Species Concepts and Evolution of Species

• What is a species? Different branches of biology have different working definitions because they work with different tools, at different levels, or with fundamentally different organisms.
  • BIOLOGICAL SPECIES CONCEPT: A species is a group of potentially interbreeding individuals. Species are "real" and defined by the limits of their gene exchange.
  • MORPHOLOGICAL SPECIES CONCEPT: A species is a group of organisms that share morphological and/or biochemical traits. Good for fossil species.
  • PHYLOGENETIC SPECIES CONCEPT: A species is a discrete lineage.
  • ECOLOGICAL SPECIES CONCEPT: Share similar niches
• Problems with the species concepts:

Chronospecies	Ammonites	Age structure or different species?	Life history problems- frogs
Life histories- parasites	Barnacle parasites	Squid Mating	Life history- horsetail
Life history- mosses	Life history- Cnidarians	Ecotypic/phemotypic variation	Shell color polymorphism
Variation within an individual over time	Hybrid zones	Viable hybrids	Dogs and Wolves