. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. BlOGEOGRAPHY OF ToDIROSTRVM ' Fttzpattick 449. Figure 7. Distribution of the Todirostrum chrysocrotaphum superspecies. Representations of the main mor- phologic types are shown in their approximate geographic positions. From left to right, the five described races of chrysocrotaphum are: guttatum, chrysocrotaphum, neglectum, similis, and illigeri. See text for de- tailed analysis of this variation. side of the Rio Negro has been borne out by collections along the lower part of the river. The superspecies thus presents
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. BlOGEOGRAPHY OF ToDIROSTRVM ' Fttzpattick 449. Figure 7. Distribution of the Todirostrum chrysocrotaphum superspecies. Representations of the main mor- phologic types are shown in their approximate geographic positions. From left to right, the five described races of chrysocrotaphum are: guttatum, chrysocrotaphum, neglectum, similis, and illigeri. See text for de- tailed analysis of this variation. side of the Rio Negro has been borne out by collections along the lower part of the river. The superspecies thus presents a reliable record of the different forest regions within which its initial populations differentiated. As previously surmised, the breast streaks of pictum and guttatum evolved second- arily on the previously clear-breasted form. The original chrysocrotaphum stock was therefore isolated either in the southeastern Peruvian forests or in one of the north- western Colombian forest refuges since these two areas retain clear-breasted popu- lations. During a period of forest expansion the population then spread through the western Amazonian region (where streaks later evolved) to the other region of cur- rently clear-breasted birds. A Peruvian precursor (of chrysocrotaphum) would pre- sumably have had sufficient time before colonizing across the Andes to evolve cer- tain of the patterns it carries today. T. nigriceps, however, lacks any trace of the distinct eye stripe of neglectum. Further- more, nigriceps retains the white throat characteristic of most other Todirostrum species but lost in neglectum. Thus it ap- pears that the superspecies precursor dif- ferentiated in one of the refuges of northern Colombia (see Fig. 5a), probably during the same period in which the initial calo- pterum population was isolated in the Napo refuge. Following initial isolation of the species, the clear-breasted population crossed the. Please note that these images are extracted from scanned page ima
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