Change in avian functional fingerprints of a Neotropical montane forest over 100 years as an indicator of ecosystem integrity.

Ecologically relevant traits of organisms in an assemblage determine an ecosystem's functional fingerprint (i.e., the shape, size, and position of multidimensional trait space). Quantifying changes in functional fingerprints can therefore provide information about the effects of diversity loss or gain through time on ecosystem condition and is a promising approach to monitoring ecological integrity. This, however, is seldom possible owing to limitations in historical surveys and a lack of data on organismal traits, particularly in diverse tropical regions. Using data from detailed bird surveys from 4 periods across more than a century, and morphological and ecological traits of 233 species, we quantified changes in the avian functional fingerprint of a tropical montane forest in the Andes of Colombia. We found that 78% of the variation in functional space, regardless of period, was described by 3 major axes summarizing body size, dispersal ability (indexed by wing shape), and habitat breadth. Changes in species composition significantly altered the functional fingerprint of the assemblage and functional richness and dispersion decreased 35-60%. Owing to species extirpations and to novel additions to the assemblage, functional space decreased over time, but at least 11% of its volume in the 2010s extended to areas of functional space that were unoccupied in the 1910s. The assemblage now includes fewer large-sized species, more species with greater dispersal ability, and fewer habitat specialists. Extirpated species had high functional uniqueness and distinctiveness, resulting in large reductions in functional richness and dispersion after their loss, which implies important consequences for ecosystem integrity. Conservation efforts aimed at maintaining ecosystem function must move beyond seeking to sustain species numbers to designing complementary strategies for the maintenance of ecological function by identifying and conserving species with traits conferring high vulnerability such as large body size, poor dispersal ability, and greater habitat specialization. Article impact statement: Changes in functional fingerprints provide a means to quantify the integrity of ecological assemblages affected by diversity loss or gain.

Cambios en las Huellas Funcionales Aviarias en un Bosque Neotropical de Montaña durante Cien Años como Indicadores de la Integridad del Ecosistema Resumen Las características ecológicamente relevantes de los organismos que pertenecen a un ensamblaje determinan la huella funcional de un ecosistema (es decir, la forma, el tamaño y la posición del espacio multidimensional de la característica en cuestión). Por lo tanto, la cuantificación de los cambios en las huellas funcionales puede proporcionar información sobre los efectos que tiene la pérdida o ganancia de diversidad a lo largo del tiempo sobre las condiciones del ecosistema; por esto se le considera una estrategia prometedora para el monitoreo de la integridad ecológica. Sin embargo, lo anterior es pocas veces posible debido a las limitaciones de los censos históricos y a la falta de datos sobre las características del organismo, particularmente en las diversas regiones tropicales. Con datos detallados de censos realizados durante cuatro periodos en más de un siglo, y utilizando las características morfológicas y ecológicas de 233 especies, cuantificamos los cambios en la huella funcional aviaria de un bosque tropical de montaña en los Andes de Colombia. Encontramos que el 78% de la variación en el espacio funcional, sin importar el periodo, estuvo descrito por tres ejes principales que resumen el tamaño corporal, la habilidad de dispersión (indicada por la forma de las alas) y la amplitud del hábitat. Los cambios en la composición de especies alteraron significativamente la huella funcional del ensamblaje y la riqueza y dispersión funcional disminuyeron en 35-60%. Debido a la pérdida de especies y a la adición de especies nuevas al ensamblaje, el espacio funcional disminuyó con el tiempo, pero, durante la década de 2010, al menos el 11% de su volumen se extendió a áreas de espacio funcional que no estaban ocupadas cien años antes. El ensamblaje ahora incluye menos especies de gran tamaño, más especies con buena habilidad de dispersión y menos especialistas de hábitat. Las especies que se perdieron eran funcionalmente únicas, lo que resultó en reducciones importantes en la riqueza y en la dispersión funcional después de su pérdida, e implicó consecuencias importantes para la integridad del ecosistema. Los esfuerzos de conservación enfocados en mantener la función del ecosistema deben ir más allá de la búsqueda de la preservación del número de especies y enfocarse también en el diseño de estrategias complementarias para el mantenimiento de la función ecológica por medio de la identificación y conservación de especies con características que otorgan una vulnerabilidad alta, como lo son el tamaño corporal grande, una habilidad de dispersión pobre y una mayor especialización de hábitat.

A morphological database for 606 Colombian bird species.

Colombia is the country with the highest bird diversity in the world. Despite active research in ornithology, compelling morphological information of most bird species is still sparse. However, morphological information is the baseline to understand how species respond to environmental variation and how ecosystems respond to species loss. As part of a national initiative, the Instituto Alexander von Humboldt in collaboration with 12 Colombian institutions and seven biological collections, measured up to 15 morphological traits of 9,892 individuals corresponding to 606 species: 3,492 from individuals captured in field and 6,400 from museum specimens. Species measured are mainly distributed in high Andean forest, páramo, and wetland ecosystems. Seven ornithological collections in Colombia and 18 páramo complexes throughout Colombia were visited from 2013 to 2015. The morphological traits involved measurements from bill (total and exposed culmen, bill width and depth), wing (length, area, wingspan, and the distance between longest primary and longest secondary), tail (length and shape), tarsus (length), hallux (length and claw hallux), and mass. The number of measured specimens per species was variable, ranging from 1 to 321 individuals with a median of four individuals per species. Overall, this database gathered morphological information for >30% of Colombian bird diversity. No copyright, proprietary, or cost restrictions apply; the data should be cited appropriately when used.

Origin and cross-century dynamics of an avian hybrid zone.

BACKGROUND: Characterizations of the dynamics of hybrid zones in space and time can give insights about traits and processes important in population divergence and speciation. We characterized a hybrid zone between tanagers in the genus Ramphocelus (Aves, Thraupidae) located in southwestern Colombia. We evaluated whether this hybrid zone originated as a result of secondary contact or of primary differentiation, and described its dynamics across time using spatial analyses of molecular, morphological, and coloration data in combination with paleodistribution modeling. RESULTS: Models of potential historical distributions based on climatic data and genetic signatures of demographic expansion suggested that the hybrid zone likely originated following secondary contact between populations that expanded their ranges out of isolated areas in the Quaternary. Concordant patterns of variation in phenotypic characters across the hybrid zone and its narrow extent are suggestive of a tension zone, maintained by a balance between dispersal and selection against hybrids. Estimates of phenotypic cline parameters obtained using specimens collected over nearly a century revealed that, in recent decades, the zone appears to have moved to the east and to higher elevations, and may have become narrower. Genetic variation was not clearly structured along the hybrid zone, but comparisons between historical and contemporary specimens suggested that temporal changes in its genetic makeup may also have occurred. CONCLUSIONS: Our data suggest that the hybrid zone likey resulted from secondary contact between populations. The observed changes in the hybrid zone may be a result of sexual selection, asymmetric gene flow, or environmental change.

Niche-tracking migrants and niche-switching residents: evolution of climatic niches in New World warblers (Parulidae).

Differences in life-history traits between tropical and temperate lineages are often attributed to differences in their climatic niche dynamics. For example, the more frequent appearance of migratory behaviour in temperate-breeding species than in species originally breeding in the tropics is believed to have resulted partly from tropical climatic stability and niche conservatism constraining tropical species from shifting their ranges. However, little is known about the patterns and processes underlying climatic niche evolution in migrant and resident animals. We evaluated the evolution of overlap in climatic niches between seasons and its relationship to migratory behaviour in the Parulidae, a family of New World passerine birds. We used ordination methods to measure seasonal niche overlap and niche breadth of 54 resident and 49 migrant species and used phylogenetic comparative methods to assess patterns of climatic niche evolution. We found that despite travelling thousands of kilometres, migrants tracked climatic conditions across the year to a greater extent than tropical residents. Migrant species had wider niches than resident species, although residents as a group occupied a wider climatic space and niches of migrants and residents overlapped extensively. Neither breeding latitude nor migratory distance explained variation among species in climatic niche overlap between seasons. Our findings support the notion that tropical species have narrower niches than temperate-breeders, but does not necessarily constrain their ability to shift or expand their geographical ranges and become migratory. Overall, the tropics may have been historically less likely to experience the suite of components that generate strong selection pressures for the evolution of migratory behaviour.