4. The shovel-nosed salamander, Desmognathus marmoratus, is a totally aquatic, e

Question

4. The shovel-nosed salamander, Desmognathus marmoratus, is a totally aquatic, endemic species found in high mountain streams in the Appalachian Mountains of Tennessee, North Carolina, South Carolina and Georgia. No gene flow occurs between river drainages due to the completely aquatic lifestyle of this salamander. Populations on either side of the Tennessee Divide (Tennessee and N. Carolina vs. Georgia and S. Carolina) have no morphological differences between them. A phylogeny based on mtDNA sequences (Jones et al. 2006) showed, however, that populations on either side of the Tennessee Divide showed greater than 14% sequence divergence and were well supported, separate, monophyletic lineages. Salamanders collected from drainages on both sides of the Tennessee Divide were brought into the laboratory and observations confirmed that salamanders from Tennessee would mate with salamanders from Georgia and made viable and fertile F1 and F2 offspring. Based upon your understanding of different species concepts (biological, morphospecies, phylogenetic), how would each classify these shovel-nosed salamanders (i.e., separate species or the same species, and why?). Under which type/mode of speciation are these salamanders likely to be diverging on opposite sides of the Tennessee Divide?

Explanation / Answer

The populations on either side did not show any morphological differences but did show sequence differences. These animals are to be supposed to be diverging on the basis of geographical speciation, specifically, parapatric speciation. in this speciation the original population gets separated on the basis of a geographic barrier, over a large area, but they would be able to mate with one another. These are not reproductive,t isolated, meaning, that when these come in contact with one another, they can be interbred. This is in contrast to allopatric or peripatetic speciation. These species are separated as a result of environmental differences, and could be referred to as different species.

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