SLIDE 6 Cane toads in Australia
Cane toads were deliberately introduced to Australia from Hawaii in 1935 in an attempt to stop French’s Cane Beetle and the Greyback Cane Beetle from destroying sugar cane crops in North Queensland. The Australian Bureau of Sugar Experimental Stations made the release of 101 cane toads at Gordonvale in Queensland in 1935. They were unsuccessful in controlling the cane beetles. Biological control = Introduction of predators to control a prey species
Cane toads in Australia
Cane Toads - An Unnatural History (1987)
Invasion and the evolution of speed in toads
Benjamin L. Phillips1, Gregory P. Brown1, Jonathan K. Webb1 and Richard Shine1 Nature 439 (2006) Cane toads seem to have honed their dispersal ability to devastating effect over the generations. Cane toads (Bufo marinus) are large anurans (weighing up to 2 kg) that were introduced to Australia 70 years ago to control insect pests in sugar-cane fields. But the result has been disastrous because the toads are toxic and highly
- invasive. Here we show that the annual rate of
progress of the toad invasion front has increased about fivefold since the toads first arrived; we find that toads with longer legs can not only move faster and are the first to arrive in new areas, but also that those at the front have longer legs than toads in older (long-established) populations. The disaster looks set to turn into an ecological nightmare because of the negative effects invasive species can have on native ecosystems1,
2; over many generations, rates of invasion will
be accelerated owing to rapid adaptive change in the invader3, with continual 'spatial selection' at the expanding front favouring traits that increase the toads' dispersal4, 5. are to us- sect he se ly he
rst ith ve in at an d) set ht- ive ve ny ill id r3,
ng ds’
–1,000 –500 500 1,000 1,500 –0.16 –0.12 –0.08–0.04 0.04 0.08 Relative distance moved (m) Relative leg length (ln mm) –0.15 –0.10 –0.05 0.05 0.10 0.15 0.20 10 20 30 40 50 60 70 Relative leg length (ln mm) Time since colonization (yr) –0.15 –0.10 –0.05 0.05 0.10 0.15 200 400 600 800 Relative leg length (ln mm) Order of arrival 1 9 4 5 – 5 4 1 9 5 5 – 6 4 1 9 6 5 – 7 4 1 9 8 – 8 4 2 1 – 5 10 20 30 40 50 60
a c b d
Radial increase in range (km yr1) Period
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- Figure 1 | Morphology of cane toads in relation to their speed and invasion
- history. a, b,Compared with their shorter-legged conspecifics, cane toads
with longer hind limbs move further over 3-day periods ( r20.34) (a), and are in the vanguard of the invasion front (based on order of arrival at the study site; r20.11) (b). c, Cane toads are relatively long-legged in recent populations, and show a significant decline in relative leg length with time in older populations (r20.05). d, The rate at which the toad invasion has progressed through tropical Australia has increased substantially since toads were first introduced in 1935 (r20.92).
How do invasives move/spread
Pattern of a “typical” invasion Latent phase (small population size) Rapid population growth and spread
Opuntia in South-Africa
Reconstructing 50 years of Opuntia stricta invasion in the Kruger National Park, South Africa: environmental determinants and propagule pressure Llewellyn C. Foxcroft, Mathieu Rouget, David M. Richardson and Sandra Mac Fadyen Diversity and Distributions, (2004) 10: 427–437
Effect of invasive species
Predation
