Laboratory evolution of population stability in Drosophila: constancy and persistence do not necessarily coevolve

1. Despite considerable theoretical work, the evolution of population stability has rarely been investigated empirically. Moreover, it is not clear whether different stability properties of a population evolve together, or independently. 2. We investigate the evolution of two aspects of population stability using laboratory populations of Drosophila melanogaster selected for faster preadult development and early reproduction, and their matched controls. 3. We show that the constancy stability of the selected populations is significantly higher than their controls, confirming a previous observation that population stability can evolve as a by-product of life-history evolution. This enhanced constancy stability is due to a reduced maximal per capita growth rate, brought about by a reduction in fecundity of the selected populations as a result of the trade-off between developmental rate and fecundity. 4. Persistence stability, as reflected by the probability of extinction, does not differ significantly between selected and control populations. 5. We also show how seemingly trivial experimental details, such as the protocol for restarting extinct populations, can interact with life-history traits to alter the manifestation of the stability properties of a population.     

Discrete three-stage population model: persistence and global stability results

A general three-stage discrete-time population model is studied. The inherent net reproductive number for this model is derived. Global stability of the origin is established provided that the inherent net reproductive number is less than one. If it is larger than one the existence of a unique positive fixed point is proved and the persistence of the system is established. Finally, for certain parameter ranges global stability of the positive fixed point is proved.     

Discrete three-stage population model: persistence and global stability results

A general three-stage discrete-time population model is studied. The inherent net reproductive number for this model is derived. Global stability of the origin is established provided that the inherent net reproductive number is less than one. If it is larger than one the existence of a unique positive fixed point is proved and the persistence of the system is established. Finally, for certain parameter ranges global stability of the positive fixed point is proved.     

Abstracts of Oral Papers not published in the Supplement

Costa, M. J. & Cabral, H. N. ( Instituto de Oceanografia, Faculdade de Ciências de Universidade de Lisboa, R. Ernesto de Vasconcelos, 1749-016 Lisboa, Portugal; Departamento de Zoologia e Antropologia, Faculdade de Ciências da Universidade de Lisboa, R. Ernesto de Vasconcelos, 1749-016 Lisboa, Portugal ), Almeida, P. R. ( Instituto de Oceanografia, Faculdade de Ciências de Universidade de Lisboa, R Ernesto de Vasconcelos, 1749-016 Lisboa, Portugal; Laboratório de Biologia da Conservação, Departamento de Biologia, Universidade de Évora, 7002-554 Évora, Portugal ), Costa, J. L., Chainho, P., Chaves, M. L., Prista, N., Vasconcelos, R. & Cabral, M. ( Instituto de Oceanografia, Faculdade de Ciêcias de Universidade de Lisboa, R. Ernesto de Vasconcelos, 1749-016 Lisboa, Portugal ).     

Global stability and persistence of simple food chains

The main purpose of this paper is to develop criteria for which a simple food-chain model of intermediate type and of arbitrary length has a globally stable positive equilibrium and to develop criteria under which such a food chain exhibits uniform persistence. The same techniques are used to obtain conditions for a model of a predator-prey system with mutual interference of the predator to possess a globally stable positive equilibrium.     

Interannual variations of the fish assemblage in the transitional zone of the Three Gorges Reservoir: persistence and stability

The construction of dams may lead to dramatic changes in fish assemblages due to the loss of lotic habitat caused by impoundment, which have been well documented. However, knowledge of the temporal variation of fish assemblages in the transitional zone, which is an ecotone between lotic and lentic environments of the reservoir, is still very rare. In the present study, fishes in the transitional zone of the Three Gorges Reservoir were sampled from 1997 to 2002 and from 2006 to 2009 to investigate interannual variations of fish assemblages. The results showed that 9 families, composed of 77 species, were found in the transitional zone with Cyprinidae as the dominant group. By cluster analysis (CLUSTER) and non-metric multidimensional scaling analysis (MDS), assemblages were separated into two groups at a Bray-Curtis similarity value of 77.26%, representing the pre-impoundment period and post-impoundment period. Following analysis of similarity percentages of species contributions (SIMPER), shifts in abundances of Coreius guichenoti, Rhinogobio cylindricus and Coreius heterodon, etc. contributed most to the difference between the two groups. Surprisingly, contrasting to the drastic changes in lacustrine region, the fish assemblage in the transitional zone appeared to be relatively stable, since the ten core species caught were consistently recorded every year, and no significant species replacement occurred during our study period. Besides, the moderate index of persistence indicated persistence of the fish assemblage as well, in spite of the shift of some species. Based on the results of ordination and time-lag analysis, the fish assemblage in the transitional zone showed no directional change. We conclude that fish assemblage in the transitional zone of the Three Gorges Reservoir was stable across the surveyed years. Based on our results, we propose that maintenance of dynamic transitional zones in reservoirs will be useful for the preservation of fishes, particularly for the endemic species inhabiting the upper Yangtze.     

Steinernema kraussei,an indigenous nematode found in coniferous forests: efficacy and field persistence against Hylobius abietis

1 More than 100 ha of forest restocking sites in Northern Britain are treated annually with the entomopathogenic nematode Steinernema carpocapsae to control larvae of the large pine weevil, Hylobius abietis. However, data on geographical distribution, thermal niche breadth and foraging strategy suggest that S. carpocapsae may be a poor choice for this application. 2 We undertook laboratory and field experiments that compared S. carpocapsae with Steinernema kraussei for efficacy towards H. abietis. Steinernema kraussei is indigenous to Northern Britain, active at low temperatures and is thought to adopt a ‘cruise’ foraging strategy particularly suitable for finding subterranean sedentary insects such as H. abietis. Conversely, S. carpocapsae has not been recorded in Northern Britain, prefers warmer temperatures and is thought to remain at the soil surface adopting an ambush foraging strategy. 3 There were no differences in the ability of the two nematodes to infect and kill larvae of H. abietis in laboratory experiments and, in two field experiments, both species were equally effective both in terms of parasitizing larvae within the stumps and reducing emergence of adult H. abietis. In one experiment, we monitored persistence of nematodes for 1 year after application and found S. kraussei persistence was much greater than that of S. carpocapsae. 4 The greater persistence of S. kraussei suggests that this nematode is better adapted to conditions in Northern Britain, but this may potentially represent a greater threat to nontarget insects. 5 Our data suggest that there would be little benefit associated with substituting S. kraussei for S. carpocapsae in integrated pest management systems for H. abietis.     

ADAM: another database of abbreviations in MEDLINE

MOTIVATION: Abbreviations are an important type of terminology in the biomedical domain. Although several groups have already created databases of biomedical abbreviations, these are either not public, or are not comprehensive, or focus exclusively on acronym-type abbreviations. We have created another abbreviation database, ADAM, which covers commonly used abbreviations and their definitions (or long-forms) within MEDLINE titles and abstracts, including both acronym and non-acronym abbreviations. RESULTS: A model of recognizing abbreviations and their long-forms from titles and abstracts of MEDLINE (2006 baseline) was employed. After grouping morphological variants, 59 405 abbreviation/long-form pairs were identified. ADAM shows high precision (97.4%) and includes most of the frequently used abbreviations contained in the Unified Medical Language System (UMLS) Lexicon and the Stanford Abbreviation Database. Conversely, one-third of abbreviations in ADAM are novel insofar as they are not included in either database. About 19% of the novel abbreviations are non-acronym-type and these cover at least seven different types of short-form/long-form pairs. AVAILABILITY: A free, public query interface to ADAM is available at http://arrowsmith.psych.uic.edu, and the entire database can be downloaded as a text file.