Size structure and dynamics of an invasive population of lineage 2 of Asparagopsis taxiformis (Florideophyceae) in the Alboran Sea

Abstract

SUMMARYIn this study, we present basic population data of the red macroalga Asparagopsis taxiformis, widely recognized as invasive in the Mediterranean Sea. A 13-month field study was carried out on a population located in southern Spain, addressing its phenology, population dynamics and demography. We further tested whether biomass variations were related to environmental variables at the study site. Gametophytes were present year-round while tetrasporophytes were only found in spring and summer. Recruitment capacity and vegetative growth of the gametophytes are discussed as important modulators for the population structure and enhancers of its persistence. Thallus size-time histograms revealed a high prevalence of small shoots that showed high mortality that was not related to self-thinning. Biomass of A. taxiformis was higher from March to July. Vegetative growth was the main way the gametophyte population was maintained, although the presence of tetrasporophytes and fertile gametophytes in the field confirms that sexual reproduction also occurs. Its continuous and high recruitment, in terms of the number of smallest shoots, makes this southern population of A. taxiformis a source of future invasive populations due to the intensive maritime traffic in the region.

Assessing global range expansion in a cryptic species complex: insights from the red seaweed genus Asparagopsis (Florideophyceae)

“…Invasion risk is herein inferred to be high for Asparagopsis taxiformis L2 on the basis of range shift dynamics predicted by SDM and superior performance of vegetative propagation capability for A. taxiformis L2 associated with constant presence of fertile individuals of A. taxiformis L2 throughout the year, indicative of sexual propagation (Zanolla et al. , ,b,c).…”

“…Along the Andalusian coastline, A. taxiformis L2 gametophytes persist and abound along a depth range of 1–15 m throughout the year (Zanolla et al. ). The presence of L2 in these habitats may compromise both diversity and species richness of native communities, including protected maërl assemblages (Zanolla et al.…”

“…These populations are well established, presenting both sexual reproduction and vegetative propagation, with the subsequent production of dispersal units (i.e., tetrasporophytes; Zanolla et al. ,b).…”

Structure and temporal dynamics of a seaweed assemblage dominated by the invasive lineage 2 of Asparagopsis taxiformis (Bonnemaisoniaceae, Rhodophyta) in the Alboran Sea

“…This feature may be related to the weak environmental gradients to which the area is exposed (Zanolla et al, 2017a). It is noteworthy that diversity (and thus evenness) values dropped to zero in the months when A. taxiformis IL2 reached its highest biomass scores.…”

“…Thus, processes such as invasional meltdown (Simberloff & Von Holle, 1999), plus a highly altered recipient ecosystem (i.e., unbalanced species composition, poor species richness) may have facilitated the settlement of A. taxiformis IL2 in the region. All these factors have been extensively cited as facilitators of macroalgal invasions (Occhipinti-Ambrogi, 2007;Andreakis & Schaffelke, 2012), to which should be added the intrinsic characteristics of the invader, such as broad phenotypic plasticity (Zanolla et al, 2015), effective vegetative propagation mechanisms (Zanolla et al, 2017a), the production of novel genetic variants through sexual reproduction (Zanolla et al, 2017b) and genetic characteristics that have rapid adaptive and expansive potential (Zanolla et al, 2018).…”