Postmating reproductive isolation in pseudophryne and the evolutionary significance of hybrid zones.

Hybrid zones involving Pseudophryne (Anura: Leptodactylidae) provide direct evidence for the operation of postmating reproductive isolating mechanisms in animals in a natural situation. Significant introgression is prevented by hybrid inviability but there is no evidence for the reinforcement of premating isolating mechanisms. These parapatric hybrid zones are of unknown etiology, but are interpreted as being relatively old and persistent.

Kin selection, social structure, gene flow, and the evolution of chimpanzees.

Hypotheses about chimpanzee social behavior, phylogeography, and evolution were evaluated by noninvasive genotyping of free-ranging individuals from 20 African sites. Degrees of relatedness among individuals in one community were inferred from allele-sharing at eight nuclear simple sequence repeat (SSR) loci. Males are related on the order of half-siblings, and homozygosity is significantly increased at several SSR loci compared to Hardy-Weinberg expectations. These data support the kin-selection hypothesis for the evolution of cooperation among males. Sequence variation patterns at two mitochondrial loci indicate historically high long-distance gene flow and clarify the relationships among three allopatric subspecies. The unexpectedly large genetic distance between the western subspecies, Pan troglodytes verus, and the other two subspecies suggests a divergence time of about 1.58 million years. This result, if confirmed at nuclear loci and supported by eco-behavioral data, implies that P. t. verus should be elevated to full species rank.

Identification of chimpanzee subspecies with DNA from hair and allele-specific probes.

We describe a non-invasive method of determining the subspecies identity of common chimpanzees (Pan troglodytes), based on subspecies-specific sequence differences in the mitochondrial genome. This procedure involves the extraction of DNA from hair, the amplification of a short (410 base pair (b.p.)) segment of the non-coding displacement loop (D-loop) by the polymerase chain reaction (PCR), and subspecies identification based on rapid allele-specific oligonucleotide (ASO) probe dot-blot typing. This approach will contribute to: (i) the colony-level management of captive chimpanzees by enabling managers to recognize hybrids between subspecies and minimize outbreeding depression; (ii) the recognition of inappropriately matched individuals in comparative behavioural and experimental studies; and (iii) forensic questions surrounding the origin of illegally traded animals.

Genetic variation and differentiation of three Schistosoma species from the Philippines, Laos, and Peninsular Malaysia.

Electrophoretically-detected allozyme variation is described in strains of Schistosoma japonicum (4 Philippine strains), S. mekongi (Laos), and an undescribed anthropophilic S. japonicum-like schistosome from Peninsular Malaysia. Result, together with those reported previously for 8 other strains (S. japonicum, China, Formosa, Japan, Philippines; S. mekongi, 2 substrains; Malaysian schistosome, 2 strains) permit a composite genetic characterization of 15 strains of Asian schistosomes at 9-18 presumptive loci. The proportion of polymorphic loci (P) and the mean heterozygosity per locus (H) were zero in all strains. Although this was expected for strains that had been in laboratory culture for up to 50 years, we expected to detect variation in strains based on 10-50 recently field-collected infected snails. We expected S. japonicum to be as variable as S. mansoni (P = 0.13 (0-0.33), H = 0.04, 18 loci, 22 strains) as it is believed to reproduce sexually, has an evolutionary history of several million years, inhabits a wide geographic range, coevolved with a genetically variable intermediate snail host, and has a diversity of mammalian hosts. No differences were detected between the 5 S. japonicum strains from Leyte and Luzon (Philippines), between the 3 S. mekongi strains, or between the 3 Malaysian schistosome strains; these groups and the remaining S. japonicum strains representing Mindoro (Philippines), China, Formosa, and Japan each have distinctive multilocus electromorphic patterns. Nei's genetic distances (D) were calculated to estimate interstrain and interspecific divergence. Interstrain genetic distances in S. japonicum averaged greater than 0.3; much higher than those reported previously for S. mansoni (D = 0.06, D(max) = 0.24). S. japonicum (Mindoro) was moderately differentiated from the Leyte-Luzon strains (D = 0.29, 12 loci). Estimates of the S. japonicum China-Philippine distance (D greater than 0.4, 11 loci) are high for conspecific populations and further studies of the still poorly characterized Chinese parasite may reveal that these are, in fact, separate species. S. japonicum is shown to be only distantly related to S. mekongi and the Malaysian schistosome (D greater than 1); the latter is closely related to, but genetically quite distinct from, S. mekongi (D = 0.61 +/- 0.275, 11 loci) and warrants recognition as a new species. The medical significance of the isogenic nature of the Asian schistosome strains and their evolutionary divergence are discussed.

Home care utilizing a ventilator in a patient with amyotrophic lateral sclerosis.

A patient with respiratory neuromuscular paralysis secondary to amyotrophic lateral sclerosis is described who was managed at home for more than 12 months on a volume cycled respirator. Although the cost is high, it is less than in an acute care hospital setting. Requirements for success include parient selection, adequate home environment, and dedicated medical and paramedical personnel.

Declines of biomes and biotas and the future of evolution.

Although panel discussants disagreed whether the biodiversity crisis constitutes a mass extinction event, all agreed that current extinction rates are 50-500 times background and are increasing and that the consequences for the future evolution of life are serious. In response to the on-going rapid decline of biomes and homogenization of biotas, the panelists predicted changes in species geographic ranges, genetic risks of extinction, genetic assimilation, natural selection, mutation rates, the shortening of food chains, the increase in nutrient-enriched niches permitting the ascendancy of microbes, and the differential survival of ecological generalists. Rates of evolutionary processes will change in different groups, and speciation in the larger vertebrates is essentially over. Action taken over the next few decades will determine how impoverished the biosphere will be in 1,000 years when many species will suffer reduced evolvability and require interventionist genetic and ecological management. Whether the biota will continue to provide the dependable ecological services humans take for granted is less clear. The discussants offered recommendations, including two of paramount importance (concerning human populations and education), seven identifying specific scientific activities to better equip us for stewardship of the processes of evolution, and one suggesting that such stewardship is now our responsibility. The ultimate test of evolutionary biology as a science is not whether it solves the riddles of the past but rather whether it enables us to manage the future of the biosphere. Our inability to make clearer predictions about the future of evolution has serious consequences for both biodiversity and humanity.

The role of memory in personality continuity: a 25 year follow-up.

Several longitudinal studies have been published showing high retest coefficients in self-report personality inventories. While the data suggest stability in personality over long periods of adulthood, critics have argued that individuals may be motivated to present themselves in consistent fashion to the investigator. It has been suggested that respondents may remember how they answered the items previously. Thus, memory and the desire for consistency may be responsible for the high stability coefficients typically observed. In the present study 85 individuals who had completed the California Test of Personality as university students in 1944 were asked to complete it again 25 years later. Respondents were instructed to remember how they had answered the inventory as students and to fill it out in that manner (Retrospective condition) in addition to responding as they were in the present (Self condition). Results indicated high retest correlations between the 1944 and 1969 Self conditions, whereas the correlations between the 1944 Self and 1969 Retrospective conditions were much lower. Subjects describing their present selves obtained scores more highly correlated with their 1944 scores than scores created by attempting to describe themselves as they had been 25 years previously. These data indicate that memory for responses to a personality inventory taken years before is inaccurate, and that it cannot account for the observed consistency in personality test scores.

EEG alpha slowing, refractory period, and reaction time in aging.

The present study was undertaken to determine if a model accounting for reaction time (RT) on the basis of the EEG alpha rhythm and refractory period (RP) could predict RT in young and old adult subjects. Ten male university undergraduates and ten community residing males over the age of 65 had resting EEG recorded at right and left occipital sites. Mean alpha frequency was 1.2 Hz slower in old subjects. RT and RP were assessed in a warned RT paradigm. Sixty-four trials of each of a 50, 100, 250, and 500 msec inter-stimulus interval (ISI) were presented in random order. The model was useful in predicting the magnitude of the age difference in RT and the difference in RT between the 50 and 100 msec ISI. However, old subjects were not disproportionately slowed at the 100 msec ISI as the model would predict and all RTs were underestimated. Thus, while a model using EEG alpha period and RP to predict age differences in RT has some weaknesses, it is useful enough to warrant additional examination.