Abstract

Extreme ecological disturbances such as floods, wildfires, and droughts are difficult to study because they are rare and unpredictable. We had the opportunity to study the effect of an historic flood on an anuran community in the Missouri River floodplain. We used occupancy estimation to estimate the proportion of wetlands occupied by calling adult male anurans. Three species—the plains leopard frog (Lithobates blairi), Woodhouse's toad (Anaxyrus woodhousii), and Blanchard's cricket frog (Acris blanchardi)—had only minor changes in occupancy rate two years after the flood. Colonization rates for these species were positively associated with wetlands that were shallower near the shore and they did not appear to be affected by reduced vegetation. Three other species or species complexes—the northern leopard frog (Lithobates pipiens), the gray treefrog complex (Hyla versicolor and Hyla chrysocelis), and the boreal chorus frog (Pseudacris maculata)—had greatly reduced occupancy rates two years after the flood. Colonization rates for these species were relatively low, while they had high extinction rates. Colonization rates for these species were not associated with any habitat characteristic we measured. Future flood events will likely continue to make northern leopard frogs, gray treefrogs, and boreal chorus frogs a less important part of the ecological community. While some species may fare well under extreme climate events, such as this flood, that are forecast under climate change scenarios, many species will struggle.

Highlights

  • Disturbance regimes are a natural part of ecosystem dynamics and species are adapted to varying magnitudes of disturbance at varying intervals

  • Three species—the plains leopard frog (Lithobates blairi ), Woodhouse’s toad (Anaxyrus woodhousii ), and Blanchard’s cricket frog (Acris blanchardi )— had only minor changes in occupancy rate two years after the flood. Colonization rates for these species were positively associated with wetlands that were shallower near the shore and they did not appear to be affected by reduced vegetation

  • Species dynamics Because some sites were only wet for part of the year and different species call at different times of the year, the number of sites surveyed for each species was sometimes different within a year

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Summary

Introduction

Disturbance regimes are a natural part of ecosystem dynamics and species are adapted to varying magnitudes of disturbance at varying intervals. Biological communities occasionally experience disturbances so extreme in magnitude that the consequences may be severe. Such disturbances may include wildfires, floods, hurricanes, and droughts, which cause drastic alterations in community composition and diversity, and extirpation of sensitive species (Poff 2002, McKenzie et al 2004, Ryan et al 2015). Such perturbations are, by definition, rare, and opportunities to directly study ecosystem impacts are rarer (Bender et al 1984). We are unaware of any studies on herpetofauna quantifying effects of extreme flooding

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