Avian distribution patterns in the Guiana Shield: implications for the delimitation of Amazonian areas of endemism

Abstract

Aim To develop a methodology for defining the boundaries of the Guianan area of endemism using complementary approaches that include GIS tools, multivariate statistics and analyses of physical barriers in the distribution patterns of an entire endemic avifauna. As a case study, I used the distribution patterns of lowland terra firme forest birds.Location Guiana Shield, northern South America.Methods I identified Guianan endemics using the ornithological literature, subsequently gathering distributional data for these taxa using mainly museum collections and my own fieldwork in the region. I used these distributional data to map the spatial patterns of endemicity in the region and to compare distributions across taxa. I employed community composition data from 34 localities from throughout the Guiana Shield to identify spatial patterns of clustering using an ordination analysis (non-metric multidimensional scaling), and to recognize the region's main biogeographical barriers for birds using Monmonier's algorithm.Results At least 88 avian taxa are restricted to the terra firme forests of the Guianan area of endemism, which is roughly delimited by the Amazon, Negro and Branco rivers. These large rivers, however, are not the only boundaries. I identified seven additional barriers, including medium-sized rivers, non-forested areas and mountains, which also contribute to delimiting the area of endemism. Within the endemic avifauna, I identified three distinct distribution patterns. The ordination analysis shows the presence of two distinct avifaunas within the Guiana Shield.Main conclusions Although the proposed boundaries of the Guianan area of endemism are consistent with previously postulated configurations, this study reveals a more complex delimitation than formerly recognized, highlighting the importance of several landscape features besides large rivers, and the existence of three distinct distributional patterns within one endemic avifauna. The Branco/ Negro interfluvium, often included within this area of endemism, actually represents a transition zone between two distinct avifaunas. The longstanding view of the Amazon Basin as a mosaic of parapatric areas of endemism delimited by major rivers appears to be an oversimplification, at least for the Guiana Shield. This finding suggests the need for more rigorous approaches to re-evaluate the traditional boundaries of such areas.

The Blattodea s.s. (Insecta, Dictyoptera) of the Guiana Shield

“…The levels of endemism we see (Figure 19) are surprisingly low compared with other known rates of endemism for the Guiana Shield (Funk et al 2007; Hollowell and Reynolds 2005; Kelloff and Funk 2004; Naka 2011). One possible explanation would simply be that cockroaches have low rates of tropical endemism.…”

Bird Communities in Amazonian White‐Sand Vegetation Patches: Effects of Landscape Configuration and Biogeographic Context

“…These landscapes are located in four different regions on opposite margins of the Negro and Branco rivers, and belong to distinct biogeographic units (Borges 2007, Naka 2011, Borges et al 2014: Rio Negro-Rio Branco interfluve (Arac a), eastern margin of Rio Branco (Viru a), western margin of Rio Negro (Ja u and Novo Airão), and eastern margin of Rio Negro (Uatumã). We pooled data from Novo Airão and Ja u since both belong to the same biogeographical region.…”

Evidence that dispersal barriers influence blaberoid cockroach assemblages in a neotropical savanna–forest matrix

“…Broad scale studies may provide the greatest evidence for the forest refuge hypothesis (Adrian Quijada‐Mascareñas et al ., ; Wuster et al ., ). Both large‐scale (Naka, ) and small‐scale (Bernard & Fenton, ) studies, however, can provide evidence for the mechanisms underlying the hypothesis. We have shown that savannas may act as boundaries for dispersal in some species of blaberoid cockroaches.…”

“…The savannas of the Guianas are dispersal boundaries for some species on the large scale (Naka, ), but not necessarily on the small scale (Bernard & Fenton, ). Migrating or dispersing individuals of many animals in the Rupununi region may use the narrow riparian corridor bordering the river.…”