Species and Speciation D. melanogasterD. simulans

Species and Speciation I. Species Concepts

Species and Speciation I. Species Concepts How we define a species depends on the goal we have in mind.

Species and Speciation I. Species Concepts How we define a species depends on the goal we have in mind. Are we categorizing existing or fossil organisms?

Species and Speciation I. Species Concepts How we define a species depends on the goal we have in mind. Are we categorizing existing or fossil organisms? Are we trying to understand correlates between populations adapting to different environments?

Species and Speciation I. Species Concepts How we define a species depends on the goal we have in mind. Are we categorizing existing or fossil organisms? Are we trying to understand correlates between populations adapting to different environments? Are we trying to reconstruct phylogenies?

Species and Speciation I. Species Concepts A. Morphological Species Concept

Species and Speciation I. Species Concepts A. Morphological Species Concept - Categorical/'essential' in a platonic sense; based on morphological similarity to a 'type' specimen

Species and Speciation I. Species Concepts A. Morphological Species Concept - Categorical/'essential' in a platonic sense; based on morphological similarity to a 'type' specimen - Useful, but:

Species and Speciation I. Species Concepts A. Morphological Species Concept - Categorical/'essential' in a platonic sense; based on morphological similarity to a 'type' specimen - Useful, but: many species are polymorphic H. erato

Species and Speciation I. Species Concepts A. Morphological Species Concept - Categorical/'essential' in a platonic sense; based on morphological similarity to a 'type' specimen - Useful, but: many species are polymorphic and some sibling species are indistinguishable morphologically. D. melanogaster (M) H. erato

Species and Speciation I. Species Concepts A. Morphological Species Concept - Categorical/'essential' in a platonic sense; based on morphological similarity to a 'type' specimen - Useful, but many species are polymorphic and some sibling species are indistinguishable morphologically. - Nonetheless, for dead or fossilized specimens, the phenotype is all we might have to analyze. As such, there are ways of quantifying the phenotype and defining "phenetic" species... by quantifying the within-group phenotypic variation, statistical analysis can ascertain whether a novel individual lies within that typical range. New Species!! old species

Species and Speciation I. Species Concepts A. Morphological Species Concept - Categorical/'essential' in a platonic sense; based on morphological similarity to a 'type' specimen - Useful, but many species are polymorphic and some sibling species are indistinguishable morphologically. - Nonetheless, for dead or fossilized specimens, the phenotype is all we might have to analyze. As such, there are ways of quantifying the phenotype and defining "phenetic" species... by quantifying the within-group phenotypic variation, statistical analysis can ascertain whether a novel individual lies within that typical range. New Species? old species Problem... need a pretty good sample to describe within- group variation with confidence.

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 "Groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups"

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 "Groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups" - Biological units are genetically defined; reproductive isolation makes populations different from one another, creating new units. So, reproductive isolation is the key characteristic of a species.

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 "Groups of actually or potetially interbreeding populations that are reproductively isolated from other such groups" - Biological units are genetically defined; reproductive isolation makes populations different from one another, creating new units. So, reproductive isolation is the key characteristic of a species. - Limitations:

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 "Groups of actually or potetially interbreeding populations that are reproductively isolated from other such groups" - Biological units are genetically defined; reproductive isolation makes populations different from one another, creating new units. So, reproductive isolation is the key characteristic of a species. - Limitations: - Process may be continuous - where do you draw the "line" of isolation?

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 "Groups of actually or potetially interbreeding populations that are reproductively isolated from other such groups" - Biological units are genetically defined; reproductive isolation makes populations different from one another, creating new units. So, reproductive isolation is the key characteristic of a species. - Limitations: - not applicable to asexual species

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 "Groups of actually or potetially interbreeding populations that are reproductively isolated from other such groups" - Biological units are genetically defined; reproductive isolation makes populations different from one another, creating new units. So, reproductive isolation is the key characteristic of a species. - Limitations: - not applicable to asexual species Bacteria, Archaeans, lots of Protists!!

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 "Groups of actually or potetially interbreeding populations that are reproductively isolated from other such groups" - Biological units are genetically defined; reproductive isolation makes populations different from one another, creating new units. So, reproductive isolation is the key characteristic of a species. - Limitations: - not applicable to asexual species - hybridization occurs in nature, even between otherwise 'good' species. Natural variability is not strictly discontinuous, so pigeon-holing on any grounds will be wrong in some cases. It becomes a matter of degree. The best example are "Ring Complexes"...series of species which breed with neighboring species but the 'end' species do not. Salamanders in California, Gulls in circumpolar regions.

Ring Species Divergence that correlates with geographical distance can create interesting patterns on a spherical globe, or around a geographical feature.

Ring Species Divergence that correlates with geographical distance can create interesting patterns on a spherical globe, or around a geographical feature.

Ring Species Divergence that correlates with geographical distance can create interesting patterns on a spherical globe, or around a geographical feature.

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 "Groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups" - Biological units are genetically defined; reproductive isolation makes populations different from one another, creating new units. So, reproductive isolation is the key characteristic of a species. - Limitations: - not applicable to asexual species - hybridization occurs in nature, even between otherwise 'good' species. Natural variability is not strictly discontinuous, so pigeon-holing on any grounds will be wrong in some cases. It becomes a matter of degree. The best example are "Ring Complexes"...series of species which breed with neighboring species but the 'end' species do not. Salamanders in California, Gulls in circumpolar regions. - Allopatric populations: Potential interbreeding means that populations that are spatially separated and morphologically/genetically distinct may be in the same species.

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts "A single lineage (ancestor-descendant sequence) of populations or organisms that maintains an identity separate from other such lineages and which has its own evolutionary tendancies and historical fate" - Wiley 1978

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts "A single lineage (ancestor-descendant sequence) of populations or organisms that maintains an identity separate from other such lineages and which has its own evolutionary tendancies and historical fate" - Wiley 1978 "Irreducible cluster of organisms diagnostically distinct from other such clusters, and in which there is a parental pattern of ancestry and descent" - Cracraft

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts "A single lineage (ancestor-descendant sequence) of populations or organisms that maintains an identity separate from other such lineages and which has its own evolutionary tendancies and historical fate" - Wiley 1978 "Irreducible cluster of organisms diagnostically distinct from other such clusters, and in which there is a parental pattern of ancestry and descent" - Cracraft "The smallest monophyletic group of common ancestry" - (de Queiroz and Donoghue ).

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts - Can't determine reproductive activity from a fossil; must rely on morphological criteria and patterns of change in a lineage.

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts - Can't determine reproductive activity from a fossil; must rely on morphological criteria and patterns of change in a lineage. - A single unique lineage is an evolutionary species. This is defined by the presence of a unique derived character. Groups of populations that share the same suite of characters are the same species. this can be based on morphometric or genetic analysis.

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts - Can't determine reproductive activity from a fossil; must rely on morphological criteria and patterns of change in a lineage. - A single unique lineage is an evolutionary species. This is defined by the presence of a unique derived character. Groups of populations that share the same suite of characters are the same species. this can be based on morphometric or genetic analysis. - If it does not 'branch' but changes dramatically, stages can be distinguished as "chronospecies".

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts - emphasize species as the product of evolution... not the process (reproductive isolation) by which their identity is produced.

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts - emphasize species as the product of evolution... not the process (reproductive isolation) by which their identity is produced. - but identity is still critical... unique lineages are defined by the presence of a unique derived character. Groups of populations that share the same suite of characters are the same species. this can be based on morphometric or genetic analysis.

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts - emphasize species as the product of evolution... not the process (reproductive isolation) by which their identity is produced. - but identity is still critical... unique lineages are defined by the presence of a unique derived character. Groups of populations that share the same suite of characters are the same species. this can be based on morphometric or genetic analysis. - but do we then differentiate populations with discrete differences in fixed alleles?

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts D. Ecological Species Concept

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts D. Ecological Species Concept - In responding to selection, populations diverge and play unique roles in the environment - filling different niches. This ecological specialization will be reflected in physiological, morphological, or behavioral differences between populations. Hawaiian Honeycreepers

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts D. Ecological Species Concept - In responding to selection, populations diverge and play unique roles in the environment - filling different niches. This ecological specialization will be reflected in physiological, morphological, or behavioral differences between populations. - Our classic example of "Character Displacement", where the morphology changes as a function of the environment - most notably the presence of other species such as competitors or predators.

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts D. Ecological Species Concept - In responding to selection, populations diverge and play unique roles in the environment - filling different niches. This ecological specialization will be reflected in physiological, morphological, or behavioral differences between populations. - Our classic example of "Character Displacement", where the morphology changes as a function of the environment - most notably the presence of other species such as competitors or predators. - In the presence of a competitior, G. fortis uses a different range of seeds and is a different ecological species than where it occurs alone. It plays a different role in the environment and fills a different niche.

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts D. Striking a Balance

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts D. Striking a Balance - So what preserves the integrity of species - reproductive isolation or ecological isolation? These are often correlated, so it is tough to tease their independent contributions apart.

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts D. Striking a Balance - So what preserves the integrity of species - reproductive isolation or ecological isolation? These are often correlated, so it is tough to tease their independent contributions apart. - Conundrums: - Selection can produce divergence when their IS gene flow. (polymorphism)

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts D. Striking a Balance - So what preserves the integrity of species - reproductive isolation or ecological isolation? These are often correlated, so it is tough to tease their independent contributions apart. - Conundrums: - Selection can produce divergence when their IS gene flow. (polymorphism) - Selection can produce uniformity in absence of gene flow (convergence)

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts D. Striking a Balance - So what preserves the integrity of species - reproductive isolation or ecological isolation? These are often correlated, so it is tough to tease their independent contributions apart. - Conundrums: - Selection can produce divergence when their IS gene flow. (polymorphism) - Selection can produce uniformity in absence of gene flow (convergence) - And, gene flow can also keep two populations in different environments similar.

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts D. Striking a Balance - So what preserves the integrity of species - reproductive isolation or ecological isolation? These are often correlated, so it is tough to tease their independent contributions apart. - Conundrums: - Selection can produce divergence when their IS gene flow. (polymorphism) - Selection can produce uniformity in absence of gene flow (convergence) - And, gene flow can also keep two populations in different environments similar. - For bacteria/archaeans, lateral gene transfer (gene flow) creates new species, with a new unique complement of genes.

Species and Speciation I. Species Concepts A. Morphological Species Concept B. Biological Species Concept - Mayr 1942 C. Evolutionary/Phylogenetic Species concepts D. Striking a Balance - So what preserves the integrity of species - reproductive isolation or ecological isolation? These are often correlated, so it is tough to tease their independent contributions apart. - Conundrums: - Selection can produce divergence when their IS gene flow. (polymorphism) - Selection can produce uniformity in absence of gene flow (convergence) - And, gene flow can also keep two populations in different environments similar. - For bacteria/archaeans, lateral gene transfer (gene flow) creates new species, with a new unique complement of genes. - Need to appreciate that the relative importance of different factors may vary depending on the organism - does it have high dispersal and isolation probability? Can it change rapidly? These things will vary with the type of organisms (large mammals vs. insects).

Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology

Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology - correlated phenotypic characters. Quantitative characteristics can have bimodal distributions. However, it is unusual for a single species to be bimodal for lots of characters.

Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology - correlated phenotypic characters. Quantitative characteristics can have bimodal distributions. However, it is unusual for a single species to be bimodal for lots of characters. - If you observe this (big ones are red, with wispy antenna, small wings and fast flight; small ones are blue with short antenna, large wings and slow flight), then you probably have two reproductively isolated groups.

Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology - correlated phenotypic characters. Quantitative characteristics can have bimodal distributions. However, it is unusual for a single species to be bimodal for lots of characters. - If you observe this (big ones are red, with wispy antenna, small wings and fast flight; small ones are blue with short antenna, large wings and slow flight), then you probably have two reproductively isolated groups. - may miss morphologically similar sibling species, or lump polymorphic species.

Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology - correlated phenotypic characters. Quantitative characteristics can have bimodal distributions. However, it is unusual for a single species to be bimodal for lots of characters. - If you observe this (big ones are red, with wispy antenna, small wings and fast flight; small ones are blue with short antenna, large wings and slow flight), then you probably have two reproductively isolated groups. - may miss morphologically similar sibling species, or lump polymorphic species. - want to focus on traits of little selective value, or copulatory organs

Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology B. Genetic Analysis - Genetic Distance - distance correlates with divergence that can occur both before and after reproductive isolation. So, there is a fairly continuous function of declining similarity as reproductive isolation develops, dependent on average size of the populations. Within a group, often we see 'species' associated with a particular amount of genetic distance.

Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology B. Genetic Analysis - Genetic Distance - Compute Nei's Genetic distance: D = -ln [ ∑p i 1p i 2/ √ ∑p i1 2 ∑ p i2 2 ] - So, for Population 1 and 2: - ∑p i 1p i 2 = (0.7*0.2) + (0.3*0.8) = denominator = √ ( ) * ( ) = D 12 = -ln (0.38/0.62) = calculate these values FOR EACH locus, and then average the I's or D's together to get the final Genetic Distance. The more loci, the better. p1 = 0.7 q1 = 0.3 p2 = 0.2 q2 = 0.8

Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology B. Genetic Analysis - Genetic Distance - distance correlates with divergence that can occur both before and after reproductive isolation. So, there is a fairly continuous function of declining similarity as reproductive isolation develops, dependent on average size of the populations. Within a group, often we see 'species' associated with a particular amount of genetic distance. - Compute Nei's Genetic Distance - CAVEATS:

Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology B. Genetic Analysis - Genetic Distance - distance correlates with divergence that can occur both before and after reproductive isolation. So, there is a fairly continuous function of declining similarity as reproductive isolation develops, dependent on average size of the populations. Within a group, often we see 'species' associated with a particular amount of genetic distance. - Compute Nei's Genetic Distance - CAVEATS: - Genetic diffs do not necessarily correlate with morphological diffs; small genetic diffs can mean large morphological change (developmental genes), or large genetic change can be hidden by morphological similarity (norms of reaction).

Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology B. Genetic Analysis - Genetic Distance - distance correlates with divergence that can occur both before and after reproductive isolation. So, there is a fairly continuous function of declining similarity as reproductive isolation develops, dependent on average size of the populations. Within a group, often we see 'species' associated with a particular amount of genetic distance. - Compute Nei's Genetic Distance - CAVEATS: - Genetic diffs do not necessarily correlate with morphological diffs; small genetic diffs can mean large morphological change (developmental genes), or large genetic change can be hidden by morphological similarity (norms of reaction). - Still, genetic similarity is a more direct measure of degree of isolation.

Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology B. Genetic Analysis - Genetic Distance - distance correlates with divergence that can occur both before and after reproductive isolation. So, there is a fairly continuous function of declining similarity as reproductive isolation develops, dependent on average size of the populations. Within a group, often we see 'species' associated with a particular amount of genetic distance. - Compute Nei's Genetic Distance - CAVEATS: - Genetic diffs do not necessarily correlate with morphological diffs; small genetic diffs can mean large morphological change (developmental genes), or large genetic change can be hidden by morphological similarity (norms of reaction). - Still, genetic similarity is a more direct measure of degree of isolation. - Also, there is no suggestion that divergence in these loci CAUSE speciation. Rather, these loci are simply used as 'markers' or indicators of general genetic distance.