Association of wintering raptors with Conservation Reserve Enhancement Program grasslands in Pennsylvania

ABSTRACT Conservation grasslands can provide valuable habitat resource for breeding songbirds, but their value for wintering raptors has received little attention. We hypothesized that increased availability of grassland habitat through the Conservation Reserve Enhancement Program (CREP) has resulted in an increase or redistribution in numbers of four species of raptors in Pennsylvania since 2001. We tested this by analyzing winter raptor counts from volunteer surveys, conducted from 2001 to 2008, for Red‐tailed Hawks (Buteo jamaicensis), Rough‐legged Hawks (Buteo lagopus), Northern Harriers (Circus cyaneus), and American Kestrels (Falco sparverius). During that period, numbers of wintering Northern Harriers increased by more than 20% per year. Log‐linear Poisson regression models show that all four species increased in the region of Pennsylvania that had the most and longest‐established conservation grasslands. At the county scale (N= 67), Bayesian spatial models showed that spatial and temporal population trends of all four species were positively correlated with the amount of conservation grassland. This relationship was particularly strong for Northern Harriers, with numbers predicted to increase by 35.7% per year for each additional 1% of farmland enrolled in CREP. Our results suggest that conservation grasslands are likely the primary cause of the increase in numbers of wintering Northern Harriers in Pennsylvania since 2001.     

Feeding preferences and performance of an aquatic lepidopteran on macrophytes: plant hosts as food and habitat

Although host preferences in phytophagous insects may be generated by several factors, few studies have simultaneously examined several potential host choice determinants. In this study we tested the impact of the following potential host choice determinants on host preference of the semi-aquatic lepidopteran Munroessa gyralis (Pyralidae): growth on different host plants; protein content, polyphenolic content, toughness, and chemical extracts of different host plants; prior feeding experience; and predation pressure on the caterpillar by fishes. Two water lilies, Brasenia schreberi and Nymphaea odorata, were preferred in cafeteria-style feeding experiments over 14 other species of vascular plants. The most preferred water lily (Brasenia) also afforded the fastest growth relative to three other species on which growth was measured. Feeding preferences across species were unrelated to protein content, polyphenolic content, or toughness. Domiciles constructed by caterpillars from leaf fragments were protective from field assemblages of fishes, but domiciles made from preferred or unpreferred host species conferred no significant protection from fish in the laboratory. Caterpillars responded positively to chemical cues of water lilies, and prior feeding experience increased preference for an otherwise unpreferred water lily (Nuphar advena) within the life-span of individual caterpillars. M. gyralis is a generalist herbivore exhibiting modest preference induction and preferences for and among members of the family Nymphaeaceae. Our results suggest that relative growth rates, chemical cues, and previous feeding experience are important factors determining feeding preference. Protein content, polyphenolic content, and toughness appear less important, and the importance of fish predators remains in question. As pupation seems to occur exclusively on Nymphaea, we suggest that host use may be restricted due to life-stage-specific developmental constraints that are not apparent from the results of growth or preference assays. It is currently unknown how often specific life-stages may restrict host use, but our work suggests this as a potentially important area of inquiry.     

Mitochondrial alternative oxidase acts to dampen the generation of active oxygen species during a period of rapid respiration induced to support a high rate of nutrient uptake

When wild type (wt) tobacco ( Nicotiana tabacum L. cv. Petit Havana SR1) suspension cells were grown under phosphate (P) limitation, they contained large amounts of mitochondrial alternative oxidase (AOX). When these cells were resupplied with P, there was a large, immediate and sustained stimulation of respiration to support a period of rapid P uptake. Two lines of evidence suggest that the abundant level of AOX present in wt cells contributed to this stimulated rate of respiration. First, when P-limited transgenic antisense tobacco cells (AS8) lacking AOX were resupplied with P, the stimulation of respiration was much less dramatic even though these cells displayed similar rates of P uptake. Second, while the stimulated rate of respiration in AS8 cells was insensitive (as expected) to the AOX inhibitor n -propyl gallate (nPG), much of the stimulated rate of respiration in wt cells could be inhibited by nPG. Given the non-phosphorylating nature of AOX respiration, wt cells required higher rates of electron transport to O₂ than AS8 cells to support similar rates of P uptake. The utilization of AOX by wt cells during P uptake was apparently not occurring because the cytochrome (Cyt) pathway alone could not fully support the rate of P uptake, as the respiration of cells lacking AOX (either untreated AS8 cells or wt cells treated with nPG) supported similar rates of P uptake as wt cells with abundant AOX. Rather, we provide in vivo evidence that the utilization of AOX during the period of high respiration supporting P uptake was to dampen the mitochondrial generation of active oxygen species (AOS).     

Cystic fibrosis: low frequency of DF508 mutation in 2 population samples from Rio de Janeiro, Brazil

Blood samples from 44 unrelated cystic fibrosis (CF) patients from Rio de Janeiro, Brazil, were analyzed for the 8 European CF mutations. Six homozygous and 15 heterozygous carriers of the DF508 mutation were found, corresponding to 47.7% of CF patients (allele frequency 0.3068). The G542X and G551D mutations were also observed with allele frequencies of 0.0227 and 0.0114, respectively. An analysis of the DF508 mutation in 291 randomly chosen, healthy individuals was performed, and only 3 heterozygous carriers were identified. These results show that the frequency of the DF508 allele in Rio de Janeiro is much lower than the world average; this may be due to the extremely heterogeneous ethnic admixture of the study population. By combining the results of these 2 different samples (CF patients and random population) and admixture data from Rio de Janeiro, we can estimate the CF incidence in this population to be 1:3542 individuals. However, taking into account the Rio de Janeiro ethnic admixture, we can find an estimate of 1:6902 individuals.     

Genetic diversity of Typha latifolia (Typhaceae) and the impact of pollutants examined with tandem-repetitive DNA probes

Genetic diversity at variable-number-tandem-repeat (VNTR) loci was examined in the common cattail, Typha latifolia (Typhaceae), using three synthetic DNA probes composed of tandemly repeated “core” sequences (GACA, GATA, and GCAC). The principal objectives of this investigation were to determine whether: (1) the previously reported almost complete lack of polymorphism at allozyme loci in this species was indicative of a reduced amount of genetic diversity at VNTR loci as well; (2) VNTR markers were informative about possible clonal propagation; and (3) significant differences in genetic structure of sampling sites were associated with differences in environmental levels of pollutants at those sites. Previously, widespread sampling across the eastern United States, surveying across ten allozyme loci, has detected only two genotypes, involving a difference at a single locus, among 104 populations. In this study, the amount of genetic diversity detected at VNTR loci: (1) among ramets (N = 40; 40 genotypes detected) collected at ∼8-km intervals along a 320-km transect; (2) among ramets (N = 220; 117 genotypes detected) from five study sites separated by 50–3000 m; and (3) even among ramets within each study site [N = 44 per site; from 13 to 34 genotypes detected per site (270 m²)] exceeds that previously found in those more geographically widespread allozyme surveys. Among the 260 ramets analyzed here, the mean number of bands scored per individual was 48.61 (SD = 2.80). Mean genetic similarity among ramets collected along the 320-km transect was 0.91, which was within the range of mean genetic similarity within the five study sites (range: 0.89–0.95). Among the five study sites, 61% of the samples analyzed appeared to be clonal ramets, with up to 12 clones detected for 44 ramets sampled within a site. Clones grew intermingled and ranged up to 39 m in extent. Permutation tests of genetic similarity revealed significant genetic differentiation between each of the five study sites. Consistent with the previous allozyme studies, T. latifolia was characterized by extremely low genetic variation relative to levels of polymorphism detected at VNTR loci in other plant species. Estimated heterozygosity among ramets along the 320-km transect ranged from 0.11 to 0.13, while that within the five study sites ranged from 0.05 to 0.12. Estimates of F_st (0.32–0.41) also indicated considerable genetic subdivision among these stands. Significantly higher genetic diversity was detected at the two study sites that chemistry and toxicity data indicate to be the most severely impacted by pollutants. Although this correlation does not establish cause and effect, the results of this study indicate that the analysis of genetic diversity at VNTR loci may be a useful tool for monitoring anthropogenic-induced changes in the genetic structure of natural populations of plants.     

Mass-transfer-limited nitrate uptake on a coral reef flat,Warraber Island,Torres Strait,Australia

Previous research has identified a relationship between the rate of dissipation of turbulent kinetic energy, , and the mass-transfer-limited rate of uptake by a surface, herein called the ^1/4 law, and suggests this law may be applicable to nutrient uptake on coral reefs. To test this suggestion, nitrate uptake rate and gravitational potential energy loss have been measured for a section of Warraber Island reef flat, Torres Strait, northern Australia. The reef flat section is 3 km long, with a 3 m tidal range, and on the days measured, subject to 6 m s^–1 tradewinds. The measured nitrate uptake coefficient, S , on two consecutive days during the rising tide was 1.23±0.28 and 1.42±0.52×10^–4 m s^–1. The measured loss of gravitational potential energy across the reef flat, GPE , on the same rising tides over a 178 m section was 208±24 and 161±20 kg m^–1 s^–2. Assuming the GPE is dissipated as turbulent kinetic energy in the water column, and using the ^1/4 law, the mass-transfer-limited nitrate uptake coefficient, S_MTL , on the two days was 1.57±0.03 and 1.45±0.04×10^–4 m s^–1. Nitrate uptake on Warraber Island reef flat is close to the mass-transfer limit, and is determined by oceanographic nitrate concentrations and energy climate.Communicated by B.C. Hatcher