These aquaculture- and conservation-oriented commentaries are not abstracts written by the original authors.  They reflect the opinions of someone else -- usually Roger Doyle.  Direct quotations from the papers or abstracts are marked with inverted commas.

162.  Graylings adapt rapidly to local temperature environments
Population differences in early life-history traits in grayling. 2000. Haugen, T.O., and L.A. Vøllestad. Journal of Evolutionary Biology 13 (6):897-905.
        How rapidly does genetic adaptation to a changed natural environment take place? The three populations of the trout-like grayling (Thymallus thymallus) studied in this experiment had common ancestors around 80–90 years, or 13-18 generations, ago. Experimental rearing under several temperature regimes in the laboratory revealed that there is now significant additive genetic variance for early growth and survival among the populations. This is the sort of genetic change one expects in an artificial selection experiment, but in this instance the selection was natural.
        "In general, each population did best [in laboratory tests] at the temperature experienced in nature. These differences in early life-history traits suggest that natural selection has resulted in local adaptation in a time period of 13–18 generations."  This nicely fits the projected time scale for global warming.  avollest@bio.uio.no 

161.  Negative outcome of a test of group selection in a fish
Experimental evolution in Heterandria formosa, a livebearing fish: group selection on population size. 2000. Baer, C.F., J. Travis, and K. Higgins. Genetical Research 76:169-178.
        The question is whether "group selection", in which a whole population rather than an individual is selected, can be an effective agent of evolutionary change. Although the matter has been controversial for decades it is now generally thought even by people other than S. J. Gould that there could be situations in which group selection supplements or overwhelms individual Darwinian selection or indirect kin selection.
        Now an experimental test with fish. The authors of this paper "imposed group selection via differential extinction for increased and decreased population size at 6-week intervals, a true population-level trait, in the poeciliid fish Heterandria formosa. In contrast to most other group selection experiments, [they] observed no evolutionary response after six rounds of group selection in either the up- or down-selected lines. Population heritability for population size was low, if not actually negative. [Their] results suggest that group selection via differential extinction may be effective only if population sizes are very small and/or migration rates are low."
        In other words there was no evolution of low-population-itis after selecting for small or large groups. This is the second negative result reported for evolutionary experiments on this species [June list #65] and the negative information is very valuable. cbaer@darkwing.uoregon.edu 

160.  Experimental evolution of markers for maturation in trout
Microsatellite allelic heterogeneity among hatchery rainbow trout maturing in different seasons. 2000. Fishback, A.G., R.G. Danzmann, and M.M. Ferguson. Journal of Fish Biology 57 (6):1367-1380.
        A lot of people are looking for DNA markers for selecting at loci that affect quantitative traits (QTL) such as rapid growth.  If such markers are ever to be useful they ought to change in frequency when the underlying traits evolve in response to selection. So, do they?
        The authors of this paper examined the maturation of fish in a commercial trout farm which has succeeded, through selection, in expanding the spawning season from 2 weeks to 8 months. The spawning time of the majority of the females, but not the males, could be predicted from genotypic information at 14 microsatellite loci. That is, the distributions of the neutral microsatellites diverged along with the selective divergence of spawning date. Furthermore, the changes in spawning date was associated with changes in the frequencies of QTL markers which had previously been identified by these authors. This is probably the most promising evidence to date of the potential utility of QTL for fish broodstock improvement. rdanzman@uoguelph.ca 

159.  Combination of desirable properties in hybrid prawns
Growth of Penaeus monodon×Penaeus esculentus tiger prawn hybrids relative to the parental species. 2000. Benzie, J.A.H., M. Kenway, and E. Ballment. Aquaculture 193 (3-4):227-237.
        Hybrids can combine the best features of the parents but they can also combine the worst, or something in between, or they can be better than either parent. What is the situation in commercial prawns?
        About 50% of the artificial inseminations were successful in producing at least some eggs, but hatching rates were less than 4%. After that, survival of the hybrids and parental species were similar, 40% at 4 weeks. "Sex ratio was significantly skewed in favour of males in the hybrids [86%]. ... The hybrids had the fast growth rate of P. monodon, and some of the attractive colour pattern of P. esculentus. " j.benzie@unsw.edu.au 

158.  More evidence for genetically successful supplementation of a Chinook population
Effective population size of winter-run chinook salmon based on microsatellite analysis of returning spawners. 2000. Hedrick, P.W., V.K. Rashbrook, and D. Hedgecock. Can. Jour. Fish. Aquat. Sci. 57:2368-2373.
        This paper is a follow-up to an earlier report [June list #61] on a supplementation program for winter-run Chinook salmon in the Sacramento river in California. Supplementation with hatchery-reared stock is one way to keep an endangered population going, but its genetic effects are controversial. In theory it has the unfortunate effect of reducing the genetically effective size of the supplemented population even though the total number of fish increased.
        The calculations in the earlier paper, based on a number of assumptions that had not been validated at the time of writing, led to the conclusion that  supplementation had stabilized and perhaps increased the effective population size. In other words, no genetic problem in a well-designed program. This new paper presents data from returning spawners that validates the earlier assumptions, confirms the earlier conclusion and that "provide an optimistic outlook for the success of this supplementation program and suggest that the overall effective population size has not been greatly reduced, since returning spawners represent a broad sample of parents and not fish from only a few families". philip.hedrick@asu.edu 

157.  A different approach to the genetics of an endangered population
Compensating for our load of mutations: freezing the meltdown of small populations. 2000. Poon, A., and S.P. Otto. Evolution 54 (5):1467-1479.
        This fascinating paper is based on a multidimensional model of fitness which is due to Fisher but which will remind ecologists of G.E. Hutchinson's n-dimensional niche. The model allows beneficial mutations on one axis to compensate for deleterious mutations in another -- including the sort of deleterious mutations that cause inbreeding depression according to the most likely explanation of that phenomenon. It turns out that the loss of fitness caused by random fixation of deleterious mutations is directly proportional to the dimensionality and inversely proportional to the effective population size. Hutchinson would have cheered.
        "The reciprocal relationship between the [loss of fitness] and Ne [effective population size] implies that the fixation of deleterious mutations is unlikely to cause extinction when there is a broad scope for compensatory mutations, except in very small populations. Furthermore ... pleiotropy plays a large role in determining the extinction risk of small populations. ... That the predictions of this model are qualitatively different from studies ignoring compensatory mutations implies that we must be cautious in predicting the evolutionary fate of small populations and that additional data on the nature of mutations is of critical importance. " poon@zoology.ubc.ca 

156.  Salmon strains differ in susceptibility to a parasite
Innate susceptibility differences in chinook salmon Oncorhynchus tshawytscha to Loma salmonae (Microsporidia). 2000. Shaw, R.W., M.L. Kent, and M.L. Adamson. Diseases of Aquatic Organisms 43:49-53.
        The parasite is an important gill pathogen of salmonids. "Three strains of chinook salmon O. tshawytscha were infected in 2 trials with L. salmonae. ... Intensity of infection was significantly higher in the Northern stream strain as compared to the Southern coastal and a hybrid strain derived from these 2 strains. ... The northern strain may represent a naive strain and be less able to mount an effective immune response against the parasite." If so, this is interesting news which reinforces the importance of carefully choosing strains for culture and rehabilitation. shawr@admin.gmcc.ab.ca 

155.  Wildflowers show outbreeding depression
Genetic introgression from distant provenances reduces fitness in local weed populations. 2000. Keller, M., J. Kollmann, and P.J. Edwards. Journal of Applied Ecology 37:647-659.
       This paper reports an experiment on outcrossing depression, the controversial reduction of fitness which may occur when plants or animals which are adapted to a local environment are crossed with "invaders" from elsewhere. The phenomenon is of considerable importance in genetic conservation where populations have to be supplemented or replaced, and in aquaculture when animals escape and reproduce in the wild. The concept of outbreeding depression is controversial because of counter arguments that introgression of new genes may often benefit small populations.
        The authors crossed local (Swiss) weeds of three species with weeds of the same species obtained from other parts of western Europe, and grew the F1 and F1 hybrid progenies in Switzerland. There was negative outbreeding, i.e. smaller plants and lower survival , in some F1 and many but not all of the F2 backcrosses. Seed mass showed positive benefits from crossing in one species in the F1 but depression occurred in the F2. "The results suggest that only plants of relatively local origin should be used in wildflower mixtures, although it is not possible to specify precisely over what distance seed can safely be transferred. The same recommendation is also valid for schemes to reinvigorate endangered plant populations. " jok@kvl.dk 

154.  A test for population mixing in earlier generations
Juxtaposed microsatellite systems as diagnostic markers for admixture: an empirical evaluation with brown trout (Salmo trutta) as model organism. 2000. Estoup, A., C.R. Largiadèr, J.-M. Cornuet, K. Gharbi, P. Presa, and R. Guyomard. Molecular Ecology 9 (11):1873-1886.
        How does one tell whether a population has interbred with another, genetically different, population in the not-too-distant past? The question is important in studies of evolution and for resolving issues in genetic conservation, and can be of importance in exposing the sordid histories of aquacultural broodstocks.
        The authors of this paper have tested a novel procedure for analysing the ancestral mixing of genetically differentiated populations. This is useful. The histories of populations that result from mixing are not easily interpreted -- to put it gently -- by procedures such as PHYLIP that use mutation rate assumptions and genetic distance data to generate hypotheses about relationships. "A juxtaposed microsatellite system (JMS) is composed of two microsatellite repeat arrays separated by a sequence of less than 200 bp and more than 20 bp. ... JMSs are expected to be reliable diagnostic markers in most divergent (i.e. Mediterranean) populations and nonreliable diagnostic markers in most closely related (i.e. Atlantic) populations." aestoup@zoology.uq.edu.au 

153.  Genetic analysis of maternal effects in salmon
Maternal effects on offspring size: variation through early development of Chinook salmon. 1999. Heath, D.D., C.W. Fox, and J.W. Heath. Evolution 53 (5):1605-1611.
        Every hatchery manager and conservationist has an opinion about the  size (or age) at which brood fish give the best offspring. The authors of this paper used an effective genetic procedure to examine the question. They estimated the influence of the size of the mother by looking at the difference between the regression slopes of sire-offspring and dam-offspring against their respective parents.
        "Early in life, offspring size is largely influenced by maternal size, but this influence decreases through early development, with the maternal effect becoming negative at intermediate offspring ages (corresponding to a period of reduced growth of progeny hatching from large eggs) and converging on zero as offspring age. Also, egg size was positively correlated with early survival, but negatively correlated with maternal fecundity." The authors point out that their experiments probably underestimate the advantage of early, large size would have in a more competitive natural environment. heath@unbc.ca 

152.  Choosing the right Fst estimator
Properties of bias and variance of two multiallelic estimators of FST. 2000. Raufaste, N., and F. Bonhomme. Theoretical Population Biology 57 (3):285-296.
        Rightly or wrongly, Fst and related calculations are often used to identify populations which are candidates for protection because of their supposed evolutionary significance, distinctiveness and isolation. The Fst estimators compared here are Weir-Cockerham and Robertson-Hill. Both are calculated by the widely-used computer package GENEPOP andit is interesting to find out how they fare.
        This paper includes mathematical analysis of the differences between these estimators as well as simulations of their performance at migration-drift equilibrium. Essentially, the conclusion is that W-C is unbiased and R-H is often negatively biased. However, the latter estimator has lower variance. The authors' recommendation is to use W-C when populations are highly differentiated and R-H (with a crucial correction for bias) when differentiation is low to moderate. nraufaste@crit.univ-montp2.fr 

151.  Tilapia and salmon database for DNA sequence and markers.
The ARKdb: genome databases for farmed and other animals. 2001. Hu, J., C. Mungall, A. Law, R. Papworth, J.P. Nelson, A. Brown, I. Simpson, S. Leckie, D.W. Burt, A.L. Hillyard, and A.L. Archibald. Nucleic Acids Research 29 (1):106-110.
        The Roslin Institute (in Scotland) has established a "comprehensive public [repository] for genome mapping data from farmed species and other animals... providing a resource similar in function to that offered by GDB or MGD for human or mouse genome mapping data, respectively". Tilapia and salmon are included. Links to other databases such as GenBank are provided. It is also a great place to look up microsatellite and other markers by name.
http://www.thearkdb.org/cgi-bin/arkdb/browsers/browser.sh?species=cattle