Mark B. Robbins

Molecular phylogenetics, vocalizations, and species limits in Celeus woodpeckers (Aves: Picidae).

Species limits and the evolutionary mechanisms that have shaped diversification of woodpeckers and allies (Picidae) remain obscure, as inter and intraspecific phylogenetic relationships have yet to be comprehensively resolved for most genera. Herein, we analyzed 5020 base pairs of nucleotide sequence data from the mitochondrial and nuclear genomes to reconstruct the evolutionary history of Celeus woodpeckers. Broad geographic sampling was employed to assess species limits in phenotypically variable lineages and provide a first look at the evolution of song and plumage traits in this poorly known Neotropical genus. Our results strongly support the monophyly of Celeus and reveal several novel relationships across a shallow phylogenetic topology. We confirm the close sister relationship between Celeus spectabilis and the enigmatic Celeus obrieni, both of which form a clade with Celeus flavus. The Mesoamerican Celeus castaneus was placed as sister to a Celeus undatus-grammicus lineage, with the species status of the latter drawn into question given the lack of substantial genetic, morphological, and vocal variation in these taxa. We recovered paraphyly in Celeus elegans; however, this result appears to be the consequence of mitochondrial introgression from Celeus lugubris considering the monophyly of elegans at the ß-FIBI7 locus. A second instance of paraphyly was observed in Celeus flavescens with deep genetic splits and substantial phenotypic variation indicating the presence of two distinct species in this broadly distributed lineage. As such, we advocate elevation of Celeus flavescens ochraceus to species status. Our analysis of Celeus vocalizations and plumage characters demonstrates a pattern of lability consistent with a relatively recent origin of the genus and potentially rapid speciation history.

Molecular systematics of the new world screech-owls (Megascops: Aves, Strigidae): biogeographic and taxonomic implications ☆

Megascops screech-owls are endemic to the New World and range from southern Canada to the southern cone of South America. The 22 currently recognized Megascops species occupy a wide range of habitats and elevations, from desert to humid montane forest, and from sea level to the Andean tree line. Species and subspecies diagnoses of Megascops are notoriously difficult due to subtle plumage differences among taxa with frequent plumage polymorphism. Using three mitochondrial and three nuclear genes we estimated a phylogeny for all but one Megascops species. Phylogenies were estimated with Maximum Likelihood and Bayesian Inference, and a Bayesian chronogram was reconstructed to assess the spatio-temporal context of Megascops diversification. Megascops was paraphyletic in the recovered tree topologies if the Puerto Rican endemic M. nudipes is included in the genus. However, the remaining taxa are monophyletic and form three major clades: (1) M. choliba, M. koepckeae, M. albogularis, M. clarkii, and M. trichopsis; (2) M. petersoni, M. marshalli, M. hoyi, M. ingens, and M. colombianus; and (3) M. asio, M. kennicottii, M. cooperi, M. barbarus, M. sanctaecatarinae, M. roboratus, M. watsonii, M. atricapilla, M. guatemalae, and M. vermiculatus. Megascops watsonii is paraphyletic with some individuals more closely related to M. atricapilla than to other members in that polytypic species. Also, allopatric populations of some other Megascops species were highly divergent, with levels of genetic differentiation greater than between some recognized species-pairs. Diversification within the genus is hypothesized to have taken place during the last 8 million years, with a likely origin in Central America. The genus later expanded over much of the Americas and then diversified via multiple dispersal events from the Andes into the Neotropical lowlands.

THE MEXICAN SHEARTAIL (DORICHA ELIZA): MORPHOLOGY, BEHAVIOR, DISTRIBUTION, AND ENDANGERED STATUS

Abstract We reviewed morphological variation, taxonomic status, geographic distribution, ecology, and behavior of the poorly known hummingbird, the Mexican Sheartail (Doricha eliza), based on museum specimens and field studies. Although the broadly disjunct distribution of the species would suggest that two taxa are involved, morphological differences between the populations appear minor, not deserving of formal taxonomic recognition. Ecological differences between the two populations are stronger, however; modeled ecological niches are nearly nonoverlapping, and ontogenetic and behavioral differences may exist. We recommend that, given its extremely restricted distribution, the Veracruz population be considered critically endangered, whereas the Yucatan population be designated as having a restricted range and accorded near-threatened status. RESUMEN.—Se revisaron la variación morfológica, estatus taxonómico, distribución geográfica, ecología y conducta de un taxón muy poco conocido, el colibrí tijereta mexicano (Doricha eliza), en base en estudios de campo y en museo. A pesar de que la amplia disyunción en su distribución geográfica sugiere la existencia de dos taxones diferentes, la diferenciación morfológica es mínima y no amerita reconocimiento taxonómico formal. Sin embargo, las diferencias ecológicas entre las dos poblaciones son más marcadas, con nichos ecológicos modelados que casi no se sobrelapan, y diferencias ontogenéticas y de conducta pueden existir. En general, la población de Veracruz debe ser considerada en peligro de extinción, mientras que la población de Yucatán debe ser designada de distribución restringida y con un estatus de conservación de casi amenazada.

Phylogenetic relationships of the Helmeted Woodpecker (Dryocopus galeatus): A case of interspecific mimicry?

ABSTRACT Examples of phenotypic convergence in plumage coloration have been reported in a wide diversity of avian taxonomic groups, yet the underlying evolutionary mechanisms driving this phenomenon have received little scientific inquiry. We document a striking new case of plumage convergence in the Helmeted Woodpecker (Dryocopus galeatus) and explore the possibility of visual mimicry among Atlantic Forest woodpeckers. Our multilocus phylogenetic analyses unequivocally place D. galeatus within Celeus, indicating that the former has subsequently converged in appearance upon the distantly related and syntopic Dryocopus lineatus, to which it bears a remarkable resemblance in plumage coloration and pattern. Although details of the Helmeted Woodpeckers ecology and natural history are only now beginning to emerge, its smaller size and submissive behavior are consistent with predictions derived from evolutionary game-theory models and the hypothesis of interspecific social-dominance mimicry (ISDM). Moreover, estimates of avian visual acuity suggest that size-related mimetic deception is plausible at distances ecologically relevant to Celeus and Dryocopus foraging behavior. In light of our results, we recommend taxonomic transfer of D. galeatus to Celeus and emphasize the need for detailed behavioral studies that examine the social costs and benefits of plumage convergence to explicitly test for ISDM and other forms of mimicry in these Atlantic Forest woodpecker communities. Future field studies examining potential cases of competitive mimicry should also take into account the mimics acoustic behavior, particularly in the presence of putative model species and other heterospecific competitors, as any discontinuity between morphological and behavioral mimicry would likely preclude the possibility of deception.

Landscape-level forest cover is a predictor of cerulean warbler abundance

Abstract We examined support for the hypothesis that abundance of Cerulean Warblers (Setophaga cerulea) increases with percentage of bottomland and upland forest, and decreases with percentage of developed land at a local-habitat scale (within a 250-m buffer) and increases with percentage of all forest at a landscape scale (within a 10-km buffer). We conducted surveys along 16 rivers in Missouri and Arkansas from 1999 to 2006 and related habitat and landscape factors to counts of Cerulean Warblers in 123 5-km segments on these rivers. We detected 576 singing male Cerulean Warblers and found support for both local and landscape effects on Cerulean Warbler abundance. Model fit was good with an average correlation of 0.841 between predicted and observed values based on an eight-fold cross-validation procedure. The abundance of Cerulean Warblers increased 390.7, 8.7, and 4.1 times across the observed range of forest within 10 km, bottomland forest within 250 m, and upland forest within 250 m, respectively. Conservation and research need to address large-scale forest patterns in addition to local habitat for Cerulean Warblers. Further research is needed on abundance patterns across riparian and upland forests and demographic rates in this part of their range.

A New Species of Scytalopus Tapaculo (Aves: Passeriformes: Rhinocryptidae) from the Andes of Central Peru

Abstract We describe a new species of Scytalopus tapaculo (Aves: Passeriformes: Rhinocryptidae) from the temperate humid montane forests (2,400–3,200 m) of Junín Department, Peru. This species has a unique song that differs strikingly from that of any known Scytalopus species, consisting of a rapidly repeated series of ascending phrases. Phenotypically, the new species is uniformly blackish in color and small-to-medium in size, most similar to members of the allopatric S. latrans complex. At least six species of Scytalopus occur along an elevational gradient on the eastern slopes of the Andes in Junín; in the vicinity of the type locality, the new species replaces S. femoralis at 2,400–2,500 m, and is replaced by S. acutirostris at 2,900–3,200 m. Throughout its elevational range, the new species is broadly syntopic with the larger S. macropus. This species is currently known from a single river drainage; although it probably occurs more broadly, it is likely a range-restricted species endemic to central Peru.

Song Rates, Mating Status, and Territory Size of Cerulean Warblers in Missouri Ozark Riparian Forest

Abstract We assessed song rates among male Cerulean Warblers (Dendroica cerulea) in Ozark riparian forest in southeastern Missouri to characterize song rate variation and estimate how many males may be missed during censuses. Average (± SD) songs per 5-min intervals for continuous 4-hr observation periods varied from 3.1 ± 4.8 (mated males) to 36.0 ± 18.7 (unmated males; n = 24 males). Unmated males averaged twice the number of songs per 5-min periods than mated males. Considerable song rate variation existed even among mated males. Song rates slightly declined over the 4-hr observation period. Song rate differences between Cerulean Warblers in Ontario and southeastern Missouri suggest caution when making assumptions about breeding status based on auditory surveys. Average male Cerulean Warbler territory size (n = 20) was 0.9 ± 0.1 ha with 27 of 31 males having at least one abutting conspecific territory. All males (n = 24) were silent for 32.7 ± 21.5 and 21.8 ± 17.4% of the 5-min and 10-min periods, respectively. Unpaired males (n = 5) were silent for 2.9 ± 3.15 and 1.2 ± 1.86% and mated males (n = 19) were silent for 37.9 ± 18.8 and 25.4 ± 16.2% of the 5-min and 10-min periods, respectively. These data demonstrate that when auditory clues are used for detection, not incorporating song rate will result in significant underestimates of density.

Voice, plumage and natural history of Anthony's nightjar (Caprimulgus Anthonyi)

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CANADA TO TIERRA DEL FUEGO: SPECIES LIMITS AND HISTORICAL BIOGEOGRAPHY OF THE SEDGE WREN (CISTOTHORUS PLATENSIS)

ABSTRACT We examined the phylogeography of the Western Hemispheric Sedge Wren (Cistothorus platensis) which occurs in grasslands from Canada to Tierra del Fuego. Genetic data indicate that Sedge Wren is paraphyletic with Mérida (Cistothorus meridae) and Apolinars (Cistothorus apolinari) wrens and the currently recognized Sedge Wren is composed of a minimum of eight species. Speciation within this complex appears to have accelerated with the formation of the Isthmus of Panama which enabled the ancestor to occupy and differentiate in grassland habitats from sea level to above tree line in the Andes on the South American continent. As a result of the dramatic, negative anthropogenic impact on grasslands across the entire Western Hemisphere all species have suffered substantial declines and several are now threatened.

A genomic investigation of the putative contact zone between divergent Brown Creeper (Certhia americana) lineages: chromosomal patterns of genetic differentiation.

Sky islands, or montane forest separated by different lowland habitats, are highly fragmented regions that potentially limit gene flow between isolated populations. In the sky islands of the Madrean Archipelago (Arizona, USA), various taxa display different phylogeographic patterns, from unrestricted gene flow among sky islands to complex patterns with multiple distinct lineages. Using genomic-level approaches allows the investigation of differential patterns of gene flow, selection, and genetic differentiation among chromosomes and specific genomic regions between sky island populations. Here, we used thousands of SNPs to investigate the putative contact zone of divergent Brown Creeper (Certhia americana) lineages in the Madrean Archipelago sky islands. We found the two lineages to be completely allopatric (during the breeding season) with a lack of hybridization and gene flow between lineages and no genetic structure among sky islands within lineages. Additionally, the two lineages inhabit different climatic and ecosystem conditions and have many local primary song dialects in the southern Arizona mountain ranges. We identified a positive relationship between genetic differentiation and chromosome size, but the sex chromosome (Z) was not found to be an outlier. Differential patterns of genetic differentiation per chromosome may be explained by genetic drift--possibly in conjunction with non-random mating and non-random gene flow--due to variance in recombination rates among chromosomes.