Aim: A better understanding of native and non-native species response to environmental conditions, historical processes, and human pressures is crucial in the face of global environmental changes affecting biodiversity. Here, we evaluate the relative roles of environmental, historical, and anthropogenic factors in influencing species richness of native and non-native freshwater fishes in watersheds across North America. Location: North America (exclusive of Mexico)

Time period: Recent

Major taxa studied: Freshwater fishes

Methods: We compiled an extensive dataset of native and non-native fish richness in 2993 watersheds across North America, together with corresponding data for environmental (climatic, geographic), historical, and anthropogenic factors. We used variance partitioning and hierarchical partitioning to quantify the relative importance of environmental, historical and anthropogenic factors in explaining richness variation in native and non-native fishes (overall, and by geographic origin [foreign/translocated] and pathway [authorized/unauthorized]), while accounting for correlations among explanatory variables and spatial autocorrelation.

Results: Overall importance of environmental and anthropogenic factors was greater than historical factors in explaining both native and non-native richness. Precipitation-related factors were more important in explaining native richness, whereas non-native richness was largely associated with temperature-related factors. However, richness related to authorized introductions was less constrained by temperature than unauthorized introductions. Dam density, road density and urbanization gradient were major anthropogenic factors related to non-native richness, yet their relative importance varied among origin- and pathway-based categories.

Conclusions: Our findings indicate different environmental drivers influence native and non-native fish richness patterns in North America. The accumulation of non-native species in watersheds depends on the interaction between environmental conditions and anthropogenic-based processes related to introduction history including geographic origin, introduction pathway, and propagule pressure, where the latter likely plays a major role. Warmer regions with high human population densities and more impoundments are more prone to fish invasions, mostly via unauthorized introductions.

Freshwater fishes in North America: Species by watershed matrix (non-native species undifferentiated)

A comma-delimited file that contains occurrence data for 949 freshwater fish species in 2993 watersheds across Canada and United States. Species occurrences are coded either as ‘native’ (native to North America, found within the native range) or ‘nonnative’ (both foreign species and native transplants), whereas ‘0’ indicates absence. See the accompanying metadata document (README_NAFWFISHdata.pdf) and the Materials and Methods section of the original article for the data sources.

sp x watershed_nonnative undifferentiated.csv

Freshwater fishes in North America: Species by watershed matrix (non-native species by origin)

A comma-delimited file that contains occurrence data for 949 freshwater fish species in 2993 watersheds across Canada and United States. The occurrences of non-native species are coded by geographic origin i.e. ‘foreign’ (not native to North America) and ‘translocated’ (native to North America, moved beyond of native range). The occurrences of species native to North America within their native ranges are coded as ‘native’ and species absences are indicated by ‘0’. See the accompanying metadata document (README_NAFWFISHdata.pdf) and the Materials and Methods section of the original article for the data sources.

sp x watershed_nonnative by origin.csv

Freshwater fishes in North America: Species by watershed matrix (non-native species by pathway)

A comma-delimited file that contains occurrence data for 949 freshwater fish species in 2993 watersheds across Canada and United States. The occurrences of non-native species are coded by introduction pathway i.e. ‘authorized’ (legally sanctioned introductions) and ‘unauthorized’ As a caveat, some species known to be introduced through authorized pathways may also have been introduced via unauthorized means. The occurrences of species native to North America within their native ranges are coded as ‘native’ and species absences are indicated by ‘0’. See the accompanying metadata document (README_NAFWFISHdata.pdf) and the Materials and Methods section of the original article for the data sources.

sp x watershed_nonnative by pathway.csv

Freshwater fishes in North America: Species richness by watershed matrix

A comma-delimited file containing richness of native and non-native (overall, and by geographic origin [foreign/translocated] and pathway [authorized/unauthorized]) freshwater fishes in 2993 watersheds across Canada and United States. See the accompanying metadata document (README_NAFWFISHdata.pdf) and the Materials and Methods section of the original article for the data sources.

species richness x watershed.csv

Metadata for data files

A pdf document that contains data sources, and definitions of variable names and codes in the comma-delimited data files.

README_NAFWFISHdata.pdf