Ch. 18 – Sympatric Speciation and Darwin’s Finches
All allopatric speciation invokes an imporobable number of range splitting and rejoinings – this leads some to consider parapatric and sympatric speciation. Sympatric speciation is a good way to account for presence of large number of sister species in environment with many niches
1st Step: A stable [...]
Archive for February, 2008
Speciation and its Consequences
Posted in Uncategorized on February 22, 2008 | Leave a Comment »
Speciation and Macroevolution
Posted in Uncategorized on February 14, 2008 | Leave a Comment »
Speciation Rate:
Speciation can occur rapidly no matter what the driving force. Transition times are generally shorter whenever the process involves an unstable intermediate stage; the forming species must either cross that unstable stage quickly or dissolve (involves sympatric phase or crossing adaptive valley). Transition times for allopatric speciation can be longer since the [...]
Selection vs. Drift
Posted in Uncategorized on February 10, 2008 | Leave a Comment »
This chapter’s question: Does natural selection or genetic drift play a larger role in the origin of species?
A lovely table directly from the book summarizes definitions nicely (p. 384):
Selection
Direct: direct natural selection for reproductive isolation. Direct selection characterizes models of sympatric speciation and reinforcement. — Definitely not ubiquitous, especially in allopatric speciation.
Indirect: [...]
Reinforcement
Posted in Uncategorized on February 8, 2008 | Leave a Comment »
Reinforcement: enhancement of prezygotic isolation in sympatry by natural selection – Two taxa diverge in allopatry; upon secondary geographic contact, hybridization occurs at some rate, yielding unfit hybrids. Because production of hybrids is maladaptive, individuals who only mate with their own taxa enjoy a fitness advantage.
Evidence: Reveals that sympatry can enhance prezygotic [...]
