Long-term responses of macroinvertebrate assemblages to the 2011 eruption of the Puyehue-Cordón Caulle volcanic complex, Chile.

In June 2011 the Puyehue-Cordón Caulle volcanic complex (PCCVC) erupted, ejecting around 950 million metric tons of volcanic ash and pyroclastic rock, generating habitat destruction, environmental deterioration and devastation of ecological communities in rivers near the volcanic fissure. We evaluate the long-term effect of this eruptive event on the recovery of the diversity of aquatic macroinvertebrates, collecting biological and environmental information from 2011 to 2018 in visibly impacted Chilean rivers (Gol-Gol and Nilahue) and not visibly impacted rivers (Calcurrupe and Chanleufu). With the macroinvertebrate records we developed a recovery coefficient based on their diversity before and after the eruption. The results show that before the eruption (2009-2010), the accumulated family richness and mean diversity in the Gol-Gol River were higher than that observed post-eruption in rivers visibly impacted and not visibly impacted. Between 2013 and 2018, 17 families recolonized the Gol-Gol River, as well as 10 new families that were not recorded before the eruption. The richness of families post-eruption was negatively related to the increase in the concentration of total suspended solids, affecting the successional changes and recovery in the medium term. The recovery coefficient indicates that seven years after the eruption the diversity of macroinvertebrates still shows lower levels than those recorded before the eruptive event, with predominance of a slow recovery phase. Families of orders Ephemeroptera, Plecoptera and Trichoptera that were dominant before the eruption of the PCCVC began to recover the richness of taxa two years later, Plecoptera reaching 50% recolonization in 2018, Ephemeroptera 33.3% and Trichoptera 30%. In contrast, Diptera reached 100% recovery by 2018 and chironomids increased since 2015, becoming the dominant taxon during intermediate recovery in the Gol-Gol River. The recovery of macroinvertebrates in the Gol-Gol River is related to their modes of dispersal, feeding and the decrease in ash concentration.

Predicting the potential distribution of the endemic seabird Pelecanus thagus in the Humboldt Current Large Marine Ecosystem under different climate change scenarios.

BACKGROUND: The effects of global climate change on species inhabiting marine ecosystems are of growing concern, especially for endemic species that are sensitive due to restricted distribution. One method employed for determining the effects of climate change on the distribution of these organisms is species distribution modeling. METHODS: We generated a model to evaluate the potential geographic distribution and breeding distribution of the Peruvian pelican (Pelecanus thagus). Based on maximum entropy modeling (MaxEnt), we identified the environmental factors that currently affect its geographic distribution and breeding. Then we predicted its future distribution range under two climate change scenarios: moderate (rcp 2.6) and severe (rcp 8.5). RESULTS: The mean daytime temperature range and marine primary productivity explain the current potential distribution and breeding of the pelican. Under the future climate change scenarios, the spatial distribution of the pelican is predicted to slightly change. While the breeding distribution of the pelican can benefit in the moderate scenario, it is predicted to decrease (near -20 %) in the severe scenario. DISCUSSION: The current potential geographic distribution of the pelican is influenced to a large extent by thermal conditions and primary productivity. Under the moderate scenario, a slight increase in pelican breeding distribution is predicted. This increase in habitable area is explained by the climatic conditions in southern Chile, and those climatic conditions will likely be similar to the current conditions of the central coast of Chile. We predict that the coasts of southern Chile will constitute an important refuge for the conservation of the Peruvian pelican under future climate change scenarios.

Genetic Differentiation and Origin of Naturalized Rainbow Trout Populations From Southern Chile, Revealed by the mtDNA Control Region Marker.

Numerous self-sustaining naturalized or introduced populations of rainbow trout (Oncorhynchus mykiss) are widely distributed throughout the freshwaters of southern Chile. In this study, analysis of the mitochondrial DNA control region (CR) marker was conducted to investigate the level of genetic divergence among populations and their phylogenetic relationships with respect to native lineages. This information provided a framework to interpret the genetic structure and origin that was shaped during historical trout introduction efforts. To this end, we analyzed eleven naturalized populations of lakes and rivers from five basins. The CR marker revealed five haplotypes. The overall haplotype (H) and nucleotide (Π) diversities were 0.684 ± 0.030 and 0.00460 ± 0.00012, respectively. Global F ST was 0.169, with several pairwise F ST estimates showing significant differences (P < 0.05). The exact test of population differentiation corroborated this result (P < 0.001). Significant geographic structure was found (P < 0.05), with variations explained primarily by differences within populations (61.65%) and among group basins (20.82%). Maximum likelihood phylogenetic analysis resolved two distinct clades with medium bootstrap support when naturalized populations were aligned in conjunction with reference native lineages. The haplotype network revealed a close association between naturalized populations and four main haplotypes representative of three native ecotypes or lineages from western North America (rainbow trout, steelhead trout and redband trout). These results indicate a genetic population structuring for naturalized rainbow trout from southern Chile and an origin probably represented by multiple lineages sources. Thus, mitochondrial DNA data strongly suggest that stocking of rainbow trout from different origins may have occurred during or after the initial introduction efforts.

Effects of exotic fish farms on bird communities in lake and marine ecosystems.

Salmon farming is a widespread activity around the world, also known to promote diverse environmental effects on aquatic ecosystems. However, information regarding the impact of salmon farming on bird assemblages is notably scarce. We hypothesize that salmon farming, by providing food subsidies and physical structures to birds, will change their local community structure. To test this hypothesis, we conducted a seasonal monitoring of bird richness, abundance, and composition at paired salmon pen and control plots in two marine and two lake sites in southern Chile, from fall 2002 to summer 2004. Overall, salmon farming had no significant effects on species richness, but bird abundance was significantly and noticeably higher in salmon pens than in controls. Such aggregation was mainly accounted for by the trophic guilds of omnivores, diving piscivores, carrion eaters, and perching piscivores, but not by invertebrate feeders, herbivores, and surface feeders. Species composition was also significantly and persistently different between salmon pens and controls within each lake or marine locality. The patterns described above remained consistent across environment types and seasons indicating that salmon farming is changing the community structure of birds in both lake and marine habitats by promoting functional and aggregation responses, particularly by favoring species with broader niches. Such local patterns may thus anticipate potential threats from the ongoing expansion of the salmon industry to neighboring areas in Chile, resulting in regional changes of bird communities, toward a less diverse one and dominated by opportunistic, common, and generalist species such as gulls, vultures, and cormorants.