Chapter 1: Evolutionary relationships and taxonomy of Suidae and Tayassuidae3
at ~5.5 Ma (Brunet & MPFT 2000; Brunet & White 2001). The
Suinae then radiated strongly in Africa during the Pliocene and
Pleistocene giving rise to the genus Metridiochoerus and lead-
ing to further divergence in Kolpochoerus. These genera are con-
sidered to be the ancestors of Phacochoerus and Hylochoerus,
respectively (White & Harris 1977; Cooke 1978; Harris &
White 1979; Bender 1992; Kullmer 1999; Geraads 2004; Souron
et al. 2015). This radiation possibly included Potamochoerus,
although it has also been proposed that this genus may have
originated in Eurasia – implying that at least some of the African
Suinae evolved outside Africa, and only later colonized the
African continent (Harris & White 1979; Harris 1983; Pickford
2006). Thus, there may have been two waves of migration from
Eurasia giving rise to the extant sub-Saharan African lineages
(Pickford 2006, 2012). It has also been suggested that once the
Suinae were established in Africa, some members of this sub-
family (Metridiochoerus, Phacochoerus, and Potamocherus)
may have spread to the Middle East, India, and Europe during
the Pliocene and Pleistocene (Pickford 2006, 2012; Arribas &
Garriod 2008; Kumar & Gaur 2013). Sus is also found in Africa,
but the consensus is that this genus originated in Eurasia and
reached western North Africa only in recent times, possibly as a
result of human introduction (Pickford 2006, 2012).
DNA estimates suggest that Babyrousa diverged from the rest
of the Suidae ~22.4–13.3 Ma (Gongora et al. 2011a). Fossils of
Babyrousa have not been found in pre-Pleistocene contexts; nev-
ertheless, fossil records show that the first fossil occurrence of the
ancestors of the subfamily Suinae was during the Middle Miocene
(~13 Ma) (Pickford 1993, 2006; Orliac et al. 2010a, 2010b).
Because of the inferred early separation date, many authors prefer
to place Babyrousa in a separate subfamily, Babyrousinae (Suyono
2009). The other endemic genus on Sulawesi, Celebochoerus, is
thought to have descended from Palaeochoerus, a primitive suid
genus known from the Lower Miocene of the Siwaliks in the
Indian subcontinent. The ancestor of C. heekereni likely crossed
the sea barrier between proto-Borneo and proto-Sulawesi during
the Middle Miocene (Suyono 2009).
DNA data also suggest that Porcula and Sus diverged from
their common ancestor in the Miocene, ~14.9–13.6 Ma, although
there is no clear fossil evidence to support this. Within the genus
Sus, DNA analysis suggests the three major groups of extant
species (S. barbatus/S. verrucosus, S. scrofa/S. celebensis and
S. cebifrons/S philippensis) diverged from a common ancestor
~7.3–5.5 Ma (Gongora et al. 2011a); these estimates are partially
consistent with the current fossil evidence, which shows that early
diversification of species of Sus, represented by extinct S. arvern-
ensis from the Late Miocene (~6–5.3 Ma) in Europe (van der
Made & Moya-Sola 1989; van der Made et al. 2006) and various
extinct species of Sus from China including S. subtriquetra (Xue
1981; Han 1987; Liu 2003; Wang & Xu 2003), could have occurred
between the Late Miocene and the Pliocene/Pleistocene.
Phylogenetic Relationships between
Extant Suidae
Phylogenetic analyses of extant Suidae using mitochondrial
and nuclear DNA multilocus analyses have shown that extant
sub-Saharan African genera (Potamochoerus, Hylochoerus
and Phacochoerus) group into a monophyletic clade sepa-
rate from Eurasian Sus, and confirm that Babyrousa is the
sister taxon to all other extant species of Suidae (Figure 1.2;
Gongora et al. 2011a). This overall phylogeny is consistent
with recent preliminary relationships derived from near-
complete genome data from nine species of Suidae (Darfour-
Oduro et al. 2015). There is still some debate about the
evolutionary relationship between these extant taxa. Some
morphological studies suggest extant sub-Saharan African
Suinae are paraphyletic in relation to Eurasian Sus (Thenius
1970; Cooke 1978; Groves 1981; Pickford 1993), in contrast
with other studies that show extant sub-Saharan African
Suinae forming a monophyletic clade (Harris & White 1979;
Bender 1992; Geraads 2004).
The position of Babyrousa as a sister clade of African and
Eurasian Suidae based on DNA (Figure 1.2) is in agreement with
cladistic analyses of the petrosal bone that places this genus apart
from the other Suinae (Orliac 2013). Another line of evidence to
support this is the chromosome differences observed between
Babyrousa and other genera of suids (Bosma et al. 1996). In
contrast, others have suggested Babyrousa to be a derivative
of Sus (Pickford 1993). Although the available studies do not
allow conclusions to be drawn as to whether Babyrousa repre-
sents a different subfamily or is part of Suinae (Groves & Grubb
1993; Grubb 2005; Harris & Liu 2007), the former proposition
has been frequently used for nomenclatural purposes (Gongora
et al. 2011a; Taber et al. 2011; Frantz et al. 2016).Sus verrucosus
Sus barbatus
Sus celebensis
Sus scrofa
Sus cebifrons
Sus philippensisPorcula salvania
Potamochoerus porcus
Potamochoerus larvatus
Hylochoerus meinertzhageni
Hylochoerus rimator
Hylochoerus ivoriensis
Phacochoerus africanus
Phacochoerus aethiopicus
Babyrousa babyrussaSUIDAETAYASSUIDAEBabyrousa togeanensis
Babyrousa celebensis
Pecari tajacu
Pecari angulatus
Tayassu pecari
Catagonus wagneri
Figure 1.2 Cladogram showing the evolutionary relationships between and
within extant Suidae and Tayassuidae based on DNA from various studies.
Polytomies indicate unresolved relationships within the clade. Drawn by Jaime
Gongora.12:28:36