The need to employ reliable and reproducible species identifications in coralline algal research

Abstract

Coralline algae perform important ecological roles in nearshore marine ecosystems globally by promoting the settlement of invertebrate larvae and enhancing biodiversity by creating habitat. However, these roles are severely threatened by global environmental changes. Most coralline algae are extremely difficult to identify, and DNA sequencing has revealed rampant inaccuracy of morpho-anatomical approaches to distinguish species, and even genera. If appropriate identification methods are not reported, or even used, we will be left with an uninterpretable body of literature where the species-specific biology of coralline algae cannot be validated. This will make it difficult to determine the impact a changing ocean may have on these ecologically important species. We reveal the magnitude of the issue in coralline algal research—both the identification methods used and the reporting of identification protocols. An analysis of 341 articles over the past decade revealed that only 7.6% used molecular methods, with over 70% not reporting any details of how species were identified. While many coralline algal taxonomists understand that the majority of species cannot be identified morphologically, this message has not disseminated to the ecological and physiological community. We provide a series of guidelines for conducting DNA-based identifications and strongly recommend the use of these methods over less informative morpho-anatomical techniques. Most importantly, the methods of identification should be adequately reported. Without following these guidelines, research on coralline algae runs the risk of collecting uninterpretable data, and conducting irreproducible science, slowing our ability to determine how these important species will respond to future ocean conditions.

Understanding coralline algal responses to ocean acidification: Meta‐analysis and synthesis

“…Scientific effort in monitoring the abundance or ecology of coralline algae beyond simply acknowledging their collective presence or absence is lacking. This is hindered by the only recent understanding that coralline algae diversity is greater than previously believed (Gabrielson et al, 2018; Peña, Bélanger, et al, 2021; Twist et al, 2019) and extends far beyond the previous mostly morphological groupings and has important implications for much of the previous work in this field (Twist et al, 2020). Recent molecular work shows that some lineages of coralline algae are more vulnerable to OA than others, and that the projected adverse effects on coralline algal biodiversity have been greatly underestimated (Peña, Harvey, et al, 2021).…”

“…However, there are still many fundamental questions left unanswered in understanding the responses of coralline algae to OA that could offer insights regarding tolerant species or populations. Taxonomic variation in responses and its influence on other factors that we explored here can only be guessed at currently with the existing issues of nonmolecular identification in the majority of studies included here (Twist et al, 2020). Better integration of molecular work while assessing their response to OA is needed in the laboratory.…”

Major loss of coralline algal diversity in response to ocean acidification

“…This is the first molecular systematic study of the effects of ocean acidification on coralline algae and shows that this approach is essential for an accurate understanding of how the diversity of coralline algae is affected by CO 2 emissions (Twist et al, 2020). Highly diverse coralline algal assemblages were simplified under elevated levels of CO 2 .…”

Geographic distance, sedimentation, and substrate shape cryptic crustose coralline algal assemblages in the world’s largest subtropical intertidal algal reef

“…Early studies identified 23 CCA species in Taiwan based on morphoanatomical evidence alone (Lewis & Norris, 1987; Wang, 1996). Without DNA barcoding, cryptic species diversity of CCA always goes undetected (reviewed in Twist et al, 2020). Recently, DNA barcoding studies revealed 13 CCA species in northern Taiwan, mostly in the TAR (Caragnano et al, 2018; Liu et al, 2018), bringing the total number of CCA species in Taiwan to 36.…”