Case Study: Evolution of Tungara Frog Mating Calls

Introduction to the Ladies
Many animals exhibit selective mating among species. This high degree of same-species preference can result from males and females sharing a communication system, in which males have evolved specific traits to aid female same-species recognition and preference. Certain aspects of how same species (conspecific) mate recognition operate are well-understood in frogs. Typically, in frog species, males produce advertisement calls, one function of which is to attract females. Although members of the same species may have some limited call variation between individuals, the variation is extremely small compared with that between species; thus, the male call is “species specific.” Within the species, females may also exhibit preferences based on specific male traits, suggesting the presence of “hardwired” ancestral preferences in female neural structure.

The genus Physalaemus currently contains about thirty species in which females exhibit preferences to specific male call characteristics. The species group (túngara frogs) consists of four species in two species pairs: P. pustulosus and P. petersi, and P. coloradorum and P. pustulatus. In addition, several groups are closely related to the túngara frogs, and are often used as outgroups to observe evolutionary changes between species.

INSTRUCTIONS:
Read the background information about each of the species, then click the NEXT button to continue.

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Species Map



Backround information about the species:

Physalaemus pustulosus: Distributed throughout much of Middle America as well as Columbia, Venezuela, and Trinidad. The ranges of P. pustulosus and P. petersi are allopatric; their closest proximity is in Columbia, where they occur within several hundred kilometers of one another.

Physalaemus petersi: Distributed throughout Amazonia, and found in Columbia, Ecuador, Peru, Bolivia, and Brazil. The ranges of P. pustulosus and P. petersi are allopatric; their closest proximity is in Columbia, where they occur within several hundred kilometers of one another.

Physalaemus coloradorum: Found in low -to mid-elevation rainforests on the western slope of the Andes in Ecuador. The ranges of P. coloradorum and P. pustulatus are allopatric, approaching within 200 km in western Ecuador. Being the only two representatives of the genus west of the Andes, these species are isolated from any others.

Physalaemus pustulatus: Ranges from southern Ecuador to northern Peru, in drier regions along the Pacific coast. The ranges of P. coloradorum and P. pustulatus are allopatric, approaching within 200 km in western Ecuador. Being the only two representatives of the genus west of the Andes, these species are isolated from any others.

Physalaemus caicai: This undescribed species is known from the arid regions of northwestern Peru. Sceintists are currently working on this and other Physalaemus species.

Physalaemus enesefae: Distributed in the llanos of Venezuela; sympatric with P. pustulosus.

Physalaemus ephippifer: Distributed along the mouth of the Amazon River in the region of Belem, Brazil; sympatric with P. petersi.

Physalaemus ‘roraima’: Undescribed species from the northernmost state of Roraima in Brazil; range is situated to the north of P. petersi and to the south of P. pustulosus; physically similar to P. ephippifer.