Geography 316:  Biogeography     In progress 12/11/2003

The Biogeography of  the California Tiger Salamander (Ambystoma californiense)
by Elizabeth Kanner, student in Geography 316  Fall 2003

Thank you for visiting our site. This web page was written by a student in Geography 316: Biogeography and edited by the instructor, Barbara Holzman, PhD.  All photos and maps are posted with specific copyright permission for the express use of education on these web pages. The students have tried to be as accurate as possible with the information provided and sources and references are cited at the end of each page.

 

Species Name: Ambystoma californiense

Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Amphibia 
Subclass: Lissamphibia
Order: Caudata
Family: Ambystomatidae
Genus: Ambystoma
Species: Ambystoma californiense

 Figure 1: California Tiger Salamander (© 2000 Joyce Gross)

 

 Description
 California Tiger Salamanders are considerably large for today’s amphibians.  The male can reach 8.5 inches long and the females 7 inches (NPWRC 2002, FWS 2003).  Males differ from females in their overall size as well as their enlarged cloacae during breeding season (FWS 2003).  The adults are stocky with round heads, protruding black eyes and long tails that curl around their body.  They are slick, glistening black with yellowish spots and stripes on their back, sides and tail.  These markings slightly resemble those of a tiger and earn the species their name.  This yellowish color also outlines their wide mouth, which gives the appearance of broad painted smile.  Like other salamanders, its body is low to the ground and its four legs protrude sideways from its body as though it were ready to run (figure 2). 

 Figure 2: California Tiger Salamander
(Gerald and Buff Corsi © 1999 California Academy of Sciences)

Ecology and Nesting Habitat
The California Tiger Salamander is found in annual grasslands and open woodlands (FWS 2003).  Here, the Mediterranean climate creates hot dry summers and cool rainy winters.  The mean annual precipitation is 20 to 40 inches per year with mean annual temperatures of 50 to 58 degrees Fahrenheit (USFS 2003).  Ecological characteristics of this area include dry soils, needlegrass grasslands, valley oaks, coast live oaks and ephemerally flooded claypan depressions called vernal pools (USFS 2003). 

Like most of their relatives, the adult California Tiger Salamander is terrestrial.  For six to nine months out of their year, they live in their nesting habitat in the grassy highlands.  Since they are poor burrowers themselves, the California Tiger Salamanders take advantage of the abandoned refuges of small mammals such as ground squirrels and gophers (Nickles 2003).  In the driest months, they enter a dormant state called estivation (FWS 2003). 

Breeding Behavior
 In early winter, just after sufficient rains have fallen for the ground to be moist and for temporary pools to begin to form, these salamanders begin their nocturnal breeding migration (NPWRC 2002). On rainy nights, the adults emerge from their underground burrows and roam, often more than a mile, to lay their eggs in these newly replenished vernal pools (CBD 2003).  Males typically outnumber females and often precede females to the ponds (LaMonte 2002). 

After the eggs are fertilized internally, a single female can lay up to 1300 eggs and deposit them individually or in small batches (CBD 2003).  Shortly after breeding, adults will return to their terrestrial habitat (LaMonte 2002).  Ten to 14 days later, larvae hatch from the eggs (CBD 2003).  The pool in which they hatch is their home for the next 2 to 3 months (NPWRC 2002).  For the first 6 weeks, the larvae are only able to eat small crustaceans, algae, and mosquito larvae.  When they are large enough, they begin to take advantage of aquatic insects, invertebrates and tadpoles of Pacific treefrogs, California red-legged frogs, western toads, and spadefoot toads (CBD 2003).  Once they reach metamorphosis, which is usually by late spring or early summer, juveniles are ready to roam to their terrestrial nesting habitat (Loredo 1996).  These juveniles are known to disperse up to two miles from their natal ponds (CBD 2003). 


Distribution
The California Tiger Salamander is endemic to California (Loredo 1996).  Their range is not only geographically restricted to the state but isolated from any other salamander species (Loredo 1996).  Historically, the California Tiger Salamander’s distribution was throughout California’s Sacramento and San Joaquin River Valleys, surrounding foothills and westward in the lower elevations of California’s central Coast (Barry 1994).  The grasslands and woodlands areas of the central valleys and foothills are relatively xeric and are characterized by hot and dry summers followed by cool and wet winters.  The California Tiger Salamanders are a stenotopic species.  Their summer estivation and winter breeding habitat needs limit them to Mediterranean climate conditions and to areas where both winter ephemeral pools form and burrowing squirrels and gophers can be found.  California’s central valleys, foothills below 1500 feet, and central coastal valleys meet these habitat conditions (Barry 1994, FWS 2003).
As is illustrated in the map below, the two coastal ranges of the Sonoma and Santa Barbara County populations are discontinuous from each other and from several populations in the valley and foothills (see figure 3) (Miller 2003).  Today, California Tiger Salamander distribution is concentrated in the northern part of their historical range and their populations exist in disjunct vernal pool complexes (Miller 2003, FWS 2003).  The limited distribution is due primarily to human induced habitat loss (Nickles 2003).  

  

 
Figure 3: Distribution map of the 
California Tiger Salamanders 
populations (map courtesy of the ARMI 
National Atlas for Amphibian Distributions,
 www.pwrc.usgs.gov/armiatlas.)

 

 

Evolution
Sometime in the Devonian period, roughly 350 million years ago, certain vertebrates made the pivotal leap out of the water and into an utterly new environment – the land.  This significant step is marked by great evolutionary changes and vertebrate adaptations to terrestrial environments (Colbert 1980).  One advantage primitive amphibians, or ichthyostegids, had to facilitate this transition is well-developed lungs which they inherited from their fish ancestors, crossopterygians (Colbert 1980).  Yet, unlike reptiles, most amphibians remain dependent on aquatic biomes and never abandon their aquatic larval stage, “Amphibians are the biological intermediates between bony fish and reptiles” (Carroll 1988).  In addition to respiration, skeletal support, and desiccation, terrestrial locomotion presented a challenge for the first land animals.  Although amphibians and fish share strikingly similar bone structures, their primary difference is in the use and structure of their appendages (Figure 5).  Most fish swim by moving their trunk back and forth laterally and by using the body muscles (Carroll 1988).  Amphibians evolved to depend on their limbs for actual locomotion (Colbert 1980). 

 

Figure 4: Evolution of Lobe-Fin fishes and Amphibians (Colbert 1980)

 

Figure 5: Fish and primitive tetrapod from the late Devonian period
(Carroll 1997)

Tracing the evolution of salamanders from their primitive amphibian ancestors has proven difficult for biologists.  First, there is a lack of amphibian fossil records from the late Permian to the Jurassic period (Carroll 1988).  There is also a significant difference in the morphology of Paleozoic/ early Mesozoic amphibians and today’s living frogs, salamanders, and caecilians (Colbert 1980).  For this reason, the modern amphibians along with their late Mesozoic and Cenozoic ancestors are grouped in the subclass Lissamphibia which means ‘living amphibian’ (Carroll 1988).  Secondly, there is continued debate over the true evolutionary relationships of the salamander (Larson 1993).  In 1993, Larson published two possible cladograms for Caudata (Figure 6).  In the first, Duellman and Trueb design a cladogram based on morphological differences in salamander families.  In the second, Larson uses molecular differences to develop the evolutionary tree (Larson 1993). 

 

 

 

 

 

 

 

 

 

Pleistocene fossil records indicate the North American Lissamphibia reacted to glacial advances and retreats by corresponding pattern of dispersal out and back from glacial areas (Carroll 1997).  In California, a high percentage of amphibians are phylogenenetically distinctive (Shaffer 2001).  Originally, biologists recognized the California Tiger Salamander as a subspecies of the geographically widespread tiger salamander (Ambystoma tigrinum).  More recently, genetic comparisons indicate that the California Tiger Salamander is a genetically distinct species that is endemic to the state (Larson 1996, Shaffer 1994). 

                Ambystomaditdae
               
                Plethodontidae
               
                Salamandridae
               
                Amphiumidae
               
                Rhyacotritonidae
               
                Dicamptodontidae
               
                Proteidae
               
                Hynobiidae
               
                Cryptobranchidae
               
             

 

 Sirenidae
               
              Ambystomaditdae
             
              Dicamptodontidae
             
              Salamandridae
             
              Proteidae
             
              Cryptobranchidae
             
              Hynobiidae
             
              Sirenidae
             
              Rhyacotritonidae