Chapter 1: Evolutionary relationships and taxonomy of Suidae and Tayassuidae5
diet, survived until the end of the last Ice Age in North America
and vanished ~10,000 years ago (Wright 1993a, 1993b, 1998;
Prothero & Grenader 2012). In South America, the Platygonus
lineage was replaced by Catagonus from the middle Pleistocene
onwards, probably due to a reduction in open environments
(Gasparini & Ubilla 2011). The fossil record shows a consider-
able generic and specific diversity of peccaries in South America
from the middle Pliocene to recent times (Gasparini 2013).
The divergence of New World tayassuids into particular
extant lineages (Figure 1.2) has been the subject of debate. On
the one hand, it has been suggested that peccaries diverged in
North America during the late Miocene less than 10 Ma, before
they independently colonized South America (Wright 1989,
1993a, 1993b). For instance, chronological stratigraphic distri-
bution patterns suggest extinct Platygonus and extant Catagonus
represent two tayassuid lineages that originated in North
America and then migrated to South America (Gasparini 2013).
It has also been suggested that some Tayassuidae diversified in
South America via adaptive radiation during the Pleistocene
(Woodburne 1969; Wetzel 1977a, 1977b; Mayer & Wetzel 1987)
and at least one of these taxa, Tayassu, spread to North America
(Gasparini 2013). The nomenclature of the Chacoan peccary
has been recently recommended to be changed to Parachoerus
wagneri to better reflect the relationship with extinct related
forms (Parisi et al. 2016). However, it does not impact on the
evolutionary relationships for the extant species described in
this chapter.
Molecular data place the divergence between the extant
peccary genera (Figure 1.2) as early as the Late Miocene. Three
divergence age intervals have been estimated for the split of the
Pecari lineage and the clade containing Tayassu and Catagonus
from a common ancestor (7.4–3.4, 7.7–6.2 and 13.2–4.3 Ma)
using different methods and node calibrations (Theimer &
Keim 1998; Gongora & Moran 2005), and it was estimated that
white-lipped and Chacoan peccaries diverged from the com-
mon ancestor only 2.5–0.5 Ma (Theimer & Keim 1998; Gongora
& Moran 2005). Although some of these DNA estimates are
consistent with fossil records, it is possible that this diver-
gence occurred earlier than previously thought. Based on fossil
analyses, it is likely that radiation between ancestral forms of
extant Tayassu, Pecari, and Catogonus lineages may have been
underway as early as the Late Miocene (~9.5–9.0 Ma) (Frailey &
Campbell 2012; Prothero & Grenader 2012).
These divergence times can be revisited by using mitochon-
drial and nuclear genomes and calibrating the nodes of the
phyogenetic trees (Gongora et al. 2011a) using the latest fossil
data which may provide different results and narrow the inter-
val for the divergence estimates, and may raise the possibility
that the three extant peccary lineages radiated before the classic
Great American Faunal (or Biotic) Interchange (GAFI/GABI)
(Marshall et al. 1979). It has been pointed out, however, that the
time frame of classic GAFI is probably incorrect, and the first
steps in faunal interchange may have begun in the late Miocene
(Frailey & Campbell 2012). These latter authors have suggested
that early forms bearing morphological similarities to the extant
genera Pecari and Tayassu may have evolved in the tropical
moist forests of the Neotropics and that they or their common
ancestors dispersed to South America earlier than thought, and
that they were abundant in the Amazon long before the time
frame proposed for the classic GAFI (Frailey & Campbell 2012).
The discovery of two new extinct genera of peccaries from the
Late Miocene deposits of the western Amazon basin (~4–3 Ma)
(Prevosti et al. 2006; Woodburne 2010), considered intermedi-
ate forms between middle Miocene peccaries and the modern
genera Tayassu and Pecari (Frailey & Campbell 2012), poses
an interesting scenario, as this implies that tayassuid dispersal
between the Americas may indeed have occurred before the
classic GAFI or that a new interpretation of the GAFI may be
needed (Frailey & Campbell 2012).
The potential for dispersal of tayassuids at any time that
GAFI took place is given by the early presence of extinct Cynorca
occidentale, which is a member of the clade that gave rise to
modern tayassuids, found from deposits 14–19 Ma old in the
Central American Isthmus of Panama (MacFadden et al. 2010;
Frailey & Campbell 2012). Eventually the Tayassuidae gave rise
to the three modern genera (Woodburne 1969; Wetzel 1977a,
1977b; Wright 1998). Based on biochronological fossil data, the
extant peccary species have been recorded from the Middle–
Late Pleistocene to the present (Gasparini 2013; Gasparini et al.
2013, 2014).Phylogenetic Relationships between Extant
Tayassuidae
Phylogenetic analyses using mitochondrial and nuclear DNA
sequences show that T. p e c a r i and C. wagneri are more closely
related to each other than to P. tajacu (Figure 1.2; Theimer & Keim
1998; Gongora & Moran 2005); this has also been confirmed
by mtDNA genome studies (Perry et al. 2017). These DNA
findings have been supported by recent principal component
analysis of 28 cranial and dental characters from 58 individuals
from the extant peccary genera (Gasparini et al. 2013), which
shows that T. p e c a r i and C. wagneri group together, separate
from P. tajacu (note that this study was done in ignorance of
the taxonomic revision of Groves & Grubb (2011), which
found at least two species of collared peccary). This contrasts
with other hypotheses about the evolution and relationships of
modern peccary species. From a cytogenetic point of view, it
is suggested that chromosomal fusion occurred from P. tajacu
(n = 30) to lower numbers in T. p e c a r i (n = 26) and C. wagneri
(n = 20) (Benirschke & Kumamoto 1989), although it is also
proposed that chromosomal fission could have augmented
the number from an ancestral diploid state of 20 (Todd 1985).
Cross-species cytogenetic studies, using chromosome paints
in tayassuids (Bosma et al. 2004; Adega et al. 2006), have not
elucidated the direction of chromosomal evolution in this
family because of lack of information from C. wagneri. Based
on osteological and dental character analyses, P. tajacu and
C. wagneri were considered to be more closely related, while
T. p e c a r i was considered to be a member of a separate clade
along with other extinct species (Wright 1989, 1993a, 1993b,
1998), but other morphological studies (Wetzel et al. 1975;
Wetzel 1977a, 1977b) have supported the proposition that
P. tajacu and T. p e c a r i are more closely related to each other than to12:28:36