Mate-finding failure as an important cause of Allee effects along the leading edge of an invading insect population

Authors

  • Mario Contarini,

    1. Dipartimento di Protezione delle Piante, Università di Sassari, via E. De Nicola, 07100 Sassari, Italy
    2. Department of Entomology, University of Wisconsin-Madison, 345 Russell Laboratories, 1630 Linden Drive, Madison, WI 53706, USA
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  • Ksenia S. Onufrieva,

    1. Department of Entomology, Virginia Polytechnic Institute and State University Blacksburg, VA 24061, USA
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  • Kevin W. Thorpe,

    1. Agricultural Research Service, US Department of Agriculture, Beltsville, MD 20705, USA
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  • Kenneth F. Raffa,

    1. Department of Entomology, University of Wisconsin-Madison, 345 Russell Laboratories, 1630 Linden Drive, Madison, WI 53706, USA
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  • Patrick C. Tobin

    Corresponding author
    1. Forest Service, US Department of Agriculture, Northern Research Station, 180 Canfield St., Morgantown, WV 26505, USA
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*Patrick C. Tobin, Forest Service, US Department of Agriculture, Northern Research Station, 180 Canfield St., Morgantown, WV26505, USA. E-mail: ptobin@fs.fed.us

Abstract

The movement of humans and goods has facilitated the arrival of non-native insects, some of which successfully establish and cause negative consequences to the composition, services, and functioning of ecosystems. The gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), is currently invading North American forests at variable rates, spreading by local and long-distance movement in a process known as stratified dispersal. Newly arriving colonizers often occur considerably ahead of the population front, and a key question is the degree to which they successfully establish. Prior research has highlighted mate-finding failures in sparse populations as a cause of an Allee effect (positive density dependence). We explored this mechanism by measuring the relationship between female mating success and background male moth densities along the gypsy moth western front in Northern Wisconsin (USA) over 2 years. The mating results were then compared with analogous previous studies in southern Wisconsin, and the southern front in West Virginia and Virginia (USA). Mate-finding failures in low-density populations were consistently observed to be density-dependent across all years and locations. Mate-finding failures in low-density populations have important ramifications to invasive species management, particularly in predicting species invasiveness, preventing successful establishment by small founder populations, and concentrating eradication efforts where they are most likely to succeed.

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