Resistance of Some Vitis Rootstocks to Xiphinema index

Thirty-eight grapevine (Vitis spp.) rootstocks were screened in pots for resistance to the dagger nematode, Xiphinema index, from 1979 to 1981. Resistance ratings were based on visible root symptoms and on changes in the nematode populations over 16 months. Nineteen of the 23 Californian hybrid rootstocks tested were resistant, as were ''Harmony'','' ''Freedom,'' ''Schwarzmann,'' and ''3309.'' Two hybrids of V. rufotomentosa, ''171-52'' and ''176-9,'' were possibly immune to X. index. The rootstocks ''ARG 1,'' '' 110 R,'' ''1202,'' and ''1616,'' which are used commercially for phylloxera resistance were susceptible.     

Captive breeding for the conservation of cichlid fishes

Cichlid fishes are by far the largest familial group of endangered vertebrates, especially the haplochromines. This paper concerns the organization and management of captive breeding of haplochromine cichlids. The setting up of a small-scale laboratory programme for the conservation of endangered species is described in terms of funding, staffing, installation and livestock husbandry. Breeding is discussed in the context of the selection of broodstock, basic reproductive biology, rearing, disease, pathological disorders and the arrangements necessary for the transfer and documentation of progeny. There are already indications in Africa and elsewhere that the dramatic decline and demise of cichlid taxa in Lake Victoria will not be an isolated phenomenon. There is no prospect that the captive breeding of cichlids can alone resolve such large-scale problems in fisheries management and ecology, or prevent the loss of taxa in nature. Nevertheless, captive breeding provides conservation options which are otherwise limited or unavailable regarding the saving of individual 'heritage' species, restocking to the wild, fundamental laboratory research and, finally, public education on the grave issue of actual and prospective mass extinctions of cichlids and other rare fishes.     

Genetic management of captive prosimian populations,a report of experience withLoris tardigradus

Extinction of small, closed populations in captivity as well as in the wild is believed to be nearly inevitable, because inbreeding will adversely effect reproductive success, mortality, sex ratio and also the susceptibility to epidemic diseases and environmental stress. An ever increasing number of primate species exist only in small isolated populations, which contain only a part of the original genetic variability. In captive breeding programs research about genetic management strategies is, therefore, of essential importance. In 1980 we imported 9Loris tardigrdus nordicus (4 females, 5 males) from NE-Sri Lanka. The founders came from one natural breeding population. All sexual mature females are breeding. Up to now the colony contains 36 living individuals. The main goal of our long-term genetic management plan was to minimize inbreeding and to preserve the genetic diversity. Therefore, we try to pass the founder bottleneck rapidly by enlarging the population to a desired minimum population size of 25 pairs and to equalize the founder representation within any generation. The need to control the spread of sublethal genes, introduced by one of the founders, conflicts directly with the aim of equalizing the founder representation. A solution of this problem is discussed. To produce a sufficiently large population we intend to give animals to other institutions and to build up an exchange-system for offspring individuals, which should lead to an international studbook.     

A high level of hybrid dysgenesis in Drosophila: High thermosensitivity, dependence on DNA repair, and incomplete cytotype regulation

Summary An unusually high level of P-M hybrid dysgenesis in Drosophila melanogaster is characteristic of hybrid offspring originating from both, A (M × ) and B (P × M) crosses of a subline of the Harwich P strain, termed H ^s . The novel properties induced by mobility of P elements carried by H ^s paternal chromosomes include: very high (over 95%) gonadal dysgenesis (GD) in both sexes at the low restrictive temperature of 21°C, and highly premature sterility when males are reared at 18°C and aged at 21°C. Although all three major chromosomes of the H ^s subline contributed to this atypical pattern of gonadal dysgenesis, chromosome 3 had the largest effect. Gonadal dysgenesis showed a temperature- and sex-dependent repression pattern by the defective P elements of Muller-5 Birmingham chromosomes; at 21°C there was virtually no repression of male sterility, but most effective repression of GD in females. At 29°C repression was effective in males, but declined in females. The high thermosensitive sterility, low fecundity, and premature aging of the male germ line were greatly exacerbated when males derived from either A or B crosses were deficient either in excision repair (mei-9 mutation) or in post-replication repair (mei-41 mutation). These findings demonstrate that both DNA repair pathways are essential for the repair of lesions induced by P element transposition and support the hypothesis that P element-induced chromosome breaks are responsible for the virtual abolition of the germ line. The relatively high premature sterility of cross B DNA repair-deficient males, reared at 18°C and aged at 21°C, indicates that there is incomplete cytotype regulation in H ^s subline hybrids.     

Numbers of sporophytic self-incompatibility alleles in populations of wild radish

Summary To estimate the numbers of sporophytic S-alleles in two adjacent populations of wild radish, we performed 701 reciprocal crosses among 50 individuals. Each cross was replicated five times in each direction. Sixteen plants were fully intercompatible, indicating the presence of at least 32 S-alleles in the two populations. A minimum of 22 S-alleles occur in a single population. The frequency of incompatibility was significantly higher for within-population crosses (14.5%) than for between-population crosses (7.8%). This suggests that the two populations differ in the composition and frequency of alleles at the S-locus.     

Patterns of paternal care in primates

An interspecific comparison was carried out to understand better the relationships among paternal care, paternal certainty, and reproductive burden in primates. Although monogamy is generally rare among mammals, a number of primate species are monogamous. Extensive paternal care is a related issue but is one that is not necessarily associated with monogamy or with paternal certainty. For example, despite paternal certainty, primate mothers in monogamous species with body weights over 2 kg still remain the primary infant caretakers, while males in the communally breeding tamarins carry infants more frequently than mothers do, even in the absence of paternal certainty. Several different tactics are used by small-bodied primates to cope with the energetic burden of raising proportionately large infants in an arboreal environment: (1) infant carrying by subadult and/or related nulliparous females (Saimiri, Lemur monogoz); (2) infant carrying by fathers and offspring (Aotus, Callicebus, Saguinus, Cebuella, Leontopithecus); (3) parking infants while family members forage (Tarsius, Galago, Microcebus, Cheirogaleus, Varecia); or (4) some combination of the above (Callithrix, Hapalemur, Loris). Lactation length and infant growth patterns appear to influence which of these tactics is employed by a given species. Moreover, although most small-bodied, mated, monogamous female primates spend no more than 9 months annually in gestation and lactation,Aotus andCallicebus mated females are either pregnant or lactating on a year-round basis. It is this heavy female reproductive burden that may be an important factor in selection for extensive paternal care in these monogamous cebids.     

Testicular development and serum sex steroid profiles during the annual sexual cycle of the male sturgeon hybrid the bester

Testicular development in the adult male F₁ sturgeon hybrid, the bester ( Huso huso L. female x Acipenser ruthenus L. male), was examined monthly in relation to serum sex steroid levels. Spermatogenesis lasted for 1 year, with meiosis generally starting in September and spermiogenesis in November, although there was considerable variation in testicular developmental stages between fish sampled monthly. Testicular development continued, slowly, during the winter months until April. Fish did not exhibit spontaneous spermiation, and phagocytotic activity of Sertoli cells became prominent from May onwards. Androgen levels increased during Spermatogenesis and remained high throughout the pre-spermiation period. In the degeneration stage, 11-ketotestosterone concentrations declined to low levels, while testoster- one levels remained high. The serum concentration of 17,20β-dihydroxy-4-pregnen-3-one was low throughout the reproductive cycle. Based on these results, it is suggested that the time appropriate for induction of final maturation would be from November–December to April when the testes are in the late stage of development.     

ALLOZYME DIVERSITY AND GENETIC IDENTITY IN SCHIEDEA AND ALSINIDENDRON (CARYOPHYLLACEAE: ALSINOIDEAE) IN THE HAWAIIAN ISLANDS

Genetic diversity of allozymes, genetic identity based on allozyme variability, and phylogenetic relationships were studied with respect to breeding system diversity, population size, and island age in 20 of the 29 species of Schiedea and Alsinidendron (Caryophyllaceae: Alsinoideae), a monophyletic lineage endemic to the Hawaiian Islands. Average levels of genetic variability in Schiedea and Alsinidendron were comparable to or higher than those found in other Hawaiian lineages for which equivalent data are available [Bidens, Tetramolopium, and the silversword alliance (Asteraceae: Madiinae)] and similar to average values for species of dicots. Allozyme variability was strongly dependent on breeding system, which varies widely in the Hawaiian Alsinoideae. Species with autogamous breeding systems showed very low variability, measured as the number of alleles per locus, percent polymorphic loci, and mean heterozygosity per locus. Outcrossing hermaphroditic and dimorphic species (those with gynodioecious, subdioecious, and dioecious breeding systems) showed significantly higher genetic variability. Small population size was associated with lower values for all measures of genetic variability. Nearly half of the species occurring in small populations are also autogamous; thus, both factors may have influenced levels of genetic variability in these species. Founder effect was apparent in one species (Schiedea adamantis), which occurs in a single large population, has a gynodioecious breeding system but a very low genetic variability. Island age appeared to have little effect on genetic variability. Slightly lower values of genetic variability for species occurring on Kaua'i and O'ahu result primarily from the occurrence of autogamous Alsinidendron species on those islands. Values for Nei's genetic identity for different species pairs were 0.201–0.942, a far greater range than in Bidens, the silversword alliance, and Tetramolopium. Using UPGMA clustering, there was only moderate support for relationships detected through cladistic analysis. Nei's unbiased genetic identity (I) was greatest among species with outcrossing breeding systems, which for the most part clustered together. Nei's genetic identities for self-fertilizing species were low, indicating that these species are less similar to one another and to outcrossing species, regardless of their affinities based on cladistic analysis. Parsimony analysis of allele frequency data supported two clades also found in phylogenetic analyses using morphological and molecular data. Clades recognized in parsimony analysis of allele frequencies were those lineages containing selfing species, indicating that conditions favoring fixation of alleles occurred in ancestral species. In contrast, maintenance of high genetic diversity in outcrossing species interferes with recognition of phylogenetic relationships using allozyme variability.     

Non-reciprocal cross-incompatibility in Trichogramma deion

In non-reciprocal cross-incompatibility (NRCI), the crossing of a female of a strain A with a male of a strain B results in hybrid offspring, whereas the reciprocal cross produces few or no hybrids. Only females are of hybrid origin in Hymenoptera because they arise from fertilized eggs; males arise from unfertilized (haploid) eggs. Crosses between many strains of Trichogramma deion showed some degree of NRCI. Crosses between a T. deion culture collected in Seven Pines, California (SVP) with one from Marysville, California (MRY) showed an extreme form of NRCI in which practically no female offspring was produced when MRY females were crossed with SVP males. The reciprocal cross produced a close to normal proportion of female and male offspring. Detailed studied of this cross indicated that 1) the female offspring produced in the compatible interstrain cross were not the result of parthenogenesis but were true hybrids, 2) the incompatible interstrain cross did not produce female offspring because fertilized eggs died during development, 3) the death of these eggs could not be prevented by either antibiotic or temperature treatment, 4) cytoplasmically inherited factors causing NRCI could be discounted because backcrossed females with the genome of MRY and the cytoplasm of SVP, exhibit the NRCI relationship characteristic of their genome. Therefore the NRCI between these strains appears to be caused by a modification coded for by the nuclear genes of MRY that results in incompatibility when SVP sperm fertilizes MRY eggs. In addition the level of incompatibility in crosses between the SVP females and MRY males is temperature sensitive, the higher the rearing temperature the lower the level of compatibility.     

LACK OF CALLING SONG DISPLACEMENT BETWEEN TWO CLOSELY RELATED GROUND CRICKETS

Thorough examinations of purported cases of reproductive character displacement are critical for reaching an understanding of the role of reinforcement in the evolution of reproductive barriers between closely related species. In this paper, we report the results of an extensive investigation of male calling song variation in the ground crickets, Allonemobius fasciatus and A. socius. Contrary to the results of an earlier study, we uncovered little evidence of displacement of songs in areas of overlap. We discuss explanations for the lack of displacement as well as for the discrepancies between the results of the current study and those of the earlier study.