties in biodiversity modelling. We examined bird abundance patterns, spatial structure and relationship to environmental factors in an agricultural–forest mosaic landscape in Finland. We used data from 105 grid squares each 25 ha in size. Using variation partitioning and hierarchical partitioning methods, we determined the independent and joint effects of habitat cover, landscape structure and spatial variables on the total number of bird pairs and that of agricultural bird pairs. The explanatory variables highlighted as important predictors of bird patterns by the two methods generally coincided well. The total number of bird pairs was negatively related to agricultural land, and positively to cover of forests and landscape heterogeneity. However, a clear majority of the explained variation in bird patterns was related to the joint effect of predictors, and the independent contributions of predictors were small. The univariate importance of landscape heterogeneity decreased greatly if the habitat cover variables were considered simultaneously. Most of the explained variation in the number of agricultural bird pairs was related to the joint effects of the explanatory variables. In addition, the independent effect of habitat cover variables was considerable and agricultural birds showed a positive relationship with semi‐natural grasslands. Synthesis and applications. Variation partitioning and hierarchical partitioning approaches provide deeper insights into bird–environment relationships than traditional regression methods. This is particularly so when they are employed in a complementary manner. Our results indicate that a major part of the spatial structure in bird patterns in agricultural–forest mosaics can be caused by the clumping of habitats either preferred or avoided by birds. Moreover, at a scale of 25 ha, the abundance of bird pairs is not necessarily related to landscape heterogeneity as such, but depends more on the distribution of the most important habitats for birds.

Variation partitioning and hierarchical partitioning are novel statistical approaches that provide deeper understanding of the importance of different explanatory variables for biodiversity patterns than traditional regression methods. Using these methods, the variation in occupancy and abundance of the clouded apollo butterfly (Parnassius mnemosyneL.) was decomposed into independent and joint effects of larval and adult food resources, microclimate and habitat quantity. The independent effect of habitat quantity variables (habitat area and connectivity) captured the largest fraction of the variation in the clouded apollo patterns, but habitat connectivity had a major contribution only for occupancy data. The independent effects of resources and microclimate were higher on butterfly abundance than on occupancy. However, a considerable amount of variation in the butterfly patterns was accounted for by the joint effects of predictors and may thus be causally related to two or all three groups of variables. Abundance of the butterfly in the surroundings of the focal grid cell had a significant effect in all analyses, independently of the effects of other predictors. Our results encourage wider applications of partitioning methods in biodiversity studies.

Significance: Plant functional traits are central instruments in developing understanding and predicting biodiversity patterns and ecosystems processes. Snow is an important ecological factor in cold climates, but its contribution to the evolution of functionality of tundra vegetation is poorly known and insufficiently addressed in the research. We show here that snow has a fundamental effect in mediating climate change impacts on functional composition and diversity of Arctic tundra vegetation. As a whole, Arctic landscapes may lose spatial heterogeneity because plant communities will be functionally more alike, although the local functional diversity may increase. Our results highlight that future snow conditions and their fine-scale variability should be acknowledged in the next generation of Arctic vegetation−ecosystem models.

Species are altering their ranges as a response to climate change, but the magnitude and direction of observed range shifts vary considerably among species. The ability to persist in current areas and colonize new areas plays a crucial role in determining which species will thrive and which decline as climate change progresses. Several studies have sought to identify characteristics, such as morphological and life-history traits, that could explain differences in the capability of species to shift their ranges together with a changing climate. These characteristics have explained variation in range shifts only sporadically, thus offering an uncertain tool for discerning responses among species. As long-term selection to past climates have shaped species’ tolerances, metrics describing species’ contemporary climatic niches may provide an alternative means for understanding responses to on-going climate change. Species that occur in a broader range of climatic conditions may hold greater tolerance to climatic variability and could therefore more readily maintain their historical ranges, while species with more narrow tolerances may only persist if they are able to shift in space to track their climatic niche. Here, we provide a first-filter test of the effect of climatic niche dimensions on shifts in the leading range edges in three relatively well-dispersing species groups. Based on the realized changes in the northern range edges of 383 moth, butterfly, and bird species across a boreal 1,100 km latitudinal gradient over c. 20 years, we show that while most morphological or life-history traits were not strongly connected with range shifts, moths and birds occupying a narrower thermal niche and butterflies occupying a broader moisture niche across their European distribution show stronger shifts towards the north. Our results indicate that the climatic niche may be important for predicting responses under climate change and as such warrants further investigation of potential mechanistic underpinnings. Over time, species have evolved to live in specific environments, and climatic conditions provide some of the most important boundaries for species’ ranges. As climate changes, temperatures tend to increase and precipitation regimes change, whereby the conditions where species currently occur will also change. If species have evolved to tolerate climate variability, they may persist by staying in place and withstanding the changing environmental conditions. However, if they are highly selective in their climate niche preferences, they may be more likely to move in space, together with the climatic conditions that match their specific requirements. On the other hand, generalists may be able to colonize new areas more effectively, in addition to adjusting in place. Thus, which option is more readily available to a species might be predictable by measuring the variability in climatic conditions across the species’ current, realized niche. Using distribution data on 383 species, we calculated the mean and breadth of climatic conditions that the species occupy within Europe. We found that the breadth of species’ climatic niche is a strong predictor of range shifts observed in Finland, northern Europe, over the past 20 years. Moths and birds that have adapted to a narrow range of temperatures are moving northward, while those tolerating a wider range of temperatures are staying put. Butterfly range shifts, however, seemed connected to broader moisture niches. Our results indicate that past evolutionary processes that have formed a continuum of species that differ in their climatic tolerance, may currently dictate how species respond to rapid anthropogenic climate change. Species’ flexibility vs. selectivity for climatic conditions may thus provide a key to understanding both observed and future range shifts.