Biological effects of climate change are expected to vary geographically, with a strong signature of latitude. For ectothermic animals, there is systematic latitudinal variation in the relationship between climate and thermal performance curves, which describe the relationship between temperature and an organism's fitness. Here, we ask whether these documented latitudinal patterns can be generalized to predict arthropod responses to warming across mid‐ and high temperate latitudes, for taxa whose thermal physiology has not been measured. To address this question, we used a novel natural experiment consisting of a series of urban warming gradients at different latitudes. Specifically, we sampled arthropods from a single common street tree species across temperature gradients in four
To test the latitudinal gradient in plant species diversity for self‐similarity across taxonomic scales and amongst taxa.
North America.
We used species richness data from 245 local vascular plant floras to quantify the slope and shape of the latitudinal gradients in species diversity (
We observed the canonical
The empirical
Latitudinal and elevational temperature gradients (
While latitudinal and elevational gradients of range size have been thoroughly studied, the ways these gradients might interact with each other to shape species distributions in complex montane environments are not well understood. We examined how elevational and latitudinal gradients interact to structure individual species’ distributions and larger geographic range size patterns.
Neotropics.
Two epiphytic plant genera:
We compiled 35,382 GBIF records for 505 species, calculated species’ latitudinal and elevational range extents, and examined gradients in richness and range size. For individual species, we analysed the relationship between elevational and latitudinal occurrences.
Approximately 50% of species demonstrate a significant, negative relationship between their elevational and latitudinal occurrences; most of these species occupy a non‐random, relatively narrow range of mean annual temperatures across their latitudinal distribution. Across species there is a positive relationship between latitudinal and elevational extent, a phenomenon we hereafter refer to as ‘Stevens’ pattern’. Average latitudinal extent of species’ ranges increased at higher latitudes, in support of Rapoport's rule. Average elevational extent increased with elevation in the global dataset (consistent with Rapoport's elevational rule), but most subsets of the data demonstrated a peak in average extent size at mid‐elevations.
The prevalence of species with negative elevation‐by‐latitude relationships, along with their non‐random tracking of temperature, suggests that many tropical species with broad geographic distributions are more temperature sensitive than their broad ranges might otherwise suggest. Consequently, even tropical species that occur across a wide range of latitudes and elevations might be threatened by climate change. These wide‐ranging species drive the occurrence of two biogeographic patterns: Rapoport's elevational rule and Stevens’ pattern. Finally, while Rapoport's rule and its elevational corollary were supported in part, the unexpected occurrence of many species restricted to high elevations near the equator suggests a possible focus for conservation effort.
Understanding factors that drive biodiversity distributions is central in ecology and critical to conservation. Elevational gradients are useful for studying the effects of climate on biodiversity but it can be difficult to disentangle climate effects from resource differences among habitat types. Here we compare elevational patterns and influences of environmental variables on ground-dwelling arthropods in open- and forested-habitats. We examine these comparisons in three arthropod functional groups (detritivores, predators, and herbivores) and two taxonomic groups (beetles and arachnids). We sampled twelve sites spanning 1,132 m elevation and four life zones, collecting 4,834 individual ground arthropods identified to 123 taxa. Elevation was a strong predicator for arthropod composition, however, patterns differed among functional and taxonomic groups and individual species between open- and forested-habitats. Beetles, arachnids, and predators decreased with elevation in open habitats but increased in forests showing a significant interaction between habitat type and elevation. Detritivores and herbivores showed no elevational patterns. We found 11 arthropod taxa with linear elevational patterns, seven that peaked in abundance at high elevations, and four taxa at low elevations. We also found eight taxa with parabolic elevational patterns that peaked in abundance at mid-elevations. We found that vegetation composition and productivity had stronger explanatory power for arthropod composition in forested habitats, while ground cover was a stronger predictor in open habitats. Temperature and precipitation were important in both habitats. Our findings demonstrate that relationships between animal diversity and elevation can be mediated by habitat type, suggesting that physiological restraints and resource limitations work differently between habitat types.
A number of recent studies have documented long-term declines in abundances of important arthropod groups, primarily in Europe and North America. These declines are generally attributed to habitat loss, but a recent study [B.C. Lister, A. Garcia,
