DOI: 10.5061/dryad.8cz8w9gt3
title: Data from: A multifaceted ecological assessment reveals the invasion of the freshwater red macroalga Montagnia macrospora (Batrachospermales, Rhodophyta) in Taiwan

description: Invasive freshwater macroalgae are rarely described. Montagnia
 macrospora is a freshwater red alga introduced from
 South America to East Asia via the global aquarium trade. The earliest
 occurrence record of this alga in Taiwan is dated 2005. To determine
 whether M. macrospora has become invasive in Taiwan and
 to understand the traits that facilitated its invasion, we took a
 multifaceted approach that combines examination of ecological background
 and population genetic analysis. Our island-wide survey showed
 that M. macrospora is widespread in the field
 across Taiwan, where the climate greatly differs from that of South
 America, and can self-sustain for nearly a decade. Our population genetic
 analysis revealed a lack of genetic diversity of M.
 macrospora in Taiwan, consistent with the hypothesis
 that the alga expanded through asexual reproduction. Moreover, during our
 long-term ecological assessments and field surveys, we observed thatM.
 macrospora is an ecological generalist that can survive in a wide
 range of temperature, pH, illumination, and nutrient enrichment. Taken
 together, our data suggest that M. macrospora has successfully
 invaded the freshwater ecosystems ofTaiwan, likely due to its
 ability to disperse asexually and to grow under broad environmental
 conditions. We hope that our study brings attention to invasive
 freshwater algae, which have been overlooked in conservation planning and
 management.
description: <strong>Nutrient_levels_location_Mmacrospora_presence</strong> For nutrient measurements, water samples of 1,000 mL were collected and stored in an ice box during transportation. Then, measurements of four nutrients (ammonia, nitrate, nitrite, and phosphate, in mg L<sup>-1</sup>) were taken in our laboratory using a SMARTSpectro spectrophotometer (LaMotte, Maryland, USA). <strong>Taoyuan_stream_survey_data</strong> Field surveys between August 2012 and October 2013 were carried out at four sites along a small spring-fed stream in Longtang District, Taoyuan City, Taiwan (24°53'09.3"N, 121°13'54.1"E), once a month. The four sites were 10 m apart from each other, going from downstream (site 1) to upstream (site 4).  The percent cover of <em>M. macrospora</em> at each site was calculated as the average of the percent cover of five quadrats of the site positioned along a transect perpendicular to the streamflow at each site. Water temperature, light intensity (µmol photons m<sup>-2</sup> s<sup>-1</sup>), pH, conductivity (µS cm<sup>-1</sup>), turbidity (mg L<sup>-1</sup>), water velocity (m s<sup>-1</sup>), and water depth (cm) were measured at each of the four sites by using a thermometer, a portable digital photometer (DL-204 EZDO, Chi-Jui Instrument Enterprise, Taiwan), a pH meter (PH30, CLEAN Instruments Co., Taiwan), a meter for both conductivity and turbidity (CON30, CLEAN Instruments Co., Taiwan), a flow probe (FP111 Global Water, Smart Scientific Corp., Taiwan), and a ruler, respectively. The levels of four nutrients (i.e., ammonia, nitrate, nitrite, and phosphate) were measured in our laboratory from 1,000 ml water samples using a SMARTSpectro spectrophotometer (LaMotte, Maryland, USA). Precipitation data at Zhongli automatic weather station, located in Zhongli District, Taoyuan City was retrieved from the Central Weather Bureau, Taiwan (https://www.cwb.gov.tw), and hours of daylight were retrieved from the National Oceanic and Atmospheric Administration (NOAA) (https://gml.noaa.gov/grad/solcalc/). 
description: # Data from: A multifaceted ecological assessment reveals the invasion of
 the freshwater red macroalga Montagnia macrospora (Batrachospermales,
 Rhodophyta) in Taiwan
 [https://doi.org/10.5061/dryad.8cz8w9gt3](https://doi.org/10.5061/dryad.8cz8w9gt3) ## Description of the data and file structure #### **Nutrient\_levels\_location\_Mmacrospora\_presence** Nutrient levels (ammonia, nitrate, nitrite, and phosphate, in mg L-1) at the eight locations in Taiwan where *M. macrospora* was found, and in the artificial reservoir pond in Okinawa (Japan), where the presence of *M. macrospora* was first reported in East Asia (Kato et al., 2009).  #### **Taoyuan\_stream\_survey\_data** *M. macrospora* percent cover and environmental parameters measured during the field survey between August 2012 and October 2013 were carried out at four sites along a small spring-fed stream in Longtang District, Taoyuan City, Taiwan (24°53'09.3"N, 121°13'54.1"E). #### **Taoyuan\_stream\_survey\_stats\_Rcodes** R codes utilized to perform one-way ANOVA, regression analysis, and Pearson correlation analysis based on the data from the field survey carried out between August 2012 and October 2013 out at four sites along a small spring-fed stream in Longtang District, Taoyuan City, Taiwan (24°53'09.3"N, 121°13'54.1"E). ## Sharing/Access information The *cox2*-*3* sequence newly generated in this study is available at NCBI GenBank under accession numbers: OK442460.