Measuring ecological niche overlap from occurrence and spatial environmental data

Abstract

Aim Concerns over how global change will influence species distributions, in conjunction with increased emphasis on understanding niche dynamics in evolutionary and community contexts, highlight the growing need for robust methods to quantify niche differences between or within taxa. We propose a statistical framework to describe and compare environmental niches from occurrence and spatial environmental data. Location Europe, North America and South America. Methods The framework applies kernel smoothers to densities of species occurrence in gridded environmental space to calculate metrics of niche overlap and test hypotheses regarding niche conservatism. We use this framework and simulated species with pre‐defined distributions and amounts of niche overlap to evaluate several ordination and species distribution modelling techniques for quantifying niche overlap. We illustrate the approach with data on two well‐studied invasive species. Results We show that niche overlap can be accurately detected with the framework when variables driving the distributions are known. The method is robust to known and previously undocumented biases related to the dependence of species occurrences on the frequency of environmental conditions that occur across geographical space. The use of a kernel smoother makes the process of moving from geographical space to multivariate environmental space independent of both sampling effort and arbitrary choice of resolution in environmental space. However, the use of ordination and species distribution model techniques for selecting, combining and weighting variables on which niche overlap is calculated provide contrasting results. Main conclusions The framework meets the increasing need for robust methods to quantify niche differences. It is appropriate for studying niche differences between species, subspecies or intra‐specific lineages that differ in their geographical distributions. Alternatively, it can be used to measure the degree to which the environmental niche of a species or intra‐specific lineage has changed over time.

Macroevolutionary consequences of profound climate change on niche evolution in marine molluscs over the past three million years

“…Models of species' abiotic niche parameters were constructed for each of three temporal intervals-the mPWP, LIG and PI-using taxon occurrence data and environmental parameters unique to each time slice. The resulting niche estimates were compared through time to statistically assess similarity using both environmental and geographical approaches [28,34,35]. In both approaches, an observed similarity metric is computed and compared with a simulated null distribution.…”

“…changes in the realized niche; RN). Studies may incorrectly indicate niche evolution if the environmental conditions that are available to a species are not taken into account [4,27,28].…”

Evolution under changing climates: climatic niche stasis despite rapid evolution in a non-native plant

“…The first two axes from a PCA of bioclimatic variables, including both species occurrences and [35]. Niche dynamics were assessed by calculating the proportion of the densities in the non-native range that occur in environments that are also occupied in the native range ('stability'), the proportion of non-native densities that occur in environments that are not occupied in the native range ('expansion') and the proportion of densities in the native range that occur in environments that are not occupied in the non-native range ('unfilling') [34].…”

“…The climatic niche in the native and non-native ranges was modelled using the framework proposed by Broennimann et al [35] and Petitpierre et al [34]. The first two axes from a PCA of bioclimatic variables, including both species occurrences and [35].…”

Improving plant functional groups for dynamic models of biodiversity: at the crossroads between functional and community ecology

“…S3) (Hutchinson et al, 2009) at 250m resolution in the Ecrins. Pairwise similarities of species abiotic niches were estimated from the overlap of their observed distributions (Dmetric, Schoener, 1970) projected into the first PCA plan (Broennimann et al, 2011).…”