The "Killer Weed"

As a marine science major I decided to take a break from blogging about the Cane Toad as much as I love reading up on the species and their effects on the ecosystem they inhabit and instead provide an example of an invasive aquatic species.  More specifically, a species that has been introduced to both where I come from in California and her in Australia as well.

Caulerpa taxifolia is a native algae to Hawaii.  Being that this algae is a native species to Hawaii it has not grown out of control but rather has its place within the ecosystem providing balance.  Unfortunately the same cannot be said for areas of the Mediterranean and California where this species has now spread (University of Hawaii 2014). 

Above is a picture to provide an example of how abundant the presence of this species can be in areas in which it inhabits.

According to CEPA (California Environmental Protection Agency 2014) Caulerpa, also referred to as “Killer Algae” was imported for aquarium purposes for its particular fast growth rate of about an inch per day and appealing appearance.  It is believed that that the “Killer Algae” began its invasion of coastal waters following an illegal dumping of algae residue into the water ways (CEPA 2014).   Caulerpa, as most introduced species, competes for resources with the native species of the area lacking natural predators and because of the toxin the algae produces local herbivores are not interested (CEPA 2014).  Controlling the spread of this algae in California poses quite a challenge for multiple reasons one of them being that the trade of this algae remains legal under federal law although efforts are currently being made to impose legislation that will prevent future trading (CEPA 2014).

The introduction to Australia and more specifically to New South Whales is believed to be the same as it were for California, dumped from an aquarium into the waterways and spreads via boat transportation and fishing nets.  According to the NSW department of Primary Industries (2014), the presence of the algae and its rapid growth rate poses threat to “alter marine habitats and affect biodiversity” such as the native seagrass and native animals of which inhabit that seagrass.  Unlike California, the trade of this algae is illegal in Australia as it is a declared “Class 1 noxious species in all NSW waters” (NSW department of Primary Industries (2014).

“Killer Algae” is another small example of an invasive species and potential effects an introduced species can have within the area.  What I find more interesting about this particular subject is how the algae was introduced into areas which allowed for the rapid spread, by dumping aquarium waters or waste without realizing the potential effects of the action.  Unfortunately, large amounts of funding and the stress on native species of these areas are the result of what must have seemed at the time, an innocent action.  I believe this to be a perfect example of what educational awareness can sometimes prevent.

References:

Botany Department, 2014, Marine algae of Hawai’I, University of Hawai’I, viewed 29 March 2014, http://www.hawaii.edu/reefalgae/invasive_algae/chloro/caulerpa_taxifolia.htm

Los Angeles Regional Water Quality Control Board, 2014, Killer algae found in southern California, California Environmental Protection Agency, Sacramento, viewed 29 March 2014, http://www.waterboards.ca.gov/losangeles/water_issues/programs/water_quality_issues/killer_algae_article.shtml

NSW Department of Primary Industries, 2014, Fishing and aquaculture Caulerpa (Caulerpa taxifolia), NSW Government, Orange, viewed 29 March 2014, http://www.dpi.nsw.gov.au/fisheries/pests-diseases/marine-pests/nsw/caulerpa-taxifolia

Picture Credit:

http://www.seaslugforum.net/find/caultaxi

Evidence for Rapid Evolution

Last week I blogged about the Cane Toad and briefly touched upon the effects that this non-native species can have or has had locally here in Australia.  While reading through the information I had looked up I also came across information that pointed to studies that have been done or are currently being done showing that one of the effects the Cane toad has had on native species is that some have adapted to better survive he deadly toxin the Cane Toad contains (Australian Government Department of the Environment 2010).

Ben Phillips is an Evolutionary Biologist at the University of Sydney working on his PhD under Richard Shine and in his interview with ABC Science he notes that the Cane Toad is a great selective pressure in regards to evolutionary biology and that through his research he believes the changes he has documented is a sign of rapid evolution (Salleh, 2004).

Phillips studied four different species of snakes through preserved specimens; “Pseudechis porphyriacus (red-bellied black snake) and Dendrelaphis punctulatus (green tree snake)” and “Hemiaspis signata (swamp snake) and Tropidonophis mairii (keelback snake)” (Salleh, 2004).  In his interview he notes that through his research of these snakes he found clear evidence that over the past 70 years since the Cane Toad had been introduced the two more sensitive snakes the red-bellied black snake and the green tree snake had increased in their length while the other two had not changed and he claims this “morphology” is a direct result of the presence of the Cane Toad (Salleh, 2004).

This is just one example of a species not going extinct due to the presence of the Cane Toad but rather adapting.  However, after doing some more research on this topic I've come across quite a few papers written by Richard Shine and his colleagues which contain scientific data to back up their claims they make contradicting popular belief  about the effects of the introduced Cane Toad.  Those papers can be found on Shines webpage, http://sydney.edu.au/science/biology/sites/Shinelab/index.html (SBI, 2012).

For example, contrary to popular belief, and as mentioned in one of my previous comments on the last blog, the Cane Toad has not driven a single species into extinction.  It is true that numbers of specific species have dwindled upon the invasion of the Cane Toad into their area but after time those numbers begin to come back up as they learn to adapt to the Cane Toad in their environment even if it is just learning to not have them for dinner (SBI, 2012).  

This is not to say that having an introduced species slowly move in and spread out over the landscape, competing with native species for space and other resources is a good thing but there is more we can learn from it at the same time.

References:

Anna Salleh, 2004, Cane toads make snakes adapt to survive, ABC Science, viewed 19 March 2014, <http://www.abc.net.au/science/articles/2004/11/30/1250708.htm>

Can Toads in Oz 2011, SBI, viewed 21 March 2014, <http://www.canetoadsinoz.com/debunkingcanetoadimpactmyths.html>

Department of the Environment 2010, Australian Government, viewed 18 March 2014,

 <http://www.environment.gov.au/node/14576>



 

 

The Famous Cane Toad

     I happen to love amphibians especially frogs and toads.  Always have since I was young.  However, not until I arrived here in beautiful Australia did I begin to hear about the famous Cane Toad.  Although I am familiar with the negative impacts invasive species can pose,  I was still surprised to hear so much hostility to this creature, and so I decided I would research this topic in some more detail.

     Australian Government Department of the Environment state Cane Toads can range anywhere from 10 cm to over 23 cm in some cases, they have moist warty skin with toxin producing glands (2005).  The toxin  produced by the Cane Toad has been known to cause death by ingestion.  The poison attacks primarily the heart (Cameron, 2013) although there may be varying reactions depending on the species that is lucky enough to experience the power of the Cane Toad.

     The Cane Toad is native to Central and South America and was brought into Australia from Hawaii in an attempt to control the pests that were destroying the sugar cane crops (Australian Government Department of the Environment, 2005).   Not only did the Cane Toad have little success in controlling the pests in the crops they also proved to "tough, adaptable" and have "few predators in Australia" (Cameron, 2013) and with that began to spread rapidly.
  
     With this introduced, non-native species Australian biodiversity takes a hit.  Native predator numbers have declined due to consumption of the Cane Toads.  (Australian Government Department of the Environment 2010).  Another effect is competition.  The Cane Toad, just like every other species competes for habitat and usually wins the battle.  For example, according to the Australian Government Department of the Environment, "a 2004 study showed that cane toads ruined one-third of nest attempts of ground-nesting rainbow bee-eaters by usurping their nest burrows and preying upon their eggs and young nestling" (2010).

     The Cane Toad provides a great example for how invasive species can effect ecosystems and biodiversity in areas in which they are not meant to inhabit.

References:

Department of the Environment 2005, Australian Government, viewed 14 March 2014, <http://www.environment.gov.au/node/14576>

Department of the Environment 2005, Australian Government, viewed 14 March 2014,<http://www.environment.gov.au/resource/cane-toad-bufo-marinus>

Elizabeth Cameron 2013, Australian Museum, New South Whales, viewed 14 March 2014, <http://www.austmus.gov.au/Cane-Toad>

Picture Credit:

The Cane Toad: http://www.abc.net.au/news/2005-04-24/german-explosions-could-they-hold-the-answer-to/1557086

The Cane Toad is tough and adaptable, as well as being poisonous throughout its life cycle, and has few predators in Australia. - See more at: http://www.austmus.gov.au/Cane-Toad#sthash.QbtBczg1.dpuftoug

The Cane Toad is tough and adaptable, as well as being poisonous throughout its life cycle, and has few predators in Australia. - See more at: http://www.austmus.gov.au/Cane-Toad#sthash.QbtBczg1.dpuf

The Cane Toad is tough and adaptable, as well as being poisonous throughout its life cycle, and has few predators in Australia. - See more at: http://www.austmus.gov.au/Cane-Toad#sthash.QbtBczg1.dpuf

Summary: Bennett et al. (2011)

Invasive, exotic, introduced, are all words used to describe a species that has been brought into an area of which it originally did not belong.  Like adding anything to a system that was not meant to contain the addition, the addition will most definitely have an affect on the system.  Whether that affect on the system is for better or for worse is to be determined.  There has been many studies conducted and observations made in regards to that exact question, what are the effects on an ecosystem or environment as a result of an introduced species?  Looking at just one specific study done on Holcus lanatus, a species of grass introduced to California in the United States, results determined that this introduced species does have a negative impact on the local communities in which the grass is found.  The study was conducted both in the greenhouse and out in the field in which the species is found, measuring growth rate, size, herbivory, competition and the soil (Bennett et al. (2011)).  the results proved that the presence of H. lanatus affects the plant community in that it interferes with "the germination, growth, and establishment" of E. glaucus, the native plant (Bennett et al. (2011)).  While growth rate was reduced due to competition and soil was affected by the H. lanatus's strong roots above and below ground, the size the plants reached were directly related to "mammalian herbivory" whom appeared to show no preference in one plant over the other.  This study provides one small example into the many factors hat need to be taken into consideration when evaluating a specific area, the continued survival of species in the area and possible restoration and continued management projects.