Adolfo G. Navarro-Sigüenza

Effects of global climate change on geographic distributions of Mexican Cracidae

Although climate change and its implications are a frequent subject of detailed study, the effects of these changes on species’ geographic distributions remain little explored. We present a first cross-species analysis of the effects of global climate change on the distributions of one bird family, the Cracidae, in Mexico, based on projecting models of ecological niches from present conditions to modeled future conditions taken from general circulation models of climate change. Based on two different scenarios of climate change and on three assumptions regarding species’ dispersal abilities, effects on species’ distributions range from drastic reduction to modest increases. These results illustrate the complex nature of species’ geographic responses to environmental change, and emphasize the need for detailed analysis of individual species’ ecological requirements.

An alternative species taxonomy of the birds of Mexico

Extensive debate has surrounded the application of alternative species concepts in Ornithology. The biological species concept (BSC) and phylogenetic species concept (PSC) have typically been set in opposition, with extensive debate on the relative merits of each. An alternative is the evolutionary species concept (ESC), which offers a perspective similar to that of the PSC, yet with several significant differences. To date, no major avifauna has been examined and compared among taxonomic viewpoints. Herein, we develop an alternative phylogenetic/evolutionary species taxonomy to the current BSC treatment for the more than 1000 bird species of Mexico. A total of 135 biological species was divided to produce a total of 323 phylogenetic/evolutionary species, 122 of which represent “new” endemic forms in Mexico.

SEASONAL NICHES OF NEARCTIC-NEOTROPICAL MIGRATORY BIRDS: IMPLICATIONS FOR THE EVOLUTION OF MIGRATION

THE EVOLUTION OF avian migratory systems has been of intense interest to ornithologists (Gauthreaux 1982; Berthold 1988, 1993; Levey and Stiles 1992; Rappole 1995; Chesser and Levey 1998). The consensus is that a sedentary ancestor began to move seasonally, within an ancestral distribution, in response to some influence-either a push (e.g. poor conditions on the ancestral distribution) or a pull (e.g. better conditions elsewhere) -and that local tracking eventually extended to long-distance, predictable movements (Berthold 1993, Rappole 1995). One particularly well-developed hypothesis is that local movements of tropical bird species tracking variable or uncertain resources (either food or space for breeding) evolved into regular seasonal and longer distance movements. That line of thought, originally based on NearcticNeotropical migrants (Levey and Stiles 1992, Rappole 1995), has been partially supported in an independent system, the austral migrants in South America (Chesser and Levey 1998). New perspectives on the evolution of migration may prove useful (Zink 2002). A question that has not received sufficient attention is the degree to which a species is tracking a single set of conditions year-round-as opposed to changing from one ecological regime to another. Seasonal differences in habitat use by migratory birds are well known (see reviews in Keast and Morton 1980, Hagan and Johnston 1995).

Evolution of seasonal ecological niches in the Passerina buntings (Aves : Cardinalidae)

The evolution of migration has long been considered complex and recent work has demonstrated additional complexity: some species follow the same ecological conditions throughout the year, whereas others ‘switch niches’ between breeding and wintering ranges. Hypotheses regarding the evolution of migration would generally predict niche–following as primitive, and niche–switching as derived. However, no test has, to our knowledge, yet determined the directionality of evolution of these states within a lineage. We present an analysis of phylogenetic dimensions of seasonal niches in the Passerina buntings that indicates greater evolutionary change in the niches of breeding populations than among those of wintering populations. These results are consistent with hypotheses of (i) niche conservatism (in winter, at least) across a recently speciated lineage; and (ii) the derived state of the breeding (rather than winter) ecological niches of each species.

Bird faunas of the humid montane forests of Mesoamerica: biogeographic patterns and priorities for conservation

Summary The distribution of 335 species of birds in 33 islands of humid montane forest in Mesoamerica is summarized, and patterns of distribution, diversity and endemism are analysed. The montane forests of Costa Rica and western Panama far exceed other habitat islands considered for species-richness, richness of species endemic to Mesoamerica, and richness of species ecologically restricted to humid montane forests. Other regions, such as the Sierra Madre del Sur of Guerrero and Oaxaca, the Los Tuxtlas region of southern Veracruz and the mountains of Chiapas and Guatemala, also hold rich and endemic avifaunas. Based on patterns of similarity of avifaunas, the region can be divided into seven regions holding distinctive avifaunas (Costa Rica and western Panama; northern Central America and northern Chiapas; southern Chiapas; eastern Mexico north of the Isthmus of Tehuantepec; Sierra Madre del Sur; interior Oaxaca; and Transvolcanic Belt and Sierra Madre Occidental), which serve as useful guides for the setting of priorities for conservation action. Se resumen las distribuciones de 335 especies de aves en 33 islas de bosque humedo de montana en Mesoamerica, y se analizan patrones de distribution, diversidad y endemismo. Los bosques montanos de Costa Rica y del oeste de Panama tienen la mas alta riqueza de especies, riqueza de especies endemicas a Mesoamerica, y riqueza de especies ecologicamente restringidas a bosque humedo de montana. Otras regiones, tales como la Sierra Madre del Sur de Guerrero y Oaxaca, la region de Los Tuxtlas y las montanas de Chiapas y Guatemala, tambien tienen avifaunas ricas en especies y en endemicas. Basado en patrones de similitud de avifaunas, se puede dividir Mesoamerica en siete regiones que tienen avifaunas distintas (Costa Rica y el oeste de Panama; el norte de Centroamerica y el norte de Chiapas; el sur de Chiapas; el este de Mexico; la Sierra Madre del Sur; el interior de Oaxaca; y el Eje Neovolcanico y la Sierra Madre Occidental), las cuales pueden servir como guias en el establecimiento de prioridades para la conservation.

Phylogeography of the Buarremon brush-finch complex (Aves, Emberizidae) in Mesoamerica

The Buarremon brush-finches represent a complex suite of populations distributed in the montane New World Tropics from Mexico south to South America. Traditional taxonomic arrangements have separated populations of this genus into three species, based on plumage variation, although plumage patterns are well known to exhibit homoplasy. We present a first detailed phylogeographic and phylogenetic study, focused on Mesoamerican populations, and signal the existence of strong differentiation among populations with a clear geographic structure. We find well differentiated clades for (1) the Sierra Madre Oriental and Sierra Madre del Sur in Oaxaca, (2) western Mexican populations, including the B. brunneinucha populations in the Sierra Madre del Sur and B. virenticeps, (3) Sierra Madre Oriental and Sierra de los Tuxtlas, (4) northern Central America, (5) southern Central America, (6) middle Central America, and (7) South America. We demonstrate a lack of concordance with plumage patterns, and argue for several additional species to be recognized in the complex.

Speciation in the Emerald Toucanet (Aulacorhynchus Prasinus) Complex

Abstract We analyzed genetic variation in the Emerald Toucanet (Aulacorhynchus prasinus), a species complex that ranges primarily along the montane forests of southern and eastern Mexico south to Bolivia. Segments of three mitochondrial DNA genes (cytochrome b, ND2, and ND3) were sequenced for a total of 1,159 base pairs. Using maximum parsimony, maximum likelihood, and Bayesian analysis, we found a set of seven differentiated populations that correspond to clear geographic breaks throughout the highlands of the Neotropics. These genetically distinct populations also correspond with the geographic breaks found in previous analyses of morphological data. Molecular evidence suggests species treatment for four of the Central American clades and three South American clades. Especiación en el Complejo de Aulacorhynchus prasinus

RECENT SPECIATION IN THE ORCHARD ORIOLE GROUP: DIVERGENCE OF ICTERUS SPURIUS SPURIUS AND ICTERUS SPURIUS FUERTESI

Abstract New World orioles (Icterus) include several closely related species and subspecies pairs that provide excellent opportunities for studying recent speciation. We examined a subspecies pair in the Orchard Oriole group: Orchard Oriole (I. spurius spurius), a long-distance migrant that breeds in eastern North America, and Fuertes’s Oriole (I. s. fuertesi), a short-distance migrant that breeds in a restricted range in Veracruz, Mexico. We sequenced parts of the mitochondrial cytochrome-b gene (925 base pairs) and control region (344 base pairs) from 23 Orchard Orioles and 7 Fuertes’s Orioles. Subspecies are not reciprocally monophyletic. Instead, our data suggest that at least one taxon is paraphyletic or polyphyletic. We found little support for any further phylogenetic structure, including whether one subspecies might be derived from the other. However, haplotype frequency analysis suggests that there is little or no current gene flow between the taxa. The phylogenetic relationship between Orchard and Fuertes’s orioles is likely a result of recent divergence and incomplete lineage sorting. That interpretation is consistent with theoretical models of speciation, which predict patterns of nonmonophyly at early stages of taxon divergence. Our findings suggest that Orchard and Fuertes’s orioles are separate species and provide a case study for evaluating the importance of monophyly in defining species limits.

Geographic variation in the rosy thrush-tanager (rhodinocichla rosea) complex of mesoamerica (aves: passeriformes)

Patterns of differentiation and geographic variation among populations of the Rhodinocichla complex are described. We document the existence of a heretofore unreported population in the vicinity of Acapulco, Guerrero, Mexico. The species occurs in 4-6 allopatric populations, each of which has unique characters that make it diagnosable. We recommend that the complex be considered a single biological species, but at least five phylogenetic species.

Speciation in an avian complex endemic to the mountains of Middle America (Ergaticus, Aves: Parulidae).

The implementation of the phylogeographic approach for the study of biodiversity is critical in poorly sampled regions like the montane systems of Middle America, as complex evolutionary histories often result in the presence of independent lineages not properly considered by traditional taxonomy. Herein we sequenced 2370 bp of mtDNA (ND2, cyt b and ATPase) from 81 individuals of Ergaticus, a complex of birds endemic to the montane forests of Middle America. Although current taxonomy recognizes two species, the results reveal considerable genetic structure with the presence of four mtDNA lineages. Two of these lineages within Ergaticus ruber evidence the need of a revaluation of the species limits for this taxon. The general phylogeographic pattern can be explained as a consequence of relative isolation of the populations in different mountain ranges separated by low elevation barriers. Most population groups did not show signals of demographic expansion with the exception of the one corresponding to clade 1. The divergence time estimates point to the Pleistocene as an important time period for the diversification of this complex.