Classification

Tigers, lions, and caracals all share kingdom, phylum, class, order, and family.

Kingdom: Animalia

Phylum: Cordata

Class: Mammalia

Order: Carnivora

Family: Felidae

Tigers, lions, and caracals are all in the family Felidae (the cat family), and lions and tigers belong to the same genus, Panthera. Johnson et al. (2006) created a phylogeny for Felidae, pictured above. The most recent common ancestor of lions, tigers, and caracals is also the most common ancestor of all other members of Felidae. Therefore, these three species do not form a monophyletic group.

Members of felidae descend from a common ancestor around 10.8 million years ago (Johnson et al. 2006). Within Felidae, the Panthera group is the first to diverge, followed by the genus Pardofelis. The next group to diverge is the genus Caracal. Other genera within the family Felidae include Leoparda, Lynx, Acinonyx, Puma, Otocolobus, Prionailurus, and Felis

Characteristics of Felidae
Synapomorphies

For our lineage, a synapomorphy would entail a trait that arose within Felidae. It is shared by the Felidae common ancestor, but is a trait that is not shared by an earlier common ancestor (i.e. earlier Carnivora ancestor). Thus, a synapomorphy is a derived trait that is shared by multiple lineages. 

After reviewing primary literature, we noted three distinct synapomorphies (solitary hunting, hyper-carnivore, and the morphological differences in skull skeletal/muscular structures that accompany these traits). In comparison to other Carnivora species, Felidae differ in their hunting strategy. Felidae are solitary hunters, while other Carnivora (i.e. wolves, hyenas, etc.) are cooperative hunters and hunt in packs (Gittleman 1985). 

On this same continuum, Felidae are hyper-carnivores. A hyper-carnivore is defined as a species whose diet is comprised of 70 % or more of meat. The majority of species within Carnivora (bears, dogs, foxes, etc.) are generalists and consume 50-60% meat along with vegetable matter (Holliday 2007). Therefore, it appears the switch to a hyper-carnivore diet is a derived character of Felidae. 

Morphological differences in skull skeletal/muscular structures have been associated with being a hyper-carnivore.  The crushing function of Felidae teeth has been reduced, their tongue is covered with numerous posteriorly-directed horny papillae, and the facial portion of the skull is shortened (Taylor 2011 and Holliday 2007). Felidae do not need the crushing/grinding function of their teeth as much as they need the lacerating/tearing ability. This has been demonstrated by the increase in the relative length of shearing edges of dentition in comparison to other Carnivora. The papillae on the tongue have been postulated to provide the feline with a better ability to grip and position the meat within the mouth (Taylor 2011).  The shortened snout component of the skull is presumed to aid in a higher bite force (Holliday 2007). Since Felidae do not cooperatively hunt, a higher bite force is necessary for the successful capture of prey by a lone individual. 

Synapomorphies within our group of species also exist. As clearly noted upon observation, caracals have triangular ears, while other Felidae have rounded ones.  Triangular ears have arisen separately from the rest of Felidae and are present in the lineages of caracal serval, caracal caracal, and caracal aurata. However, this trait is not a synapomorphy with other pointed ear cats, as it is hypothesized pointed ears arose independently in these other genera (Felis and Lynx). See section labeled "Hypothesis" below for a phylogenetic tree including our traits of interest. 

Plesiomorphies

In the Felidae family plesiomorphies are found to be traits that are seen in the carnivora or ancestral species and our 3 focal species: tigers, lions, and caracals.  

Traits such as tooth structure is a big key to identifying how species are classified and related. Predators such as the three focal species above all have carnassial teeth that allow them to shear flesh. Species that were around before all three focal species possessed these meat incising teeth that allowed them to hunt larger prey. Bone cracking teeth are essential, because each focal species and the ancestral species hunt prey that are generally larger. Specialized muscle structure was found to be shared by both the focal species and ancestral species. These muscles increased their hunting efficiency, allowing them to be stealthier as they hunted, but also enabling them to pounce from great distances with accuracy.These various findings have helped scientist link species with distant common ancestors. (Savage1976)(Valkeburgh1999)

Focal Traits
Body Size

Since body size is a continuous, quantitative trait involving many genes, it is difficult to give an exact point in which large body size arose. However, given the smaller size of the clouded leopard (Neofelis nebulosa), which weighs around 17kg (Sunquist & Sunquist 2002), the larger body size of tigers, lions, and other members of the genus Panthera, it seems likely that large body size arose after the clouded leopard and Panthera lineages diverged. In addition, the oldest known common ancestor of the Felidae, Proailurus lemanesis, was small compared to cats of the genus Panthera, giving extra weight to the hypothesis that small body size is an ancestral trait (Turner et al. 2011).

Ear Shape

Cats of the genera Panthera and Pardofelis, which diverged from other cats before Caracal, had rounded ears. This implies that rounded ears are ancestral in Felidae. Understanding when exactly these traits arose, however, is difficult. Most genera in Felidae have rounded ears, however cats in the distantly related genera Caracal, Lynx, and Felis have pointed ears. Pointed ears may have arisen before Caracal diverged and reverted in Leopardus and after Lynx diverged, then arisen again later in Felis. However, it is most parsimonious to say that pointed ears is a homoplastic character that arose independently in Caracal, Lynx, and Felis

Tail Length

Cats of the genus Pardofelis, which diverged from other cats after Panthera but before Caracal, had long tails relative to their body size. This implies that long tails are the ancestral trait in Felidae. Cats in the genus Caracal have slightly shorter tails relative to other cats (excluding the genus Lynx). Cats in the genus Leoparda, which diverged from other cats after Caracal, have longer tails (Sunquist & Sunquist, 2002), making it most likely that short tails arose after Caracal diverged.

Hypothesis


Based on phylogeny from Johnson et al. (2006).

We hypothesize that small body size, rounded ears, and long tails are ancestral characters in Felidae. Large body size likely arose within the genus Panthera. Short tails and pointed ears are likely both homoplastic traits. Pointed ears probably arose separately in the genera Caracal, Lynx, and Felis. Short tails appear to have arisen in Lynx and Caracal separately.

References

Gittleman, John L. 1985. Carnivore body size: Ecological and taxonomic correlates. Oecologia, Vol. 67 No. 4: 540-554

Holliday, Jill A. Phylogeny and Character Change in the Feloid Carnivora. 2007. pp. 3. Florida State University. 

Johnson, WE, Eizirik, E, Pecon-Slattery, JP, Murphy, WJ, Antunes, A, Teeling, E, and O'Brien, SJ. 2006. The Late Miocene Radiation of Modern Felidae: A Genetic Assessment. Science 311:73-77.

Savage, J.G.. "Evolution in Carnivorous Animals ." . N.p., 17 Mar 1976. Web. 6 Oct 2013. <http://palaeontology.palass-pubs.org/pdf/Vol 20/Pages 237-271.pdf>.

Sunquist, M and Sunquist, F. 2002. Wild cats of the world. Chicago: University of Chicago Press. pp. 278-284. ISBN 0-226-77999-8.

Taylor, Christopher. 2011. "Variety of Life: Felidae." Taxon Diversity

Turner, A, Antón, M, Salesa, MJ, and Morales, J. 2011. Changing ideas about the evolution and functional morphology of Machairodontine felids. Estudios Geologicos 67:255-276.

Valkeburgh, Blaire. "Major Patterns in The history of Carnivorous Mammals." . Earth Planet , n.d. Web. 6 Oct 2013. <http://www.annualreviews.org/doi/pdf/10.1146/annurev.earth.27.1.463>.

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