Study Guide 7 Speciation Flashcards
Define each of the species concepts provided below. What are the pros and cons for each species concept? For what organisms does each species concept work well? For what organisms does each species concept not work well?
a. Biological Species Concept
-a species is a group interbreeding individuals that are reproductively isolated from other groups
-pros: straightforward and easy to understand; based on HWE mechanisms
-cons: requires knowledge of mating systems; does not apply to asexual species; inadequate for complex mating systems (eg ensatina salamander ring species)
-limitations: does not work for extinct organisms, asexual species, or populations with continuum of interbreeding (ring species)
Define each of the species concepts provided below. What are the pros and cons for each species concept? For what organisms does each species concept work well? For what organisms does each species concept not work well?
b. Morphological Species Concept
-a species is a group of organisms with similar physical traits (morphology)
-pros: useful when other data are limited
-cons: morphological similarity can be misleading; ineffective for species experiencing convergent evolution(overestimates relatedness); generally less accurate/reliable than other species concepts
Define each of the species concepts provided below. What are the pros and cons for each species concept? For what organisms does each species concept work well? For what organisms does each species concept not work well?
c. Phylogenetic Species Concept
-a species is a group of organisms sharing a common ancestor, distinguished by specific traits (especially genetic similarity)
-pros: based on evolutionary history; applicable to all organisms (all have DNA)
-cons: requires modern genetic and computational tools; does not work for extinct species (limited DNA access for recently extinct groups)
Rank these concepts in order of most general to most specific:
a) gametic isolation
b) reproductive isolating mechanism
c) sperm-egg incompatibility in sea urchins
d) prezygotic isolating mechanism
b) reproductive isolating mechanism
d) prezygotic isolating mechanism
a) gametic isolation
c) sperm-egg incompatibility in sea urchins
For each of the types of speciation listed below, describe the general pattern of how speciation occurs and provide an example of speciation that has followed this pattern
a. Allopatry through vicariance
-geographic barrier: a physical barrier separates a population into two roughly equal halves
-genetic divergence: over time, mutations, genetic drift, and selection create genetic differences between the halves
-reproductive barriers: differences become significant enough that they cannot interbreed if they come into contact again
-result: the groups are considered separate species
For each of the types of speciation listed below, describe the general pattern of how speciation occurs and provide an example of speciation that has followed this pattern
b. Allopatry through the founder effect
-initial colonization: a small subset of the population moves to a new geographically separate area
-genetic divergence: over time, mutations, genetic drift, and selection create genetic differences between the two groups
-reproductive barriers: differences become significant enough that they cannot interbreed if they come into contact again
-results: the groups are considered separate species
For each of the types of speciation listed below, describe the general pattern of how speciation occurs and provide an example of speciation that has followed this pattern
c. Sympatry
-initial change: genetic change (mutation/behavior shift) occurs in a few individuals within a population
-reproductive barrier: this change creates a barrier between these individuals and the rest of the population
-emergence of species: as the change becomes more common, two distinct groups form, considered separate species
-sympatry vs parapatry: groups are fully intermixed vs groups are adjacent or tangential to each other
The figure below shows the proportion of individuals attacked by birds in a population of butterflies in central Panama. The red bar represents Heliconius melpomene (labeled ME), the white bar represents Heliconius cydno (labeled CY), and the gray bar represents F1 hybrids between the two. Do the data in the figure indicate a reproductive barrier between these two species? If so, what kind of barrier is suggested?
yes, the data indicate a reproductive barrier between these two species
-F1 Hybrids: attacked by birds at higher rates than parent species, indicating reduced hybrid viability (shorter lifespan).
In class, we showed examples of how plants that specialize on one type of pollinator have higher speciation rates than plants that attract a variety of pollinators (generalists) and insects whose diets are specialized on one species of plant have higher speciation rates than insects that feed on a variety of food sources (generalists). Why does specialization lead to faster speciation rates than groups that are generalists?
-behavioral isolation: specialization on a particular pollinator prevents pollen transfer between species
-ecological habitat isolation: insects specializing on a specific plant diet will likely mate only with others on that plant type
In class, we showed examples of how birds that are better dispersers (can travel far) have lower speciation rates than birds that are poorer dispersers (can travel less far). Students often find this counter-intuitive. Why does increased dispersal ability lead to lower speciation rates?
-distance and isolation: distance require for allopatric populations varies by dispersal ability
-poor dispersers: small distances can isolate them into separate, non-connected populations
-better dispersers: can travel further and maintain reproductive connectivity between populations
-speciation likelihood: better disperser are less likely to experience allopatric speciation than poor dispersers
What is an adaptive radiation? Describe an example of an adaptive radiation.
adaptive radiation: rapid speciation producing many new species within a group, adapted to specific niches (over geologic time scales, eg a few million years)
example: Hawaiian honeycreepers– 55 species evolved from a common ancestor (european rosefinches) in about 3 million years, with adaptations to different food sources and morphological changes in beak structure
What is the difference between homologous traits and analogous traits?
homologous traits: result from shared ancestry and descent with modification
analogous traits: result from convergent evolution; species develop similar traits due to similar natural selection pressures, not inherited from a common ancestor
Determine whether each of the traits listed below are homologous or analogous traits.
a. Limb bones of humans and cats
b. Wings of birds and insects
c. Streamlined body shape in dolphins and sharks
d. Cactus spines and conifer needles
a. Homologous
b. Analogous
c. Analogous
d. Homologous
