Diagnoses of Hybrid Hummingbirds (Aves: Trochilidae). 16. Characterization of a Striking Intergeneric Hybrid (Lampornis Clemenci
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PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 120(1):106–112. 2007. Diagnoses of hybrid hummingbirds (Aves: Trochilidae). 16. Characterization of a striking intergeneric hybrid (Lampornis clemenciae 3 Calypte anna) from Ramsey Canyon, Huachuca Mountains, southeastern Arizona Gary R. Graves Department of Vertebrate Zoology, MRC-116, National Museum of Natural History, Smithsonian Institution, P.O. Box 37012, Washington, D.C. 20013-7012, U.S.A., e-mail: [email protected] Abstract.—A hummingbird specimen from Ramsey Canyon, Huachuca Mountains, southeastern Arizona, represents a hybrid of Lampornis clemenciae (Blue-throated Hummingbird) 3 Calypte anna (Anna’s Hum- mingbird). The specimen, which constitutes the only verified instance of hybridization between a species in the ‘‘mountain gem’’ group of hummingbirds and a species in the ‘‘bee’’ group, exhibits a blended mosaic of plumage characters of the parental species. Mayr and Short (1970:54) announced ty, Arizona, by Joan Peabody on 26 Apr one of the more striking examples of 1968. The unsexed specimen (Fig. 1), intergeneric hybridization discovered thus head turned to the side with wings slightly far among trochiline hummingbirds in splayed, was deposited in the University a terse annotation: ‘‘A recently collected of Arizona Zoological Collections (Russell, unpubl.) hybrid of L.[ampornis] (No. 9359) by Stephen M. Russell. Two clemenciae 3 Archilochus [Calypte] costae notations are penciled on the specimen (or possibly A. anna) has been seen by label: (a) ‘‘Calypte costae 3 Lampornis Short.’’ Although a formal diagnosis of clemenciae,’’ and (b) ‘‘5 anna 3 clem- the hybrid was never published, the enciae. Note pink throat & size. ARP record has been uncritically cited in the [Allan R. Phillips] ‘69.’’ I subjected the secondary literature (Panov 1989, Powers specimen to an analytical procedure 1999, Stiles 1999, Williamson 2000, termed the hybrid diagnosis (Graves McCarthy 2006). My analysis indicates 1990), which focuses on the identification that the specimen represents a hybrid of of apomorphic character states in puta- Lampornis clemenciae (Blue-throated tive hybrids. Complete dominance and hummingbird) 3 Calypte anna (Anna’s polygenic inheritance of plumage charac- hummingbird). Here I provide a compre- ters may prevent or obscure the expres- hensive assessment of the specimen em- sion of parental apomorphies in hybrids. ploying the methods and assumptions When parental apomorphies cannot be outlined in Graves (1990) as modified by identified, the parentage of a hybrid may subsequent papers (Graves & Zusi 1990, be indicated, although less conclusively, Graves 1998, 1999a). by the presence or absence of a suite of plesiomorphic characters (Graves 1990, Materials and Methods Graves & Zusi 1990, Graves 1998, 1999a). Contrary to an earlier assessment The mummified specimen was found (Baldridge et al. 1983), the specimen dead in Ramsey Canyon, Cochise Coun- appears to be an adult male in definitive VOLUME 120, NUMBER 1 107 Hummingbird), Calothorax lucifer (Luci- fer Hummingbird), Heliomaster constantii (Plain-capped Starthroat), Eugenes ful- gens (Magnificent Hummingbird), Lam- pornis clemenciae, Amazilia beryllina (Beryline Hummingbird), A. violiceps (Violet-crowned Hummingbird), Hylo- charis leucotis (White-eared Humming- bird), and Cynanthus latirostris (Broad- billed Hummingbird). Measurements were taken with digital calipers and rounded to the nearest 0.1 mm: wing chord; bill length (from anterior extension of feathers); rectrix length (from point of insertion of the central rectrices to the tip of each rectrix), and width of the outermost rectrix (8 mm from tip). Rectrices (R1–R5) are num- bered from the innermost to the out- ermost. A scatterplot of measurements was used to illustrate size differences Fig. 1. Ventral view of a probable hybrid, among specimens. General color descrip- Lampornis clemenciae 3 Calypte anna (University tions presented in Appendix 1 were made of Arizona 9359). under natural light. plumage as judged by the smooth maxil- Results and Discussion lary ramphotheca and the presence of a large iridescent gorget and coronal I considered three hypotheses—the patch. Consequently, all description in Ramsey Canyon specimen represents (i) this paper refers to definitive male plum- a color morph of Calypte anna or C. age. Given the migratory behavior of costae, (ii) an undescribed species, or (iii) North American hummingbirds, the a hybrid. The first hypothesis can be Ramsey Canyon specimen could have rejected because the external measure- been hatched at some distant location ments and proportions of the specimen (e.g., California or Sonora, Mexico). are substantially different from those of Thus, I compared the specimen with all age classes of male C. anna (Table 1) series of all trochiline species (National and C. costae (Graves 2006). Although Museum of Natural History, Smithsonian the second hypothesis seems highly im- Institution) that regularly breed in Cali- probable, a handful of recognized trochi- fornia, Arizona, Sonora, and northwest- line species are known from one or two ern Chihuahua (Friedmann et al. 1950, specimens (Graves & Olson 1987, Graves Phillips et al. 1964, Howell & Webb 1995, 1993, 1999b). In any event, hybridization Russell & Monson 1998) : Calypte anna, must be ruled out before species status is C. costae (Costa’s Hummingbird), Selas- conferred. Evidence presented below sug- phorus platycercus (Broad-tailed Hum- gests that the specimen represents an mingbird), S. rufus (Rufous Humming- intergeneric hybrid, Lampornis clemenciae bird), S. sasin (Allen’s Hummingbird), 3 Calypte anna. For brevity I refer to the Stellula calliope (Calliope Hummingbird), specimen as a hybrid in the remainder of Archilochus alexandri (Black-chinned the paper. 108 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON Table 1.—Ranges (mean 6 one standard deviation) of measurements (mm) of adult males of Calypte costae, C. anna, Lampornis clemenciae, and the hybrid (Lampornis clemenciae 3 Calypte anna; University of Arizona No. 9359). Calypte costae Calypte anna Lampornis clemenciae Hybrid Characters (n 5 22) (n 5 10) (n 5 10) AZ 9359 Wing chord 41.3–45.9 (43.9 6 1.1) 48.2–50.3 (49.0 6 0.8) 74.2–77.5 (75.3 6 1.0) 60.4 Bill length 14.3–16.9 (15.6 6 0.6) 15.2–17.7 (16.3 6 0.9) 20.6–22.5 (21.6 6 0.6) 19.9 Rectrix 1 length 17.7–20.6 (19.3 6 0.8) 22.8–26.7 (24.7 6 1.1) 42.2–44.3 (43.5 6 0.7) 31.6 Rectrix 2 length 18.6–21.9 (20.5 6 0.9) 23.3–25.5 (24.5 6 0.7) 43.3–47.0 (45.3 6 1.2) 33.6 Rectrix 3 length 20.8–24.7 (22.6 6 0.9) 26.5–29.4 (28.1 6 0.8) 45.2–48.0 (46.5 6 1.1) 35.7 Rectrix 4 length 20.8–24.8 (22.8 6 0.9) 31.1–33.4 (32.1 6 0.9) 44.8–48.8 (47.0 6 1.5) 36.0 Rectrix 5 length 20.1–23.6 (22.2 6 1.0) 30.6–33.2 (31.9 6 0.9) 45.1–49.7 (47.5 6 1.6) 37.0 Rectrix 5 width 1.4–1.8 (1.7 6 0.11) 3.0–3.6 (3.2 6 0.2) 9.5–12.0 (10.5 6 0.8) 4.8 Three plumage characters of the hybrid duce offspring with a bluish-violet gorget. facilitated the identification of its parental The dull pinkish-rose iridescence emitted species: (a) brilliant gorget; (b) brilliant by the coronal patch and gorget of the frontlet and crown; and (c) rounded white hybrid is much more suggestive of the spots at the tips of R4 and R5 (Figs. 1, 2; expected phenotype of L. clemenciae 3 C. Appendix). Only two of the potential anna (rose-red gorget). parental species, Calypte costae and C. I tested this parental hypothesis with an anna, possess brilliant frontlets that con- examination of size and external propor- trast with the remainder of the capital tions (Table 1). External measurements of feather tract (the crown but not the trochiline hybrids invariably fall within frontlet of Eugenes fulgens is brilliant), the mensural ranges exhibited by their but neither species of Calypte has large parental species as a consequence of white spots on the tips of R4 and R5. This a polygenic mode of inheritance (Banks indicates that one of the parental species & Johnson 1961, Buckley 1982, Graves was either Calypte costae or C. anna and 1990, Graves & Zusi 1990, Graves 1996). that the white rectricial spots were con- Measurements of the hybrid fall within tributed by the other parental species. the cumulative range of measurements of Only two of the potential parental species Lampornis clemenciae and Calypte anna. (Lampornis clemenciae and Heliomaster However, morphometric data do not rule constantii) exhibit white rectricial spots. out the possibility that Calypte costae was However, the rectrices (R3–R5) of H. the smaller parental species. In summary, constantii are merely edged with white, evidence obtained from plumage color eliminating that species from further and pattern, as well as from external size consideration. Furthermore, the hybrid and shape, is consistent with the hypoth- does not express the bold white malar esis that the Ramsey Canyon specimen stripe or white rump patch of H. con- represents a hybrid of Lampornis clem- stantii. Thus, plumage characters quickly enciae 3 Calypte anna. As such, it is the lead to the conclusion that the hybrid only documented hybrid between a species represents the offspring of L. clemenciae in the ‘‘mountain gem’’ group (i.e., and Calypte sp. (Mayr & Short 1970). Lampornis) of hummingbirds and a spe- The inheritance of iridescent color in cies from the ‘‘bee’’ group (i.e., Calypte) hybrid hummingbirds is poorly under- (Bleiweiss et al. 1997). stood. However, I assume that hybridiza- Lampornis clemenciae occurs during the tion between L.