Internal controls of biogeographic patterns

1. Internal controls of biogeographic patterns • Objectives • Explain how phenotypic diversity can enhance potential species diversity • Compare and contrast allopatric, sympatric, ecological and reverse speciation • Compare and contrast convergent, divergent and parallel evolution • Define adaptive radiations, what drive them and provide examples as well as their controls • Describe why sympatric speciation is difficult to distinguish from allopatric speciation • Explain difference between genetics, epigenetics, and DNA regulation • Explain how gene flow and natural selection influence each other • Compare and contrast the three types of photosynthesis • Know examples for these concepts as presented in slides, including the one for beach mice

2. Natural selection and speciation • Natural selection is the non-random process thru with biological traits become more or less common in a population as a result of differential reproduction • Genotypes can vary and not result in a new species (speciation) • Natural selection is not necessarily an emergence of new species, or speciation, but it can be. • Phenotypic change is not natural selection, although it can initiate it • Taxa with high phenotypic plasticity are more likely to undergo speciation

3. Phenotypic plasticity

5. Modes of speciation • Allopatric speciation • Requires geographic isolation of population • Physical barrier, such as a mountain range or a long distance dispersal event • Exposure to different physical environment and evolutionary adaptation • Pre and post-zygotic reproductive isolation from original population • Separated populations considered different species • Sensitive to founder effects

6. Hawaiian silverswords

8. Allopatric speciation Cuban anole

9. Ring species • An example of allopatric speciation • A ring species arises when a parental population expands around an area of unsuitable habitat in such a way • When the two fronts meet they behave as distinct species while still being connected through a series of intergrading populations.

12. Modes of speciation • Sympatric speciation • Does not require geographic isolation • Isolation initiated through disruptive selection and assortive mating • Reproductive isolation from original population • Separated populations considered different species

13. African firefinch Black bellied firefinch Blue indigo bird of Cameroon – sympatric speciation

16. Adaptive radiation • Evolutionary divergence of members of a single phylogenetic lineage into a variety of different adaptive forms • Examples: • Lemurs in Madagascar • Cichlid fishes in Africa • Galapagos tortoises • Darwin’s finches

18. Adaptive radiation (need example) • Causality attributed to ecological opportunity • Appearance of new resources • Extinction of species previously using resources • Colonization of area where resources not used • Evolution of a new trait that permits use of new resource

19. Adaptive radiation of cichlids of the Rift Valley Lakes of East Africa

23. Adaptive radiation (need example) • Does not occur on all islands • Minimum ‘island’ size (radiations on small islands less common) • Small island archipelagos do exemplify radiations • Not all lakes with cichlids in Africa underwent adaptive radiations • Radiation potential correlated with lake depth, not size of lake • More solar radiation: more radiation • Traits for sexual dichromatism more pronounced where radiations have occured

24. Speciation outcomes in the context of adaptive radiations • Convergent evolution • Similar phenotypes, distantly related genetically • Divergent evolution • Different phenotypes, closely related genetically • Parallel evolution • Same phenotypes, closely related genetically

25. Convergent evolution

29. Divergent evolution

33. Parallel evolution • A form of convergent evolution • Same, often very recent ancestor at different locations • Similar natural selection outcomes repeated at these locations • Similarity in species behaviors and morphology repeats • However, different genetically • In convergent evolution proper, common ancestor is distant

36. Ecological speciation • The evolution of reproductive isolation between populations as a result of ecologically-based divergent natural selection. • An alternative to the allopatric-sympatric dichotomy • More species of anole on a given Caribbean island like Cuba than can be accounted for via isolation events

38. Reverse speciation

46. Evolutionary genetics • Focuses on the changes in DNA sequence and its association with the formation of distinctive taxonomic or functional groupings • Scenarios for a population of organisms: • Neutral genetic drift in the absence of natural selection • Natural selection via selection on phenotype • Natural selection occurs, but gene flow does not allow it to proceed • Artificial selection

47. Adaptive radiation of beach mice

48. Peromyscus polionotus Pigmentation traits of subspecies on different barrier islands. All derived from ancestral old field mouse

49. Panhandle beach mice • Founder effects? • Neutral genetic drift? • Natural selection? • Convergent evolution? • Divergent evolution?