The legacy of past climate and landscape change on species' current experienced climate and elevation ranges across latitude: a multispecies study utilizing mammals in western North America

Aim Elevation and climate ranges across latitude experienced by 21 wide‐ranging mammal species in western North America were summarized to examine two questions: (1) do populations in the northern and southern portions of a species’ range experience different climates or are environments selected to remain similar to climates at the core of ranges; and (2) how do species’ elevational ranges, experienced temperature seasonality and temperature ranges change across latitude? Given the larger effects of climate oscillations in the north vs. the south, a predicted outcome is for species to conserve climate niches across latitude and to show reduced climate and elevation ranges in the north. An alternative outcome is latitudinal niche diversification and increased climate variation in the north. Location Western North America. Methods The questions above were examined using a combination of species occurrence data bases, climate data bases, simple summaries of means and standard deviations and by testing summaries against random distributions across latitude for 21 mammal species from a variety of orders. Results The results showed that: (i) most species conserve their niche strongly or weakly given overall temperature gradients from north to south; (ii) seasonality experienced by species is relatively static until the highest latitudes despite directional trends across the region; and (iii) the elevation range and temperature variation that species experience decreases from south to north. Main conclusions Populations at range edges appear to partition environments to remain closer to temperature values similar to those at the core of the range. In addition, seasonality is not a likely explanatory factor of genetic diversity in latitudinal gradients. The data are instead more consistent with predictions that a combination of higher gene‐flow, increasing environmental instability and decreasing elevation gradients in the north compared to the south may lead to negative correlations between latitude and species’ climate variation. The results corroborate risks faced by northern mammal populations to global climate changes.     

The role of climate,habitat, and species co‐occurrence as drivers of change in small mammal distributions over the past century

Species distribution models are commonly used to predict species responses to climate change. However, their usefulness in conservation planning and policy is controversial because they are difficult to validate across time and space. Here we capitalize on small mammal surveys repeated over a century in Yosemite National Park, USA, to assess accuracy of model predictions. Historical (1900–1940) climate, vegetation, and species occurrence data were used to develop single‐ and multi‐species multivariate adaptive regression spline distribution models for three species of chipmunk. Models were projected onto the current (1980–2007) environmental surface and then tested against modern field resurveys of each species. We evaluated models both within and between time periods and found that even with the inclusion of biotic predictors, climate alone is the dominant predictor explaining the distribution of the study species within a time period. However, climate was not consistently an adequate predictor of the distributional change observed in all three species across time. For two of the three species, climate alone or climate and vegetation models showed good predictive performance across time. The stability of the distribution from the past to present observed in the third species, however, was not predicted by our modeling approach. Our results demonstrate that correlative distribution models are useful in understanding species' potential responses to environmental change, but also show how changes in species‐environment correlations through time can limit the predictive performance of models.     

Effects of decadal climate change on zooplankton over the last 50 years in the western subarctic North Pacific

Decadal‐ to multi‐decadal variations have been reported in many regional ecosystems in the North Pacific, resulting in an increasing demand to elucidate the link between long‐term climatic forcing and marine ecosystems. We detected phenological and quantitative changes in the copepod community in response to the decadal climatic variation in the western subarctic North Pacific by analyzing the extensive zooplankton collection taken since the 1950s, the Odate Collection. Copepod species were classified into five seasonal groups depending on the timing of the annual peak in abundance. The abundance of the spring community gradually increased for the period 1960–2002. The spring–summer community also showed an increasing trend in May, but a decadal oscillation pattern of quasi‐30‐year cycles in July. Phenological changes coincided with the climate regime shift in the mid‐1970s, indicated by the Pacific decadal oscillation index (PDO). After the regime shift, the timing of the peak abundance was delayed one month, from March–April to April–May, in the spring community, whereas it peaked earlier, from June–July to May–June, in the spring–summer community, resulting in an overlap of the high productivity period for the two communities in May. Wintertime cooling, followed by rapid summertime warming, was considered to be responsible for delayed initiation and early termination of the productive season after the mid‐1970s. Another phenological shift, quite different from the previous decade, was observed in the mid‐1990s, when warm winters followed by cool summers lengthened the productive season. The results suggest that climatic forcing with different decadal cycles may operate independently during winter–spring and spring–summer to create seasonal and interannual variations in hydrographic conditions; thus, combinations of these seasonal processes may determine the annual biological productivity.