Introduced cats Felis catus eating a continental fauna: inventory and traits of Australian mammal species killed

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Caffeine sensitivity of native RyR channels from normal and malignant hyperthermic pigs: effects of a DHPR II-III loop peptide

Enhanced sensitivity to caffeine is part of the standard tests for susceptibility to malignant hyperthermia (MH) in humans and pigs. The caffeine sensitivity of skeletal muscle contraction and Ca²⁺ release from the sarcoplasmic reticulum is enhanced, but surprisingly, the caffeine sensitivity of purified porcine ryanodine receptor Ca²⁺-release channels (RyRs) is not affected by the MH mutation (Arg⁶¹⁵Cys). In contrast, we show here that native malignant hyperthermic pig RyRs (incorporated into lipid bilayers with RyR-associated lipids and proteins) were activated by caffeine at 100- to 1,000-fold lower concentrations than native normal pig RyRs. In addition, the results show that the mutant ryanodine receptor channels were less sensitive to high-affinity activation by a peptide (C_S) that corresponds to a part of the II–III loop of the skeletal dihydropyridine receptor (DHPR). Furthermore, subactivating concentrations of peptide C_S enhanced the response of normal pig and rabbit RyRs to caffeine. In contrast, the caffeine sensitivity of MH RyRs was not enhanced by the peptide. These novel results showed that in MH-susceptible pig muscles 1) the caffeine sensitivity of native RyRs was enhanced, 2) the sensitivity of RyRs to a skeletal II–III loop peptide was depressed, and 3) an interaction between the caffeine and peptide C_S activation mechanisms seen in normal RyRs was lost. calcium ion homeostasis; excitation-contraction coupling; ryanodine receptor polymorphisms; muscle contraction     

Modeling and Analysis of a Density-Dependent Stochastic Integral Projection Model for a Disturbance Specialist Plant and Its Seed Bank

In many plant species dormant seeds can persist in the soil for one to several years. The formation of these seed banks is especially important for disturbance specialist plants, as seeds of these species germinate only in disturbed soil. Seed movement caused by disturbances affects the survival and germination probability of seeds in the seed bank, which subsequently affect population dynamics. In this paper, we develop a stochastic integral projection model for a general disturbance specialist plant-seed bank population that takes into account both the frequency and intensity of random disturbances, as well as vertical seed movement and density-dependent seedling establishment. We show that the probability measures associated with the plant-seed bank population converge weakly to a unique measure, independent of initial population. We also show that the population either persists with probability one or goes extinct with probability one, and provides a sharp criteria for this dichotomy. We apply our results to an example motivated by wild sunflower (Helianthus annuus) populations, and explore how the presence or absence of a “storage effect” impacts how a population responds to different disturbance scenarios.     

Within-tree distributions of the Sirex noctilio Fabricius (Hymenoptera: Siricidae)--parasitoid complex and development of an optimal sampling scheme

Little is known about the introduced European woodwasp, Sirex noctilio F. (Hymenoptera: Siricidae), and its hymenopteran parasitoid complex in North America. To assess within-tree and landscape-level densities and distributions of these insects, and develop a more cost effective approach for sampling and monitoring S. noctilio, 18 infested pines (12 P. resinosa Aiton and six P. sylvestris L.) were felled from six stands within three regions in central New York and cut into 0.5-m bolts. Bolts were carefully split to recover all siricids (S. noctilio and native siricids) and parasitoids. In total, 2,558 siricids were recovered; 1,972 siricid larvae and 586 teneral adult S. noctilio. Parasitism of siricids, a majority of which were S. noctilio based on larval rearing results, was 16.4% with Ibalia leucospoides ensiger Norton causing 10.7% of the documented mortality. Numbers of siricids and parasitoids declined 33-86% from the northern to the southern sampling regions, peak insect densities occurred in sections of the bole 15-19 cm in diameter and numbers of insects were generally higher in P. sylvestris than P. resinosa according to the highest ranked zero-inflated poisson and probit regression models. Bark thickness was not correlated with siricid or parasitoid species densities. We also describe sampling plans where as few as two 0.5-m samples from infested trees provided reliable within-tree insect densities.     

Global asymptotic stability of plant-seed bank models

Many plant populations have persistent seed banks, which consist of viable seeds that remain dormant in the soil for many years. Seed banks are important for plant population dynamics because they buffer against environmental perturbations and reduce the probability of extinction. Viability of the seeds in the seed bank can depend on the seed’s age, hence it is important to keep track of the age distribution of seeds in the seed bank. In this paper we construct a general density-dependent plant-seed bank model where the seed bank is age-structured. We consider density dependence in both seedling establishment and seed production, since previous work has highlighted that overcrowding can suppress both of these processes. Under certain assumptions on the density dependence, we prove that there is a globally stable equilibrium population vector which is independent of the initial state. We derive an analytical formula for the equilibrium population using methods from feedback control theory. We apply these results to a model for the plant species Cirsium palustre and its seed bank.