Cryptic Species in Ecotoxicology

Abstract

The advent of genetic methods has led to the discovery of an increasing number of species that previously could not be distinguished from each other on the basis of morphological characteristics. Even though there has been an exponential growth of publications on cryptic species, such species are rarely considered in ecotoxicology. Thus, the particular question of ecological differentiation and the sensitivity of closely related cryptic species is rarely addressed. Tackling this question, however, is of key importance for evolutionary ecology, conservation biology, and, in particular, regulatory ecotoxicology. At the same time, the use of species with (known or unknown) cryptic diversity might be a reason for the lack of reproducibility of ecotoxicological experiments and implies a false extrapolation of the findings. Our critical review includes a database and literature search through which we investigated how many of the species most frequently used in ecotoxicological assessments show evidence of cryptic diversity. We found a high proportion of reports indicating overlooked species diversity, especially in invertebrates. In terrestrial and aquatic realms, at least 67% and 54% of commonly used species, respectively, were identified as cryptic species complexes. The issue is less prominent in vertebrates, in which we found evidence for cryptic species complexes in 27% of aquatic and 6.7% of terrestrial vertebrates. We further exemplified why different evolutionary histories may significantly determine cryptic species' ecology and sensitivity to pollutants. This in turn may have a major impact on the results of ecotoxicological tests and, consequently, the outcome of environmental risk assessments. Finally, we provide a brief guideline on how to deal practically with cryptic diversity in ecotoxicological studies in general and its implementation in risk assessment procedures in particular. Environ Toxicol Chem 2023;00:1–26. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

DNA Barcoding as a Plant Identification Method

“…By combining the strengths of two molecular biology methods, PCR amplification and sequencing, DNA barcoding offers a quick and accurate approach to identify different groups. Interestingly, at the species level, DNA barcoding can be used to characterize novel, unknown species, or cryptic species [9], two or more species that are classified as a single, as they are superficially morphologically similar and hence cannot be identified using classical taxonomy [10,11]. Notably, the highest cryptic diversity so far has been found in animals, particularly in invertebrates [9,[12][13][14].…”

Uncovering the Grinnellian niche space of the cryptic species complex Gammarus roeselii

“…However, one major challenge is often not yet addressed: In most cases modelling approaches are applied to species identified by morphological rather than molecular differences. This leaves the large part of cryptic biological diversity unconsidered ( Bickford et al, 2007 ; Fišer, Robinson & Malard, 2018 Jourdan et al, 2023 ). The fact that we have characterised niches mainly for morphologically determined species so far bears the risk of overestimating the sensitivity to environmental conditions.…”

“…1 ). This is especially crucial for ecotoxicological data, as studies indicate that cryptic species can differ in their tolerance to pollutants ( Feckler et al, 2012 ; Major et al, 2013 ; Soucek et al, 2013 ; Feckler et al, 2014 ; Monteiro et al, 2018 Jourdan et al, 2023 ). This raises the question if there actually are differences in the Grinnellian niches between the cryptic species and if so, if this can influence the persistence in a changing environment.…”