Bradley C. Livezey

Phylogeny and evolutionary ecology of modern seaducks (Anatidae: Mergini)

Phylogenetic relationships of modem seaducks (Mergini) were investigated using a cladistic analysis of 137 morphological characters. The analysis produced a single tree (consistency index = 0.692, excluding autapomorphies) with complete resolution of the relationships among the 25 taxa recognized. Phylogenetic inferences include: (1) the eiders (Polysticta and Somateria) constitute a monophyletic group and are the sister-group of other Mergini; (2) the remaining generic groups of Mergini, sequenced in order of increasingly close relationship, are Histrionicus, Melanitta + Camptorhynchus, Clangula, Bucephala + Mergellus, Lophodytes, and Mergus; (3) Somateria is monophyletic with S. ficheri the sister group of its congeners; (4) the black scoters (Melanitta nigra-group) are the sister-group of other scoters; (5) the Bufflehead (Bucephala albeola) is the sister-group of the goldeneyes (B. clangula and B. islandica); and (6) relationships among mergansers are as presented by Livezey (1989). Bootstrapping revealed that the placement of the Smew as the sister-group of the goldeneyes is only weakly supported, and ancillary analyses revealed that this placement is only one step shorter than its reduction to a trichotomy with the goldeneyes and mergansers (including Lophodytes). A phylogenetic classification of modem seaducks is presented. The Harlequin Duck (H. histrionicus), Long-tailed Duck (Clangula hyemalis), and Stellers Eider (Polysticta stelleri) are highly autapomorphic. Evolutionary patterns of selected ecomorphological characteristics-including body mass, sexual size dimorphism, clutch size, relative clutch mass, nest site, diet, diving method, formation of creches, and biogeography-are examined with respect to the phylogenetic hypothesis

FLIGHTLESSNESS IN STEAMER-DUCKS (ANATIDAE: TACHYERES): ITS MORPHOLOGICAL BASES AND PROBABLE EVOLUTION

Flightlessness in Tachyeres is caused by wing‐loadings in excess of 2.5 g·cm–2, which result from the large body size and small wing areas of the flightless species. Reduced wing areas of flightless species are related to absolutely shorter remiges, and to relatively or absolutely shortened wing bones, although these reductions differ among species. Reduced lengths of the ulna, radius, and carpometacarpus are associated most strongly with flightlessness. Pectoral muscles and the associated sternal keel are well developed in all species of Tachyeres, largely because of the use of wings in “steaming,” an important locomotor behavior. Relative size of these muscles was greatest in largely flighted T. patachonicus; however, sexual dimorphism in wing‐loadings results in flightlessness in some males of this species. Proportions in the wing skeleton, intraspecific allometry, and limited data on growth indicate that the relatively short wing bones and remiges of flightless Tachyeres are produced developmentally by a delay in the growth of wing components, and that this heterochrony may underlie, in part, skeletal sexual dimorphism. Increased body size in flightless steamer‐ducks is advantageous in territorial defense of food resources and young, and perhaps diving in cold, turbulent water; reductions in wing area probably reflect refinements for wing‐assisted locomotion and combat. Flightlessness in steamer‐ducks is not related to relaxed predation pressure, but instead was permitted selectively by the year‐round habitability of the southern South American coasts. These conditions not only permitted the success of the three flightless species of Tachyeres, but at present may be moving marine populations of T. patachonicus toward flightlessness.

Morphometric patterns in Recent and fossil penguins (Aves, Sphenisciformes)

A total of 622 skin specimens, 527 skeletons, and myological data compiled by Schreiweis (1972) were used to investigate morphometric patterns within and among the 18 Recent species of Spheniscidae, and to compare the family with a fighted species, the common diving‐petrel (Pelecanoides urinator), considered by some authorities to be similar to the flighted ancestor of penguins. Fossil penguins also were studied using measurements from 111 skeletal elements representing 18 species. Most external and skeletal measurements follow interspecific rankings in body mass; the latter span a 30‐fold range from 1 kg in Eudyptula minor to 30 kg in Aptenodytes forsteri. Flighted Pelecanoides is only one‐tenth the mass of the smallest spheniscid. Wing areas and body masses of penguins maintain approximate geometric similitude among species; the allometric coefficient is 0.62 ± 0.04. Several skeletal elements are less derived in conformation in the fossil penguins than in modern confamilials. Despite great variation in the lengths of wing and leg skeletons, penguins show relative consistency in proportions of wing elements; pelvic proportions were more variable within the Spheniscidae. Proportions within both limbs are distinctly different from those of Pelecanoides. Analysis of correlation structures within species of penguin revealed three major subsets of skeletal variables that are highly intercorrelated: trunk‐skull lengths, appendicular‐trunk widths, and appendicular lengths. Within these groups, measurements tend to separate by anatomical region and, to a lesser degree, by limb. Canonical analysis of skin and skeletal measurements revealed groupings of spheniscids on the basis of size and relatively complex shape variables. Cluster analyses of taxa on the canonical variates confirmed the similarity of congeners in Eudyptes, Eudyptula and Spheniscus; species of Aptenodytes and, to a lesser degree, Pygoscelis, are more heterogeneous. A cluster analysis of principal components of myological measurements tabulated by Schreiweis (1972) corresponded closely with phenetic groupings using external and skeletal variables. A canonical contrast between spheniscids and Pelecanoides indicated that the families differ in a relatively complex skeletal dimension that only in part reflects overall size. Multivariate assessment of sexual dimorphism in external and skeletal variables indicated that: Eudyptula is least dimorphic; Aptenodytes, Eudyptes, Megadyptes and Spheniscus are moderately dimorphic; and Pygoscelis is most dimorphic. Pelecanoides shows comparatively low dimorphism. Among‐species and within‐species first principal components of skeletal measurements (multivariate axes of skeletal ‘size’) differ from one another in their orientation, and both deviate from isometric size. The first principal component for skeletons of Pelecanoides also deviated from isometric size, but the direction of this allometry is fundamentally different from that in penguins. Estimates of body mass for fossil penguins, based on principal components of available skeletal measurements, indicate that fossil species ranged from 3 kg to 81 kg in total mass; the largest fossil species was approximately 2.5 times as massive as the largest extant spheniscid. Much of the morphometric variation in the Spheniscidae is explainable on locomotory, ecological and thermodynamic grounds, and the associated phenetic groupings conform broadly with traditional generic classifications. The evolutionary significance of mensural correlations, allometric trends and differences between fossil and Recent species are discussed, and the need for a phylogenetic analysis of this highly specialized family of winged‐propelled diving birds is stressed.

Flightlessness in grebes aves podicipedidae its independent evolution in three genera

The morphological bases of flightlessness in three genera of grebes were studied using 790 study skins, 322 skeletons, myological data from 40 anatomical specimens studied by Sanders (1967), and ancillary data on wing‐loadings. Three species, Rollandia microptera, Podilymbus gigas, and Podiceps taczanowskii, are considered to be flightless; each is endemic to a high‐altitude, neotropical lake or lake system. Compared to their flighted (capable of flight) sister‐species, the three flightless species shared several broadly convergent characters: larger body mass and skeletal dimensions (exclusive of the sternal carina), reductions in relative lengths of wing, tail, and primary remiges, and reduction in the relative size of breast muscles. Rollandia microptera exhibited the greatest morphological differences from its flighted sister‐species; these differences were comparable to intergeneric morphometric differences in magnitude and involved a tripling of body mass, a modal loss of one primary remex in each wing, absolute reduction of the sternal carina, flattening of proximal wing elements, a large morphometric shift in skeletal dimensions, an increase in the scapulocoracoid angle, and six qualitative differences in the pectoral musculature. Morphological differences between Podilymbus gigas and its flighted congener were comparatively minor; flightlessness in this species, if genuine, evidently results from an allometric increase in size combined with a large decrease in relative bulk of breast musculature and shift of alar muscle mass. Podiceps taczanowskii was intermediate in degree of anatomical difference from its flighted relatives, but was unique in its slight reduction in absolute length of the wings and decrease in absolute widths of the skeletal wing elements. Multivariate differences in external characters associated with flightlessness were strongly convergent in the three genera, but multivariate differences in skeletal proportions differed substantially among genera in detail. An estimate of wing‐loading indicated that Podilymbus gigas and, especially, Podiceps taczanowskii may be only “flight‐impaired” rather than flightless. Relative wing lengths and conformation of sterna in Rollandia microptera and Podiceps taczanowskii indicate that morphological changes associated with flightlessness are paedomorphic; intraspecific allometry in Rollandia indicates that the underlying ontogenetic change may involve a delay in the start of pectoral‐alar development (postdisplacement). Flightlessness in grebes, a family typified by moderately heavy wing‐loadings and relatively small pectoral muscles, is related in all three instances to the year‐round residency afforded by large lakes at low latitudes. The primary selective advantages of morphological changes leading to flightlessness probably are related to the thermodynamic advantages of increased body sizes, feeding specialization associated with enlargement of the bill, and reduction of intraspecific niche overlap through increased sexual dimorphism; the changes are also possibly related to economy of pectoral‐alar development.

Sexual Dimorphism in Continental Steamer-Ducks

Analyse du dimorphisme sexuel chez les trois especes continentales (133 specimens, biometrie du squelette et des muscles, mensurations externes): Tachyeres pteneres, T. leucocephalus, T. patachonicus et recherche des causes de ce dimorphisme

Morphological corollaries and ecological implications of flightlessness in the kakapo psittaciformes strigops habroptilus

The morphological corollaries of flightlessness of the kakapo (Strigops habroptilus) have been studied using skin specimens, skeletons, and pectoral dissection of an anatomical specimen. These have been compared with the closely related, flighted kea (Nestor notabilis), and secondarily with other Psittaciformes and the convergent hoatzin (Cuculiformes: Opisthocomus hoazin). S. habroptilus is the most massive and sexually dimorphic psittaciform in the world, and has the smallest relative wing size of any parrot. Alar pterylography of S. habroptilus is similar to that of other parrots, but remiges of the species are shorter, comparatively rounded, show less asymmetry of vanes, and have fewer interlocking barbules distally. S. habroptilus shows peculiarities of the sternum (vestigial carina, shortened spina externa), coracoid (elongate processus lateralis, enlarged angle with scapula), and humerus (prominent tuberculum ventrale, undercut crista bicipitalis). Pectoral skeletal dimensions of S. habroptilus are smaller than those of N. notabilis, whereas the reverse is true for pelvic dimensions. Most skeletal dimensions of S. habroptilus are more variable (within sexes) than those of N. notabilis. Proximal wing elements are disproportionately long and distal elements disproportionately short in S. habroptilus. The legs of S. habroptilus are characterized by disproportionately long femora and disproportionately short tarsometatarsi. Distinctive features of the pectoral musculature of S. habroptilus include a greatly reduced Mm. pectoralis thoracica and supracoracoideus, the absence of a distinct proximal muscle belly of M. propatagialis tendo longus, an extensive M. cucullaris capitis clavicularis associated with a voluminous crop, and an essentially tendinous M. sternocoracoideus. Relative to mean body mass, all dimensions of the antebrachial, carpometacarpal, digital, and patagial muscles are smaller in S. habroptilus than in N. notabilis. These aspects are compared to those of other flightless birds. Discussed are implications of flightlessness and associated large body size of S. habroptilus for issues of thermodynamics, metabolism, activity patterns, digestive anatomy, diet, reproduction, and insularit.

Territoriality and interspecific aggression in steamer-ducks

indicates that Burrowing Owls modify prairie dog burrows used as nest sites. Presumably, sandy soil would facilitate enlarging burrow passageways. Coulombe (1971) stated that in California burrow diameters averaged 20 cm, and suggested that owls may modify burrows that have been abandoned by rodents. In addition, sandy soils drain rapidly, which would reduce nest flooding during frequent spring and summer rainstorms.

The systematic position of the Miocene anatid Anas[?] blanchardi Milne-Edwards

ABSTRACT Anas[?] blanchardi (Milne-Edwards, 1863), an abundantly represented fossil duck from the lower Miocene of Saint-Gerand-le-Puy, Allier, France, has been recognized as systematically problematic in recent decades. Most recently, Cheneval (1983b) moved this fossil and closely related forms to Dendrochen (Miller, 1944), a purportedly dendrocygnine genus from the lower Miocene of South Dakota. We reexamined blanchardi using characters shown to be of phylogenetic utility in a recent phylogenetically analysis of the Anseriformes (Livezey, 1986). This reappraisal showed that blanchardi diverged from the rest of the Anatidae after Dendrocygna but before Stictonetta. A single “best” branching sequence for the included taxa—blanchardi, Thalassornis, and the Anserinae (geese and swans)—is not possible at present. Several possibly convergent characters indicate that blanchardi was moderately specialized for diving. We conclude that blanchardi (and provisionally its close relatives Anas[?] consobrina and Anas[...

Morphology of flightlessness in Chendytes, fossil seaducks (Anatidae: Mergini) of coastal California

ABSTRACT The anatid genus Chendytes comprises two species from the Pleistocene and early Holocene of California: the comparatively large C. lawi and the smaller (poorly represented) C. milleri. Osteological comparisons confirm that Chendytes is a member of the Mergini, probably most closely related to the eiders (Somateria). Peculiarities of the pectoral skeleton of C. lawi include features of the humerus, ulna, and carpometacarpus. C. lawi exceeded the largest extant seaduck, the Common Eider (Somateria mollissima), in most dimensions of the skull and pelvic limb. Pectoral reduction in C. lawi was among the most extensive known for Anseriformes; reductions in C. milleri were of lesser magnitude. Distal wing elements of C. lawi had undergone the greatest shortening, whereas the elongate pelvic limb of C. lawi was characterized by disproportionately short femora and long tibiotarsi. Based on femur lengths and body masses of modern Mergini, estimated body masses of C. lawi and C. milleri are 2,550–3,700 g a...

Genetic differentiation among steamer-ducks (Anatidae: Tachyeres): an electrophoretic analysis

Electrophoretic and isoelectric focusing analyses of liver proteins of the steamer-ducks, Tachyeres patachonicus, T. pteneres, T. brachypterus, and T. leucocephalus, how these species to be distinct genetically, with the latter three species being more closely related to one another than any one of them is to T. patachonicus. There is also significant differentiation among populations of T. patachonicus. Estimates of the average calculated heterozygosity per species are high: 0.185, 0.160,O. 165, and 0.084, respectively, and observed heterozygosities are 0.115 I 0.090, 0.202 f 0.118, 0.201 i0.085, and 0.080 f 0.069, respectively. The genetic distances of Cavalli-Sforza and Edwards, Nei, and Rogers were estimated and used with a Wagner tree algorithm to prepare a consensus tree based on 1,000 subsets of allelic frequency data prepared by bootstrapping over loci. Estimates of F,, for comparisons among populations of T. patachonicus and estimates of Nm based on the distribution of private alleles indicate that gene flow between some pairs of populations is significantly reduced. Values of F,, are much higher than those prev-iously found for other pairs of avian populations. Genotypic distributions that deviate significantly from equilibrium expectations are found for several of the polymorphic loci of one or more species.