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Hotspots of exotic free-spawning sex: man-made environment facilitates success of an invasive seastar


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Ling, SD, Johnson, CR, Mundy, CN, Morris, A and Ross, DJ 2012 , 'Hotspots of exotic free-spawning sex: man-made environment facilitates success of an invasive seastar' , Journal of Applied Ecology, vol. 49 , pp. 733-741 , doi: 10.1111/j.1365-2664.2012.02133.x.

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1. The introduction of exotic species to new areas poses a major threat to the environment. For
those introduced species that establish and survive beyond the short term, the opportunities to manage
the risk of continuing spread often rest with limiting reproductive output. The introduced
northern Pacific seastar Asterias amurensis is an ecologically important pest that has established in
the Derwent Estuary (Australia). Driven by oversupply of bivalve prey, it is persistent, abundant
and fecund when associated with man-made structures such as docks, marinas, jetties and piers, that
is, ‘wharves’.
2. As a free-spawning invertebrate, fertilization by A. amurensis is a critical life-history stage constrained
by strong Allee effects. Eggs must be released in close proximity to sperm sources because
the chances of achieving fertilization drastically reduce with increasing distances of spawner separation.
3. Investigation of zygote production in the Derwent Estuary using a spatially explicit model of
free-spawning fertilization shows that A. amurensis at wharves, while representing <10% of the
total population in the estuary and concentrated in<0Æ1%of the total area, may contribute>90%
of total zygote production. Given the seastars’ long-lived and highly dispersive larvae, we show that
wharves not only represent important sites of invasion but also facilitate propagule pressure
promoting secondary invasions.
4. Synthesis and applications. In the absence of effective pest control solutions, focusing on reproductive
hotspots has the potential to reduce further spread of established marine pests and to alleviate
ongoing ecological impacts. In the case of the northern Pacific seastar, elimination of highly
localized wharf populations annually prior to spawning can reduce overall zygote production by up
to estimated 90%. The long-termprotection of key sources of larval production is a common goal
for marine reserve design and fisheries management. However, the same concept but in reverse,
whereby larval production is minimized at key sources, could be effective in the management of
introduced pests in subtidal marine environments.

Item Type: Article
Authors/Creators:Ling, SD and Johnson, CR and Mundy, CN and Morris, A and Ross, DJ
Keywords: allee effect, anthropogenic habitat, artificial habitat, Asterias amurensis, coastal infrastructure, ecological restoration, fertilization modelling, free-spawning ecology, introduced marine pest, pest management
Journal or Publication Title: Journal of Applied Ecology
DOI / ID Number: 10.1111/j.1365-2664.2012.02133.x
Additional Information:

Copyright 2012 The Authors. Copyright 2012 British Ecological Society

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