IntroductionSince Mammal Species of the World (1982),

760 new mammal species have been described, and400 new mammal species since 1993 alone.

These discoveries result from:• recent explorations in remote parts of the world

• taxonomic revisions of problematic groups

• evaluation of DNA evidence for cryptic species.

New Tools

• New fossil discoveries• Molecular biology tools• Satellite tracking, radio-tracking, and camera

trapping• Computer modeling• Patient observation• Interdisciplinary approaches

Classification

Binomial Scientific Name Common Name

Lepus californicus (blacktail jackrabbit)

Genus = LepusSpecies = californicus

May also recognize Subspecies – Lepus californicus deserticola

Species“Species are groups of actually or potentially interbreeding natural

populations, which are reproductively isolated from other such groups.”

E. Mayr 1942

Kingdom AnimaliaPhylum Chordata Class Mammalia

Order Lagomorpha Family Leporidae

Genus Lepus Species Lepus californicus

Subspecies Lepus californicus deserticola

Phylogeny Reconstruction

Classification—ordering species into groups and naming the groups

Phylogenetics (or cladistics)—developing hypotheses to reconstruct the evolutionary history or relatedness among species.

Phylogenetic Data

Data for creating a phylogenetic hypothesis comes from:

• Paleontology • Morphology • Biogeography • Molecular characters • Ecological traits • Behavioral traits

CladogramA branching, tree-like diagram in which:• ends of the branches represent species or taxa • branching points or nodes indicate the point at which species

(or taxa) separated from one another to follow their own evolutionary pathways.

The data are called characters and usually consist of morphological features or molecules such as DNA or proteins.

Molecular and Morphological Data

Taxa Sequence data Trait X Trait Y

H AAA GCT ACT yes no G AAA GCT ACT yes no F AAA GGT ACT yes no E CAA GGT ACT yes no D CAA GGT ACT yes no C CAA GGT ACG yes yes B CAA GGT ACG yes yes A CAA GGT ACG yes yes

Example Cladogram

FIGURE 02: A phylogeny of eight taxa A through H based on DNA sequence data

and two morphological traits (X and Y)

Cladistic TerminologySynapomorphy—a trait shared by two or more taxa and their

last common ancestor.

Symplesiomorphy—a trait shared by two or more taxa, but which is also shared with other taxa that have an earlier last common ancestor (e.g. an ancestral trait).

Terminology

Ingroup—the group under study

Outgroup—a group or lineage closely related to the group under study

Terminology

Monophyletic—A group descended from a single ancestral stock.

Paraphyletic—A group that includes some but not all of the descendants of a single ancestor.

Polyphyletic—A group containing taxa that do not all share the most recent common ancestor.

Molecular Clock• Uses rates of molecular

change (mutations) calibrated with fossil dates to deduce the time in geologic history when two taxa diverged

• Produces phylogenetic hypotheses with estimated divergence dates in millions of years

Adapted from Hallström, B.M. and A. Janke, BMC Evolutionary Biology 8 (2008): 1-13.

FIGURE 04: Molecular phylogeny of mammals showing estimated

divergence times