1. Divergent Evolution in the Ferns Botany 209 16 March, 2010

2. DIVERGENT SPECIATION in the FERNS 1.Incomplete divergence (versus secondary contact) in Athyrium filix-femina 2.Allopatric speciation in Polypodium 3.Peripatric speciation in Pleopeltis 4.Species limits and speciation in Asplenium nidus

3. Phylogeny of Isoetes species based on ITS sequence data

6. Kelloff et al. 2002. Differentiation of eastern North American Athyrium filix-femina taxa: evidence from allozymes and spores. Amer. Fern Journal 92:185-213.

7. Athyrium filix-femina subsp. angustum Athyrium filix-femina subsp. asplenioides

8. Characterangustumasplenioides Rhizome habiterect or ascendingascending or creeping Leaf shapetapered at basebarely tapered at base Spore coloryellowishbrownish-yellow to black Spore surface featuressparsely papillatewrinkled or reticulated

10. A. f.-f. subsp. angustumA. f.-f. subsp. asplenioides

11. At the four most polymorphic loci (Idh- 1, Pgm-2, Pgi-2, and Tpi-2) population allele frequencies were quite similar within taxon, but quite different between taxa. Isozyme Results

15. DIVERGENT SPECIATION in the FERNS 1.Incomplete divergence (versus secondary contact) in Athyrium filix-femina 2.Allopatric speciation in Polypodium 3.Peripatric speciation in Pleopeltis 4.Species limits and speciation in Asplenium nidus

16. Lisa Andrews Hooper Chris Haufler Haufler, C. H., E. A. Hooper, and J. P. Therrien. 2000. Modes and mechanisms of speciation in pteridophytes: implications of contrasting patterns in ferns representing temperate and tropical habitats. Plant Species Biology 15: 223- 236.

17. Polypodium virginianum (4x) Polypodium appalachianum (2x) Polypodium sibiricum (2x) Polypodium amorphum (2x)

20. Mean genetic identity between species = 0.460

21. Haufler’s divergence scenario for Polypodium:  P. sibiricum occurs in glaciated regions. Perhaps, like other boreal taxa, P. sibiricum populations migrated south in advance of the ice sheet.  Following retreat of the ice, populations returned to their northern haunts, but perhaps some populations persisted in the mountains of eastern and western North America. Isolation and divergence perhaps led to speciation of P. amorphum in the west and P. appalachianum in the east.

22. The low I values for the three species suggest that did not take place in the most recent these events did not take place in the most recent ice age. ice age. In fact, secondary contact following southerly migration of P. sibiricum during more recent episodes of glaciation may have initiated both P. virginianum and P. saximontanum, a western tetraploid.

23. The mode of speciation in the P. sibiricum allopatric complex is thus fits the classic allopatric model.

24. DIVERGENT SPECIATION in the FERNS 1.Incomplete divergence (versus secondary contact) in Athyrium filix-femina 2.Allopatric speciation in Polypodium 3.Peripatric speciation in Pleopeltis 4.Species limits and speciation in Asplenium nidus

25. So why the low identities among congeneric species in the ferns?  One possibility is that they diverged long ago.  Another is that, in the absence of pre-zygotic isolating mechanisms (pollination biology, pollen-stigma interactions, different flowering times, etc.) to maintain barriers between there may be strong selection for the evolution of species, there may be strong selection for the evolution of post-zygotic isolating mechanisms. post-zygotic isolating mechanisms.

26. Pleopeltis sp.

27. Pleopeltis polypodioides

28. Mean genetic identity between species = 0.849

30. Why the difference? Perhaps the mode of speciation here is peripatric, including peripheral isolation and rapid adaptation to differing habitats.

31. The greater complexity of tropical habitats may provide increased opportunities for ecological isolation ecological isolation and speciation.

32. DIVERGENT SPECIATION in the FERNS 1.Incomplete divergence (versus secondary contact) in Athyrium filix-femina 2.Allopatric speciation in Polypodium 3.Peripatric speciation in Pleopeltis 4.Species limits and speciation in Asplenium nidus

33. Yatabe on the Asplenium nidus complex Yoko Yatabe with Kato and Gong Wu su. China 2001

34. Yatabe on the Asplenium nidus complex Yatabe et al. 2009

35. Yatabe on the Asplenium nidus complex Yatabe et al. 2009

36. Yatabe on the Asplenium nidus complex Yatabe et al. 2009

37. Yatabe on the Asplenium nidus complex Yatabe et al. 2009

38. Yatabe on the Asplenium nidus complex Yatabe et al. 2009

39. Yatabe on the Asplenium nidus complex Yatabe et al. 2009

40. Yatabe on the Asplenium nidus complex Yatabe et al. 2009

41. DIVERGENT SPECIATION in the FERNS 1.Incomplete divergence (versus secondary contact) in Athyrium filix-femina 2.Allopatric speciation in Polypodium 3.Peripatric speciation in Pleopeltis 4.Species limits and speciation in Asplenium nidus