Hidden introductions of freshwater red algae via the aquarium trade exposed by DNA barcodes

Abstract

<jats:title>ABSTRACT</jats:title><jats:p>The global aquarium trade can introduce alien freshwater invaders, potentially impacting local aquatic ecosystems and their biodiversity. The role of the aquarium trade in spreading freshwater red macroalgae that hitchhike on ornamental aquatic plants and animals is unassessed. We investigated this human-mediated phenomenon via a broad biodiversity survey and genetic analysis of freshwater red algae in the field and aquarium shops in East Asia. Using <jats:italic>rbc</jats:italic>L-based DNA barcoding, we surveyed 125 samples from 46 field sites and 88 samples from 53 aquarium shops (213 samples in total) mostly across Taiwan – a key hub in the global aquarium trade – as well as in Hong Kong, Okinawa (Japan), the Philippines, and Thailand. We augmented our <jats:italic>rbc</jats:italic>L sequences with GenBank <jats:italic>rbc</jats:italic>L sequences that represent 40 additional countries globally. We found 26 molecular operational taxonomic units (mOTUs) in Taiwan, some of which are cryptic. Phylogeographical analysis revealed three potential introduced mOTUs in Taiwan, which exhibit no local genetic variation in Taiwan and are distributed across continents. Also, we posit that some presumably endangered freshwater red algae may be preserved in aquaria, an unintentional <jats:italic>ex situ</jats:italic> conservation site for these organisms that are vulnerable to water pollution from anthropogenic disturbances. Collectively, these data suggest that freshwater red algae have been hitchhiking and dispersed via the aquarium trade, an important and overlooked mechanism of introduction of these organisms across the globe.</jats:p>

A multifaceted ecological assessment reveals the invasion of the freshwater red macroalga Montagnia macrospora (Batrachospermales, Rhodophyta) in Taiwan

“…As a turf-like diploid sporophyte (also known as chantransia; Figure 1B), the alga produces mostly asexual monospores and vegetative fragments (which can attach to other aquatic organisms and surfaces) and rarely sexual meiospores (Kato et al, 2009). In fact, the specimens of M. macrospora previously observed in a survey of Taiwan aquaria and streams were mostly spore-producing chantransia (Zhan et al, 2021).…”

“…including Hat Ya (southern Thailand, Mayla Peninsula), Hong Kong, Taiwan, and Okinawa (Japan). A genetic analysis based on the plastid marker rbcL suggested that there were at least two independent introductions of M. macrospora into East Asia (Zhan et al, 2021). One of the introductions was revealed by a haplotype in aquarium shops in Taiwan and Japan, and the other introduction by a different haplotype in aquarium shops in Hong Kong and Thailand (Zhan et al, 2021).…”

“…A genetic analysis based on the plastid marker rbcL suggested that there were at least two independent introductions of M. macrospora into East Asia (Zhan et al, 2021). One of the introductions was revealed by a haplotype in aquarium shops in Taiwan and Japan, and the other introduction by a different haplotype in aquarium shops in Hong Kong and Thailand (Zhan et al, 2021). Thus, Zhan et al (2021) proposed that M. macrospora was introduced into East Asia via the global aquarium trade.…”

“…One of the introductions was revealed by a haplotype in aquarium shops in Taiwan and Japan, and the other introduction by a different haplotype in aquarium shops in Hong Kong and Thailand (Zhan et al, 2021). Thus, Zhan et al (2021) proposed that M. macrospora was introduced into East Asia via the global aquarium trade. Although not traded as an ornamental organism, M. macrospora can hitchhike on ornamental organisms (e.g., aquatic plants), which are traded between South America and Taiwan (Zhan et al, 2021).…”

“…Thus, Zhan et al (2021) proposed that M. macrospora was introduced into East Asia via the global aquarium trade. Although not traded as an ornamental organism, M. macrospora can hitchhike on ornamental organisms (e.g., aquatic plants), which are traded between South America and Taiwan (Zhan et al, 2021). It is unclear whether or not M. macrospora has become a naturalized species or an invasive species since its introduction into East Asia.…”