Species & Speciation Notes
Lecture 15: Species & Speciation 1
Page 1
- Introduction to the lecture's focus on species and the concept of speciation.
Page 2
- What is a species?
- How are species formed?
- Allopatric speciation by dispersal
- Allopatric speciation by vicariance
Page 3
- Recall: Microevolution
- Definition: Evolution on a small scale, pertaining to changes within a population.
- Key aspects:
- Changes in allele frequency within a species
- Processes include natural selection, genetic drift, and mutation
- Focus is mainly on living species.
Page 4
- Recall: Macroevolution
- Definition: Evolution occurring on a large scale, often resulting in the emergence of new species.
- Key aspects include:
- Speciation processes
- Origins of new lineages, rates of divergence, and extinction events
- Evidence gathered from the fossil record.
Page 5
- What is a species?
- Conceptual definitions include:
- Morphological species
- Phylogenetic species
- Biological species
Page 6
- Morphological species
- Example: Mocker swallowtail in Africa - females have 14 different morphs.
- Batrachoseps salamanders appear similar but do not interbreed, illustrating cryptic species.
- Definition: Groups defined by unique morphological characters that reliably distinguish them.
- Challenges arise as many species exhibit diverse morphologies or sometimes cryptic differences.
Page 7
- Phylogenetic species
- Definition: The smallest diagnosable group that evolves from a single ancestral population and exhibits new, derived traits.
- Necessitates an understanding of evolutionary history.
Page 8
- Example of phylogenetic species
- Asian elephants (India) vs. African forest and savannah elephants.
- Each population evolves separately, accumulating mutations leading to geographical variations and distinct species.
Page 9
- Continuation of the phylogenetic species example showing distinct populations and genetic divergence.
Page 10
- Biological species concept
- Defines species as groups of actually or potentially interbreeding natural populations that are reproductively isolated from others.
- Example: Different species of Anolis lizards occurring in various Caribbean islands.
Page 11
- Key reference: Ernst Mayr
- Important figure in systematics and evolutionary biology known for his contributions to the biological species concept.
Page 12
- Limitations of the Biological Species Concept
- Challenges in applying this concept to fossils, asexual species, or in instances where mating is not observed.
- Alternatives may be morphological similarity or genetic relatedness.
Page 13
- Addressing the limitations previously mentioned and emphasizing the subjective nature of defining species.
Page 14
- What is a subspecies?
- Subspecies differ but do not warrant separation into different species.
- Typically refers to geographically separate variants.
Page 15
- Conservation dilemma: Whether to protect all morphological subspecies or only designated phylogenetic species, illustrated by the seaside sparrows.
Page 16
- Yellow-breasted Chat Example
- Discusses conservation measures for its subspecies in Canada.
Page 17
- Further details on specific subspecies and their conservation status (endangered or not at risk).
Page 18
- How does speciation occur?
- Allopatry: Resulting from physical separation reducing gene flow.
- Sympatry: Possible gene flow but leading to divergence.
Page 19
- Allopatric Speciation
- Definition: Splitting of a species into two groups by dispersal or vicariance due to geographic barriers.
- Over time, genetic divergence occurs.
- Sympatric Speciation: Divergence within the same geographical area where interbreeding is possible.
Page 20
- Allopathy - Dispersal
- Illustrative model showing the process of divergence when populations become isolated, e.g., on an island.
Page 21
- Hawaiian Islands as a case study of dispersal speciation
- Timeline of the islands' emergence and species diversification.
Page 22
- Hawaiian Drosophila Example
- About 800 endemic fruit fly species, histrorically analyzed for complex patterns of speciation across islands.
Page 23
- Nene - The Hawaiian Goose
- Derived from Canada goose ancestors, illustrating allopatric speciation through isolation.
Page 24
- Allopathy - Vicariance
- Speciation through geological events that separate populations.
- Example: Changes in landscape that create isolation.
Page 25
- Example of Ratites
- Speciation through vicariance explained via the breakup of Gondwana, leading to distinct species on separate continents.
Page 26
- Amazon River case study
- Geological events leading to vicariance, creating barriers that promote species diversification.
Page 27
- High biodiversity noted in the Amazon due to vicariant events leading to distinct genera of species.
Page 28
- Sympatric Speciation
- Mechanism where divergence occurs despite the potential for interbreeding, typically linked to specialized usage of food or habitat.
Page 29
- How can divergence occur in sympatry?
- Changes in food or habitat can lead to morphological differences, genetic drift, and eventual speciation.
Page 30
- Soapberry Bugs
- Example where differences in diet (native vs. nonnative fruit sources) lead to trait evolution such as beak length.
Page 31
- Further exploration of the beak length variation based on feeding habits on native versus nonnative plants.
Page 32
- Repeat of findings highlighting disruptive selection due to different fruit sizes, influencing the morphology of soapberry bugs.
Page 33
- Next Lecture
- Continuation on Speciation 2.