Download Biological Species Concept

Species
Concepts
Consider the following…
Bald Eagle
Painted Bunting
Common
Loon
Roseate
Spoonbill
Wood Thrush
Barn Owl
Canada
Goose
Northern
Mockingbird
What makes each an individual species?
Why identify species?
• A few reasons:
– Scientific communication:
for scientists to categorize
and communicate their work
on particular organisms
– Phylogeny: to study and
determine what makes
groups unique and how
organisms are related to one
another
– Conservation: to track the
status and diversity of
populations within an
ecosystem
What is a species?
• According to the Oxford English Dictionary, a
species is:
“A group or class of animals or plants (usually
constituting a subdivision of a genus) having
certain common and permanent characteristics
which clearly distinguish it from other groups.”
But, what qualifies as “clearly distinct”?
Species Concepts
• Scientists have developed various ideas on how to
best define a species. Here are a few of the over 20
possible species concepts:
BIOLOGICAL SPECIES CONCEPT
ECOLOGICAL SPECIES CONCEPT
PHYLOGENETIC SPECIES CONCEPT
MORPHOLOGICAL SPECIES CONCEPT
PHENETIC SPECIES CONCEPT
RECOGNITION SPECIES CONCEPT
What defines a species?
Morphological Species Concept
• A set of distinct physical features of a population
of animals which sets it apart from others
• May be applied to both sexual and asexual
organisms and fossils
• This general idea
was revived later
with more
statistical rigor as
the Phenetic
Species Concept
Strengths?
Weaknesses?
Biological Species Concept
Proposed by Ernst Mayr in 1942
• A population whose members can successfully
breed with one another in a natural
environment, and not with another species
Biological Species Concept
• While a strong delimitation, the biological species
concept continues to face discussion for the
following reasons…..
– Some organisms reproduce through binary fission,
fragmentation, regeneration, budding, or other asexual
means
– Mating may be possible, yet
hybrids sterile or unable to
produce offspring successfully
Other
Weaknesses?
Examples of Hybridization
Tufted Titmouse X Black-Capped Chickadee
Northern Goshawk X Cooper’s Hawk
Lazuli Bunting
X
Indigo Bunting
Reproductive Isolating Mechanisms
• Pre-mating or Pre-zygotic
Ecological, temporal, or
behavioral (courtship songs or
displays) barriers to isolation
• Post-mating or Postzygotic
Hybrid inviability, sterility, or
reduced fitness of hybrid
offspring
Phylogenetic Species Concept
• Smallest set of organisms that share an ancestor and
can be distinguished from other such sets
• Subspecies not recognized
– Strengths: considers ancestry, genetic similarity,
evolutionary process
– Weaknesses: does not consider reproductive habits
Ecological Species Concept
• Focus of species characterization is on similarity of
niche and ecological role
– Strengths: considers species’ role in an ecosystem
– Weaknesses: geographically widespread populations
that don’t actually interbreed may be considered the
same species
Case Study: Ensatina salamanders
• Find a group of 3 other classmates
• Take 10 minutes to look for
information on these salamanders
• Then, discuss your group findings
for 5 minutes and be ready to
share your thoughts with the
class!
How would each species concept
describe these salamanders?
Which categorization do you think
is best, and why?
In Conclusion
• The categorization and maintenance of species
records is important for science and conservation
• For identifying an individual species, typically
scientists will first consider Biological Species
Concept, then descent from common ancestry and
genotypic and phenotypic cohesion
• Species concepts are still subject to debate