Nidicolous arthropods associated with different chromosomal types of Spalax ehrenbergi Nehring*

The mole rat, Spalax ehrenbergi Nehring, is a complex group involving four chromosomal types of In = 52, 54, 58 and 60. These are clinally distributed from Mount Hermon in the north to the Negev in the south, covering humid, semihumid, semiarid and arid climates. Forty-seven breeding nests of Sehrenbergi were collected from 23 localities throughout the range and processed for nidicolous arthropods. A total of five species of fleas and 53 species of gamasid mites were collected. Their distribution in the investigated area has been analysed in relation to that of the chromosomal types of S.ehrenbergi. The following conclusions have been reached:(a) Only three of the species (two haematophagous gamasids and one fungivorous acarid) range across the whole investigated area, showing strong host specificity, (b) A correlation is apparent between the distribution of several nidicolous arthropods (fleas and gamasids) and the ‘54’ geographic region. This probably reflects geographical distribution rather than host specificity, (c) Palaearctic species reach their southern limit of distribution on Mount Hermon and the Golan Heights; possibly Ethiopian ones reach their northern limit in the Negev. (d) No direct correlation has been found between nidicolous arthropods and the chromosomal types of S. ehrenbergi. (e) Subjects for future investigation are outlined.     

Models of Syringeal Mechanisms

There are presently two hypotheses concerning the modulationof avian vocalizations, one holding that resonance phenomenaplay an important role, the other that modulations are sourcegenerated. A wide variety of data tend to question the formerand support the latter. The Greenewalt model is examined in the light of recent findings,many of which support its major contentions and implications.On the other hand, the model seems to have certain weaknessesin describing the interactions of pressure, tension, and membranemovement, hence the linkage of AM and FM. Mathematical expressionsof these relationships are developed. They show that the amplitudeof oscillation will vary with the magnitude of the driving pressureperturbation and with the interaction of the frequencies ofthe perturbation and the resonant frequency of the membrane.This suggests an alternative mechanism for the AM-FM linkage. Caution is advised in the development of generalized models.Although all birds may exploit certain fundamental principles,the possibility remains that a variety of techniques may beemployed. A major difference between the techniques utilizedby oscines and non-oscines is especially probable.     

Ex Bouillabaisse Lux: The Charm of Comparative Physiology and Biochemistry

The successes in comparative physiology during the last 25 yearshave resulted from the study of those cellular or subcellularphenomena common to all animals, but approachable most easilyin a few model species. In contrast, complex systems comprisingmany cooperating tissues and organs are characteristic of narrowtaxa; analysis of such systems does not yield widely applicablegeneralities. An analogy between the distribution of commoditiesand products in biological systems and in marketing channelsis developed, and the function of the circulation is consideredin that context. The accumulation and assorting of productsby the flow of blood from the tissues to the collecting vesselsemerges as a particularly important role. The techniques thathave been developed for coping with man's highly complex organizationsand activities should be applicable to analogous biologicalsystems.     

Ribosomal DNA Sequence of Nucleospora salmonis Hedrick, Groff and Baxa, 1991 (Microsporea: Enterocytozoonidae): Implications for Phylogeny and Nomenclature

ABSTRACT. Rules of zoological nomenclature, morphological data, and robosomal DNA sequence data support the validity of the genus Nucleospora , and its placement in the family Enterocytozoonidae. Although Nucleospora exhibits most of the distinguishing morophological characteristics of the family Enterocytozoonidae Cali and Owne, 1990, the distinctively different hosts (fish and humans, respectively) and sites of development (the nuclei of immature blood cells and the cytoplasm of enterocutes) supprot the placement Nucleospora and Enterocytozoon into separate genera. Ribosomal DNA sequence comparisons between Nucleospora salmonis and Enterocytozoon bieneusi showed 19.8% genetic divergece in the large and small subunit regions. Although more inter- and intrageneric divergence between the two species is sufficiently larg to deter suppression of the genus Nucleospora as a junior synonym of Enterocytozoon. A polymerase chain reaction test for the detection of N. salmonis in chinook salmon ( Oncorhynchus tshawytscha ), based on N. salmonis -specific ribosomal DNA sequence, is described.     

Competitive speciation

A new mode of speciation, competitive speciation, is suggested. It assumes that fitness is depressed by the density of a phenotype's competitors, and that the adaptive landscape of phenotypes is complex. From this it follows that some intermediate forms may be fit if and only if some extreme forms are rare or absent. Subsequent to the evolution and population growth of both extreme forms, the intermediate may disappear and homogamy evolve among each of the extremes because of disruptive selection If so, sympatric speciation has occurred and niche space has been rendered into discrete segments.
The limitations of the forces leading to competitive speciation are explored. Competitive speciation is discussed in relation to stasipatric speciation and host race formation. It may be responsible for both. Finally the rates of geographical speciation and polyploidy are compared to those of competitive speciation. The latter should be almost as fast as polyploidy and may be at the root of adaptive radiation. Unlike either polyploidy or geographical speciation, competitive speciation accelerates when species diversity declines.     

GROWTH, SURVIVORSHIP, AND POPULATION SIZE IN THE LAND SNAIL RHAGADA CONVICTA COX, 1870 (PULMONATA: CAMAENIDAE) FROM A SEMIARID ENVIRONMENT IN WESTERN AUSTRALIA

Basic characteristics of a population of the camaenid land snailRhagada convicta were studied in a semiarid environment nearNorth West Cape, in Western Australia. Consistent evidence frommark-recapture studies and analysis of size-frequency distributionindicates an average annual increase in shell diameter of 3.6mm, with an average period of 5 years from hatching to reachadult size. These rates are low, compared with most other landsnails studied, including cama-enids from wetter environments.Estimates of mortality rate and the rate of recruitment intothe adult population indicate that the snails live an averageof approximately 5 years after reaching adult size, which meansthat the period of turnover for this population is approximately10 years. The population density was estimated to be 0.8 adultsper m², with a total population size (± s.e.) of 875± 164. The population is very localised, with an estimateddiameter of the neighbourhood area of only 38 m. (Received 28 August 1990; accepted 12 February 1991)     

Ecodevelopment planning at India’sGreat Himalayan National Parkfor biodiversity conservationand participatory rural development

The existing network of Protected Areas (PAs) in India is the major effort aimed at biodiversity conservation at the national level. The sustainability of PAs is heavily influenced by local people who are largely dependent on natural resources (fuel, fodder, minor forest products) for their livelihood. While all PAs are surrounded by historically resource-dependent communities, several of them have villages within their core areas, too. This has necessitated an alternative approach to natural resource management which aims to integrate the interests of conservation with those of the nearby resource dependent communities. The case of the Great Himalayan National Park illustrates and incorporates the lessons from Integrated Conservation and Development Projects (ICDPs) implemented elsewhere in the world.