Hierarchical effects of historical and environmental factors on lizard assemblages in the upper Madeira River, Brazilian Amazonia

Abstract

Investigating the role of historical and ecological factors structuring assemblages is relevant to understand mechanisms and processes affecting biodiversity across heterogeneous habitats. Considering that community assembly often involves scale-dependent processes, different spatial scales may reveal distinct factors structuring assemblages. In this study we use arboreal and leaf-litter lizard abundance data from 83 plots to investigate assemblage spatial structure at two distinct scales in southwestern Brazilian Amazonia. At a regional scale, we test the general hypothesis that the Madeira River acts as a barrier to dispersal of some lizard species, which results in distinct assemblages between river banks. At a local scale, we test the hypothesis that assemblages are not evenly distributed across heterogeneous habitats but respond to a continuum of inadequate-to-optimal portions of environmental predictors. Our results show that regional lizard assemblages are structured by the upper Madeira River acting as a regional barrier to 29.62% of the species sampled. This finding suggests species have been historically isolated at one of the river banks, or that distinct geomorphological features influence species occurrence at each river bank. At a local scale, different sets of environmental predictors affected assemblage composition between river banks or even along a river bank. These findings indicate that environmental filtering is a major cause of lizard assemblage spatial structure in the upper Madeira River, but predictor variables cannot be generalized over the extensive (nearly 500 km) study area. Based on a single study system we demonstrate that lizard assemblages along the forests near the banks of the upper Madeira River are not randomly structured but respond to multiple factors acting at different and hierarchical spatial scales.

The role of environmental gradients and microclimates in structuring communities and functional groups of lizards in a rainforest-savanna transition area

“…The influence of environmental variables, such as canopy openness, number of trees, density vegetation, elevation and soil structure in structuring ectothermic vertebrate communities on a local scale has been reported for the mid-upper Madeira River ( e.g. , Garda et al, 2013 ; Dias-Terceiro et al, 2015 ; Peixoto et al, 2020 ). The fact that temperature is not the main variable or determining factor for lizard assembly is intriguing ( Fig.…”

“…Spatial heterogeneity of vegetation and vegetation cover are known to affect the occurrence and abundance of squamates in the tropics, as they are related to the availability of resources and sites for nesting, foraging, thermoregulation ( Vitt & Zani, 1998 ; Vitt et al, 2007 ; Pringle, Webb & Shine, 2003 ; Masseli et al, 2019 ; Mesquita et al, 2015 ) and variation of light incidence, humidity and temperature ( Pringle, Webb & Shine, 2003 ; Peixoto et al, 2020 ). The communities sampled herein are also affected by these factors since they are structured along a gradient of plant structure, which is represented by canopy reflectance, varying in the availability of open environments with a high incidence of light, temperature, and humidity, as well as forest environments with a lower incidence of direct light and milder temperatures.…”

Disentangling the effects of environmental and geographic distances on lizard assemblages in Amazonian forests

“…Although large Amazonian rivers are commonly reported as vicariant barriers promoting biodiversity in Amazonia (Antonelli et al, 2010; Boubli et al, 2015; Haffer, 1997; Ribas et al, 2012; Simões et al, 2008; Smith et al, 2014), the current habitat heterogeneity within the Madeira‐Purus interfluve, which is hierarchically dependent on historical processes operating at wider spatial scales (Peixoto et al, 2020), efficiently predicts lizard assemblages. Future studies should investigate physiological traits, such as temperature sensitivity and resistance to desiccation, or genetic loci under adaptive selection to assess whether climatic seasonality creates enough stress for ecophysiological barriers to inhibit some evolutionary lineages, which would limit phylogenetic and functional diversity (Coronado et al, 2015; Miller et al, 2013; Qian et al, 2013) within open forests.…”

“…Distinguishing ecological and evolutionary processes and mechanisms structuring assemblages is not an easy task (Cadotte & Tucker, 2017), because they generally result from hierarchically related environmental and historical factors (e.g. Dias‐Terceiro et al, 2015; Peixoto et al, 2020). However, regardless of the ecological and evolutionary processes behind non‐random assemblages, testing spatial heterogeneity in assemblage taxonomic and functional structure is useful for determining levels of biotic complementarity and redundancy between sites (Diaz & Cabido, 2001; McGill et al, 2006), which makes it an efficient approach to conservation of local assemblies (Bueno et al, 2012; Faria et al, 2019; Fraga et al, 2011).…”

Habitat turnover in Iberian and Italian lizards: Is it climatically, spatially, or phylogenetically determined?

“…The composition of reptile assemblages shows particularly high geographical variability because reptiles strongly depend on external thermal sources for their activity and have relatively narrow environmental optima (Ortega et al, 2016; Rodríguez et al, 2005). This variability in reptile assemblages is also regulated at a finer scale by species interactions and certain habitat properties, such as heterogeneity in habitat structure and vegetation cover (Escoriza & Pascual, 2021; Marques Peixoto et al, 2020; Pianka & Huey, 1978). Ecologically analogous species avoid costly negative interactions by microhabitat partitioning (i.e., at vegetation stratum) or by foraging behavior (Buckley & Jetz, 2010; Huey & Pianka, 1977; Losos et al, 1993).…”