Systematics and the Origin of Species On Ernst Mayr's 100th Anniversary (2005) / Chapter Skim
Currently Skimming:
8 Evolutionary Animation: How Do Molecular Phylogenies Compare to Mayr’s Reconstruction of Speciation Patterns in the Sea?--STEPHEN R. PALUMBI AND H. A. LESSIOS
8 Evolutionary Animation: How Do Molecular Phylogenies Compare to Mayr’s Reconstruction of Speciation Patterns in the Sea?--STEPHEN R. PALUMBI AND H. A. LESSIOS
Pages 143-161
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 143... ...
By contrast, early-stage genera with few sympatric species are not necessarily earlier in the divergence process; they happen to be those with slow rates of bindin evolution. These results show that the rate of speciation in sea urchins does not only depend on the steady accumulation of genome divergence over time, but also on *
|
From page 144... ...
The trajectory from homogeneous populations to overlapping sympatric species encompassed Mayr's view of the process and pacing of geographic speciation. In addition to describing these separate elements, a major contribution by Mayr was to order these elements in a series.
|
From page 145... ...
Groups 1 and 2 included genera that had strictly allopatric species, the only difference between the groups being that group 2 genera included nontropical species. These two groups represented the earliest step in species formation, with a surfeit of polytypic species, and, presumably, low divergence among allopatric sister species.
|
From page 146... ...
In this paper, we collate these phylogenies and use them to test general predictions from Ernst Mayr's reconstruction of sea urchin speciation patterns. General predictions across all genera in the study include familiar tenets of allopatric speciation.
|
From page 147... ...
Based on a molecular rate estimate provided by the rise of the isthmus of Panama, the latter two sister species diverged 2 million years ago. An allopatric neighbor of these species, the widely distributed PacificIndian ocean species Eucidaris metularia is not a close relative of the eastern Pacific species.
|
From page 148... ...
from eight sea urchin genera. Data are from Lessios et al.
|
From page 149... ...
. In addition, there is evidence for acceleration of bindin evolution in the two sympatric species compared to COI, although maximum likelihood analysis fails to show positive selection, possibly because of low statistical power in these closely related sequences.
|
From page 150... ...
In this genus, major differences in bindin gene sequence are associated with strong reproductive isolation among closely related species (Landry et al.,
|
From page 151... ...
. In particular, sympatric species of Echinometra show much less genetic divergence than sympatric species of Diadema.
|
From page 152... ...
erythrogramma. General Tests of Predictions The prediction that genetic divergence of sister species increases from stage to stage of speciation is borne out by comparison of phylogenies and genetic distances among the eight genera of sea urchins (Fig.
|
From page 153... ...
Dividing the species into allopatric and sympatric comparisons shows that divergence between sympatric species increases stage by stage but that divergence between allopatric species does not (Fig.
|
From page 154... ...
In the genera Echinometra and Strongylocentrotus, sympatric species are common, whereas in genera with slow rates of bindin evolution, sympatric species are rare. Among genera with rapid bindin evolution, 10 of 16 sister species comparisons are between sympatric species.
|
From page 155... ...
Divergence in bindin between these two species appears to be accelerated relative to COI divergence, although there is no statistically significant signal of positive selection. DISCUSSION Evolutionary series based on geography and taxonomy can be independently investigated by comparing molecular phylogenies of species groups at different stages of diversification.
|
From page 156... ...
Genera with rapid bindin evolution include many closely related sympatric species. By contrast, in genera without rapid change in bindin, closely related or moderately related species are nearly exclusively allopatric (Fig.
|
From page 157... ...
Groups 1 and 2 genera have slow bindin evolution, have largely allopatric species, and are therefore earlier frames in the evolutionary animation. Groups 3 and 4 genera, with many more sympatric species, are classified later in the evolutionary series, but their species are not necessarily older.
|
From page 158... ...
suggested that rapid evolution of bindin in Caribbean Echinometra was due to divergence of the fertilization systems of two sympatric species. In this case, rapid bindin evolution in one species was associated with evolution of egg specificity in the same species (Lessios and Cunningham, 1990; McCartney and Lessios, 2002)
|
From page 159... ...
Overall, the clear relationship between bindin evolution and young, sympatric species remains a strong signal that gamete recognition and species formation are tightly linked. But the underlying mechanisms driving this pattern remain poorly explained.
|
From page 160... ...
(2003) Recent speciation in the Indo-West Pacific: rapid evolution of gamete recognition and sperm morphology in cryptic species of sea urchin.
|
From page 161... ...
(2004) Adaptive evolution of sperm bindin tracks egg incom patibility in neotropical sea urchins of the genus Echinometra.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.