ANACARDIACEAE
Cashew and Sumac Family

                 

Distribution

Anacardiaceae has about 70 genera worldwide, 11 of which can be found in the United States. Anacardiaceae is distributed in tropical areas and it also extends into temperate regions.  Members of this family are not found in dry, desert areas.  In the figure below, blue denotes the presence of members of this family. Note the absence of Anacaridaceae at regions 30ºN and 30ºS of the equator, in Saudi Arabia, the Sahara, and Australia. At these lattitudes there is less moisture which gives rise to drier climates.  The same is true for regions beyond 60ºN and 60ºS.


Overview

Within the angiosperms, Anacardiaceae belongs to the eudicots  – a monophyletic group that contains up to roughly 75% of all the flowering plants.  A main trait for the eudicots is that the embryo contains two cotelydons. However this is not a solid characteristic for determining the evolution and phylogeny of flowering plants.  Having two cotyledons in the embryo is believed to be the basal condition for angiosperms which was lost in the monocotelydons. Eudicots can more reliably be categorized based on the tricolpate derived pollen grains. A tricolpate pollen grain has three apertures, or slits, which are spaced evenly on the surface and aligned parallel to the grain's longitudinal axis. Apertures may allow for the pollen grain to contract or expand in moist environments and may also function as the site for siphonogamy during fertilization.


Since the dicots account for such a large percentage of all plants, there is a great amount of diversity found within this monophyletic group.  Anacardiaceae belongs to the order Sapindales, which falls under Rosids II.   Another group within Sapindales is Rutaceae, the economically important citrus family.


A Note on Toxicodendron

The genus toxicodenrdon contains the plants poison sumac, poison oak, and poison ivy.  They contain the toxin urushiol, which may cause people to have mild to severe allergic reactions, called urushiol induced contact dermatitis. The name urushiol comes from the Japanese word urushi, which refers to the chemical’s capability to produce a hard lacquer.  It is essentially the sap which is produced by the plant, and the lacquer is created when it oxidizes in a moist environment.  Once the toxin has come into contact with skin, it causes blisters or a rash  at the area of contact.  If the urushiol oil is not washed off or neutralized through various chemicals, it can spread across the body and onto other surfaces which may act as transmitters of the oil to other sensitive people.  Serious reactions can even lead to scarring.  Burning poison ivy will only release urushiol into the air and can be inhaled where it will affect the lungs.  Even allegedly dead poison ivy plants, especially their vines, have been known to cause a reaction.  Toxicodendron thrive in moist environments but they also survive well in northern temperate regions.  Urushiol is also found in the shells of cashew nuts, which connects this family that contains an unlikely array of species.

Many people are allergic to poison ivy and poison oak, yet not that many people know what to look out for in the woods.  Both plants have trifoliate leaves which are uneven.  The edges can be entire or serrate, and other minute variations like this in its morphology can  make it confusing to identify.  Poison ivy can also grow as a vine around the base of trees, and without intervention it can grow up a tree and over the years grow as thick or thicker than the tree's own trunk.  In these cases, it's weight can bring the tree down or slowly cause it to die. Sometimes as the vine reaches the upper levels of the forest, it outcompetes the tree's leaves for sunlight.  Although these plants prove a hindrance to humans, deer, birds, and insects use them as a food source.

Other genera within Anacardiaceae which cause dermatitis reactions are Semecarpus and Metopium.

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References:

"Anacardiaceae." PlantSystematics.org.
http://www.plantsystematics.org/  4/11/07

"Anacardiaceae classification." USDA Plant Database.
http://www.plants.usda.gov/  4/11/07

Hoeggemeier, Annette. "Annacadrium occidentale. Ruhr-Universität Bochum  
http://www.ruhr-uni-bochum.de/boga/html/Anacardium_occidentale_Foto.html   4/11/07

Kuo, M. (2002, June). Poison ivy. MushroomExpert.Com.
http://www.mushroomexpert.com/poison_ivy.html

Simpson, Michael G. Plant Sytematics. Elsevier Academic Press. Burlington, MA. 2006

Zomlefer, Wendy B. Guide to Flowering Plant Families. University of North Carolina Press. Cambride. 1994

Other Links:

Poison Ivy, Oak, and Sumac Information Center

NYS Horticulture Study Guide for Youth