On the Estimation of Heritability from Unbalanced Data

The distribution and moments, of ANOVA estimator of heritability are given under unbalanced random model. These expressions are used to investigate the effect of unbalancedness on the bias and variance/MSE of the estimator and also the validity of certain approximations for its variance, numerically. The computed results reveal that the unbalancedness increases both the bias and variance/MSE of the estimator and the Smith-approximation for the variance of the estimator provides better accuracy.     

Hydrozoan and protozoan epibionts on two decapod species, Liocarcinus depurator (Linnaeus, 1758) and Pilumnus hirtellus (Linnaeus, 1761), from Scotland

Crabs of the species Liocarcinus depurator and Pilumnus hirtellus, collected on the west coast of Scotland, showed hydrozoan and protozoan epibionts. The epibionts of Liocarcinus depurator were the protozoan Ephelota plana and the hydrozoans Clytia gracilis and Leuckartiara sp. The epibionts of Pilumnus hirtellus were the protozoans E. plana and Zoothamnium sp. For Liocarcinus depurator the number of Ephelota per crab fluctuated between 0 and 47 and the greatest number of suctorians were located on the chelipeds, carapace and anterior pereiopods. The hydrozoans, for Liocarcinus depurator, showed densities of 0-20 (Clytia gracilis on the second pereiopod) and 0-507 individuals per crab (Leuckartiara sp., principally on chelipeds, carapace and the fourth right pereiopod). For Pilumnus hirtellus, Ephelota plana showed densities between 3 and 56 individuals per crab, the greatest number of suctorians being located on the same areas as on Liocarcinus depurator. There was a density of 10-69 individuals per crab of Zoothamnium sp. on Pilumnus hirtellus (located on the carapace). Ephelota plana has not been observed previously as an epibiont on crustacea, nor had Zoothamnium sp. as an epibiont on Pilumnus hirtellus. Both hydrozoans, Leukartiara and Clytia, have not been previously described as epibionts on Liocarcinus depurator. Data about the morphological characteristics and distribution of these epibionts are included.     

Nothacrobeles,n. gen., with Descriptions of Four New Species (Nematoda: Cephalobidae)

A new nematode genus, Nothacrobeles, is proposed in the subfamily Acrobelinae. Four new species are described and one new combination made. The five species exhibit a progression from short-to-long, bifurcate, elaborately fringed labial probolae, the longest probolae resembling those of species of Acrobeles.     

Orchid seed sensitivity to nitrate reflects habitat preferences and soil nitrate content

• Orchids are distributed around the world, however, the factors shaping their specific distribution and habitat preferences are largely unknown. Moreover, many orchids are at risk of becoming threatened as landscapes change, sometimes declining without apparent reason. One important factor affecting plant distribution is nutrient levels in the environment. Nitrates can inhibit not only orchid growth and persistence, but also seed germination.
• We used in vitro axenic cultures to exactly determine the germination sensitivity of seven orchid species to nitrates and correlated this with soil properties of the natural sites and with the species’ habitat preferences.
• We found high variation in response to nitrate between species. Orchids from oligotrophic habitats were highly sensitive, while orchids from more eutrophic habitats were almost insensitive. Sensitivity to nitrate was also associated with soil parameters that indicated a higher nitrification rate.
• Our results indicate that nitrate can affect orchid distribution via direct inhibition of seed germination. Nitrate levels in soils are increasing rapidly due to intensification of agricultural processes and concurrent soil pollution, and we propose this increase could cause a decline in some orchid species.

     

Habitat characteristics contributing to local occupancy and habitat use in rock pool <Emphasis Type="Italic">Daphnia</Emphasis> metapopulations

The effects of invasive macrophytes, water level fluctuations and predation on freshwater unionids Pyganodon grandis and Utterbackia imbecillis were studied in three small impoundments in Northeastern Texas in 2003–2005. Mussel density was sampled with quadrats. Mortality, associated with the water level fluctuations and predation, was estimated by collecting dead shells on the shore at about two month intervals. In two ponds, horizontal distribution of unionids was limited by dense beds of invasive and noxious macrophytes (mainly Eurasian watermilfoil Myriophyllum spicatum and American lotus Nelumbo lutea): mussel densities were significantly lower in these macrophyte beds (P < 0.001). In the third pond with the lowest density of macrophytes (stonewort Chara sp.), unionids were distributed more evenly, and the average unionid biomass was the highest among all ponds studied. Vertical distribution of unionids in all ponds was likely limited by low oxygen at depth >2 m. The total amount of shells found on the shore per year varied from 0.1% to 28% of the total population in the pond and was negatively correlated with water level (r = −0.72 to −0.81, P < 0.005). Mammalian predators consumed up to 19% of the total unionid population and predation was facilitated by water level fluctuations. Handling editor: K. Martens     

Spatial distribution and mortality process ofAnoplophora malasiaca (Coleoptera: Cerambycidae) eggs in citrus groves

The study was carried out in two (A and B) citrus groves to clarify the spatial distribution patterns of eggs and larvae, and to analyse the mortality process of eggs. From the analysis by using the mean density and the mean crowding, it was clarified that the distributions of eggs were contagious and that larvae were more contagiously distributed than eggs. The τ and z indices showed that the operation of egg mortality was inversely density-dependent in both groves, and that the degree of inverse density-dependence was greater in A than in B grove. The spatial correlations between the emergence holes and the eggs or larvae in each tree, which were analysed by using ω index, showed that the distributions were more overlapping between the emergence holes and the larvae than the eggs. As the result of dividing trees into several groups according to the number of emergence holes, it was clarified that the survival rates of eggs were positively correlated with the number of emergence holes. In conclusion, inversely density-dependent mortality process was considered to be caused by lower mortality rates of eggs in the trees with more emergence holes. Especially in A grove, because the trees with more emergence holes were larger in diameter and more egg oviposition, the inversely density-dependent mortality process was considered to be detected more conspicuously than in B grove.     

A new species of Rhytidognathus (Carabidae,?Migadopini) from Argentina

The Migadopini are a small tribe of Carabidae with 47 species that occur in South America, Australia, and New Zealand, in the sub-Antarctic areas. In South America, most of the genera inhabit areas related to sub-Antartic Nothofagus forest except two monogeneric genera, the Ecuadorian genus Aquilex Moret and the Pampean genus Rhytidognathus Chaudoir. These two genera are geographically isolated from the remaining five South American genera. New material of Rhytidognathus from the northeast of Buenos Aires province and from Entre Ríos province permits establishing that the previous records of Rhytidognathus ovalis (Dejean) for Argentina were erroneous and that it belongs to a new species. Based on external morphological characters and from male and female genitalia we describe Rhytidognathus platensis as a new species. In this contribution we provide illustrations, keys, habitat characteristics and some biogeographic considerations on the distribution of Rhytidognathus.     

An Estimation Procedure for the Joint Distribution of Spatial Direction and Thickness of Flat Bodies Using Vertical Sections. Part II: An application in soil micromorphology

In soil micromorphology fissures are considered in vertical sections. To get information about the properties of the soil the joint distribution of spatial direction and width of these fissures is of interest. The fissures are mathematically generalized to flat bodies which are defined as stationary weighted surface processes with the weight “thickness”. In a typical point of the surface process suitable, joint parametric distributions of direction and thickness are assumed. The parameters have to be estimated from measurements on vertical sections which are taken from the soil. On these sections only a visible thickness and a visible angle can be observed. The joint distribution of these variables can be expressed by the joint distribution of spatial direction and thickness with the same parameters and in this indirect way the parameters can be estimated. The paper describes how to randomize the vertical section and how to measure the visible variables on the sections. The Chi-Square method is proposed for the parameter estimation. Further it is discussed how to derive good starting values for the numerical procedure. All this is demonstrated in a simulation study using the Bingham-Mardia distribution for the direction and the lognormal distribution for the thickness including a way to correlate the mean thickness and the direction. Finally an application in soil micromorphology is demonstrated for one soil horizon.