The addition of molecular data into the search for relationships between organisms is welcome, but introduces new complexities. The problem is that the traditional morphological data—similarities and differences among body parts of organisms—don't always truly reveal relationships. We've long known of so-called cryptic species. These are two populations of organisms whose members look extremely similar but are unable to interbreed, thus belonging to different species despite their basic morphological similarity. Now, with the addition of molecular evidence, such as from the genetic material, DNA, we're finding populations that are different even though the differences were never detected by morphological data.
Packrats are an example. We've long considered the geographic range
of the White-throated Packrat, Neotoma albigula, to extend from southeastern
California to central Texas and from Colorado to central Mexico. The molecular data
indicate else wise; that the populations west of the Rio Grande and Rio Conchos are one
species and populations east of these rivers a different one. So let's welcome a
newly recognized species, Neotoma leucodon, to the eastern reaches of our
Chihuahuan Desert.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
Edwards, C. W., C. F. Fulhorst, and R. D. Bradley. 2001. Molecular phylogenetics of the Neotoma albigula species group: Further evidence of a paraphyletic assemblage. Journal of Mammalogy 82(2):267-279.
Schmidly, D. J. 2004. The mammals of Texas. 6th ed., University of Texas Press, Austin. 501 pp.