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Less can be more: loss of MHC functional diversity can reflect adaptation to novel conditions during fish invasions.

ABSTRACT: The ability of invasive species to adapt to novel conditions depends on population size and environmental mismatch, but also on genetic variation. Away from their native range, invasive species confronted with novel selective pressures may display different levels of neutral versus functional genetic variation. However, the majority of invasion studies have only examined genetic variation at neutral markers, which may reveal little about how invaders adapt to novel environments. Salmonids are good model systems to examine adaptation to novel pressures because they have been translocated all over the world and represent major threats to freshwater biodiversity in the Southern Hemisphere, where they have become invasive. We examined patterns of genetic differentiation at seven putatively neutral (microsatellites) loci and one immune-related major histocompatibility complex (MHC class II-?) locus among introduced rainbow trout living in captivity (farmed) or under natural conditions (naturalized) in Chilean Patagonia. A significant positive association was found between differentiation at neutral and functional markers, highlighting the role of neutral evolutionary forces in shaping genetic variation at immune-related genes in salmonids. However, functional (MHC) genetic diversity (but not microsatellite diversity) decreased with time spent in the wild since introduction, suggesting that there was selection against alleles associated with captive rearing of donor populations that do not provide an advantage in the wild. Thus, although high genetic diversity may initially enhance fitness in translocated populations, it does not necessarily reflect invasion success, as adaptation to novel conditions may result in rapid loss of functional MHC diversity.

SUBMITTER: Monzon-Arguello C

PROVIDER: S-EPMC3797483 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature

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Less can be more: loss of MHC functional diversity can reflect adaptation to novel conditions during fish invasions.

Monzón-Argüello Catalina C Garcia de Leaniz Carlos C Gajardo Gonzalo G Consuegra Sofia S

Ecology and evolution 20130822 10

The ability of invasive species to adapt to novel conditions depends on population size and environmental mismatch, but also on genetic variation. Away from their native range, invasive species confronted with novel selective pressures may display different levels of neutral versus functional genetic variation. However, the majority of invasion studies have only examined genetic variation at neutral markers, which may reveal little about how invaders adapt to novel environments. Salmonids are go ...[more]

PMID: 24223274

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Project description:AimExotic species' introductions together with extinction of native species represent the main mechanisms driving biotic homogenization of freshwater fish assemblages around the world. While generally ichtyofaunistic realms transit towards biotic homogenization, for conservation purposes it is essential to understand what specific mechanisms are promoting it on particular areas or regions. Here, we report the occurrence of biotic homogenization in 29 Chilean watersheds, analyzing its β-diversity (including turnover and nestedness) and predicting future trends.LocationContinental Chile (18o-56o S).MethodsWe determined fish composition per basin for historical and current assemblages; extant native, exotic, and extinct species were recorded as 1 (presence) or 0 (absence) in two matrices basins × species. For each matrix, we calculated the turnover (βsim), nestedness (βnes), and β-diversity (βsor); then, we obtained Δβsim, Δβnes, and Δβsor, as the arithmetical difference between basin pairs over time. In addition, we search for explanatory variables correlating Δβsim, Δβnes, and Δβsor with geographical and land use variables. Finally, simulating events of species introduction (i.e., invasion) and extinction, we generated 15 hypothetical assemblages, looking to establish future trends towards biotic change in Chilean basins.ResultsSpecies turnover and β-diversity significantly decreased from historical to current assemblages (Δβsim = -0.084; Δβsor = -0.061, respectively), while the species nestedness did not show significant changes (Δβnes = 0.08). Biotic changes have been driven mainly by the introduction of 28 exotic species, with a minor role of extinctions (one species) and translocations (0 species) of native species. Changes in β-diversity were negatively correlated with area, elevation, and geographical distance between basins but not with land-use nor human population. Finally, the analysis of 15 future assemblages predicts a significant decrease of β-diversity and turnover, and an increase for species nestedness, this time promoted by an increase in the extinction of native species.Main conclusionChilean basins show a significant decrease of the distributional β-diversity and species turnover of the freshwater fish fauna, evidencing a trend towards biotic homogenization. This trend is shared with other Neotropical basins; however, specific mechanisms driving it show different magnitude. Changes in the β-diversity components do not show correlation with variables associated to land use, thus suggesting that casual introductions of freshwater fishes in Chile follow an opportunistic mode related to commercial use. According to future scenarios simulated, biotic homogenization should increase further, mainly as consequence of increased native extinctions.

Project description:BackgroundPlants are always exposed to dynamic light. The photosynthetic light use efficiency of leaves is lower in dynamic light than in uniform irradiance. Research on the influence of environmental factors on dynamic photosynthesis is very limited. Nitrogen is critical for plants, especially for photosynthesis. Low nitrogen (LN) decreases ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and thus limits photosynthesis. The decrease in Rubisco also delays photosynthetic induction in LN leaves; therefore, we hypothesized that the difference of photosynthetic CO2 fixation between uniform and dynamic light will be greater in LN leaves compared to leaves with sufficient nitrogen supply.ResultsTo test this hypothesis, soybean plants were grown under low or high nitrogen (HN), and the photosynthetic gas exchange, enzyme activity and protein amount in leaves were measured under uniform and dynamic light. Unexpectedly, dynamic light caused less photosynthetic suppression, rather than more, in LN leaves than in HN leaves. The underlying mechanism was also clarified. Short low-light (LL) intervals did not affect Rubisco activity but clearly deactivated fructose-1,6-bisphosphatase (FBPase) and sedoheptulose-1,7-bisphosphatase (SBPase), indicating that photosynthetic induction after a LL interval depends on the reactivation of FBPase and SBPase rather than Rubisco. In LN leaves, the amount of Rubisco decreased more than FBPase and SBPase, so FBPase and SBPase were present in relative excess. A lower fraction of FBPase and SBPase needs to be activated in LN leaves for photosynthesis recovery during the high-light phase of dynamic light. Therefore, photosynthetic recovery is faster in LN leaves than in HN leaves, which relieves the photosynthetic suppression caused by dynamic light in LN leaves.ConclusionsContrary to our expectations, dynamic light caused less photosynthetic suppression, rather than more, in LN leaves than in HN leaves of soybean. This is the first report of a stress condition alleviating the photosynthetic suppression caused by dynamic light.

Project description:Implantable chemoport is a very useful device for long-term venous access for infusion of chemotherapeutic drugs and other agents. There are few studies from resource poor countries reporting complications of chemoport. The aim of the present study is to evaluate the feasibility of chemoport insertion without image guidance and by closed technique without direct visualisation of a major vein (mainly IJV) and to study the complications associated with the procedure. This was a prospective observational study which analysed 263 patients who underwent chemoport insertion. The medical records of these patients were analysed for the patient characteristics, diagnosis, port-related complications, and their management. A total of 263 patients who were harbouring either locoregionally advanced or metastatic tumour requiring either chemotherapy or targeted treatment or both were included in the study. In total, 133 (50.57%) were female patients and 130 were male patients (49.43%). A total of 236 patients (89.73%) underwent port insertion procedures under local anaesthesia. None of the patients had any major intra-operative complications. Postoperatively, 4 patients (1.52%) were found to have port catheter malposition; 3 out of this 4 were corrected under IITV guidance as a second procedure under local anaesthesia only. One patient (0.38%) required formal removal and replacement of port. Four patients (1.52%) developed IJV thrombosis requiring port removal and anti-coagulation. One patient (0.38%) developed thrombus in the right atrium. There were 2 port site infections (0.74%) requiring port removal (SSI cat. 5). Low complication rates of port insertion were observed in the present, large, prospective study. Complication rates may be further reduced by using a well-designed procedure, experienced surgeons, an aseptic environment, ultrasound-guided puncture, and fluoroscopy with contrast media.Supplementary informationThe online version contains supplementary material available at 10.1007/s13193-020-01265-6.

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Less can be more: loss of MHC functional diversity can reflect adaptation to novel conditions during fish invasions.

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Less can be more: loss of MHC functional diversity can reflect adaptation to novel conditions during fish invasions.

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