Contrasting patterns of elevational zonation for birds and mammals in the Andes of southeastern Peru

Abstract

Abstract. To determine the generality of avian diversity patterns, we investigated patterns of elevational zonation shown by birds and mammals along the eastern slope of the Andes Mountains in southeastern Peru. The strong environmental gradient sampled, entirely within Peru's Manu National Park and Biosphere Reserve, supports highly diverse faunas. Elevational distributions of 901 bird species, 129 bat species, and twenty‐eight species of native mice exhibit contrasting patterns in species richness, species composition, and species turnover. Birds and bats showed smooth declines of species richness with elevation, whereas the richness of mouse assemblages was unrelated to elevation. For all three groups, the greatest differences were between lowland and highland faunas, although cutoff points for this contrast varied among groups (≈ 500 m for birds, 750 m for bats, and 1000 m for mice). Differences in composition also separated bird and bat faunas on either side of c. 1400 m (the boundary between montance forest and cloud forest); for mice, this faunal transition may take place nearer to 2000 m. Bird and bat faunas lacked the more discrete zonations suggested for mouse assemblages, as indicated by elevational range profiles and nested subset analyses. Distinct highland assemblages are apparent in two‐dimensional histograms of range limits of birds and mice, but not for bats. Highland bat species occupy broader elevational ranges than lowland bat species, but for both birds and mice, species at intermediate elevations had the broadest amplitudes. Finally, clumping of range maxima and minima along the gradient identified zones of pronounced species turnover in each group, but these were generally not strongly associated with the locations of ecotones. Differences in zonation of these groups appear to reflect their different biological attributes and phylogenetic histories. Such differences obviously complicate discussions of ‘general’ diversity patterns, and limit the usefulness of birds to forecast or predict diversity patterns in other more poorly known groups—other groups may show elevated diversity and endemism in areas where avian diversity patterns appear unremarkable. The pronounced contrasts between bats and mice, and the generally intermediate character of avian patterns, suggest that future analyses might profitably partition birds into finer, more homogeneous groups of historically and/or ecologically similar species. Group differences in zonation may ultimately prove explicable with information on both species‐abundance patterns and resource distributions.

Dinámica temporal y espacial de una comunidad de aves en un gradiente altitudinal de la Cordillera Volcánica Central de Costa Rica, vertiente Caribe

“…Por otro lado, Rahbek (1997) y Patterson et al (1998), desarrollaron investigaciones de la estructura espacial de comunidades de aves neotropicales en gradientes altitudinales de los Andes suramericanos y sostienen que dentro de las zonas más diversas están las que se denominan "comunidades aves de tierras bajas" las cuales se ubican en zonas boscosas que van desde el nivel del mar hasta los 1500 m de altura. Rahbek (1997), afirma que dentro de esta "Gran comunidad" la diversidad debe ser muy homogénea y por ende se debería mantener la composición de especies entre elevaciones.…”

“…Es necesario entender que existe una fuerte asociación entre grupos de aves y tipos de vegetación como bosque húmedo de tierras bajas, bosque húmedo montano, bosque nuboso, bosque enano donde cada grupo presenta diferentes ensambles de especies a lo largo del gradiente (Terborgh 1971, Patterson, et al 1998 presenta una diversidad de aves homogénea a lo largo del gradiente. Esto en términos ecológicos estaría relacionado con que las zonas de vida reflejan patrones de humedad que determinan la distribución de las plantas y a su vez estas determinan la distribución del recurso de la avifauna como insectos, frutos y semillas (Hartshorn 1983).…”

“…Así, en un gradiente altitudinal probablemente estos factores abióticos varían de tal forma que la productividad, y por ende la diversidad de especies de aves, debería tener un pico hacia los límites inferiores del gradiente (Patterson et al 1998). Así, si el intervalo de altitud del transecto Volcán Barva -La Selva se considerara de 0 m hasta los 3000 m como se debería evaluar, aunque en el muestreo de aves de TEAM no se haya incluido arriba de los 500 m, su pico o mayor valor de riqueza se podría dar hacia sus límites inferiores o a los 500 m.…”

Morcegos em área de Floresta Montana, Visconde de Mauá, Resende, Rio de Janeiro

“…Porém, ainda existem áreas com pouca ou nenhuma amostragem para os diferentes grupos taxonômicos (Bergallo et al 2009). As faixas de altitudes mais elevadas estão entre essas áreas pouco amostradas (e.g., Geise et al 2004, Olifiers et al 2007), sendo estas de extrema importância, uma vez que os gradientes altitudinais podem influenciar a ocorrência e a abundância das espécies de mamíferos, incluindo os morcegos (Patterson et al 1998, Geise et al 2004, McCain 2005, 2007.…”

Bats (Mammalia: Chiroptera) of the southeastern Truong Son Mountains, Quang Ngai Province, Vietnam

“…Two ecological factors may contribute to the differences in diversity between lower and higher elevations in the southeastern Truong Son Mountains. In other tropical and subtropical areas, the diversity of bats declines with increasing elevation (e.g., Graham 1983;Patterson et al 1998). Additionally, some differences in diversity between lower and higher elevations at our study area might reflect seasonal movements of bats.…”