Species

Concepts

What makes each an individual species?

Consider the following…

Painted Bunting

Roseate Spoonbill

Barn Owl

Northern Mockingbird

Bald Eagle

CommonLoon

Wood Thrush

Canada Goose

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

MORPHOLOGICAL SPECIES CONCEPT

PHENETIC SPECIES CONCEPTRECOGNITION SPECIES CONCEPT

PHYLOGENETIC SPECIES CONCEPT

What defines a species?

• This general idea was revived later with more statistical rigor as the Phenetic Species Concept

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

Strengths?Weaknesses?

Biological Species ConceptProposed 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, yethybrids sterile or unable toproduce offspring successfully

Other Weaknesses?

Examples of Hybridization

Lazuli Bunting

X

Indigo Bunting

Tufted Titmouse X Black-Capped Chickadee

Northern Goshawk X Cooper’s Hawk

Reproductive Isolating Mechanisms• Pre-mating or Pre-zygotic

• Post-mating or Post-zygotic

Ecological, temporal, or behavioral (courtship songs or displays) barriers to isolation

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