Using Statistical Population Reconstruction to Estimate Demographic Trends in Small Game Populations

ABSTRACT Statistical population reconstruction offers a robust approach to demographic assessment for harvested populations, but current methods are restricted to big-game species with multiple age classes. We extended this approach to small game and analyzed 14 years of age-at-harvest data for greater sage-grouse (Centrocercus urophasianus) in Oregon, USA, in conjunction with radiotelemetry data to reconstruct annual abundance levels, recruitment, and natural survival probabilities. Abundance estimates ranged from a low of 26,236 in 1995 to a high of 39,492 in 2004. Annual abundance estimates for adult males were correlated with a spring lek count index (r = 0.849, P < 0.029). We estimated the average annual harvest mortality for the population to be 0.028, ranging from 0.021 to 0.031 across years. We estimated the probability of natural survival of adult females to be 0.818 ( = 0.052), somewhat higher than that of adult males (Ŝ = 0.609, = 0.163). Our precision in reconstructing the population was hampered by low harvest rates and the few birds tagged in the radiotelemetry investigations. Despite these issues, our analysis illustrates how modern statistical reconstruction procedures offer a flexible framework for demographic assessment using commonly collected data. This approach offers a useful alternative to small-game indices and would be most appropriate for species with 5 or more years of age-at-harvest data and moderate-to-heavy harvest rates.     

Sex pheromones and trail‐following pheromone in the basal termites Zootermopsis nevadensis (Hagen) and Z. angusticollis (Hagen) (Isoptera: Termopsidae: Termopsinae)

In the context of an evolutionary study of the chemical communication in termites, sex pheromones and trail‐following pheromones were investigated in two Termopsidae, Zootermopsis nevadensis and Z. angusticollis. In these species, in which the presence of sex‐specific pheromones has been demonstrated previously, the chemical structure of the female sex pheromone has now been identified as (5E)‐2,6,10‐trimethylundeca‐5,9‐dienal and the male sex pheromone as (+)‐ or (?)‐syn‐4,6‐dimethyldodecanal. The amount of sex pheromone was estimated at 5–10 ng per individual in females and 2–5 ng in males. Because these two sympatric species do not differ in their pheromonal chemical composition, reproductive isolation is probably mediated chiefly by differences in dispersal flight chronology. The trail‐following pheromone was shown to be composed of the same compound as the male sex pheromone, that is syn‐4,6‐dimethyldodecanal. The compound syn‐4,6‐dimethyldodecanal was 10 times more active than the racemic (+/?)‐syn + (+/?)‐anti‐4,6‐dimethyldodecanal in eliciting trail‐following. The amount of syn‐4,6‐dimethyldodecanal was estimated at 0.1–0.5 ng per pseudergate. Regarding the phylogenetic aspects, the nature of the female sex pheromone of Zootermopsis is structurally akin to the trail‐following pheromone of Mastotermes darwiniensis of Mastotermitidae and Porotermes adamsoni and Stolotermes victoriensis of Termopsidae. Interestingly, the nature of the trail‐following pheromone of the Termopsinae Zootermopsis is clearly different from that of the Porotermitinae P. adamsoni and the Stolotermitinae S. victoriensis, which mirrors recent molecular data on the paraphyly of Termopsidae. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 519–530.     

Action of the herbicides neburon and siduron on membrane permeabilities in potato tuber mitochondria

The herbicides neburon and siduron are uncouplers of oxidative phosphorylation in potato tuber (Solanum tuberosum L. cv. Bintje) mitochondria. Their effect on the ion permeabilities of the mitochondrial membrane was investigated using the acid-base pulse technique, swelling experiments and integrity tests. Both herbicides permeabilize the membrane to H⁺ ions. They have no action on the permeabilities of K⁺ and Fe(CN)^3?₆. The swelling observed with Ca²⁺ was better interpreted as an effect on membrane structure than as a true swelling. Diuron, a parent compound that does not uncouple oxidative phosphorylation, does not act on Ca²⁺-induced apparent swelling.     

Hybridization and introgression across different ploidy levels in the Neotropical orchids Epidendrum fulgens and E. puniceoluteum (Orchidaceae)

The hypothesis of gene flow between species with large differences in chromosome numbers has rarely been tested in the wild, mainly because species of different ploidy are commonly assumed to be reproductively isolated from each other because of instantaneous and strong postzygotic barriers. In this study, a broad‐scale survey of molecular variation was carried out between two orchid species with different ploidy levels: Epidendrum fulgens (2n = 2x = 24 chromosomes) and Epidendrum puniceoluteum (2n = 4x = 52 chromosomes). To test the strength of their reproductive barriers, we investigated the distribution of genetic variation in sympatric and allopatric populations of these two species and conducted crossing experiments. Nuclear and plastid microsatellite loci were used to genotype 463 individuals from eight populations across the geographical range of both species along the Brazilian coastal plain. All six sympatric populations analysed presented hybrid zones, indicating that hybridization between E. fulgens and E. puniceoluteum is a common phenomenon. Bayesian assignment analysis detected the presence of F₁ and F₂ individuals and also signs of introgression, demonstrating a high potential for interspecific gene flow. Introgression occurs preferentially from E. fulgens to E. puniceoluteum. Pure parental individuals of both species display strong genotype–habitat associations, indicating that environment‐dependent selection could be acting in all hybrid zones. This study suggests that hybridization and introgression are evolutionary processes playing a role in the diversification of Epidendrum and indicates the importance of investigations of hybrid zones in understanding reproductive barriers and speciation processes in Neotropical orchid species.     

Productivity Estimates From Upland Bird Harvests: Estimating Variance and Necessary Sample Sizes

Abstract: Harvest of upland game birds in concert with sampling of age ratios from wings can yield important biological information about populations. Although estimates of productivity are commonly produced, they are often not accompanied by a measure of variance. Thus, we developed standard error estimates for sample productivity ratios, compared 4 methods for creating confidence intervals for population productivity ratios, and developed a test and the corresponding sample size requirements for comparing 2 population productivity ratios. We applied these techniques to greater sage-grouse (Centrocercus urophasianus) wing-data collected in Oregon, USA (1993–2005). Computer simulations indicated that backtransforming the Wilson's score interval on the proportion of immatures in the sample results in the most reliable confidence intervals among the methods considered. We recommend to managers measuring conservation action outcomes with productivity ratios to consider the appropriate sample sizes for the spatial and temporal scale of their monitoring programs.     

Kinesis in Euplotes vannus-Ethological and Electrophysiological Characteristics of Chemosensory Behavior

ABSTRACT. Equally dispersed Euplotes vannus cells accumulate inside a drop of supernatant of a bacteria suspension that is surrounded by a reference solution. In the drop, frequencies of stops and backward jerks are tenfold increased. The sequences of directional changes and translocations prevent cells from leaving the chemostimulant region, as if they were trapped. This behavior is quickly induced after casual arrival in the drop and not by chemotactic influence over a larger distance. With intracellular recordings, we have found a K⁺ conductance decrease in chemically stimulated cells that prolongs the duration of spontaneously occurring depolarizations to 600-1,700 ms by delaying repolarization. The freely fluctuating membrane potential shifts to more depolarized levels, although the total potential range is expanded in the positive and negative direction by 5.5 and 3.8 mV, respectively. Chemosensory behavior is explained and discussed with respect to these electrophysiological events.     

Thermal and hydric implications of diurnal activity by a small tropical frog during the dry season

Amphibians are typically intolerant of high temperatures and dehydrating conditions, and small species are particularly susceptible to desiccation. The rockhole frog, Litoria meiriana (Hylidae), is diurnal and is often observed on rocks in the sun near streams in tropical Australia. These hot, desiccating conditions are avoided by most frog species. We measured the microclimate in the areas used by frogs and the activity, body temperatures and hydric state of free‐ranging individuals of this small frog. We also used plaster models to further explore the dynamic nature of hydric state by combining estimates of water loss and water uptake with behavioural observations of activity and microhabitat selection. Both direct measures and estimates of dynamic hydric state indicated that free‐ranging frogs generally maintained a hydric state above 95% of full hydration, but occasionally, particularly during the afternoon, frogs allowed their hydric state to fall as low as 85%. Body temperatures of frogs remained below the critical thermal maximum (CT_max) even when the frogs were in the sun, because this species has no cutaneous resistance to evaporative water loss and so they cool by evaporation. However, during the hotter part of the day, on dry sunny substrates, the hydric state of the frogs could fall to near lethal hydration states (approximately 70% of full hydration) within a short period (approximately 20 min). Thus, the threat of desiccation appears to be more limiting than the threat of overheating. These diurnal frogs rely on frequent bouts of rehydration to support their ability to venture onto hot, dry rocks during the day.