8
Many of the Old and New World acacias seem related. For example, the African
swollen-thorn acacias seem to have an ant mutualism similar to the Central American
swollen-thorn acacias (Janzen 1974 ). Vachellia farnesiana (= Acacia farnesiana = A.
smallii ) is a widespread species in the New World, occurring across the southeastern
USA, through most of southeastern, south central, and southwestern Texas. Its distribution continues south and west through the arid and semiarid regions of northern
Mexico, southern New Mexico, Arizona, and California and south into the tropical
region including the Caribbean, central America, and northern South America
(Turner 1959 ; Correll and Johnston 1979 ; Turner et al . 2003 ). In addition, it is
reported from parts of southern Africa, arid parts of Australia, and some Pacifi c
Islands (Dharani 2006 ). It seems to be a New World species, possibly transplanted
in recent times into various Old World locations. Apparently, approximately 12 %
of the species in the former genus Acacia s. l. mostly species in the genera Senegalia
and Vachellia are reported from the Americas (Seigler and Ebinger 2005 ; Seigler
et al . 2006 ), and 12 or 13 species are reported in Texas and surrounding areas
(Turner 1959 ; Correll and Johnston 1979 ; Turner et al . 2003 ; Seigler et al . 2007 ).
Descriptions of the morphological characteristics that separate the genera
Senegalia and Vachellia can be found in Seigler’s recent publications (Seigler and
Ebinger 2005 ; Seigler et al . 2006 ). Characteristics in Senegalia would include the
lack of stipular spines, the presence of vegetative stipules, and the occurrence of
prickles and a few other characteristics (Fig. 2.1 ). On the other hand, Vachellia has
stipular spines (usually two) with the absence of prickles (Fig. 2.1 ). In addition, they
list the names of the species of Senegalia and Vachellia present in the Americas.
They also present some molecular genetics including a most parsimonious consensus tree comparing a number of Senegalia and Vachellia species , with a few Acacia
Fig. 2.1 Left picture above shows the presence of prickles on the stem of Senegalia greggii
(= Acacia greggii , catclaw acacia). On the right is a picture of Vachellia farnesiana (= Acacia farnesiana , huisache) that has two stipular spines and usually the absence of prickles. Photographs are
courtesy of Ms. Wendy Leonard and were taken in the San Antonio, Texas area
2 Species Systematics
Many of the Old and New World acacias seem related. For example, the African
swollen-thorn acacias seem to have an ant mutualism similar to the Central American
swollen-thorn acacias (Janzen 1974 ). Vachellia farnesiana (= Acacia farnesiana = A.
smallii ) is a widespread species in the New World, occurring across the southeastern
USA, through most of southeastern, south central, and southwestern Texas. Its distribution continues south and west through the arid and semiarid regions of northern
Mexico, southern New Mexico, Arizona, and California and south into the tropical
region including the Caribbean, central America, and northern South America
(Turner 1959 ; Correll and Johnston 1979 ; Turner et al . 2003 ). In addition, it is
reported from parts of southern Africa, arid parts of Australia, and some Pacifi c
Islands (Dharani 2006 ). It seems to be a New World species, possibly transplanted
in recent times into various Old World locations. Apparently, approximately 12 %
of the species in the former genus Acacia s. l. mostly species in the genera Senegalia
and Vachellia are reported from the Americas (Seigler and Ebinger 2005 ; Seigler
et al . 2006 ), and 12 or 13 species are reported in Texas and surrounding areas
(Turner 1959 ; Correll and Johnston 1979 ; Turner et al . 2003 ; Seigler et al . 2007 ).
Descriptions of the morphological characteristics that separate the genera
Senegalia and Vachellia can be found in Seigler’s recent publications (Seigler and
Ebinger 2005 ; Seigler et al . 2006 ). Characteristics in Senegalia would include the
lack of stipular spines, the presence of vegetative stipules, and the occurrence of
prickles and a few other characteristics (Fig. 2.1 ). On the other hand, Vachellia has
stipular spines (usually two) with the absence of prickles (Fig. 2.1 ). In addition, they
list the names of the species of Senegalia and Vachellia present in the Americas.
They also present some molecular genetics including a most parsimonious consensus tree comparing a number of Senegalia and Vachellia species , with a few Acacia
Fig. 2.1 Left picture above shows the presence of prickles on the stem of Senegalia greggii
(= Acacia greggii , catclaw acacia). On the right is a picture of Vachellia farnesiana (= Acacia farnesiana , huisache) that has two stipular spines and usually the absence of prickles. Photographs are
courtesy of Ms. Wendy Leonard and were taken in the San Antonio, Texas area
2 Species Systematics