Few regions in Middle America are so important zoogeographically as...

Few regions in Middle America are so important zoogeographically as is the Isthmus of Tehuantepec, that neck of land connecting North America with Central America, separating the Pacific Ocean from the Gulf of Mexico by a distance of only about 220 kilometers, and forming a low break between the highlands of México and those of Central America.
Before World War II the isthmus could be reached readily only by railroad or by ocean vessel to Salina Cruz or Coatzacoalcos; with the advent of roads, principally the Trans-isthmian Highway, vast areas of the interior of the isthmus became accessible. Since even long before roads were built in the isthmian region, as early as the 1870’s, biologists visited it, it is rather surprising that no attempt has been made to present a faunal list of the amphibians or reptiles of the isthmus.
Even if in recent years there have been only a few papers reporting species from the isthmus, the zoogeographic significance of the Isthmus of Tehuantepec is exemplified by the works of several authors, who in their discussions of evolution and dispersal of various genera of reptiles, pointed out its zoogeographic importance.
While I originally intended to study the entire herpetofauna of the isthmus, the study was finally concerned only with the amphibians of the lowlands as the highland species were commented but not systematic studied. Among the species of amphibians that I would expect to occur in the isthmus, the only one not yet found there is Hyla phaeota. Sufficient specimens of most of the species are available to show their variation in the isthmus, allowing the systematics of these amphibians to be on a fairly substantial basis. Probably certain species in the isthmian region will be found to be conspecific with others to the south, for example Hyla ebraccata with Hyla leucophyllata and Hyla robertmertensi with Hyla underwoodi, this taxonomic changes not significant enough to affect the distributional picture of the species.

Our greatest lack of knowledge concerning the amphibians is about their ecology and life habits, such as the location where the small frogs migrate during the dry season, the amount, if any, of interspecific competition among the several species of tree frogs, and the factors that permit certain amphibians to live in the humid rainforests and others in the arid tropical scrub forest."

The author’s primary purpose is to:

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A) exemplify the fauna of the isthmus of Tehuantepec

B) provide examples of the animal species living in the isthmus

C) to illustrate the species of amphibians living in the Isthmus of Tehuantepec, their environment and distribution

D) to provide an overview of the biological significance of the isthmus of Tehuantepec

E) make a case for the ecological vulnerability of the amphibians of the isthmus

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