A Dichotomy Theorem for Homomorphism Polynomials

In the present paper we show a dichotomy theorem for the complexity of polynomial evaluation. We associate to each graph H a polynomial that encodes all graphs of a fixed size homomorphic to H. We show that this family is computable by arithmetic circuits in constant depth if H has a loop or no edge and that it is hard otherwise (i.e., complete for VNP, the arithmetic class related to #P). We also demonstrate the hardness over the rational field of cut eliminator, a polynomial defined by B\"urgisser which is known to be neither VP nor VNP-complete in the field of two elements, if VP is not equal to VNP (VP is the class of polynomials computable by arithmetic circuit of polynomial size)

Pond canopy cover: a resource gradient for anuran larvae

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72395/1/j.1365-2427.2005.01497.x.pd

Speed kills? Migrating sea lamprey increase speed when exposed to an antipredator cue but make worse short-term decisions

© 2024 The Author(s). Published by Elsevier B.V. on behalf of International Association for Great Lakes Research. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).There is growing evidence that a natural repellent, injury-released alarm cues, can be used to guide the movements of invasive fishes to achieve management goals. However, because this process involves perception, downstream cognitive processing of sensory information affects decisions regarding expression of antipredator behavior. Response habituation, wherein repeated or continuous exposure to a cue reduces behavioral response rates, is an oft-cited challenge for use of predation cues as conservation tools. Habituation may be delayed or prevented by altering the concentration and/or the temporal pattern of odor release (pulses of odor vs continuous application). We examined the effects of varying odor concentration and exposure regime (continuous vs pulsed) on behavioral response of adult sea lamprey (Petromyzon marinus) to conspecific alarm cue in a two-choice maze. We found that exposure to alarm cue induced more frequent and rapid upstream movement, regardless of exposure regime. There was also clear evidence of a speed-accuracy tradeoff, wherein sea lamprey that took longer to arrive at the bifurcation in the maze were more likely to avoid the arm activated with alarm cue. We could not ascertain the value of increasing concentration or pulsing the alarm cue on preventing habituation, as habituation did not occur. We hypothesize dishabituation to the alarm cue occurred immediately prior to testing due to handling that may have inadvertently simulated an unsuccessful predator attack. If true, incorporating dishabituating stimuli may prove a useful means to maintain the efficacy of alarm cue when applied as a repellent to manipulate the movements of sea lamprey. © 2024 The Author(s)Great Lakes Fishery CommissionWe thank the US Fish and Wildlife Service staff for their technical assistance and the US Geological Survey Hammond Bay Biological Staff for the use of their facilities. Madison Perry, Kris Rygiel, Emily Suominen, and Anna Tursky provided assistance in the laboratory. We would also like to thank the two anonymous reviewers and the editor of this manuscript for their time and helpful suggestions. Financial support for the work reported here was provided by the Great Lakes Fishery Commission Sea Lamprey Research Program [ 2018-WAG-54070 ]

Laboratory selection at different temperatures modifies heat-shock transcription factor (HSF) activation in Drosophila melanogaster

The magnitude and time course of activation of the heat-shock transcription factor (HSF) differ among Drosophila melanogaster lines evolving at 18 degrees C, 25 degrees C or 28 degrees C for more than 20 years. At lower heat-shock temperatures (27–35 degrees C), flies from the 18 degrees C population had higher levels of activated HSF (as detected by an electrophoretic mobility shift assay) than those reared at 25 degrees C and 28 degrees C. At higher temperatures (36 and 37 degrees C), however, the 28 degrees C flies had the highest levels of HSF. These differences persisted after one generation of acclimation at 25 degrees C, suggesting that phenotypic plasticity was limited. In addition, larvae from the 28 degrees C lines activated HSF less rapidly after a 35 degrees C heat shock than those from the 18 degrees C and 25 degrees C populations. These results are similar but not identical to previously reported differences in expression of Hsp70 (the major heat-inducible stress protein in Drosophila melanogaster) among the experimental lines. We conclude that HSF activation evolves rapidly during laboratory culture at diverse temperatures and could play an important role in the evolution of the heat-shock response.</jats:p

Ecological and evolutionary functional genomics - How can it contribute to the risk assessment of chemicals?

Ecological and evolutionary functional genomics has progressed enormously over the last 10 years. One of the developments most relevant for environmental science is genome-wide gene expression profiling, using microarrays and RNAseq, of organisms exposed to toxic chemicals. In this way, the action spectrum of chemicals can be characterized on the basis of an extremely large number of endpoints. In this paper we identify a number of formidable problems for the use of transcription profiling in risk assessment. We raise four issues (1) Is it possible at all to assess environmental quality based on transcriptomes (mRNA abundance)? (2) Does gene expression classify treatments according to exposure or effect? (3) Do gene expressions allow identification of chemicals in mixtures? (4) Is it possible to discriminate fitness-neutral gene expressions from those associated with adverse outcomes? We call for the generation of more background data under normal, clean conditions. A close connection between traditional ecotoxicology and genomics seems to be particularly fruitful. Only in this way can transcriptome data be connected to endpoints accepted in risk assessment schemes. © 2011 American Chemical Society