Re: Bovids vs. Antilocaprids (new question)

["Jaime A. Headden" <qilongia@yahoo.com>]

Mike Keesey (keesey@gmail.com) wrote:

<Incidentally, although I first learned this topology:
 ((Giraffidae, Cervidae), (Antilocapridae, Bovidae))
  ...I've heard that genetic studies suggest this instead:
 ((Antilocapridae, Cervidae), (Giraffidae, Bovidae))>

  Basal pecorans might be paraphyletic, and the need to shoehorn basal pecorans
into cervoids may result in this topology. Another gene analysis (Beintema et
al., 2003) implies that antilocaprids may be nested within a paraphyletic
arrangement of noncervid "cervoids" outside the geriaffoid/bovoid node.
Features such as a short diastema, large fangs, and a "deer/sheep"-like
appearance are apparently basal to Pecora. It also suggests giraffes are basal
to cervids and bovoids. I tend to think a neat Bovoidea, Giraffoidea,
Cervoidea, and Antilocaproidea are rather ... outmoded ... and are likely
erroneous.

  Beintema, J. J., H. J. Bruekelman, J. Y. Dubois, H. W. Warmels. 2003.
    Phylogeny of ruminants secretory ribonuclease gene sequences of pronghorn
    (*Antilocapra americana*). _Molecular Phylogenetics and Evolution_
    26(1):18-25.

Abstract:
  "Phylogenetic analyses based on primary structures of mammalian
ribonucleases,
   indicated that three homologous enzymes (pancreatic, seminal and brain
   ribonucleases) present in the bovine species are the results of gene
   duplication events, which occurred in the ancestor of the ruminants after
   divergence from other artiodactyls. In this paper sequences are presented of
   genes encoding pancreatic and brain-type ribonuclease genes of pronghorn
   (*Antilocapra americana*). The seminal-type ribonuclease gene could not be
   detected in this species, neither by PCR amplification nor by Southern blot
   analyses, indicating that it may be deleted completely in this species.
   Previously we demonstrated of a study of amino acid sequences of pancreatic
   ribonucleases of a large number of ruminants the monophyly of bovids and
   cervids, and that pronghorn groups with giraffe. Here we present
phylogenetic
   analyses of nucleotide sequences of ribonucleases and other molecules from
   ruminant species and compare these with published data. Chevrotain
   (*Tragulus*) always groups with the other ruminants as separate taxon from
   the pecora or true ruminants. Within the pecora the relationships between
   Bovidae, Cervidae, Giraffidae, and pronghorn (*Antilocapra*) cannot be
   decided with certainty, although in the majority of analyses *Antilocapra*
   diverges first, separately or joined with giraffe. Broad taxon sampling and
   investigation of specific sequence features may be as important for reliable
   conclusions in phylogeny as the lengths of analyzed sequences."

Hassanin and Douzery (2003) also rejected the neat topologies and the placement
for Antilocapridae within Cervoidea and agree with Beintema et al. by arguing
*Tragulus* as a nonpecoran, but in this case ally it as a sister taxon to
Pecora as the onyl extant member of the "equivalent" Tragulina (no surprise
there).

  Hassanin, A. and E. J. P. Douzery. 2003. Molecular and morphological
    phylogenies of ruminants, and the alternative position of the Moschidae.
    _Systematic Biology_ 52: 206-228.

Abstract:
  "The ruminants constitute the largest group of ungulates, with >190 species,
   and its distribution is widespread throughout all continents except
Australia
   and Antarctica.
  "Six families are traditionally recognized within the suborder?Ruminantia:
   Antilocapridae (pronghorns), Bovidae (cattle, sheep, and antelopes),
Cervidae
   (deer), Giraffidae (giraffes and okapis), Moschidae (musk deer), and
   Tragulidae (chevrotains). The interrelationships of the families have been
an
   area of controversy among morphology, palaeontology, and molecular studies,
   and almost all possible evolutionary scenarios have been proposed in the
   literature.
  "We analyzed a large DNA data set (5,322 nucleotides) for 23 species
including
   both mitochondrial (cytochrome b, 12S ribosomal RNA (rRNA), and 16S rRNA)
and
   nuclear (k-casein, cytochrome P-450, lactoferrin, and a-lactalbumin)
markers.
  "Our results show that the family Tragulidae occupies a basal position with
   respect to all other ruminant families, confirming the traditional view that
   separates Tragulina and Pecora. Within the pecorans, Antilocapridae and
   Giraffidae emerge first, and the families Bovidae, Moschidae, and Cervidae
   are allied, with the unexpected placement of *Moschus* close to bovids
rather
   than to cervids. We used these molecular results to assess the homoplastic
   evolution of morphological characters within the Ruminantia.
  "A Bayesian relaxed molecular clock approach based on the continuous
   autocorrelation of evolutionary rates along branches was applied to estimate
   the divergence ages between the major clades of ruminants. The evolutionary
   radiation of Pecora occurred at the Early/Late Oligocene transition, and
   Pecoran families diversified and dispersed rapidly during the Early and
   Middle Miocene. We propose a biogeographic scenario to explain the
   extraordinary expansion of this group during the Cenozoic era."

  The phylogeny made the front cover of the issue, and can be seen here:

  http://www.isem.univ-montp2.fr/PPP/PM/RES/Phylo/Cet/SystBiol-Cover_Pecora.jpg

  Cheers,

Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


        
                
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