Effects of Detritus on the Mosquito Culex pipiens: Phragmites and Schedonorus (Festuca) Invasion Affect Population Performance.

Paul T Leisnham,Andrew H Baldwin,Brandon Scott,Shannon L Ladeau

doi:10.3390/ijerph16214118

Abstract

Species interactions that influence the performance of the exotic mosquito Culex pipiens can have important effects on the transmission risk of West Nile virus (WNV). Invasive plants that alter the vegetation communities of ephemeral ground pools may facilitate or resist the spread of C. pipiens (L.) by altering allochthonous inputs of detritus in those pools. To test this hypothesis, we combined field surveys of roadside stormwater ditches with a laboratory microcosm experiment to examine relationships between C. pipiens performance and water quality in systems containing detritus from invasive Phragmites australis (Cav.) Trin. Ex Steud., introduced Schedonorus arundinaceus (Schreb.) Dumort., or native Juncus effusus L. or Typha latifolia L. In ditches, C. pipiens abundance was unrelated to detritus species but female C. pipiens were significantly larger from ditches with S. arundinaceus and smaller with J. effusus. Larger and smaller C. pipiens were also produced in microcosms provisioned with S. arundinaceus and J. effusus, respectively, yet the per capita rate of population of change did not vary. Larger females from habitats with S. arundinaceus were likely caused by faster decay rates of S. arundinaceus and resultant increases in microbial food, but lower survival as a result of fouling and higher tannin-lignin concentrations resulted in little changes to overall population performance. Larger female mosquitoes have been shown to have greater potential for transmitting arboviruses. Our findings suggest that changed community-level interactions from plant invasions in urban ephemeral ground pools can affect the fitness of C. pipiens and possibly increase WNV risk.

Highlights

As the coexistence of exotic species becomes more common, understanding how their interactions affect the success and impacts of biological invasions is increasingly important
Our findings suggest that changed community-level interactions from plant invasions in urban ephemeral ground pools can affect the fitness of C. pipiens and possibly increase West Nile virus (WNV) risk
In surveys of roadside stormwater ditches, mean C. pipiens densities did not differ among habitats that varied in litter species, but female C. pipiens were larger from ditches with S. arundinaceus and smaller with J. effusus compared to other plant species (P. australis and T. latifolia)

Summary

Introduction

As the coexistence of exotic species becomes more common, understanding how their interactions affect the success and impacts of biological invasions is increasingly important. Interactions among exotic species’ can be divided into two general categories based on how they affect invasion success. Exotic species can have inhibitory effects on other exotics that are already established in or are newly colonizing a system, by decreasing niche opportunities [2], altering the physical environment and nutrient fluxes, or impacting food webs [3]. Mosquitoes that use small ephemeral water bodies, such as stormwater structures (e.g., catch basins, ditches) or containers (e.g., tree holes, trash) for their developmental stages (eggs and larvae), provide excellent model systems to investigate the effects of interactions between exotic species on invasions. Public Health 2019, 16, 4118; doi:10.3390/ijerph16214118 www.mdpi.com/journal/ijerph

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