Testing the Relationship between Human Occupancy in the Landscape and Tadpole Developmental Stress

Abstract

Amphibian population declines are widespread; the main causal factors are human related and include habitat fragmentation due to agriculture, mining, fires, and urban development. Brazil is the richest country in species of amphibians, and the Brazilian regions with the greatest amphibian diversity are experiencing relatively high rates of habitat destruction, but there are presently relatively few reports of amphibian declines. It is thus important to develop research methods that will detect deterioration in population health before severe declines occur. We tested the use of measurements of fluctuating asymmetry (FA) taken on amphibian larvae to detect anthropogenic stress. We hypothesized that greater human occupancy in the landscape might result in more stressful conditions for amphibians. We conducted this study at the Espinhaço mountain range in southeastern Brazil, using as a model an endemic species (Bokermannohyla saxicola, Hylidae). We chose two tadpole denticle rows and eye-nostril distance as traits for FA measurement. We measured percent cover of human-altered habitats in the landscape around tadpole sampling points and measured FA levels in sampled tadpoles. We found FA levels to differ among localities but found no relationship between human modification of the landscape and tadpole FA levels. Levels of FA in the traits we examined may not be strongly affected by environmental conditions, or may be affected by local variables that were not captured by our landscape-scale measures. Alternatively, populations may be genetically differentiated, affecting how FA levels respond to stress and obscuring the effects of anthropogenic disturbance.

Past vicariance promoting deep genetic divergence in an endemic frog species of the Espinhaço Range in Brazil: The historical biogeography of Bokermannohyla saxicola (Hylidae)

“…Specimens were collected for other studies by B. G. Pacheco and P. C. Eterovick (permanent collection permit for PCE: Sisbio/ICMBio10748-1), F. F. R. Oliveira and P. C. Eterovick (permits IEF 085/06 and Sisbio/ICMBio 12813–1) and F. S. F. Leite (permits Sisbio/ICMBio 21185–1). Many individuals were tadpoles and were used for fluctuating asymmetry measurements [ 24 ] that turned them unsuitable for museum collections. Other are still being used for other studies by B. G. Pacheco and PCE.…”

Agropastoral activities increase fluctuating asymmetry in tadpoles of two neotropical anuran species

“…For tadpoles, the information of the prevalence of fluctuating asymmetry is practically inexistent, being available only for tadpoles of Bokermannohyla saxicola (Eterovick et al . ). These authors also observed a variation of FA among localities, but were unable to demonstrate any evidence of relationship between an increase in anthropogenic disturbance and FA.…”

Tadpoles Inhabiting Natural and Anthropogenic Temporary Water Bodies: Which Are the Environmental Factors that Affect the Diversity of the Assemblages?

“…Environmental gradients in ephemeral ponds change over time and show an irregular distribution of resources in space and time (Wells, 2007;Schalk et al, 2017). The ecological dynamics in these assemblages of tadpoles could not depend only on predation but on the trophic plasticity of the species to exploit a wide range of resources and reduce inter and intra-specific competition (McDiarmid & Altig, 1999;Wells, 2007;Eterovick et al, 2015;Schalk et al, 2017).…”

“…The anurans that successfully disperse through anthropogenic matrices possess high phenotypic plasticity in the face of abiotic variations (Figueroa et al, 2009;Eterovick et al, 2015). However, the distance between natural forest cover and aquatic habitats is a limitation for effective colonization, which is reflected in the composition of anuran assemblages at the larval stage (Wells, 2007;Souza et al, 2008;Costa et al, 2016;Ouchi-Melo et al, 2017).…”

“…Thus, breeding seasons may vary from one species to another, depending on both the phenology of the species, the size and age of the female, and postural characteristics (e.g., eggs deposited in water, bubble nest, foam nest, embedded in the dorsum of aquatic females, or carried by adults) and the responses of populations to habitat fragmentation (Wells, 2007). However, it is unknown the effect of anthropogenic matrix management and distance to different landscape elements on the anuran's ability to colonize bodies of water in tropical flooded savanna (Eterovick et al, 2015;Costa et al, 2016;Pelinson et al, 2016).…”