Alejandro Bortolus

Invasion of a Reef-builder Polychaete: Direct and Indirect Impacts on the Native Benthic Community Structure

In this work, we evaluate the effect of the introduced reef-building polychaete Ficopomatus enigmaticus on the benthic community and on sediment characteristics of a southwestern Atlantic coastal lagoon. When reefs were experimentally added, density of the native crab Cyrtograpsus angulatus dramatically increased in a short time period. After reefs and crabs were experimentally transplanted as a unit, they decreased the density of the free-living soft-bottom polychaetes Heteromastus similis and Laeonereis acuta. Exclusion/inclusion caging experiments showed that Cyrtograpsus negatively affect the density of soft-bottom polychaetes (H. similis, L. acuta, Nephtys fluviatilis) and ostracodes. Our results showed that this effect is much higher in areas populated by reefs because of the increased density of crabs that find shelter under the reefs. Thus, reefs have a cascading effect on the native benthic community within the areas colonized by them. Analysis of crab stomach contents indicated that crabs feed on a wide variety of prey, including infaunal organisms, small gastropods and also algae. When reefs and crabs were experimentally added, the amount of bivalve shells on superficial sediments increased. Our results suggest that this bivalve shell accumulation and sediment composition are due to the reworking activity of Cyrtograpsus in the sediment where they dig burrows. The invasive habits of Ficopomatus may be favoring crabs to have a major effect on the integrity of the native community in the lagoon. Ficopomatus should be considered a bioengineer organism by creating and regulating refuge for other species, altering the interactions between preexistent species and also by changing the physical factors of the invaded environment.

The enigmatic invasive Spartina densiflora: A history of hybridizations in a polyploidy context

The aim of this study was to explore the origin of the invasive Spartina densiflora by analysing samples from the native region (South America) and from a recently colonized area (California). A combination of various molecular data (chloroplast and nuclear sequences, molecular fingerprint) and ploidy level estimations was used to answer the question whether the reticulate phylogenetic pattern previously detected in S. densiflora was restricted to California, or alternatively, whether a more ancient hybrid origin preceded formation of this species in its native area. We found that this species is heptaploid in both its native and introduced range. Identification of nuclear homeologous sequences indicate that this species has a reticulate origin in its native range, involving a lineage related to the hexaploid clade formed by S. alterniflora, S. foliosa, and S. maritima, and another lineage related to the sub‐Antarctic endemic S. arundinacea that provided the chloroplast genome. The samples from California displayed similar multilocus patterns to the samples from Chile, supporting the hypothesis that this species originated on the southeast American coast (Argentina), from where it eventually spread to the west coast of South America (Chile) first and to the Northern Hemisphere (California) later.

A Characterization of Patagonian Salt Marshes

We combined literature reviews with an analysis of regional cartography, aerial photographs, and satellite images to identify the locations of heretofore-unknown salt marshes along the Patagonian coastline of Argentina. Subsequent ground surveys confirmed the presence of the marshes. While numerous sites still require verification, our surveys confirmed the existence of 27 large coastal salt marshes, which had estimated areas of between 3 and 2400 ha distributed along ∼225 km of coastline. We described the major patterns of landscape physiognomy and community structure at eight of these sites. We classified these marshes as either muddy or rocky marshes, and subdivided them into Spartina and Sarcocornia marshes depending on the dominant vegetation. Muddy marshes were the most common type and showed a clear regional pattern with Spartina-dominated communities in the north (≤ 42°S) and Sarcocornia-dominated systems in the south (≥ 42°S). Plant height and standing crop biomass tended to be lower at higher latitudes, but plant cover showed the opposite trend. Spartina marshes had a more diverse marine macro-invertebrate fauna than Sarcocornia marshes, when the two marsh types occur at similar latitudes. Although the diversity of invertebrates was relatively low along the entire latitudinal range, most marshes supported unique species assemblages.

Habitat complexity and community composition: relationships between different ecosystem engineers and the associated macroinvertebrate assemblages

Several species of ecosystem engineers inhabiting coastal environments have been reported structuring different kinds of communities. The magnitude of this influence often depends on the habitat complexity introduced by the engineers. It is commonly accepted that an increase in habitat complexity will result in an increase in diversity and/or abundance in the associated fauna. The rocky salt marshes along the coast of Patagonia are dominated by cordgrasses, mussels, and barnacles forming a mosaic of engineered habitats with different complexity. This system allows us to address the following questions: how different is a macroinvertebrate assemblage when dominated by different ecosystem engineers? And, is there a positive relationship between increasing habitat complexity and the species richness, diversity and total density of the assemblages? To address these questions, we compared the three ecological scenarios with decreasing habitat complexity: cordgrass–mussel, mussel, and barnacle-engineered habitats. We found a total of 22 taxa mostly crustaceans and polychaetes common to all scenarios. The three engineered habitats showed different macroinvertebrate assemblages, mainly due to differences in individual abundances of some taxa. The cryptogenic amphipod Orchestia gammarella was found strictly associated with the cordgrass–mussel habitat. Species richness and diversity were positively related with habitat complexity while total density showed the opposite trend. Our study suggests that species vary their relative distribution and abundances in response to different habitat complexity. Nevertheless, the direction (i.e., neutral, positive or negative) and intensity of the community’s response seem to depend on the physiological requirements of the different species and their efficiency to readjust their local spatial distribution in the short term.

Running Like Alice and Losing Good Ideas: On the Quasi-Compulsive Use of English by Non-native English Speaking Scientists

The profuse publication of articles and books debating the use and abuse of English as a global language for science (Garfield 1962; Amonn 2001; Montgomery 2004) evidences the timeless persistence of a complex and unsolved problem with deep multi-cultural roots. Many non-native English speaking (hereafter, non-NES) countries currently exert enormous explicit or implicit pressure on their scientists to publish in international high-impact peer-reviewed journals, which are in English. This pressure is promoted under the premise that the impact factor of a journal is positively related to the quality of the science it publishes. This premise implies that publishing in high-impact peer-reviewed journals is the best way to demonstrate the excellence of local scientists. Whether we agree with this premise or not, and independently of its legitimacy (Clavero 2010a, b; Guariguata et al. 2010), we have long accepted it as the paradigmatic scenario that rules the way we do science and publish scientific results worldwide. Indeed, “this is the way it is”, as Gannon (2008) wrote in a singular editorial for the prestigious journal EMBO-Reports. In Argentina, for instance, the National Council for Scientific and Technologic Research evaluates a researcher’s professional performance with a system that assigns decreasing scores to papers in the first, second, and third portions of a list of international journals with decreasing impact factors. Below the third portion of that list, the system places papers published in local journals, usually with no impact factor. Consequently, most of our researchers do anything in their power to publish their papers in journals in the first and second thirds of the list, indirectly withdrawing their support from local editorials and journals (including manuscript submissions and valuable editorial assistance). Hence, the aim of publishing papers in high-impact peer-reviewed journals eventually leads non-NES scientists to almost exclusively produce papers in English, leading to a self-perpetuating cycle in which English becomes an increasingly important and ineludible tool to communicate scientific findings (Tardy 2004). In this article, I propose that the ultimate problem in this scenario is that the obligation to write exclusively in English is progressively deteriorating non-NES schools of thought, the quality of interactions between scientists and people and between advisors and advisees, and the integrity of local natural resources and biodiversity. Furthermore, this obligation hinders the emergence of many potentially brilliant minds.

What would Darwin have written now

We often wonder how many of the pristine places left on Earth we can protect from deterioration before it is too late. The assumption that remote regions remain pristine plays a key role in directing policies for regional environmental management and conservation, and affects the local and global financial impetus to do so. In this paper, we use Argentinean Patagonia and the SW Atlantic as examples to argue that the assumption ‘remote region = pristine region’ is unjustified and based on a lack of information rather than on scientific evidence. We also discuss the major existing environmental threats to this supposedly ‘pristine’ region, and use emblematic examples to provide a more realistic picture of the regional environmental integrity and to set recommendations directed to improve environmental management and conservation within this context.

Guiding authors to reliably use taxonomic names.

I thank E. Schwindt and anonymous reviewers for valuable suggestions. My work is supported by CONICET (PIP190) and FONCyT (PICT N°2206).

Flooding Effect on the Distribution of Native Austral Cordgrass Spartina densiflora in Patagonian Salt Marshes

ABSTRACT Idaszkin, Y.L.; Bortolus, A., and Bouza, P.J., 2014. Flooding effect on the distribution of native austral cordgrass Spartina densiflora in Patagonian salt marshes. Plant zonation is one of the most conspicuous ecological features of salt marshes worldwide. In Patagonian salt marshes the cordgrass Spartina alterniflora forms dense monospecific stands along the lowest marsh level, while the higher levels are dominated by Spartina densiflora or Sarcocornia perennis. In this study, we coupled field transplants combined with neighbor exclusion treatments and greenhouse experiments to evaluate the effect of submersion and waterlogged anoxic soil in the determination of the lower distribution limit of S. densiflora in Central Patagonian salt marshes within its native range. In the field experiment, no S. densiflora survived the frequent tidal submersion by approximately 2 m of seawater in the low marsh, independent of the S. alterniflora neighbors presence, while in the greenhouse experiment, all plants were able to tolerate strongly reducing soil conditions. Our results suggest that the absence of S. densiflora in the low marsh level is a consequence of the effect of the submersion, independent of the presence of S. alterniflora neighbors and of the strong soil anoxia. Our results contribute to optimize the efforts addressed to control or eradicate this exotic species in salt marshes where it is invading.

Ecological impacts of the austral-most population of Crassostrea gigas in South America: a matter of time?

Abstract The Pacific oyster Crassostrea gigas is one of the most invasive species worldwide. This oyster has a preponderant ecological role in the invaded environments, for example structuring the benthic community through the provision of micro-habitats. Twenty-five years after its introduction in Argentina, the species is colonizing new areas along the coast, extending northwards and southwards its local distribution. In this study, we provide the first ecological characterization of the southern-most population of C. gigas; where the composition, density, richness and diversity of the macroinvertebrate assemblages associated with zones with oysters were compared with zones where it is absent at four different times of the year. Additionally, the main epibionts taxa settled on the oyster shells were studied. Our results showed differences in the assemblage composition between zones. However, these differences were not consistent throughout the year. Furthermore, density, richness and diversity were higher in the zones with oysters only in one of the surveys and the parameters did not differ between zones in the remaining months. Moreover, the majority of oysters were used as settlement substrate by the sessile common species present in the area. Thus, our work provides new information about the ecology of C. gigas in recently invaded areas that enhance our understanding of the role that facilitation plays in physically stressful ecosystems and the importance that density and time since the invasion may have in the engineering effects of the species.

Differential benthic community response to increased habitat complexity mediated by an invasive barnacle

Invasive species threaten native ecosystems worldwide. However, these species can interact positively with local communities, increasing their richness, or the abundance of some species. Many invasive species are capable of influencing the habitat itself, by ameliorating physical stress and facilitating the colonization and survival of other organisms. Barnacles are common engineer species that can change the physical structure of the environment, its complexity, and heterogeneity through their own structure. Balanus glandula is a native barnacle of the rocky shores of the west coast of North America. In Argentina, this invasive species not only colonizes rocky shores but it also has successfully colonized soft-bottom salt marshes, where hard substrata are a limiting resource. In these environments, barnacles form three-dimensional structures that increase the structural complexity of the invaded salt marshes. In this work, we compared the composition, density, richness, and diversity of the macroinvertebrate assemblages associated with habitats of different structural complexity in two Patagonian salt marshes where B. glandula is well established. Our results showed differences in the relative distribution and abundances of the invertebrate species between habitats of different complexities. Furthermore, the response of the communities to the changes in the structural complexity generated by B. glandula was different in the two marshes studied. This highlights the fact that B. glandula facilitates other invertebrates and affect community structure, mainly where the settlement substrata (Spartina vs. mussels) are not functionally similar to the barnacle. Thus, our work shows that the rocky shore B. glandula is currently a critical structuring component of the native invertebrate community of soft-bottom environments where this species was introduced along the coast of southern South America.