SYSTEMATICS AND BIOGEOGRAPHY OF THE TYRANNID GENUS TODIROSTRUM AND RELATED GENERA (AVES) JOHN W. FITZPATRICK 1 Abstract. Of 32 Tody-tyrant species (family positions immediately preceding that of Todi- Tyrannidae), 14 comprise the genus Todirostrum rostrum, reflecting their affinities with Todirostrum and 12 are currently placed within Idioptilon. The capitate; 3) Todirostrum and Idioptilon should remaining species represent six monotypic genera. continue to stand as separate genera; 4) the genera Todirostrum species fall into two major species Microcochlearius and Snethlagea are best merged groups (labelled cinereum and sylvia), and the with Idioptilon, while Oncostoma should continue affinities of one additional, relict species (capi- to be generically recognized. A phylogeny of the tate) lie outside the genus. The distributional Tody-tyrants and a revised classification of the history of each species group can be approximately group are proposed (Figure 4 and Table 1, re- traced from the isolation of two ancestral popu- spectively ) . lations. Alternating contraction and expansion of lowland South American forests, corresponding INTRODUCTION with dry and humid climatic phases, generated new species within each lineage. Their modern Large complexes of closely related, often and distribution were de- compositions patterns morphologically similar species are common termined and by dispersal ability competitive in the diverse avifauna of South America. interactions between related species. Current A number of recent studies have focused distributions and plumage patterns appear to re- flect the history of this radiation within Todi- on ecological relationships between sym- rostrum. patric members of potentially competing Two relict species groups (one includes T. some in species complexes ( examples Cody, capitate, the other is an intermediate assemblage 1974). However, the evolutionary history between Todirostrum and Idioptilon placed in the behind modern distributions and latter genus) illustrate the potential fate of many ecological taxa in the rapidly radiating South American avi- interactions is disregarded in many such fauna. As the number of increases with species studies, at the expense of an adequate cyclic production of new forms within lowland perspective on the problems examined. The forest refuges, each faces increasing competitive aim of the is to reconstruct pressure as it disperses. Certain species and whole present study lineages may be secondarily contracted into local this evolutionary background for a widely distributions by dispersing, competitively superior sympatric group of tropical, insectivorous relatives. The process culminates either in morpho- bird species. logic and ecological divergence by the inferior The Euscarthminae population, or in its eventual extinction. Inter- Tyrannid subfamily mediate stages in this "continental taxon cycle" (Hellmayr, 1926) contains roughly 65 spe- are found in the Tyrannid group examined here. cies, all of which are small and wholly Four specific taxonomic suggestions are offered insectivorous. This forms one of in addition to comments on affinities within subfamily Todirostrum: 1) the genus Ceratotriccus should the four major phylogenetic lineages of be with the Tacnio- merged Idioptilon; 2) genera small Tyrannidae (Smith, 1970), as shown triccus and Poecilotriccus should be moved to in Figure 1. The core of the subfamily 1 consists of an of 32 broad-billed Department of Biology, Princeton University, assemblage Princeton, New Jersey 0S540 species, placed in 10 genera by de Schauen- Bull. Mus. Comp. Zool, 147(10): 435-463, June, 1976 435 436 Bulletin Museum of Comparative Zoology, Vol. 147, No. 10 "% Ar Myiarchinae Platyrhynchinae Serpophag inae TYRANNIDAE Cotingidae JU Pipridae suboscine ancestor of Figure 1 Schematic phylogeny of the family Tyrannidae, showing postulated relationships the Euscar- thminae within the "small" lineage. The seven subfamilies shown are those of Hellmayr (1926). Adapted from W. J. Smith (1970). see (1966). The genera Todirostrum and none at all since Zimmer's brief comments Idioptilon contain 26 of these species (14 on some of them (1940, 1953, 1955). and 12 respectively), and each of the re- As an initial stage in the investigation of maining 6 species is currently placed in a the evolution and modern competitive monotypie genus. Together, the 32 species structure of the group, the distributions of clearly represent a well-circumscribed, all Euscarthminc species were carefully monophyletic group, though their affinities plotted on maps. These distributions were have received little critical attention, and examined in relation to recent theories in Biogeography of Todirostrum • Fitzpatrick 437 South American biogeography. It became the subfamily Euscarthminae. It is now apparent that the patterns of radiation possible to assess the validity of certain of within several subgroups could be traced these genera. Specimens of all but two of with reference to Pleistocene climate and the 32 Euscarthmine species in the Tody- vegetation fluctuations, the occurrence of tyrant lineage were assembled and exam- which has been convincingly demonstrated ined in conjunction with the present study. by Haffer (1969, 1974) and Vanzolini and The following comments and suggestions Williams (1970). are based largely on morphologic patterns Distributional and morpholigic data and biogeographic considerations covered relevant to two particular topics are pre- later. sented in this 1 detailed de- The considered in this paper: ) A species treatment scription of speciation patterns in the genus of the genus Todirostrum Lesson, 1831 are Todirostrum is given. The account includes those listed by de Schauensee (1966) with of three related here- the three 1 T. discussion species following exceptions: ) pictum tofore placed in the monotypic genera is considered to be one of three members of Poecilotriccus, Taeniotriccus, and Cerato- the chrysocrotaphum superspecies, as dis- triccus, and four additional species in the cussed in detail in the speciation section. genus Idioptilon. 2) Certain general impli- It should therefore be listed as an allo- cations of the findings to modern biogeo- species along with nigriceps and chrysocro- graphic theory are discussed as they relate taphum. 2) T. hypospodium Berlepsch, to the evolutionary history of certain mem- 1907 is considered a synonym of T. sylvia bers of the Euscarthmine assemblage. superciliare Lawrence, 1871. Known from a Ultimately, the goals of present and single unsexed specimen from the Bogota forthcoming studies are to determine, 1) trade market, hypospodium was listed as "a the modes of ecological and morphological very doubtful species" bv de Schauensee radiation in this large group of similar, (1966: 365). Both Zimmer (1955) and insectivorous species, 2) the varying com- Hellmayr (1926: 308) considered it a petitive pressures placed on each other by dark individual variant of T. sylvia super- such closely related forms, and 3) the ways ciliare, a fairly common species in the in which various populations selectively Magdalena Valley near Bogota. The un- respond to these pressures. Such analyses likely event of hypospodium s proven clearly depend upon establishing an evo- validity as a species would have little bear- lutionary perspective with which to view ing on the patterns discussed in this paper. modern geographical and ecological con- 3) T. albifacies Blake, 1959 is considered ditions. The present study is a first step, conspecific with T. capitale tricolor ( Berla, therefore, in that it focuses primarily upon 1946). Blake (1959) listed the sex of the the affinities within a subset the collected to date phylogenetic type ( only specimen ) of the Euscarthminae, and secondarily upon as uncertain, possibly male. Its close simi- certain brief dis- ecological implications. A larity to the female of sexually dimorphic cussion of taxonomic considerations ger- T. c. capitale has led Blake and Traylor mane to this the historical analysis precedes (personal communication) to reidentify it reconstruction of in Todirostrum. speciation as a female tricolor. The latter form was— TAXONOMIC COMMENTS heretofore known from a single type unequivocally male—from the Bio Madeira, Division of distinct morphologic groups about 200 km downstream in the same into numerous, often monotypic genera was as the of the rule during the early twentieth century drainage type locality "albifacies" examined the classification of the Tyrannidae (e.g., Hell- (see Fig. 10). Having type mayr, 1926). With several exceptions this of albifacies and the photographs in Bella's has revision within 1946 of the I early taxonomy escaped ( ) description male tricolor, Bulletin Museum of Com para five Zoology, Vol. 147, No. 10 chrysocrotaphum superspecies e r u m c a I opt sylvia turn if ronsl Nip" N v (russatum) Figure 2. Head patterns in the three species groups making up the genus Todirostrum. Eleven of four- teen species are illustrated. Dotting about the faces in the sylvia group represents buffy plumage; lighter dots represent yellow plumage in the cinereum group; the crown of capitate female is dark rufous. consider their similarities to nominate from rich green (in chrysocrotaphum, capitale sufficient to agree with Zimmer maculatum, and nominate calopterum) to 1955 in the two as or ( ) treating populations grey grey-green (cinereum and polio- subspecies. cephalum) to solid black (the isolated The 14 species in Todirostrum fall into Peruvian race