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Invasive marine algae in the Mediterranean was misidentified for decades

Invasive non-indigenous species (referred to as invasive species here) are one of the greatest threats to marine and coastal biodiversity. Invasive species are those that spread or are introduced beyond their natural range, often because of human activity, causing economic and environmental harm. For example, the zebra mussel (Dreissena polymorpha) is a well-known invasive that has spread throughout the world because of uncontrolled release of ballast water from ships.

Because of their potential negative impact, understanding and predicting the future spread of an invasive species is critical, especially with anticipated climate change impacts. Modelling frameworks are one tool commonly used to identify environmental drivers and forecast potential distribution patterns of invasives. However, as this study shows, model outputs are only as good as the data behind them. Misidentification of species can lead to questionable model outputs, e.g., too high or too low thereby making it extremely difficult to predict and manage invasions. For example, over 20% misidentifications have been documented in the Mediterranean and 7-70 % worldwide depending on the taxonomic group.

Fig1

Figure 1. This graphic illustrates how a model using an incorrect species will make inaccurate predictions of its potential distribution.

The authors of this study use the example of the highly invasive red algae (Lophocladia lallemandii) to demonstrate how taxonomic misidentifications can lead to erroneous model predictions. This native of the Red Sea likely spread to the Mediterranean through the Suez Canal. It poses a significant threat to already vulnerable benthic communities in the Mediterranean, but the authors prove it had been misidentified and is actually the species Lophocladia trichoclados.

How OBIS was used in this study

Modern molecular tools were used to verify the taxonomic identity of Lophocladia from the Mediterranean and define future trends. Genetic analysis provided evidence that all sampled specimens across the Mediterranean Sea (the Balearic Islands, Columbretes, Sicily, Croatia, and Israel) unequivocally corresponded to L. trichoclados which likely entered from the Atlantic through Gibraltar Strait, not L. lallemandii from the Red Sea as was accepted until now.

The authors used OBIS, and the Global Biodiversity Information Facility (GBIF), to extract all georeferenced records to complete a presence table and generate habitat suitability distribution maps as seen in Figure 2. This data helped confirm the misidentification.

Fig2

Figure 2. Map of the presence data points, red, yellow and green represent L. species invading the Mediterranean Sea, L. trichoclados and L. lallemandii, respectively according to species identification. Data were extracted from OBIS, GBIF and personal databases.

With climate change affecting all marine life, it is becoming increasingly important to accurately document and understand the future trends of invasive species in the Mediterranean and elsewhere. This study highlights that correct identification via genetic analysis, especially when cryptic or not easily distinguishable invasive species are involved, should be a mandatory first step. This is essential when informing policies to prioritise conservation areas while allowing scientists and managers to concentrate monitoring efforts in the most vulnerable zones.

Full publication available at:

Golo, R., A. Vergés, P. Díaz-Tapia and E. Cebrian. 2023. Implications of taxonomic misidentification for future invasion predictions: Evidence from one of the most harmful invasive marine algae. Marine Pollution Bulletin, Volume 191.