Stage‐dependent responses to emergent habitat heterogeneity: consequences for a predatory insect population in a coffee agroecosystem

Interactions among members of biological communities can create spatial patterns that effectively generate habitat heterogeneity for other members in the community, and this heterogeneity might be crucial for their persistence. For example, stage‐dependent vulnerability of a predatory lady beetle to aggression of the ant, Azteca instabilis, creates two habitat types that are utilized differently by the immature and adult life stages of the beetle. Due to a mutualistic association between A. instabilis and the hemipteran Coccus viridis – which is A. orbigera main prey in the area – only plants around ant nests have high C. viridis populations. Here, we report on a series of surveys at three different scales aimed at detecting how the presence and clustered distribution of ant nests affect the distribution of the different life stages of this predatory lady beetle in a coffee farm in Chiapas, Mexico. Both beetle adults and larvae were more abundant in areas with ant nests, but adults were restricted to the peripheries of highest ant activity and outside the reach of coffee bushes containing the highest densities of lady beetle larvae. The abundance of adult beetles located around trees with ants increased with the size of the ant nest clusters but the relationship is not significant for larvae. Thus, we suggest that A. orbigera undergoes an ontogenetic niche shift, not through shifting prey species, but through stage‐specific vulnerability differences against a competitor that renders areas of abundant prey populations inaccessible for adults but not for larvae. Together with evidence presented elsewhere, this study shows how an important predator is not only dependent on the existence of two qualitatively distinct habitat types, but also on the spatial distribution of these habitats. We suggest that this dependency arises due to the different responses that the predator's life stages have to this emergent spatial pattern. Interactions among members of biological communities can create spatial patterns that effectively generate habitat heterogeneity for other members in the community and this heterogeneity might be crucial for their persistence. Here we report how a voracious predatory ladybeetle in a coffee farm in Chiapas, Mexico undergoes an ontogenetic niche shift, not through shifting prey species, but through stage‐specific vulnerability differences against a competitor that renders areas of abundant prey populations inaccessible for adults but not for larvae. Our study suggests that the resulting spatial separation of resources may be crucial for the predator population persistence.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108324/1/ece31161.pd

Histoenzymatic and Immunocytochemical Characteristics of Extravillous Trophoblast Cells of Placental Basal Plate as Parameter of Their Function in Hypertensive Pregnancy

An intense activity of enzymes which actively participate in the renin-angiotensinaldosterone system was shown in extravillous trophoblast cells which are involved in the performing of spiral arteries into uteroplacental vessels. The hydrolase activity in villous trophoblast underwent important variations, but it was constant in cells of the extravillous trophoblast. Activity of lysosomal hydrolases, of leucine aminopeptidase and N-acetyl glucosaminidase type, was markedly positive in X-cells, while negative in the villous trophoblast. Beta glucuronidase activity has shown moderate activity in cells of extravillous trophoblast, while in villous trophoblast it was weakly emphasized or negative. Intense activity of prostaglandin E2 dehydrogenase in the way of strongly emphasized microsomal reaction was noted exclusively in extravillous cells of basal plate, especially in perivascular cell groupings. Within all examined enzymes activities, only the membranous activity of alkaline phosphatase was of the same intensity in cells of extravillous trophoblast. Lacking of penetration of these cells into the spiral arteries wall in EPH-gestosis, which also means loss of their close contact with the blood of a pregnant, implicates the practical meaning of these observations

Cytochrome P450-mediated metabolism of N-(2-methoxyphenyl)-hydroxylamine, a human metabolite of the environmental pollutants and carcinogens o-anisidine and o-nitroanisole

N-(2-methoxyphenyl)hydroxylamine is a human metabolite of the industrial and environmental pollutants and bladder carcinogens 2-methoxyaniline (o-anisidine) and 2-methoxynitrobenzene (o-nitroanisole). Here, we investigated the ability of hepatic microsomes from rat and rabbit to metabolize this reactive compound. We found that N-(2-methoxyphenyl)hydroxylamine is metabolized by microsomes of both species mainly to o-aminophenol and a parent carcinogen, o-anisidine, whereas 2-methoxynitrosobenzene (o-nitrosoanisole) is formed as a minor metabolite. Another N-(2-methoxyphenyl)hydroxylamine metabolite, the exact structure of which has not been identified as yet, was generated by hepatic microsomes of rabbits, but its formation by those of rats was negligible. To evaluate the role of rat hepatic microsomal cytochromes P450 (CYP) in N-(2-methoxyphenyl)hydroxylamine metabolism, we investigated the modulation of its metabolism by specific inducers of these enzymes. The results of this study show that rat hepatic CYPs of a 1A subfamily and, to a lesser extent those of a 2B subfamily, catalyze N-(2-methoxyphenyl)hydroxylamine conversion to form both its reductive metabolite, o-anisidine, and o-aminophenol. CYP2E1 is the most efficient enzyme catalyzing conversion of N-(2-methoxyphenyl)hydroxylamine to o-aminophenol

Antagonistic interactions between an invasive alien and a native coccinellid species may promote coexistence

1. Despite the capacity of invasive alien species to alter ecosystems, the mechanisms underlying their impact remain only partly understood. Invasive alien predators, for example, can significantly disrupt recipient communities by consuming prey species or acting as an intraguild predator (IGP). 2. Behavioural interactions are key components of interspecific competition between predators,yet these are often overlooked invasion processes. Here, we show how behavioural, nonlethal IGP interactions might facilitate the establishment success of an invading alien species. 3. We experimentally assessed changes in feeding behaviour (prey preference and consumption rate) of native UK coccinellid species (Adalia bipunctata and Coccinella septempunctata),whose populations are, respectively, declining and stable, when exposed to the invasive intraguild predator, Harmonia axyridis. Using a population dynamics model parameterized with these experimental data, we predicted how intraguild predation, accommodating interspecific behavioural interactions, might impact the abundance of the native and invasive alien species over time. 4. When competing for the same aphid resource, the feeding rate of A. bipunctata significantly increased compared to the feeding in isolation, while the feeding rate of H. axyridis significantly decreased. This suggests that despite significant declines in the UK, A. bipunctata is a superior competitor to the intraguild predator H. axyridis. In contrast, the behaviour of non-declining C. septempunctata was unaltered by the presence of H. axyridis. 5. Our experimental data show the differential behavioural plasticity of competing native and invasive alien predators, but do not explain A. bipunctata declines observed in the UK. Using behavioural plasticity as a parameter in a population dynamic model for A. bipunctata and H. axyridis, coexistence is predicted between the native and invasive alien following an initial period of decline in the native species. We demonstrate how empirical and theoretical techniques can be combined to understand better the processes and consequences of alien species invasions for native biodiversity

PP2A/B55 and Fcp1 regulate Greatwall and Ensa desphorylation during mitotic exit

Entry into mitosis is triggered by activation of Cdk1 and inactivation of its counteracting phosphatase PP2A/B55. Greatwall kinase inactivates PP2A/B55 via its substrates Ensa and ARPP19. Both Greatwall and Ensa/ARPP19 are regulated by phosphorylation, but the dynamic regulation of Greatwall activity and the phosphatases that control Greatwall kinase and its substrates are poorly understood. To address these questions we applied a combination of mathematical modelling and experiments using phospho-specific antibodies to monitor Greatwall, Ensa/ARPP19 and Cdk substrate phosphorylation during mitotic entry and exit. We demonstrate that PP2A/B55 is required for Gwl dephosphorylation at the essential Cdk site Thr194. Ensa/ARPP19 dephosphorylation is mediated by the RNA Polymerase II carboxy terminal domain phosphatase Fcp1. Surprisingly, neither Fcp1 nor PP2A appear to essential to dephosphorylate the bulk of mitotic Cdk1 substrates following Cdk1 inhibition. Taken together our results suggest a hierarchy of phosphatases coordinating Greatwall, Ensa/ARPP19 and Cdk substrate dephosphorylation during mitotic exit

Effect of within-species plant genotype mixing on habitat preference of a polyphagous insect predator

The effects of within-species plant genotype mixing on the habitat preference of a polyphagous ladybird were studied. Plant species diversity is often claimed to positively affect habitat preferences of insect predators, but the effects of within-species genotype diversity have not been extensively studied. In a field experiment with different barley (Hordeum vulgare) genotypes in mixed and pure stands, adult seven-spot ladybird Coccinella septempunctata, a polyphagous predator, preferred a specific combination of genotypes over the single genotypes alone before aphids had arrived in the crop, and again when aphids were emigrating. In laboratory experiments on adult ladybird orientation to odour from barley, ladybirds were attracted/arrested by the mixed odour of the same barley genotype mixture that was preferred in the field. Exposure of one barley genotype to volatiles from the other also caused the odour of the exposed plants to become more attractive to ladybirds. The results support the hypothesis that plant volatiles may attract or arrest foraging adult ladybirds, contributing to the selection of favourable habitats, and they show that within-species plant genotype mixing can shape interactions within multitrophic communities

Herbivory by a Phloem-Feeding Insect Inhibits Floral Volatile Production

There is extensive knowledge on the effects of insect herbivory on volatile emission from vegetative tissue, but little is known about its impact on floral volatiles. We show that herbivory by phloem-feeding aphids inhibits floral volatile emission in white mustard Sinapis alba measured by gas chromatographic analysis of headspace volatiles. The effect of the Brassica specialist aphid Lipaphis erysimi was stronger than the generalist aphid Myzus persicae and feeding by chewing larvae of the moth Plutella xylostella caused no reduction in floral volatile emission. Field observations showed no effect of L. erysimi-mediated floral volatile emission on the total number of flower visits by pollinators. Olfactory bioassays suggested that although two aphid natural enemies could detect aphid inhibition of floral volatiles, their olfactory orientation to infested plants was not disrupted. This is the first demonstration that phloem-feeding herbivory can affect floral volatile emission, and that the outcome of interaction between herbivory and floral chemistry may differ depending on the herbivore's feeding mode and degree of specialisation. The findings provide new insights into interactions between insect herbivores and plant chemistry

Oxidation of the carcinogenic non-aminoazo dye 1-phenylazo-2-hydroxy-naphthalene (Sudan I) by cytochromes P450 and peroxidases: a comparative study

Sudan I [1-(phenylazo)-2-hydroxynaphthalene, C.I. Solvent Yellow 14, CAS No: 842-07-9] is used as the compound employed in chemical industry and to color materials such as hydrocarbon solvents, oils, fats, waxes, plastics, printing inks, shoe and floor polishes and gasoline. Such a wide used could result in a considerable human exposure. Sudan I is known to cause developments of tumors in the liver or urinary bladder in rats, mice, and rabbits, and is considered a possible weak human carcinogen and mutagen. This carcinogen is also a potent contact allergen and sensitizer. Here, we compare the data concerning the Sudan I oxidative metabolism catalyzed by cytochrome P450 (CYP) and peroxidase enzymes, which has been investigated in our laboratory during the last two decades. These two types of enzymes are responsible both for Sudan I detoxication and activation. Among the Sudan I metabolites, C-hydroxylated derivatives and a dimer of Sudan I are suggested to be the detoxication metabolites formed by CYPs and peroxidases, respectively. Metabolic activation of Sudan I by both types of enzymes leads to formation of reactive species (the benzenediazonium ion by CYP and Sudan I radicals by peroxidase) that bind to DNA and RNA, generating covalent adducts in vitro and in vivo. Whereas the structure of the major adduct formed by the benzenediazonium ion in DNA has already been identified to be the 8-(phenylazo)guanine adduct, the structures of adducts formed by peroxidase, have not been characterized as yet. Biological significance of the DNA adducts of Sudan I activated with CYP and peroxidase enzymes and further aims of investigations in this field are discussed in this study