How the abiotic factors affect the ecology of amphibians.

Published: 5 May 2026| Version 1 | DOI: 10.17632/pr57x8vyx4.1
Contributors:
Jonas Pederassi,
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Description

Abiotic factors influence the reproductive behavior of anurans. Although temperature and precipitation are the most studied, atmospheric pressure seems to be the only factor that indicates the predictability of meteorological changes in the near future. It is, therefore, likely to be perceived by anurans that initiate reproduction before rainfall. The anurans were monitored in the Municipality of Bocaina de Minas, State of Minas Gerais, Brazil, encompassing part of the Serra da Mantiqueira in the upper basins of Rio Preto and Rio Grande. Our objectives included analyzing species distribution by altimetry, determining the similarity of active species between river basins, testing the hypothesis that species within a river basin tend to vocalize in association, establishing the probability of species encounter in the sampling, categorizing the species’ constancy and dominance, analyzing the influence of temperature, relative humidity, rainfall and barometric pressure on the species’ vocal activity, and constructing a climogram to illustrate the range of these variables associated with the optimal, tolerant and rare occurrence of vocal activity. Of the 52 species sampled, 28 were common to both river basins. When categorizing species constancy, only eight species were constant, 18 were accessory, and 26 were accidental. Four species were classified as dominant, 43 as subdominant, and 22 as recessive. When analyzing the influence of abiotic factors on the reproductive activity of the local anuran community, the dominant predictive climatic factor is barometric pressure, followed by relative humidity, temperature, and rainfall.

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Steps to reproduce

The vocal activity of anurans was monitored in the Municipality of Bocaina de Minas (22°09'S; 44°23'W), southern mesoregion of the State of Minas Gerais, Southeastern Brazil, comprising part of the Serra da Mantiqueira Environmental Protection Area, in the upper Rio Grande and upper Rio Preto basins. We used visual and acoustic searches in the different habitats and breeding sites (Lima and Pederassi 2015). Surveys lasted 8 hours per day for a total of 140 days between 2014 and 2021, covering both the dry season (April-October) and wet season (November-March). Surveys were alternated between the Rio Preto and Rio Grande basins so that the sampling effort was equivalent between the two areas. The total altitudinal range sampled was from 574 meters (minimum elevation) to 1804 meters (maximum elevation), which was divided into 10 altitudinal class intervals across the two basins. Sampling in the Rio Preto basin ranged from 574 to 1,401 meters, while sampled elevations in the Rio Grande basin ranged from 1,140 to 1,804 meters, resulting in an overlapping altitudinal range between 1,140 and 1,401 meters. For quantitative recording, the number of individuals per species was determined through active visual and acoustic searches during sampling. This count included all vocalizing individuals encountered. For large choruses with the number of individuals exceeding accurate counting, the number for analysis was standardized to 20. This standardized value represented the minimum estimate, as such choruses were visually and acoustically verified to contain significantly more than 20 individuals. To analyze the altimetric distribution of species across the river basins, species occurrence data (absolute frequencies) were grouped into altitudinal class intervals. This approach allowed us to assess distributional variation and the symmetry of sampling effort between the two basins. Constancy and dominance were calculated based on the absolute number of individuals and species recorded in each river basin. The constancy is expressed as C = (p100)/N, where p is the number of samples containing the species and N is the total number of samples. This method classifies species as constant when they exhibit an index greater than 50%, as accessory when they have an index between 25 and 50%, and as accidental when they present a rate below 25%. The dominance is expressed as D% = (i/t)100, where i is the total number of individuals of a species and t is the total number of individuals sampled. A species is classified into one of the following categories: • Eudominant when its index value exceeds 10% • Dominant when its index value falls between 5% and 10%. • Subdominant when its index value is between 2% and 5%. • Recessive when its index value is between 1% and 2%. • Rare when its index value is less than 1%.

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Categories

Ecology, Zoology, Conservation Ecology

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