The uncertainty about who's who among the Sunshine State's lookalike Casuarinas poses a problem to ARS scientists who may someday need to match Casuarina-quelling insects from Australia--the tree's homeland--to invader Casuarina trees in Florida.
To solve the Casuarina puzzle, he's using samples of DNA of Casuarinas from Australia--where their identification is certain.
Technicians Kim Mann and Jeannie Lassey--with Gaskin's research unit--extract DNA from pine-needle-like leaves that Gaskin collected in 2006 from Casuarinas growing along Australia's eastern coast, as well as from specimens that colleagues Matt Purcell, Gary Taylor, and Greg Wheeler gathered elsewhere in Australia and in Florida.
The study is the first to use DNA to definitively identify the Florida Casuarinas. Making the correct identification is "a problem that can't be solved by merely looking at the shape of the trees' leaves or conelike flowers," says Gaskin.
Their trips Down Under were to search for biological control agents for highly invasive Casuarina species, commonly called "ironwood," "horsetail tree," or "Australian pine."
"While there are some fine qualities to Casuarina," says Wheeler, who's in ARS's Invasive Plant Research Laboratory (IPRL) in Fort Lauderdale, Florida, "its negatives far outweigh its positives."
The Australian pine problem includes three Casuarina species: C.
Purcell, Brown, Taylor, and John Gaskin, research leader of ARS's Pest Management Research Unit in Sidney, Montana, comprise a Casuarina research team.
The saga of finding helpful Australian insects to stave off the spread of unwanted, pinelike Casuarina trees in Florida comes complete with its own mystery: It is often difficult to tell the various Casuarina species and subspecies apart.
Rehabilitation started with the planting of the tall casuarina tree or 'whistling pine' (Casuarina equisetifolia) interspersed with conocarpus (Conocarpus lancifolius) and the coconut palm (Cocos nucifera).
* Well over 1.5 million casuarina trees have been planted and many of these are felled after 5 to 7 years to be sold as building poles to substitute for the over-exploited mangroves - wood that is unsuitable for the building trade is sold as firewood and charcoal;