Adapting generalized frequency coding to use colour spectra in the determination of phylogenetic relationships: an example with hummingbirds

We introduce a methodology to perform phylogenetic analyses on bird taxa using parsimony based on plumage colour characters obtained as spectra. The generalized frequency coding method was adapted to transform continuous colour spectral data into discrete variables. As an example of the application of the methodology, we analysed two species of the hummingbird genus Campylopterus and all species of the genera Anthracothorax and Eulampis , which occur in South and Central America and the Caribbean islands. The genus Topaza was used as an outgroup because of its basal position within the hummingbirds. The results were mostly in accordance with both traditional morphological as well as molecular analyses indicating that there is phylogenetic information in plumage colours measured in an integral and objective way and that the new method is appropriate for phylogenetic analyses at this lower taxonomic level.     

A higher-level taxonomy for hummingbirds

In the context of a recently published phylogenetic estimate for 151 hummingbird species, we provide an expanded informal taxonomy, as well as a formal phylogenetic taxonomy for Trochilidae that follows the precepts of the PhyloCode, but remains consistent with the hierarchical nomenclature of the Linnaean system. We compare the recently published phylogenetic hypothesis with those of prior higher-level and more taxonomically circumscribed phylogenetic studies. We recommend the recognition of nine new clade names under the PhyloCode, eight of which are consistent with tribes and one with a subfamily under the Linnaean system.     

Biogeography, geographic variation and habitat preference in the Amazilia Hummingbird,Amazilia amazilia Lesson (Aves: Trochilidae), with notes on the status ofAmazilia alticola Gould

Summary This paper reviews the biogeography, geographic variation, and habitat characteristics of the Amazilia Hummingbird (Amazilia amazilia). Based on morphological features, habitat preferences, and bioacoustics, I propose that the currently recognized subspeciesA. a. alticola should be regarded as a species distinct fromA. amazilia. Synapomorphic characters found in both taxa indicate membership of the same superspecies, together with the Colombian speciesA. castaneiventris. Considering the distributional focus ofA. alticola in the Andes of southern Ecuador, the English species name Loja Hummingbird is suggested.

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Biogeographie, geographische Variation und Habitatwahl der Lesson-Amazilie (Amazilia amazilia Lesson; Aves: Trochilidae), mit Anmerkungen zum Status vonAmazilia alticola Gould

Zusammenfassung Die vorliegende Studie stellt die Ergebnisse von Untersuchungen zur Biogeographie, geographischen Variation, Habitatwahl und Taxonomie der Lesson-Amazilie (Amazilia amazilia) vor. Das Taxon umfaßt gegenwärtig fünf Unterarten, die von W-Ecuador bis SW-Peru verbreitet sind und überwiegend submontane Lebensräume besiedeln. Die Ventralfärbung unterliegt klinaler Variation; weiße Gefiederanteile nehmen von nördlichen zu südlichen Populationen ab, rotbraune Partien dagegen zu. Eigenständige morphologisch-morphometrische Kennzeichen sowie Unterschiede in den Habitatpräferenzen und in der Gesangsstruktur rechtfertigen es, die bisherige UnterartA. a. alticola als Paraspezies (A. alticola, Loja-Amazilie) anzuerkennen. Der Vulgärname weist auf den rezenten Verbreitungsschwerpunkt in den südecuadorianischen Anden hin. Aufgrund der engen Verwandtschaft bildenA. amazilia undA. alticola sowie die in Kolumbien endemische ArtA. castaneiventris eine Superspezies.

     

Origin of hummingbird faunas

Ecological studies of hummingbird communities have emphasized the importance of local conditions and contemporary interactions in the development of these varied faunas. A time-calibrated, DNA hybridization-based phylogeny of the principal hummingbird lineages was used to examine historical aspects of hummingbird faunas in the species-rich tropical lowlands and Andes, and the relatively depauperate West Indies and temperate regions of Central and North America. Parsimony reconstructions of ancestral distributions indicate that these faunas are polyphyletic in origin, comprising several to many independent lineages. Based on the timing of geologic and cladogenic events, hummingbird faunas appear to have arisen more often by colonization than by large-scale vicariance, with multiple dispersals across water gaps, elevational gradients, and latitude. The extent to which particular lineages colonized different regions depended, however, on lineage ecology as well as on the habitat and age of the fauna. In general, the oldest extant trochilofauna, which today occupies the tropical lowlands, was the principal source of colonizing taxa. However, all regions except possibly the West Indies contributed taxa now found elsewhere, including in the tropical lowlands. The Andean fauna comprises several lineages with lowland origin (hermits, Mangoes, Brilliants, Coquettes, Emeralds) as well as at least one that arose in temperate regions outside South America (Bees). At least two lineages that colonized the West Indies gave rise to endemic genera (Mangoes to Eulampis, and Emeralds to Orthorhyncus). Even groups that diversified in the highlands (Brilliants and Bees) gave rise to taxa that subsequently reinvaded the tropical lowlands. As the result of these varied histories, hummingbird communities cannot be arranged easily with respect to organizational complexity and coevolution with nectar sources. Although the physically insular faunas in the Andes and West Indies differ markedly in diversity, both were more strongly affected by colonization than the other faunas. A high potential for coevolution between hummingbirds and plants probably facilitated the successful establishment and radiation of the several Andean-associated lineages. However, coexistence between the two most diverse Andean clades may have been favoured initially through different habitat preferences by their extra-Andean ancestors. In the tropical lowlands, by comparison, the basic separation between the forest-dwelling hermits and canopy and edge-dwelling nonhermits appears to have evolved in situ. The low species and morphologic diversity of hummingbirds breeding north of Mexico reflects the predominance there of a single relatively recent lineage. The regional coexistence of numerous unrelated lineages implies that patterns of ancestry, colonization, and extinction contribute to the make-up of contemporary species-rich hummingbird faunas and serves to qualify the view that hummingbird communities are coadapted assemblages that resist change.     

Tempo and mode of hummingbird evolution

Lack of adequate historical data has hindered understanding of the evolutionary tempo and mode of many ecologically well-characterized avian radiations. DNA hybridization distances among 28 hummingbirds (Trochilidae) were used to establish a timescale for this family's radiation into more than 330 species. Under a variety of analytical assumptions, genetic distances calibrated with a fossil divergence date corrected for incompleteness in the geologic record indicated that all extant hummingbird lineages began to diverge in the Early Miocene, approximately 40 Myr (million years) after the Paleocene date estimated for the divergence of hummingbirds and swifts. The long period prior to the radiation of living forms provides ample time for divergent evolution to produce the large morphological gap that has tended to obscure the sister-relationship of hummingbirds and swifts. The Miocene radiation of extant hummingbird lineages itself began with the divergence of the hermit and nonhermit subfamilies approximately 17 Ma (million years ago), followed by the rapid divergence of two Andean and one principally Central and North American clade at approximately 12 Ma. Younger subsidiary lineages, including ones found mainly in the Andes or in North America, date to the later Miocene-earlier Pliocene, approximately 6 Ma. The DNA hybridization-based chronology thus indicates a protracted, rather than stricdy rapid, radiation. Evidence from a broader spectrum of organisms supports the general pattern that higher taxonomic structure within many extant continental families evolved in the Miocene, suggesting that a common environmental pacemaker initiated radiation in unrelated groups. Compared to those in the Pleistocene, radiations tracing to the Miocene may have depended less on rapid climate cycling than on creation of new habitats by major geologic and climatic upheavals. For extant hummingbirds, a principal cause for their Miocene diversification probably was the ability of the ecologically generalized subfamily of nonhermits to radiate in montane areas created by the Andean and other orogenies. Similar interactions between new habitats and their exploitation by ecological generalists may explain, at least in part, the contemporaneous radiation of Passeriformes, the most diverse avian order.     

BIRD EGGSHELL IN DOMINICAN AMBER

Abstract:  Here we report an eggshell in Dominican amber, representing the first vertebrate egg in any amber deposit. The eggshell is compared with present-day eggs of lizards, snails and birds. Based on the surface structure and type of shell breakage, it appears that the most likely candidate is a bird, and with that consideration, an avian group that produces eggs similar to the fossil in shape, size and colouration is the Trochilidae (hummingbirds). Several possible explanations of how the fossil could be preserved in amber are provided. If indeed a hummingbird was involved, this discovery would represent the first New World record of a fossil trochilid.     

Phylogeny of the hermit hummingbirds (trochilidae: Phaethornithinae)

A phylogeny of the hummingbirds of the genera Ramphodon, Eutoxeres, Glaucis, Threnetes, and Phaethornis is presented on the basis of external morphological characters. All 34 species of hermit hummingbirds are included in this study. Differences in 96 characters were examined with regard to their apomorphic (derived) or plesiomor‐phic (primitive) states, resulting in evolutionary trees drawn on the basis of cladistic principles. The most important results are: (1) “Ramphodon “ dohrnii is closer to Glaucis than to Ramphodon; (2) “Phaethornis” gounellei is the sister species to all Phaethornis and merits reevaluation as a separate genus, Anopetia; (3) Phaethornis philippii and P. koepckeae are the sister group to P. syrmatophorus, their straight bill having evolved independently of P. bourcieri; (4) the Phaethornis superciliosus/malaris species group includes P. longirostris as a third species; (5) Phaethornis subochraceus, P. pretrei, and P. augusti share a common ancestor, and (6) Phaethornis longuemareus (sensu Peters 1945) is polyphyletic, being comprised of four seperate species. Due to the lack of synapomorphies, the relationships of some species cannot be reliably determined on the basis of external morphological characters alone.     

Male-like ornamentation in female hummingbirds results from social harassment rather than sexual selection

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Nectar secretion dynamic links pollinator behavior to consequences for plant reproductive success in the ornithophilous mistletoe Psittacanthus robustus

The mistletoe Psittacanthus robustus was studied as a model to link flower phenology and nectar secretion strategy to pollinator behaviour and the reproductive consequences for the plant. The bright‐coloured flowers presented diurnal anthesis, opened asynchronously throughout the rainy season and produced copious dilute nectar as the main reward for pollinators. Most nectar was secreted just after flower opening, with little sugar replenishment after experimental removals. During the second day of anthesis in bagged flowers, the flowers quickly reabsorbed the offered nectar. Low values of nectar standing crop recorded in open flowers can be linked with high visitation rates by bird pollinators. Eight hummingbirds and two passerines were observed as potential pollinators. The most frequent flower visitors were the hummingbirds Eupetomena macroura and Colibri serrirostris, which actively defended flowering mistletoes. The spatial separation between anthers, stigma and nectar chamber promotes pollen deposition on flapping wings of hovering hummingbirds that usually probe many flowers per visit. Seed set did not differ between hand‐, self‐ and cross‐pollinated flowers, but these treatments set significantly more seeds than flowers naturally exposed to flower visitors. We suggest that the limitation observed in the reproductive success of this plant is not related to pollinator scarcity, but probably to the extreme frequency of visitation by territorial hummingbirds. We conclude that the costs and benefits of plant reproduction depend on the interaction strength between flowers and pollinators, and the assessment of nectar secretion dynamics, pollinator behaviour and plant breeding system allows clarification of the complexity of such associations.     

Genetic divergence of the Mesoamerican azure‐crowned hummingbird (Amazilia cyanocephala,Trochilidae) across the Motagua‐Polochic‐Jocotán fault system

The cloud forests of Mesoamerica are highly endangered habitats and the existence of narrowly distributed cryptic endemics will increase the number of taxa at potential risk of extinction. Here, we investigate genetic divergence between populations of the azure‐crowned hummingbird (Amazilia cyanocephala), a species complex of endemic hummingbirds to the montane forests of Mesoamerica, by analysing DNA sequences of four mitochondrial markers, morphological data and ecological niche modelling. Our results revealed the presence of two mtDNA lineages corresponding to subspecies A. c. cyanocephala distributed from Tamaulipas to Chiapas in Mexico and Amazilia c. guatemalensis distributed from southern Chiapas to Guatemala. The lineage split can be explained as a consequence of relative isolation of the populations in the different mountain ranges separated by the Motagua‐Polochic‐Jocotán fault system and corresponds to differences in morphology and to the lack of overlap in environmental space between subspecies. The divergence time estimates do not support the proposed model of a highly constrained temporal window at the end of the Pliocene as divergence at this barrier between cyanocephala and guatemalensis and splits of other bird taxa occurred during the Pleistocene.