Discrimination between native and non-native disulfides by protein-disulfide isomerase

The folding assistant and chaperone protein-disulfide isomerase (PDI) catalyzes disulfide formation, reduction, and isomerization of misfolded proteins. PDI substrates are not restricted to misfolded proteins; PDI catalyzes the dithiothreitol (DTT)-dependent reduction of native ribonuclease A, microbial ribonuclease, and pancreatic trypsin inhibitor, suggesting that an ongoing surveillance by PDI can test even native disulfides for their ability to rearrange. The mechanism of reduction is consistent with an equilibrium unfolding of the substrate, attack by the nucleophilic cysteine of PDI followed by direct attack of DTT on a covalent intermediate between PDI and the substrate. For native proteins, the rate constants for PDI-catalyzed reduction correlate very well with the rate constants for uncatalyzed reduction by DTT. However, the rate is weakly correlated with disulfide stability, surface exposure, or local disorder in the crystal. Compared with native proteins, scrambled ribonuclease is a much better substrate for PDI than predicted from its reactivity with DTT; however, partially reduced bovine pancreatic trypsin inhibitor (des(14-38)) is not. An extensively unfolded polypeptide may be required by PDI to distinguish native from non-native disulfides.     

Morphological differences between native and non-native pumpkinseed in traits associated with locomotion

Adaptive strategies in morphology can significantly influence the successful invasion and establishment of non-native species. Since its introduction, the pumpkinseed (Lepomis gibbosus), a sunfish of North American origin, has spread throughout most of Europe, including the Iberian Peninsula. We hypothesized that 12 morphological traits, functionally significant for locomotion, would differ according to geographic origin (native/non-native) and habitat type (fluvial/lacustrine). Using flow-through raceways, we simultaneously reared F₁ young-of-the-year pumpkinseed from two native and two non-native populations, produced from adults kept in a common environment. Morphometric measurements were recorded at the beginning and end of the 90-day rearing period. Median-fin size and placement differed significantly between native and non-native populations, whereas paired fin size differed between fluvial and lacustrine populations. Other functionally significant traits, such as body width, also differed between native and non-native populations. Spanish populations were considered to have acquired these adaptive external morphologies through successive generations, following the species’ range expansion through the variable environments of the Iberian Peninsula.     

A role for N-glycanase in the cytosolic turnover of glycoproteins

Successful maturation determines the intracellular fate of secretory and membrane proteins in the endoplasmic reticulum (ER). Failure of proteins to fold or assemble properly can lead to their retention in the ER and redirects them to the cytosol for degradation by the proteasome. Proteasome inhibitors can yield deglycosylated cytoplasmic intermediates that are the result of an N-glycanase activity, believed to act prior to destruction of these substrates by the proteasome. A gene encoding a yeast peptide:N-glycanase, PNG1, has been cloned, but this N-glycanase and its mammalian homolog were reported to be incapable of deglycosylating full-length glycoproteins. We show that both the yeast PNG1 enzyme and its mammalian homolog display N-glycanase activity towards intact glycoproteins. As substrates, cytosolic PNGase activity prefers proteins containing high-mannose over those bearing complex type oligosaccharides. Importantly, PNG1 discriminates between non-native and folded glycoproteins, consistent with a role for N-glycanase in cytoplasmic turnover of glycoproteins.     

Leaf morpho-physiological comparison between native and non-native plant species in a Mediterranean island

Biological Invasions - Islands tend to be more prone to plant invasions than mainland regions, with the Mediterranean ones not being an exception. So far, a large number of studies on comparing...     

Ecological niche differentiation between native and non-native shrimps in the northern Baltic Sea

Invasions of non-native species are modifying global biodiversity but the ecological mechanisms underlying invasion processes are still not well understood. A degree of niche separation of non-native and sympatric native species can possibly explain the success of novel species in their new environment. In this study, we quantified experimentally and in situ the environmental niche space of caridean shrimps (native Crangon crangon and Palaemon adspersus, non-native Palaemon elegans) inhabiting the northern Baltic Sea. Field studies showed that the non-native P. elegans had wider geographical range compared to native species although the level of habitat specialization was similar in both Palaemon species. There were clear differences in shrimp habitat occupancy with P. elegans inhabiting lower salinity areas and more eutrophicated habitats compared to the native species. Consequently, the non-native shrimp has occupied large areas of the northern Baltic Sea that were previously devoid of the native shrimps. Experiments demonstrated that the non-native shrimp had higher affinity to vegetated substrates compared to native species. The study suggests that the abilities of the non-native shrimp to thrive in more stressful habitats (lower salinity, higher eutrophication), that are sub-optimal for native shrimps, plausibly explain the invasion success of P. elegans.     

Multiple spatial scales affect direct and indirect interactions between a non-native and a native species

Plant Ecology - Plant–plant interactions influence community assembly and species responses to environmental change. However, species interactions are complex phenomena influenced by context...     

Misfolding of glycoproteins is a prerequisite for peptide: N-glycanase mediated deglycosylation

Peptide:N-glycanase (PNGase) is a deglycosylating enzyme that catalyzes the hydrolysis of the beta-aspartylglycosylamine bond of aspargine-linked glycopeptides and glycoproteins. Earlier studies from our laboratory indicated that PNGase catalyzed de-N-glycosylation was limited to glycopeptide substrates, but recent reports have demonstrated that it also acts upon full-length misfolded glycoproteins. In this study, we utilized two glycoprotein substrates, yeast carboxypeptidase and chicken egg albumin (ovalbumin), to study the deglycosylation activity of yeast PNGase and its mutants. Our results provide further evidence that PNGase acts upon full-length glycoprotein substrates and clearly establish that PNGase acts only on misfolded or denatured glycoproteins.     

Fbs1 protects the malfolded glycoproteins from the attack of peptide:N-glycanase

Fbs1 is a cytosolic lectin putatively operating as a chaperone as well as a substrate-recognition subunit of the SCF(Fbs1) ubiquitin ligase complex. To provide structural and functional basis of preferential binding of Fbs1 to unfolded glycoproteins, we herein characterize the interaction of Fbs1 with a heptapeptide carrying Man3GlcNAc2 by nuclear magnetic resonance (NMR) spectroscopy and other biochemical methods. Inspection of the NMR data obtained by use of the isotopically labeled glycopeptide indicated that Fbs1 interacts with sugar-peptide junctions, which are shielded in native glycoprotein, in many cases, but become accessible to Fbs1 in unfolded glycoproteins. Furthermore, Fbs1 was shown to inhibit deglycosylation of denatured ribonuclease B by a cytosolic peptide:N-glycanase (PNGase). On the basis of these data, we suggest that Fbs1 captures malfolded glycoproteins, protecting them from the attack of PNGase, during the chaperoning or ubiquitinating operation in the cytosol.     

Response of native and non-native ruderals to natural and human disturbance

The ruderal strategy is widely shared among non-native plants, providing a general explanation for the commonly observed positive effects of disturbance on invasions. How native ruderals respond to disturbance and how their abundance compares to that of non-native ruderals remains, however, poorly understood. Similarly, little is known about the role that disturbance type plays in the coexistence between native and non-native ruderals. We proposed that natural disturbance favors native over non-native ruderals, whereas novel anthropogenic disturbance favors non-natives over natives. To assess our general hypothesis, we conducted extensive field samplings in which we measured relative abundance, richness, and diversity of native and non-native ruderals in sites with natural and anthropogenic disturbance in central Argentina, a system where the ruderal strategy is common to a large number of native and non-native species. We found that natives dominated ruderal communities growing in recently burned grasslands, whereas non-natives dominated in roadsides. Additionally, the richness and diversity of native ruderal species were much greater than those of non-natives in sites with fire and in sites with grazing, but species richness and diversity did not differ between groups in roadsides. Because vegetation evolved with fire in our system and, in contrast, the construction and maintenance of roads is recent in it, these results support our hypothesis. Our work indicates that the ruderal strategy does not seem to suffice to explain why disturbance facilitates invasions. According to our data, species origin interacts with disturbance type to determine dominance in communities with coexisting native and non-native ruderals.     

Germination responses of an invasive species in native and non-native ranges

Studying germination in the native and non‐native range of a species can provide unique insights into processes of range expansion and adaptation; however, traits related to germination have rarely been compared between native and non‐native populations. In a series of common garden experiments, we explored whether differences in the seasonality of precipitation, specifically, summer drought vs summer rain, and the amount and variation of annual and seasonal precipitation affect the germination responses of populations of an annual ruderal plant, Centaurea solstitialis, from its native range and from two non‐native regions with different climates. We found that seeds from all native populations, irrespective of the precipitation seasonality of the region in which they occurred, and non‐native populations from regions with dry summers displayed similarly high germination proportions and rates. In contrast, genotypes from the non‐native region with predominantly summer rain exhibited much lower germination fractions and rates. Also, percent germination was strongly correlated with variation in precipitation in winter, the season that follows germination for C. solstitialis. Specifically, germination was lower for native and non‐native populations experiencing greater variation in winter precipitation. This correlation, however, was greatly influenced by the non‐native region with summer rain, which also exhibited the greatest variation in winter precipitation among studied regions. These results suggest that rather than general climatic patterns, the degree of risk experienced at early developmental stages could exert an important control over the germination strategy of C. solstitialis populations in both native and non‐native ranges. Also, these findings reveal a largely unique germination response in C. solstitialis genotypes growing in the non‐native region with summer rain and high variation in winter precipitation. Our work raises the possibility that rapid adaptive changes in germination strategies may contribute to the success of globally distributed invaders.     

Influences of native and non-native benthivorous fishes on aquatic ecosystem degradation

Invasive common carp Cyprinus carpio has long been identified as a contributor to water quality deterioration, disrupted ecosystem processes, and shifts in biological assemblage structure. In contrast, little information is available regarding the effects of native benthivorous species on aquatic systems despite their functional similarity to common carp. Effects of common carp and the native black bullhead Ameiurus melas on sediment resuspension, nutrient concentrations, macrophytes, and assemblage structure of zooplankton and macroinvertebrates, were experimentally evaluated. We observed decreased water clarity, increased nutrient concentrations, decreased macrophyte biomass, and decreased benthic macroinvertebrate abundance and biomass associated with common carp, regardless of the presence of black bullhead. In contrast, black bullhead increased total phosphorus, and chlorophyll a concentrations and copepod abundance, but had little or no effect on other measured water quality and biological variables when compared to control conditions. Overall, experimental results suggest that although black bullhead tend to be tolerant of degraded ecosystems, they are not a source of physical changes to the environment known to be responsible for perpetuating degraded water quality (e.g., stable state shifts). Therefore, increased abundance of native species, such as black bullhead, following the invasion of common carp, may serve as an indicator of ecological conditions and should not to be assumed as causative.     

Fitness costs of butterfly oviposition on a lethal non-native plant in a mixed native and non-native plant community

Non-native plants may be unpalatable or toxic, but have oviposition cues similar to native plants used by insects. The herbivore will then oviposit on the plant, but the offspring will be unable to develop. While such instances have been described previously, the fitness costs at the population level in the wild due to the presence of the lethal host have not been quantified, for this or other related systems. We quantified the fitness cost in the field for the native butterfly Pieris macdunnoughii in the presence of the non-native crucifer Thlaspi arvense, based on the spatial distributions of host plants, female butterflies and eggs in the habitat and the survival of the larvae in the wild. We found that 2.9 % of eggs were laid on T. arvense on average, with a survival probability of 0, yielding a calculated fitness cost of 3.0 % (95 % confidence interval 1.7–3.6 %) due to the presence of the non-native in the plant community. Survival probability to the pre-pupal stage for eggs laid on two native crucifers averaged 1.6 % over 2 years. The magnitude of the fitness cost will vary temporally and spatially as a function of the relative abundance of the non-native plant. We propose that the fine-scale spatial structure of the plant community relative to the butterflies’ dispersal ability, combined with the females’ broad habitat use, contributes to the fitness costs associated with the non-native plant and the resulting evolutionary trap.     

Dominance of an invasive earthworm in native and non-native grassland ecosystems

More attention is currently being focused on earthworm invasions; however, in many ecosystems the relative abundance of native and invasive earthworm species is unknown. We characterized earthworm populations of two grassland types within the Palouse region: native prairie remnants and Conservation Reserve Program (CRP) set asides planted with exotic grasses. The earthworm community in both grassland types was completely dominated by the exotic-invasive Aporrectodea trapezoides. Only one individual of a native species, Driloleirus americanus (the giant Palouse earthworm), was found in a prairie remnant. No differences were found between prairie remnants and CRP sites for mean earthworm density (24–106 individuals m⁻²) or fresh weight (12–45 g m⁻²). Our results suggest that the combined effects of land-use change, habitat fragmentation and competitive interactions have resulted in the decimation of native earthworm populations and dominance of invasive earthworms in native and non-native grasslands of the Palouse region.     

Variation in inbreeding depression and plasticity across native and non-native field environments

Background and Aims

Since the early 1990s, research on genetic variation of phenotypic plasticity has expanded and empirical research has emphasized the role of the environment on the expression of inbreeding depression. An emerging question is how these two evolutionary ecology mechanisms interact in novel environments. Interest in this area has grown with the need to understand the establishment of populations in response to climate change, and to human-assisted transport to novel environments.

Methods

We compare performance in the field of outcrossed (O) and inbred lines (S1, S2) from 20 maternal families from each of two native populations of Mimulus guttatus. The experiment was planted in California in each population''s home site, in the other populations''s home site, in a novel site within the native range of M. guttatus, and in a novel site within the non-native range in North America. The experiment included nearly 6500 individuals. Survival, sexual reproduction and above-ground biomass were examined in order to evaluate inbreeding depression, and stem diameter and plant height were examined in order to evaluate phenotypic plasticity.

Key Results

Across all field sites, approx. 36 % of plants survived to flowering. Inbreeding depression differed among sites and outcrossed offspring generally outperformed selfed offspring. However, in the native-novel site, self-progeny performed better or equally well as outcross progeny. Significant phenotypic plasticity and genetic variation in plasticity was detected in the two architectural traits measured. The absolute value of plasticity showed the most marked difference between home and non-native novel site or non-native-novel site. Evidence was detected for an interaction between inbreeding and plasticity for stem diameter.

Conclusions

The results demonstrate that during initial population establishment, both inbreeding depression and phenotypic plasticity vary among field sites, and may be an important response to environments outside a species'' currently occupied range. However, the interaction between inbreeding and plasticity may be limited and environment-dependent.     

Parasitism and epibiosis in native and non-native gammarids in freshwater in Ireland

The introduced amphipod crustaceans Gammarus pulex and G. tigrinus are displacing the native G. ducheni celticus in a number of freshwater sites in Northern Ireland. We investigated parasite and epibiont infection in populations in the Rivet Lagan and Lough Neagh where both native and invading species occur. Prevalence of the four parasites and epibionts observed was higher in the native G. d. celticus than in the invading amphipods at both field sites. In Lough Neagh. G. d. celticus individuals suffered higher burdens of the rotifer Embata parasitica and the protozoan Epistylis in comparison with the invading species. These patterns may reflect host specificity by the parasites or may result from different susceptibilities of the native and invading host species. We consider the influence of parasitism on host invasions and resulting species distributions.     

Difference in seasonal activity pattern between non-native and native ants in subtropical forest of Okinawa Island,Japan

Biological invasions by non-native tramp ants are reported throughout the world, particularly in island ecosystems. In Okinawa Island, a subtropical island in south-western Japan, many tramp ants including the invasive ant, Anoplolepis gracilipes, already occur. In this study activity patterns of the ground-foraging tramp and native ants were investigated for one year by using food bait traps at the forest edges where both categories of ants coexist. On a seasonal time scale, activity patterns were different between exotic and native ants. Native ants are active and seemingly more dominant from spring to summer whereas tramp ants become more dominant from autumn to winter. These results suggest there might be temporal niche partitioning between tramp and native ants, and native ants might be able to dominate tramp ants in their suitable seasons.