The Mexican Transition Zone by Juan J. Morrone

Author:Juan J. Morrone
Language: eng
Format: epub
ISBN: 9783030479176
Publisher: Springer International Publishing

Corral-Rosas and Morrone (2017) undertook a time-sliced cladistic biogeographic analysis, based on 49 taxa, including plants, insects, and vertebrates. Each of the taxa was assigned to a particular cenocron, based on their phylogenies, the distribution of their related taxa, and molecular dating (when available). The matrix for the parsimony analysis of paralogy-free subtrees was partitioned into three submatrices, each corresponding to a particular time-slice, in order to represent the successive incorporation of the cenocrons. The Miocene time-slice includes the taxa of the Mountain Mesoamerican cenocron, the Pliocene time-slice includes the taxa of the Mountain Mesoamerican and Nearctic cenocrons combined, and the Pleistocene time-slice includes the taxa of the Mountain Mesoamerican, Nearctic, and Typical Neotropical cenocrons. Four general area cladograms were obtained (Fig. 3.10): one for the Miocene time-slice, one for the Pliocene time-slice, and two for the Pleistocene time-slice. The general area cladogram for the Miocene time-slice (Fig. 3.10a) shows the following sequence: Sierra Madre Occidental, Nearctic region, Sierra Madre Oriental, Chiapas Highlands-Neotropical region, and Transmexican Volcanic Belt-Sierra Madre del Sur. The general area cladogram for the Pliocene time-slice (Fig. 3.10b) shows a dichotomy between a southern clade and a northern clade; the southern clade shows the Chiapas Highlands as the sister area of the Neotropical region; the northern clade separates the Sierra Madre Oriental and Sierra Madre del Sur as sister areas and the remaining areas in the following sequence: Nearctic region, Sierra Madre Occidental, and Transmexican Volcanic Belt. Two general area cladograms were obtained for the Pleistocene time-slice. One corresponds to the same as obtained for the Pliocene time-slice (Fig. 3.10b), and the other (Fig. 3.10c) shows a dichotomy between a northern clade and a southern clade. The northern clade shows the sequence Nearctic region, Sierra Madre Occidental, and Transmexican Volcanic Belt, and the southern clade shows two dichotomies: Chiapas Highlands-Neotropical region and Sierra Madre Oriental-Sierra Madre del Sur. Some of the relationships shown by the different general area cladograms are coincidental. The close relationship between the Chiapas Highlands and the Neotropical region is shown in the general area cladograms of the three time-slices; this situation might be because the Chiapas highlands are situated in the southernmost part of the Mexican Transition Zone, thus having a stronger Neotropical influence. A close relationship between the Sierra Madre Oriental and Sierra Madre del Sur is shown by the Pliocene and Pleistocene time-slices.

Fig. 3.10General area cladograms obtained by Corral-Rosas and Morrone (2017) and the maps representing geographically the main clades. (a) Miocene time-slice; (b) Pliocene and Pleistocene time-slices; (c) Pleistocene time-slice

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