209 research outputs found
Can Males Successfully Invade Hermaphroditic Populations of Clam Shrimp (Eulimnadia Texana)?
Androdioecy (mixtures of males and hermaphrodites) is distinguished by its rarity, being found in only similar to 40 animal species. Many of these species are clam shrimp in the genus Eulimnadia. A metapopulation model for the maintenance of androdioecy is tested herein by examining male success in aquaria with a single male-producing hermaphrodite introduced into an otherwise all-hermaphrodite population. This migration experiment did allow males to persist in these populations for seven generations, although at levels below those found in other populations of these shrimp. These results suggest that the maintenance of androdioecy via \u27reproductive assurance\u27 is unlikely by way of migration of male-producing hermaphrodites
Maintenance of Androdioecy in the Freshwater Shrimp, Eulimnadia Texana: Field Estimates of Inbreeding Depression and Relative Male Survival
Androdioecy is a rare form of reproduction, only found in a few plant and animal species, wherein males co-exist with hermaphrodites. This particular form of mixed mating (mixtures of outcrossing and self-fertilization) is predicted to be evolutionarily unstable, with most androdioecious populations thought to be in a transition from hermaphroditism to dioecy, or vice versa. One well-studied androdioecious species is the freshwater clam shrimp Eulimnadia texana. A model by Otto et al. (1993), exploring the stability of this androdioecious system, predicts that males can co-exist with hermaphrodites when males fertilize an average of over twice the number of offspring that an average hermaphrodite produces in a lifetime. This value proportionally increases if males survive less well than hermaphrodites, and proportionally decreases with increased inbreeding depression. In the present study, we measured relative male longevity and inbreeding depression using laboratory-produced selfed and outcrossed eggs reared in the field. Males had lower survival than hermaphrodites in both mating treatments, but the survival difference was greater in the outcrossed relative to the selfed mating treatments (19 vs 9% difference). Inbreeding depression (6) was estimated at 0.58-0.69, depending on the level of selfing among the parents in the outcrossed treatments. Both estimates of relative male viability and inbreeding depression corresponded well with earlier laboratory estimates of these parameters. Thus the within-pond dynamics outlined in the model of Otto et al. (1993), which are driven by high inbreeding depression and high relative male fertility, may still explain the maintenance of androdioecy in these shrimp. Field estimates of male mating effectiveness are required as a final test of the accuracy of this model
Inbreeding Effects On Sperm Production in Clam Shrimp (Eulimnadia Texana)
Hypothesis: Inbreeding depression is manifest in lower sperm production. Organism: Freshwater crustaceans (clam shrimp - Eulimnadia texana), from the southwestern United States, which have high levels of inbreeding. Methods: Comparisons of semi-thin sections of the male gonad among selfed and outcrossed siblings from four families. Results: There was a twofold reduction in sperm production in inbred relative to outcrossed males. Inbreeding depression in males was higher than previous estimates from hermaphrodites. Conclusions: Inbreeding markedly reduces sperm production. The observed low levels of sperm production can explain both the low average outcrossing rates as well as the variation in these rates reported in previous studies of these crustaceans
Feeding behavior in sexual and clonal strains of Poeciliopsis
Sexual and clonal fish of the genus Poeciliopsis occur together in desert streams of Sonora, Mexico. Their coexistence has been explained in terms of niche partitioning for food and space. We examined predatory behavior that might influence niche relationships, and found significant differences among two coexisting sperm-dependent clonal strains and their two sexual progenitors. Handling time and prey manipulation of free-swimming ( Artemia ) and benthic (chironomid larvae) prey differed significantly among sexual and clonal strains. Analyses of gut contents from field-collected fish revealed that the laboratory estimates of predatory efficiency were related to their feeding behavior in nature. Behavior differences, such as those described herein, contribute to our understanding of the mechanisms of unisexual/bisexual coexistence in Poeciliopsis .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46898/1/265_2004_Article_BF00168589.pd
Structure and kinetics in the freezing of nearly hard spheres
We consider homogeneous crystallisation rates in confocal microscopy
experiments on colloidal nearly hard spheres at the single particle level.
These we compare with Brownian dynamics simuations by carefully modelling the
softness in the interactions with a Yukawa potential, which takes account of
the electrostatic charges present in the experimental system. Both structure
and dynamics of the colloidal fluid are very well matched between experiment
and simulation, so we have confidence that the system simulated is close to
that in the experiment. In the regimes we can access, we find reasonable
agreement in crystallisation rates between experiment and simulations, noting
that the larger system size in experiments enables the formation of critical
nuclei and hence crystallisation at lower supersaturations than the
simulations. We further examine the structure of the metastable fluid with a
novel structural analysis, the topological cluster classification. We find that
at densities where the hard sphere fluid becomes metastable, the dominant
structure is a cluster of m=10 particles with five-fold symmetry. At a particle
level, we find three regimes for the crystallisation process: metastable fluid
(dominated by m=10 clusters), crystal and a transition region of frequent
hopping between crystal-like environments and other (m\neq10) structuresComment: 10 page
Can Systemic Interventions Designed to Reduce Reoffending by Youth also Reduce their Victimization?
Previous research indicates considerable overlap between populations of boys who are victimized and boys who victimize others. This study was concerned with whether a systems-focused treatment program designed to address individual and systemic risk factors associated with the perpetration of sexual and violent crimes might also be successful in reducing boys’ victimization by others. Boys adjudicated for sexual offences who received ‘treatment as usual’ (TAU; n = 335) were compared with similarly adjudicated boys who completed the treatment program (n = 200) on their histories of contact with police either as offenders or victims. Despite their higher rates of pre-intervention victimization, the treatment group were victimized less frequently post-intervention than the TAU group. Continued offending was the strongest predictor of victimization post-intervention. These findings suggest that offending and victimization share common risk factors that may be addressed simultaneously within offence-focused treatment
Long-term genetic consequences of mammal reintroductions into an Australian conservation reserve
Available online 05 January 2018Reintroduction programs aim to restore self-sustaining populations of threatened species to their historic range. However, demographic restoration may not reflect genetic restoration, which is necessary for the long-term persistence of populations. Four threatened Australian mammals, the greater stick-nest rat (Leporillus conditor), greater bilby (Macrotis lagotis), burrowing bettong (Bettongia lesueur) and western barred bandicoot (Perameles bougainville), were reintroduced at Arid Recovery Reserve in northern South Australia over the last 18 years. These reintroductions have been deemed successful based on population growth and persistence, however the genetic consequences of the reintroductions are not known. We generated large single nucleotide polymorphism (SNP) datasets for each species currently at Arid Recovery and compared them to samples collected from founders. We found that average genetic diversity in all populations at the Arid Recovery Reserve are close to, or exceeding, the levels measured in the founders. Increased genetic diversity in two species was achieved by admixing slightly diverged and inbred source populations. Our results suggest that genetic diversity in translocated populations can be improved or maintained over relatively long time frames, even in small conservation reserves, and highlight the power of admixture as a tool for conservation management.Lauren C. White, Katherine E. Moseby, Vicki A. Thomson, Stephen C. Donnellan, Jeremy J. Austi
Crop Updates 2000 - Weeds
This session covers thirty six papers from different authors:
INTRODUCTION, Vanessa Stewart Agriculture Western Australia
INTEGRATED WEED MANAGEMENT
Effect of seeding density, row spacing and Trifluralin on the competitive ability of Annual Ryegrass in a minimum tillage system, David Minkey, Abul Hashem, Glen Riethmuller and Martin Harries, Agriculture Western Australia
High wheat seeding rates coupled with narrow row spacing increases yield and suppresses grass, Peter Newman1 and Cameron Weeks2,1Agronomist, Elders Limited 2Mingenew/Irwin Group
Resistant ryegrass management in a wheat – lupin rotation, Abul Hashem, Harmohinder S. Dhammu, Aik Cheam, David Bowran and Terry Piper, Agriculture Western Australia
Integrated weed management – Will it work with my rotation? Alexandra Wallace, Agriculture Western Australia
Long term herbicide resistance trial – Mingenew, Peter Newman Elders, Cameron Weeks Mingenew-Irwin Group
Is two years enough? Bill Roy, Agricultural Consulting and Research Services
The fate of ryegrass seed when sheep graze chaff cart heaps, Keith L. Devenish1 and Lisa J. Leaver2 1 Agriculture Western Australia, 2Curtin University of Technology, Muresk Institute of Agriculture
Can blanket wiping and crop topping prevent seed set of resistant wild radish and mustard? StAbul Hashem, Harmohinder Dhammu, Vanessa Stewart, Brad Rayner and Mike Collins, Agriculture Western Australia
The value of green manuring in the integrated management of ryegrass, Marta Monjardino1,2, David Pannell2, Stephen Powles1 ,1Western Australia Herbicide Resistance Initiative, 2Agricultural and Resource Economics, University of Western Australia
Some ways of increasing wheat competitiveness against ryegrass,, Mike Collins Centre for Cropping Systems, Agriculture Western Australia
WEED BIOLOGY
Understanding and driving weed seed banks to very low levels, Sally Peltzer, Agriculture Western Australi
HERBICIDE RESISTANCE
Cross resistance of chlorsulfuron-resistant wild radish to imidazolinones, Abul Hashem, Harmohinder Dhammu and David Bowran, Agriculture Western Australia
Investigation of suspected triazine resistant ryegrass populations for cross-resistance and multiple resistance to herbicides, Michael Walsh, Charles Boyle and Stephen Powles, Western Australian Herbicide Resistance Initiative, University of Western Australia
Genetics and fitness of glyphosate resistant ryegrass, S. Powles1, P. Neve1, D. Lorraine-Colwill2, C. Preston2 ,1WAHRI, University of Western Australia 2 CRC Weed Management Systems, University of Adelaide
Managing herbicide resistance – the effect of local extinction of resistance genes, Art Diggle1, Paul B. Neve2, Stephen B. Powles2 ,1Agriculture Western Australia, 2WAHRI, Faculty of Agriculture, University of Western Australia
The double knock - the best strategy for conserving glyphosate susceptibility? Paul B. Neve1, Art Diggle2, Stephen B. Powles1,1WAHRI, Faculty of Agriculture, University of Western Australia, 2Agriculture Western Australia
Wild radish had evolved resistance to triazines, Abul Hashem, Harmohinder S. Dhammu, David Bowran and Aik Cheam, Agriculture Western Australia
Ryegrass resistance in Western Australia – where and how much? Rick Llewellyn and Stephen Powles, Western Australian Herbicide Resistance Initiative, Faculty of Agriculture, University of Western Australia
Wild radish herbicide resistance survey, Michael Walsh, Ryan Duane and Stephen Powles, Western Australian Herbicide Resistance Initiative, University of Western Australia
Knockdown resistance in the Western Australian wheatbelt – a proposed survey, Paul B. Neve1, Abul Hashem2, Stephen B. Powles1,1Western Australian Herbicide Resistance Initiative, University of Western Australia, 2Agriculture Western Australia
Diflufenican resistant wild radish, Aik Cheam, Siew Lee, David Bowran, David Nicholson and Abul Hashem, Agriculture Western Australi
Multiple resistance to triazines and diflufenican further complicates wild radish control, Aik Cheam, Siew Lee, David Bowran, David Nicholson and Abul Hashem, Agriculture Western Australia
HERBICIDE TOLERANCE
25. Herbicide tolerance of lupins, Terry Piper, Weed Science Group, Agriculture Western Australia
26. Tanjil lupins will tolerate metribuzin under the right conditions, Peter Newman, Agronomist Elders Limited and Cameron Weeks, Mingenew/Irwin Group
27. Herbicide damage does not mean lower yield in Lupins, Peter Carlton, Trials Coordinator, Elders Limited
28. Herbicide tolerance of new pea varieties, Dr Terry Piper, Agriculture Western Australia
29. Herbicide tolerance of (waterlogged) wheat, Dr Terry Piper, Agriculture Western Australia
30. Wheat tolerance trials – Mingenew 1999, Peter Newman1, Cameron Weeks2 and Stewart Smith3,1Elders, Mingenew, 2Mingenew-Irwin Group,3Agriculture Western Australia
ISSUES OF TRIFLURALIN USE
31. Trifluralin works better on ryegrass when no-tilling into thick wheat stubbles as granules, or mixed with limesand, Bill Crabtree, WANTFA Scientific Officer
32. Increasing trifluralin rate did not compensate for delaying incorporation, Bill Crabtree, WANTFA Scientific Officer
33. Poor emergence survey, 1999, Terry Piper, Weed Science Group, Agriculture Western Australia
HERBICIDES – ISSUES AND OPTIONS
34. AFFINITY 400DF – A new herbicide with a new mode of action (Group G) for Broadleaf Weed Control in Cereals, Gordon Cumming, Technical Officer, Crop Care Australasia
35 Herbicide screening for Marshmallow, David Minkey1 and David Cameron2,1Agriculture Western Australia, 2Elders Ltd, Merredin
36. The control of Capeweed in Clearfield Production System for Canola, Mike Jackson and Scott Paton, Cyanamid Agriculture Pty Ltd
37.Effect of herbicides Tordonä 75D and Lontrelä,used for eradication of Skeleton Weed, on production of Lupins I the following seasons, John R. Peirce and Brad J. Rayner, Agriculture Western Australia
INDUSTRY PROTECTION
38. Graingaurd – Opportunities for agribusiness to help protect the West Australian grains industry, Greg Shea, Executive Officer, GrainGuard Agriculture Western Australi
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