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The Capreolinae, in contrast to the Cervinae, are found primarily in
North and South America - of the 22 modern species, only four species are
found in Eurasia (two - Alces alces and Rangifer tarandus -
have specific or subspecific counterparts in the New World). Due to
a lack of strong competition from other ungulate groups, the Capreolinae
have become the most successful present-day New World ungulates. They
are more specialized and more widely adapted than the Old World Cervinae,
containing both the largest modern deer (Alces sp., with some individuals
weighing over 800 kg) as well as the smallest cervid species (Pudu
sp., never weighing more than 15 kg).
Until recently, the Capreolinae were known as the Odocoileinae - named after
the highly-successful genus Odocoileus. Indeed, the white-tailed
deer (Odocoileus virginianus) has one of the broadest geographical
distributions of any deer, ranging from the Arctic Circle to below the Equator,
and is the oldest modern cervid species, indistinguishable from fossils from
3.5 million years ago.
The origins of the Capreolinae are uncertain due to a scarcity of early fossils.
However, molecular data indicates that this subfamily likely diverged
from the Old World cervid radiation (Cervinae)
at some time during the middle Miocene. The earliest known fossil evidence
of this subfamily appear in North America and Eurasia around 5 million years
ago. Members of the Capreolinae reached South America via the Panama
land bridge during the late Pliocene or early Pleistocene, and rapidly evolved
into many forms specialized for various niches. Again, the fossil record
at this time is scant, but it has been suggested that all South American
species are descended from Odocoileus.
Four tribes are generally recognized:
-
Alceini - moose
-
Capreolini - roe deer
-
Rangiferini - caribou
-
Odocoileini - New World deer
Alceini and Rangiferini are sometimes treated as separate cervid subfamilies.
As discussed with the Hydropotinae,
molecular evidence is becoming stronger that the water deer (Hydropotes
inermis) is in fact an atypical member of the Capreolinae, clustering
next to the genus Capreolus (and sometimes included in the tribe
Capreolini). These two genera, plus the adjacent Alceini cluster separately
from the rest of this subfamily, sharing several cerebral and cytogenetic
characters.
The telemetacarpal foot structure is the most characteristic feature of this
group (a diagnostic feature if Hydropotes is included within the
subfamily) - the second and fifth metacarpals are present as distal splinters
of bone (by the dewclaws). Pedal glands are found in the hind legs
of all species, and tarsal glands are always present (if rudimentary). Unlike
the Cervinae, the antler cycle includes a pause
between when the antlers are shed and when the new pair begins growing. |
