The shovel-nosed salamander, Desmognathus marmoratus , is a totally aquatic, end

Question

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

No gene flow occurs naturally between the salamanders from different streams but 14% divergence is DNA is seen. However the F1 and F2 offsprings between the salamanders from different streams are Fertile.

Since the offspings of the salamanders from different divides are fertile at both filial 1 & 2. They can all still be considered part of the same specie. But since divergence in their genome sequences are seen, they are currently in the process of speciation, and haven't reached a point of distinction yet.

The salamanders are likely to be diverging into Peripatric speciation, a type of speciation where speciation occurs in an isolated peripheral population, they reside in adjacent not overlapping zones. Here since all the salamanders are aquatic, their stream paths never cross each others and they are isolated from each other.

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