Publicaciones

Landscape connectivity among remnant populations of guanaco (Lama guanicoe Müller, 1776) in an arid region of Chile impacted by global change

Espinoza, M. I., Gouin, N., Porcile, F. A. S., Aspe, D. L., & Bertin, A.

Connectivity between populations plays a key role in the long-term persistence of species in fragmented habitats. This is of particular concern for biodiversity preservation in drylands, since water limited landscapes are typically characterized by little suitable habitat cover, high habitat fragmentation, harsh matrices, and are being rapidly degraded at a global scale. In this study, we modelled landscape connectivity between 11 guanaco Lama guanicoe populations in Chile’s arid Norte Chico, a region that supports the last remnant coastal populations of this emblematic herbivore indigenous to South America. We produced a habitat suitability model to derive a regional surface resistance map, and used circuit theory to map functional connectivity, investigate the relative isolation between populations, and identify those that contribute most to the patch connectivity network. Predicted suitable habitat for L. guanicoe represented about 25% of the study region (i.e., 29,173 km2) and was heterogeneously distributed along a continuous stretch along the Andes, and discontinuous patches along the coast. As a result, we found that high connectivity current flows in the mid and high Andes formed a wide, continuous connectivity corridor, enabling connectivity between all high Andean populations. Coastal populations, in contrast, were more isolated. These groups demonstrate no inter-population connectivity between themselves, only with higher altitude populations, and for two of them, animal movement was linked to the effectiveness of wildlife crossings along the Pan-American highway. Our results indicate that functional connectivity is an issue of concern for L. guanicoe in Chile’s Norte Chico, implying that future conservation and management plans should emphasize strategies aimed at conserving functional connectivity between coastal and Andean populations, as well as the protection of habitat patches likely to act as stepping stones within the connectivity network.

Año: 2018

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Selective byssus attachment behavior of mytilid mussels from hard-and soft-bottom coastal systems

Aguilera, M. A., Thiel, M., Ullrich, N., Luna-Jorquera, G., & Buschbaum, C

In both sedimentary and rocky coastal habitats, epibenthic mytilid mussels use byssal threads for attachment to the substratum and to form beds with high densities of individuals. Number and attachment strength of byssal threads can be adjusted according to external factors such as hydrodynamic forces or predators, but it is unknown whether mytilid mussels distinguish between substrata of different quality for byssus attachment in different habitat types. In field studies, we examined the attachment strength of the mussel Perumytilus purpuratus growing on Pacific hard- and soft-bottom shores in Chile and of the blue mussel Mytilus edulis from an Atlantic rocky shore in France and a sedimentary shore in the North Sea (Germany), respectively. In additional laboratory experiments, we studied mussel substratum selectivity of both bivalve species from soft and hard bottoms by offering living versus dead, barnacle-fouled vs. unfouled, and firmly attached vs. loose conspecifics. In the field, attachment strength of P. purpuratus on hard bottoms was substantially higher than on soft bottoms even though mussels produced more byssus in the latter habitat. In contrast, blue mussels M. edulis showed only a slightly reduced attachment strength on soft compared to hard bottoms. In the soft-bottom habitat, fouled individuals from the edge of a blue mussel bed were especially strongly attached. In the byssus attachment behavior experiments, P. purpuratus from both habitats showed a significant preference for living conspecifics and those from soft bottoms preferred firmly attached conspecifics. Blue mussels had no preference for particular conspecifics except those from soft-bottom habitats, which preferred fouled over clean mussels. In general, in the choice experiments hard-bottom M. edulis produced more byssus. Our results confirmed that mytilid mussels may show active substratum choice for byssus attachment, which depends on mussel species and habitat type. The results suggest that mussels are adapted to a particular habitat type, with P. purpuratus showing lower adaptation to soft-bottom areas while M. edulis shows successful strategies for both environments.

Año: 2017

Palabras claves: Attachment strength, Byssus production, Mytilid mussels, Selective behavior, Substratum choice

Phylogeography of two intertidal seaweeds, Gelidium lingulatum and G. rex (Rhodophyta: Gelidiales), along the South East Pacific: patterns explained by rafting dispersal?

López, B. A., Tellier, F., Retamal-Alarcón, J. C., Pérez-Araneda, K., Fierro, A. O., Macaya, E. C., Tala, F., & Thiel, M.

Rafting on floating seaweeds facilitates dispersal of associated organisms, but there is little information on how rafting affects the genetic structure of epiphytic seaweeds. Previous studies indicate a high presence of seaweeds from the genus Gelidium attached to floating bull kelp Durvillaea antarctica (Chamisso) Hariot. Herein, we analyzed the phylogeographic patterns of Gelidium lingulatum (Kützing 1868) and G. rex (Santelices and Abbott 1985), species that are partially co-distributed along the Chilean coast (28°S–42°S). A total of 319 individuals from G. lingulatum and 179 from G. rex (20 and 11 benthic localities, respectively) were characterized using a mitochondrial marker (COI) and, for a subset, using a chloroplastic marker (rbcL). Gelidium lingulatum had higher genetic diversity, but its genetic structure did not follow a clear geographic pattern, while G. rex had less genetic diversity with a shallow genetic structure and a phylogeographic break coinciding with the phylogeographic discontinuity described for this region (29°S–33°S). In G. lingulatum, no isolation-by-distance was observed, in contrast to G. rex. The phylogeographic pattern of G. lingulatum could be explained mainly by rafting dispersal as an epiphyte of D. antarctica, although other mechanisms cannot be completely ruled out (e.g., human-mediated dispersal). The contrasting pattern observed in G. rex could be attributed to other factors such as intertidal distribution (i.e., G. rex occurs in the lower zone compared to G. lingulatum) or differential efficiency of recruitment after long-distance dispersal. This study indicates that rafting dispersal, in conjunction with the intertidal distribution, can modulate the phylogeographic patterns of seaweeds.

Año: 2017

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Population variation in drought-resistance strategies in a desert shrub along an aridity gradient: Interplay between phenotypic plasticity and ecotypic differentiation

Carvajal, D. E., Loayza, A. P., Rios, R. S., Gianoli, E., & Squeo, F. A.

Adaptations to drought of deciduous and evergreen species in arid environments are associated with resource-acquisitive (drought avoidance) and resource-conservative (drought tolerance) strategies of water use, respectively. Few studies have addressed whether a single species can exhibit both drought avoidance and drought tolerance strategies along an aridity gradient, and none have evaluated the role of ecotypic differentiation and phenotypic plasticity in shaping such strategies. In the desert shrub Encelia canescens, distributed along an aridity gradient in the Atacama Desert, we hypothesized that populations located in sites with lower and more variable rainfall (northern populations) would exhibit patterns of trait means and plasticity reflecting a water-conservative strategy, while populations in less arid and less variable environments (southern populations) would exhibit a water-acquisitive strategy. We also tested the hypothesis that functional variation in trait means and plasticity are not alternative mechanisms of adaptation to the environment. In a common garden experiment using plants from seeds collected from six populations spanning the species distribution range we found that plants from the northern populations were smaller, had fewer leaves, lower photosynthetic rates and had higher plasticity for root:shoot ratios and lower plasticity for leaf shedding, suggesting a resource-conservative strategy compared to plants from the southern populations, which showed a resource-acquisitive strategy. We found no association between variation in trait means and plasticity, which indicates that these are not alternative mechanisms of plant adaptation to environmental variation. Results suggest that E. canescens populations have evolved different strategies to cope with drought stress depending on their location along the Atacama Desert’s aridity gradient. This gives us a better understanding of the ecological and evolutionary processes that drive phenotypic variation among populations.

Año: 2017

Palabras claves: Atacama desert, Arid environments, Drought resistance, Intraspecific variation, Phenotypic plasticity, Encelia canescens

Conspecific plants are better ‘nurses’ than rocks: consistent results revealing intraspecific facilitation as a process that promotes establishment in a hyper-arid environment

Loayza, A. P., Herrera-Madariaga, M. A., Carvajal, D. E., García-Guzmán, P., & Squeo, F. A.

Harsh environmental conditions in arid ecosystems limit seedling recruitment to microhabitats under nurse structures, such as shrubs or rocks. These structures, however, do not necessarily afford the same benefits to plants because nurse rocks provide only physical nurse effects, whereas nurse plants can provide both physical and biological nurse effects. Nevertheless, if the nurse plant is a conspecific, the benefits it provides may be outweighed by higher mortality due to negative density-dependent processes; consequently, negative density-dependence is expected to limit plants from acting as nurses to their own seedlings. The degree to which an abiotic nurse may be more beneficial than a conspecific one remains largely unexplored. Here, we examine the role and elucidate the mechanisms by which conspecific plants and rocks promote plant establishment in a hyper-arid desert. For 4 years, we examined establishment patterns of Myrcianthes coquimbensis (Myrtaceae), a threatened desert shrub that recruits solely in rock cavities and under conspecific shrubs. Specifically, we characterized these microhabitats, as well as open interspaces for comparison, and conducted germination, seed removal and seedling survival experiments. Our results revealed that conspecific shrubs and nurse rocks modified environmental conditions in similar ways; soil and air temperatures were lower, and water availability was higher than in open interspaces. We found no evidence on negative density-dependent recruitment: seed removal was lowest and seedling emergence highest under conspecific plants, moreover seedling survival probabilities were similar in rock cavities and under conspecific plants. We conclude that the probability of establishment was highest under conspecific plants than in other microhabitats, contrasting what is expected under the Janzen–Connell recruitment model. We suggest that for species living in stressful environments, population regulation may be a function of positive density-dependence and intraspecific facilitation may be a process that promotes the persistence of some plant species within a community.

Año: 2017

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Gall-forming protistan parasites infect southern bull kelp across the Southern Ocean, with prevalence increasing to the south

Blake, C., Thiel, M., López, B. A., & Fraser, C. I.

Protistan pathogens can have devastating effects on marine plants, yet the processes that affect their distributions and infection intensities are poorly understood. Species within the brown algal genus Durvillaea are major ecosystem engineers throughout the sub-Antarctic and cold-temperate Southern Hemisphere, and a newly described genus of protistan parasite, Maullinia, was recently found infecting D. antarctica in Chile. We set out to address 3 key questions. (1) Is there evidence for trans-oceanic dispersal of Maullinia? (2) Does Maullinia infect other Durvillaea species? (3) Does infection prevalence vary throughout the hosts’ ranges? We sampled Maullinia on Durvillaea populations along coasts in Chile (D. antarctica, from 32° to 42°S: 8 sites), Australia (D. potatorum and D. amatheiae, from 36° to 38°S: 5 sites) and sub-Antarctic Marion Island (46°53’47’’S, 37°43’32’’E). We used a genetic marker (18S rRNA) to verify the presence of Maullinia on Durvillaea at all sites and visual surveys of Maullinia galls to assess infection prevalence in Chile and Australia. We confirm that Maullinia infects Australian Durvillaea species, but our results indicate that each host species is parasitised by a different Maullinia lineage. Maullinia infection prevalence increased with latitude. Long- and short-distance dispersal events are inferred to have occurred based on genetic patterns. We conclude that Maullinia protists are broadly distributed and affect multiple host species, including at least 3 Durvillaea species (2 in Australia, and 1 in both Chile and Marion Island), and that environmental factors influence host susceptibility to infection.

Año: 2017

Palabras claves: Pathogen, Macroalgae, Host-specificity, Intertidal, Dispersal, Durvillaea, Maullinia

Uso del Test de Rendimiento Continuo de Conners para diferenciar niños normales y con TDAH en Chile.

Salas-Bravo, S., Gonzalez-Arias, M., Araya-Piñones, A., Valencia-Jimenez, M., & Oyarce-Cortes, S.

El trastorno de déficit atencional con hiperactividad (TDAH) constituye uno de los cuadros de mayor prevalencia durante la niñez. El presente trabajo se focalizó en evaluar si el Test de Rendimiento Continuo de Conners era capaz de discriminar entre niños con y sin TDAH diagnosticados por el docente. Se conformó una muestra no probabilística de 30 niños escolares (15 clínicos y 15 normales) a través de la aplicación del cuestionario de atención. Todos los niños completaron la aplicación del test computarizado de Conners. Se observaron diferencias significativas entre la muestra normal y clínica. Todos los niños seleccionados como normales no encajaron el perfil clínico. Solo el 50% de los casos considerados con TDAH encajaron el perfil clínico. Se analizan las implicancias del sobre/diagnóstico del trastorno.

Año: 2017

Palabras claves: TDAH, Test de rendimiento continuo, Diagnóstico, Escalas diagnósticas

Surface water quality in a sulfide mineral‐rich arid zone in North‐Central Chile: Learning from a complex past, addressing an uncertain future

Flores, M., Núñez, J., Oyarzún, J., Freixas, G., Maturana, H., & Oyarzún, R.

This study presents an analysis of up to 30 years of hydrological variables and selected waterquality parameters (pH, SO4, Fe, Cu, and As) in the upper area of the Elqui River basin inNorth‐Central Chile. A correlation analysis determined statistically significant positive relation-ship for SO4‐Cu, Fe‐As, and Fe‐Cu. In terms of historical behaviour, no statistically significanttrends were detected for precipitation or temperature. In contrast, for flow, there is an overalldecreasing pattern for the entire area of study, although only in one case this trend was statisti-cally significant. Along with the aforementioned analysis, a characterization of the flow‐waterquality relationships is considered for the time period analyzed. Although erratic behaviours wereconfirmed, a negative (i.e., inverse) flow‐concentration relationship was identified for SO4, a pos-itive (i.e., direct) relationship for Fe, and undefined relationships for As and Cu were obtained.From these analyses and based on previous studies on projections regarding climate change forthe Andean region, and in particular for the upper Elqui zone, an estimation of the possible effectsof the change in water regimes on water quality in the area of study is developed. It is likely that adecrease in surface flow, as a consequence of climate change could translate into improvementsin water quality in terms of Fe and eventually As and Cu, but into an impairment in the case ofSO4. In any case, this is a complex situation that demands special attention in the face of indus-trial activities that could be developed in tributaries like the Claro River, which currently play animportant role in depurating or diluting contaminants in the waters of the Elqui River. Finally, itshould be noted that this study addresses an issue that goes beyond the local interest and couldbe used as a reference to compare other transitional environments containing sulphide ores orareas of hydrothermal alterations, which are considered to be highly vulnerable to climate changeand variability.

Año: 2016

Palabras claves: Acid rock drainage, Andean river, arid zone, Coquimbo region

Demography and ecology of southern right whales Eubalaena australis wintering at sub-Antarctic Campbell Island, New Zealand

Torres, L. G., Rayment, W., Olavarría, C., Thompson, D. R., Graham, B., Baker, C. S., Patenaude, N., Bury, S.J., Boren, L., Parker, G., & Carroll, E. L.

Since the decimation of the southern right whale Eubalaena australis population in New Zealand by whaling, research on its recovery has focused on the wintering ground at the Auckland Islands, neglecting potentially important wintering habitat at Campbell Island. For the first time in 20 years we conducted an expedition to sub-Antarctic Campbell Island to document and describe E. australis occupying this wintering habitat. We used a variety of methods including photo-identification, genetic and stable isotope analyses of tissue samples, and visual surveys of abundance and distribution, to provide details on the demography, population connectivity and ecology of E. australis wintering at Campbell Island. Our primary findings include (1) a lack of calves observed at Campbell Island, (2) an age-class bias toward sub-adults encountered at Campbell Island, (3) nine photo-identification matches between individuals observed at Campbell Island and previously documented elsewhere in New Zealand, (4) no genetic differentiation between E. australis at Campbell Island and the broader New Zealand population, (5) increased abundance estimates of E. australis at Campbell Island over the last 20 years, and (6) indications that E. australis forage within the sub-Antarctic region based on stable isotope analyses. Our results confirm that the Auckland Islands are currently the only significant calving area for E. australis in New Zealand, and therefore previous abundance estimates based on demographic data from the Auckland Islands are applicable to the entire New Zealand population of E. australis. However, future periodic surveys to Campbell Island are recommended to monitor population recovery and expansion.

Año: 2017

Palabras claves: Age-class, Genetic analysis, Population connectivity, Stable isotope, Sub-Antarctic, Wintering ground, Parentage analysis