Ned K. Johnson

NEW MITOCHONDRIAL DNA DATA AFFIRM THE IMPORTANCE OF PLEISTOCENE SPECIATION IN NORTH AMERICAN BIRDS

Abstract The timing of origin of modern North American bird species in relation to Pleistocene glaciations has long been the topic of significant discussion and disagreement. Recently, Klicka and Zink (1997) and Avise and Walker (1998) enlivened this debate by using calibrated molecular distance values to estimate timing of speciations. Here we use new molecular studies to test their conclusions. Molecular distance values for 39 pairs of proven sister species, 27 of which are based on new data, alter the currently perceived pattern that avian species splits occurred mainly in the Pliocene and early‐mid‐Pleistocene. Mitochondrial DNA divergence values for this set of taxa showed a skewed distribution pointing toward relatively young speciation times, in contrast to the pattern presented by Klicka and Zink (1997) for 35 sister plus non‐sister species pairs. Our pattern was not significantly different from that of Avise and Walker (1998) for “intraspecific phylogroups,” some of which are species. We conclude that the entire Pleistocene, including the last two glacial cycles (<250,000 years ago), was important in speciations of modern North American birds. A substantial number of speciations were both initiated and completed in the last 250,000 years. Simultaneously, many taxa began to diverge in the Pleistocene but their speciations are not yet complete (per Avise and Walker 1998). The suggestion that durations of speciations average two million years is probably a substantial overestimate.

Size Dimorphism and Food Habits of North American Owls

Although in most species of birds the male is characteristically larger than the female, the direction of size dimorphism among many birds of prey is reversed; the female is larger than the male. This reversal is present in the orders Falconiformes and Strigiformes and in the families Stercorariidae and Fregatidae (Amadon 1959:534). Several authors have discussed the possible origin and significance of sexual dimorphism in size in raptorial birds. Briill (1937), Hagen (1942), Dementiev (1951), Storer (1952, 1966), and Selander (1966) believe that the increased size of the female over the male permits differential niche utilization by the sexes; that is, a difference in sizes of the sexes would allow an

Turnover and Equilibria in Insular Avifaunas, with Special Reference to the California Channel Islands

According to current biogeographical theory, the number of species comprising an insular biota is the result of a dynamic interaction between extinction and immigration rates. These rates, in turn, are thought to depend primarily on island size and distance from sources of potential colonists (MacArthur and Wilson 1963, 1967). This equilibrium model has been tested in a number of ways, including studies of recolonization of Krakatau, an island whose entire biota was destroyed by a natural catastrophe (MacArthur and Wilson 1967, after Dammerman 1948; Docters van Leeuwen 1936), tallies of the species of terrestrial arthropods present on tiny mangrove islands before and after intentional defaunation (Simberloff 1969; Simberloff and Wilson 1969, 1970; Wilson and Simberloff 1969), and through comparisons of the results of repeated surveys of insular avifaunas (Diamond 1969, 1971; Hunt and Hunt 1974; Terborgh and Faaborg 1973). It is understandable that ornithology should play an important role in the maturation of this body of theory, as it has in other areas of evolutionary biology. Compared with most other kinds of organisms, birds are relatively easy to observe and are well known taxonomically and biologically. Moreover, birds have been studied over a sufficient period in some regions so that it is possible to compare recent surveys with others going back 50 years or

CONTROLS OF NUMBER OF BIRD SPECIES ON MONTANE ISLANDS IN THE GREAT BASIN

variety, in the absence of more direct information, inasmuch as area and environmental diversity are closely correlated (MacArthur and Wilson, 1967). In addition to island area, absolute distance (relative isolation) of an island from sources of colonists on other islands or continents has long been recognized as a variable crucial to processes that regulate composition of insular biotas. A dynamic interaction between immigration rates and extinction rates, which are assumed to vary according to the effects of distance and of area, respectively, forms the heart of equilibrium theory. Aside from directly impeding access of organisms to islands, distance probably also influences insular species numbers in an important indirect way, namely through suppression of general insular habitat variety and resource diversity. Such suppression of habitats occurs because organisms live in complex webs of inter-dependence and association; it is likely that retardation of colonization by members of anyone group (e.g., plants) influences the quality of the habitats available on the island for several other groups (e.g., herbivorous insects). Lack of suitable pollinators similarly might exclude possible colonization or survival of certain plant species. Among birds, then, the distance effect could reduce insular species numbers in two ways: primarily and directly through reduction of colonization rates of immigrant birds themselves and, secondarily and indirectly, through interference of access of plants and insects upon which the birds depend for shelter, nest materials, and food. Thus, insular biotic diverFor over a decade the distribution of birds on islands has provided rich source material for the analysis of species diversity-area relationships (Preston, 1962) and for the testing of predictions derived from the theory of insular species equilibrium (Preston, 1962; MacArthur and Wilson, 1963, 1967). In recent years these concepts have been extended to avifaunas and to other animal and plant groups occupying isolated habitats on continents, for example, birds and plants of paramo islands in the Andes (Vuilleumier, 1970; Simpson, 1974), invertebrates of caves in Switzerland (Vuilleumier, 1973), leaf-mining insects on host species of oaks in California (Opler, 1974), small mammals of locally-isolated rock piles in the Sierra Nevada (Smith, 1974), and fishes of the lakes of the world (Barbour and Brown, 1974). Although a satisfying degree of unification of theory and empirical evidence already has been achieved in the maturation of this area of modern biogeography (Simberloff, 1974), several general problems persist either because their solutions are complex and/or because their existence has not been recognized. Partly because of serious difficulties in the measurement of relative ecologic differences among islands, the role of habitat diversity per se in controlling species numbers is seldom clearly identified. Instead, habitat differences are assessed by necessarily-indirect means, through more easily-measured parameters such as total area, maximum elevation, and number of plant species. Total area especially serves as a good general predictor of habitat

Genetic relationships of North American cardueline finches

Starch gel electrophoresis was used to examine variation at 33 genetic loci in 19 taxa (15 species in 6 genera) of cardueline finches (family Fringillidae). Levels of heterozygosity and genetic distances were comparable to those reported from surveys of other avian taxa. Twentythree loci (70%) were polymorphic within taxa and/or were fixed at alternative alleles among taxa. Rogers’ genetic distances were used to construct phenograms, distance Wagner trees, and F-M trees; these provided hypotheses for the evolutionary relationships of taxa. The genetic data indicate that: (1) Coccothraustes, Pinicola, Leucosticte, Carpodacus, Carduelis, and Loxia are distinctive genera that vary in estimated age (as measured from nearest branch point) from approximately 14 MY (Coccothraustes) to 5 MY (Loxia); (2) species treated by the AOU (1983) as congeners within Carpodacus, Carduelis, and Loxia are correctly classified to genus; (3) the subgenera Acanthis, Astragalinus. Spinus, and Carduelis, within the genus Carduelis, are recognizable; (4) the crossbills (Loxia) are most closely allied to Carduelis among the genera examined; (5) Carpodacus purpureus and C. cassinii are closely related sister species whereas C. mexicanus is very distinct; (6) Loxia curvirostra and L. Zeucoptera re moderately different electrophoretically; (7) in contrast, the redpolls, Carduelisflammea and C. hornemanni exilipes, are similar genetically; (8) most speciation events in North American carduelines range from mid-late Pliocene (4 MY) to mid-Pleistocene (500,000 years) in age; but (9) subspecies diverged in the late Pleistocene. A phylogeny ofcardueline genera derived from these electrophoretic data agrees in major respects with one proposed by Raikow on the basis of hindlimb myology. The sequence of appearance of older taxa is still not resolved with certainty, however, because ofpartially conflicting molecular and morphologic results.

Genetic evidence for the origin and relationships of Hawaiian honeycreepers (Aves: Fringillidae)

Using starch gel electrophoresis of proteins, we examined variation at 36 genetic loci in nine species (eight genera) of Hawaiian honeycreepers (Class Aves; Family Fringillidae; Subfamily Drepanidinae). Two species of cardueline finches and two emberizids served as outgroup taxa. Twenty-three loci (64%) were either polymorphic within taxa and/or were fixed at alternative alleles among taxa. In seven of nine species, low levels of mean Hobs (0.015), percentage of polymorphic loci (4.16) and average number of alleles per polymorphic locus (2.03) may reflect population bottlenecks that occurred either during or after initial colonization. Phenograms, distance Wagner trees, F-M trees, and a cladistic analysis provided hypotheses for the evolutionary relationships of taxa and suggest hat: (1) The drepanidines are monophyletic. (2) The Hawaiian honeycreepers are more similar genetically to the two species of emberizids than to the two species of carduelines, a result that conflicts with a recent consensus of opinion based on morphologic and other biochemical data. (3) The species ancestral to modem drepanidines colonized the Hawaiian Archipelago at an estimated 7-8 million years before present (MYBP). This date agrees generally with the timing of emergence of Nihoa, now largely submerged, but antedates the appearance of Kauai (5 MYBP), the oldest of the present “high” Hawaiian Islands. (4) The creepers Oreomystis and Paroreomyza represent the oldest and most divergent lineage of living drepanidines. (5) The youngest lineages are represented by the nectar feeders (Himatione and Vestiaria), the thick-billed “finch types” (Loxioides and Telespiza), and a diverse array of other forms (Loxops and Hemignathus). (6) Hemignathus “virens” stejnegeri is a full species, possibly allied to Loxops coccineus. Our genetic data conflict with the two major phylogenetic hypotheses that have been proposed for the radiation of the drepanidines: (1) origin from tubular-tongued, nectar-feeding ancestors; and (2) origin from thick-billed and thick-tongued, seedand fruit-eating ancestors. Instead, the evidence suggests that the earliest Hawaiian honeycreepers had generalized bills, tongues, and diets. This ancestral group gave rise to the lineages that eventually led to both (1) modern Paroreomyza and Oreomystis and (2) a complex group of (a) nectar feeders (Himatione, Vestiaria, and relatives); (b) seed and fruit eaters (Loxioides, Telespiza, and relatives); and (c) a diverse group of species that feed on both arthropods and nectar (Loxops, Hemignathus, and relatives). We speculate that the most immediate ancestor of all of the heavy-billed species was a thin-billed, tubular-tongued, nectarivorous form and that this major morphologic shift was expedited by the alteration of developmental patterns and rates.

Origin and Differentiation of the Avifauna of the Channel Islands, California

The biota of the Channel Islands off the coast of southern California (fig. 1) for years has attracted the attention of evolutionists and biogeographers (Cockerell 1938). This interest focused in October 1965, when 102 participants convened at the Santa Barbara Botanic Garden for papers and discussion relating to the geology, biology, and archeology of the islands. Two years later, the results of the symposium were published (Philbrick 1967). Notably lacking among the several papers dealing with major vertebrate groups was an analysis of the resident avifauna of the islands; birds were mentioned only briefly in discussion following papers whose principal themes dealt with other topics. In their patterns of distribution and differentiation, the land birds of the Channel Islands present a zoogeographic puzzle-complex enough to be fascinating, yet simple enough to encourage an attempt at solution. In this paper, I will review the kinds of differentiation shown by the endemic forms and will outline a general hypothetical model for the origin and course of evolutionary change in the avifauna considered in the light of information from geologic and paleobotanic history. As Mayr (1943) demonstrated in a discussion of the origin of the birds of the Hawaiian Islands, remote island avifaunas are composed of elements which have accumulated from different sources and at different times. He viewed the land and fresh-water birds of the

Macrogeographic patterns of morphometric and genetic variation in the sage sparrow complex

We examined morphometric and genetic variation in 22 populations of three subspecies of the Sage Sparrow (Amphispiza belli belli, A. b. canescens, and A. b. nevadensis). The sum of squares simultaneous test procedure (SS-STP) demonstrated clear patterns of geographic change in six linear characters and in cube root of body mass. A UPGMA dendrogram and ordination plots using principal component analysis (PCA) and multidimensional scaling (MDS) defined two major groups of populations based on morphometric criteria: (I) those in the Coast Ranges and west slope of the Sierra Nevada (A. b. belli) plus those in the southern San Joaquin Valley and northern Mojave Desert (A. b. canescens), and (II) those in the Great Basin (A. b. nevadensis). Seventeen of 41 genetic loci scored (41.5%) were polymorphic. Genetic data identified the same two groups of populations delimited on morphometric grounds. Populations in group I were significantly less heterozygous than those of group II. Nei’s genetic distances among populations of one taxon ranged from D = 0.0007 (in A. b. nevadensis) to b = 0.0015 (in A. b. canescens) and D = 0.0019 (in A. b. belli). Intertaxon Nei’s D ranged from 0.0027 (A. b. belli vs. A. b. canescens) to 0.0056 (A. b. canescens vs. A. b. nevadensis) and 0.0077 (A. b. belli vs. A. b. nevadensis). An overall mean F,, value of 0.112 points to pronounced genetic structuring of the 22 populations. Sedentary populations are less panmictic than migratory populations. Gene flow is estimated at 24 immigrants per generation. Although intergradation is unknown, A. b. belli and A. b. canescens are genetically closely related. In contrast, A. b. nevadensis and A. b. canescens differ strongly on both morphologic and genetic grounds.

Refined colorimetry validates endangered subspecies of the least tern

In contrast to the results of Thompson et al. (1992), refined colorimetry validates three subspecies of Least Tern in North America, Sterna antillarum antillarum (Lesson), S. a. browni Mearns, and S. a. athalassos Burleigh and Lowery. Four of nine color characters exhibited significant seasonal differences, presumably a result of plumage wear and bleaching. The sexes differed in lightness and hue of dorsum and hind neck. Males of S. a. athalassos differed significantly from those of both S. a. antillarum and S. a. browni in lightness of dorsum, and males of S. a. browni differed significantly from those of S. a. antillarum in lightness of hind neck. Females generally showed patterns concordant with males. Because S. a. browni and S. a. athalassos are listed as endangered, the validity of these taxa is important to conservationists and managers. Rigorous systematic methodology and scientific collections of high quality are indispensable to conservation biology.

A NEW SPECIES OF TODY-TYRANT (TYRANNIDAE: POECILOTRICCUS) FROM NORTHERN PERU

Abstract We describe a new species of tody-tyrant of the genus Poecilotriccus, isolated in midelevation forests of the Cordillera de Colán and nearby mountains to the east in the northeastern Andes of Peru. The new species is allopatric from, and forms a probable superspecies with, the Rufous-crowned Tody-Tyrant (P. ruficeps), the nearest known populations of which inhabit the Cerro Chinguela of northern Peru. The geographic ranges of those sister taxa are divided by the North Peruvian Low, occupied by the Río Marañón, the major break in east-slope Andean forest between Venezuela and Bolivia. The new species and its allospecies, P. ruficeps are identical in color of the back and in lightness and hue of the crown, but are 100% separable in lightness, chroma, and hue of the belly; in color and pattern of the face; and in song. We infer that differences in vocalizations and facial markings would serve as premating reproductive isolating mechanisms should the two forms become sympatric.