Effects of Urbanization on California’s Fish Diversity: Differentiation, Homogenization and the Influence of Spatial Scale

SMC Author

Michael Marchetti

SMC Affiliated Work

1

Status

Faculty

School

School of Science

Department

Environmental and Earth Science

Document Type

Article

Publication Date

2006

Publication / Conference / Sponsorship

Biological Conservation

Description/Abstract

Human development of freshwater ecosystems has lead to drastic changes in freshwater fish faunas, including the loss of many native species and the gain of non-natives. Typically conservation ecologists view these two opposing forces as contributing to biological homogenization, and consider homogenization as one of the principle negative consequences of urbanization. However, homogenization is only one outcome out of many that can result from the loss and gain of species. In particular, it is possible for invasions and extinctions to lead to differentiation; a process whereby two (or more) regions become less similar to one another through time. Using the freshwater fishes of California, we show that urbanization is highly positively correlated to both the endangerment of native fish and the invasion of non-native fish within watersheds. Despite this, the fish faunas of California’s watersheds have differentiated from one another through time. Furthermore, the degree of differentiation is positively correlated with measures of urbanization, which is contrary to expectation. We suggest that this result reflects: (1) the haphazard manner in which non-native fishes have been introduced into California watersheds, (2) the difficulty that both native and non-native fishes have in expanding their geographical ranges, and (3) the continued presence of vestiges of formerly distinct regional faunas. This pattern of differentiation among watersheds is likely a matter of scale, as previous work on freshwater fishes has demonstrated homogenization at both larger and smaller spatial scales. In addition the observed pattern is probably a short-term (temporal) phenomena and will disappear with continued invasion and extinction. We suggest that similar patterns may occur for other taxa that have limited natural dispersal abilities and that are idiosyncratically released as non-natives via human activities (e.g. herptiles).

Keywords

Invasion, Extinction, Homogenization, Urbanization, Freshwater fish, California, Watershed, Development, Non-metric multidimensional scaling

Scholarly

yes

DOI

10.1016/j.biocon.2005.04.025

Volume

127

Issue

3

First Page

310

Last Page

318

Disciplines

Earth Sciences | Environmental Sciences

Original Citation

Marchetti, M.P., Lockwood, J.L. and Light, T.S. 2006. Effects of urbanization on California’s fish diversity: Differentiation, homogenization and the influence of spatial scale, Biological Conservation, vol. 127, issue 3, pg.310-318. doi:10.1016/j.biocon.2005.04.025

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