Ecological Indicators (Nov 2024)
Identification and use of suitable metrics for calling male count-based community assessments in amphibian monitoring in temperate Europe
Abstract
Calling amphibian male counts (CAMC) is a cost-effective non-invasive acoustic monitoring method that needs amphibian community quality assessment system. In our survey we considered breeding amphibian assemblages as entities having three main ecological traits, size, richness and evenness, and tested the reliability of potentially suitable metrics that each characterize separate ecological trait. We also aimed at finding out the site and surrounding land-use characteristics linked to low or high-quality amphibian community state assessments, and studied differences in responses of community traits to these external factors.In this CAMC study that covered 400 amphibian breeding sites across Latvia, we tested responses of 11 metrics (5 CAMC for community size, 2 richness metrics, 4 evenness and dominance indices) to five sets of predictors (two sets of anthropogenic land use variables, two natural/mixed effect sets, and a climate variable set) using GLMs, to find out statistically significant anthropogenic factors, site and surrounding land use characteristics and model ranks according to their corrected Akaike information criterions. Then, we used anthropogenic factors to classify sites with natural and strongly impacted site groups, compared their metrics by Wilcoxon rank-sum tests and Box plots, and assessed metric congruences in site classifications.Based on their properties, we recommend using three metrics, each being the best in representing their own breeding amphibian assemblage trait in the communities of temperate Europe: the total number of calling males (CAMCtot), the community completeness, and the reciprocal form of Berger-Parker dominance index.Despite of good responses to anthropogenic pressure indicators showed by the metrics, local site characteristics were still the highest-ranked factor, with waterbody dimensions being the most important for amphibian population size, and macrophyte vegetation largely determining their taxonomic richness and community evenness. Among anthropogenic threats, the strongest effects were from the transportation corridors (roads) and infrastructure developments that had particularly adverse effects on community richness and evenness, and on CAMC for some taxa. Wetlands in surrounding areas were more important for CAMCtot. The climate factor was generally among the least important in ranks, probably due to its general similarity among the study sites throughout Latvia.Our study shows opportunities for using amphibian-based metrics in ecological indicator systems, where they may substitute fish metrics in some waterbody types, and suggests the necessity of paying more attention to wetland size and location against the road network in amphibian habitat restoration projects.
