Interplay of population size and environmental fluctuations: A new explanation for fitness cost rarity in asexuals

2021 ◽  
Author(s):  
Yashraj Chavhan ◽  
Sarthak Malusare ◽  
Sutirth Dey
Keyword(s):  
Population Size ◽  
Fitness Cost ◽  
Environmental Fluctuations

Ecological Aspects of Smaller Cetaceans, with Emphasis on the Striped Dolphin (Stenella coeruleoalba)

1975 ◽  
Vol 32 (7) ◽  
pp. 1069-1072 ◽  
Author(s):  
Masaharu Nishiwaki
Keyword(s):  
Population Size ◽  
Stenella Coeruleoalba ◽  
Striped Dolphin ◽  
Ecological Aspects ◽  
Environmental Fluctuations

The striped dolphin (Stenella coeruleoalba) is captured by drive fisheries as it migrates along the coast of Japan. The largest school of striped dolphins captured contained 2838 individuals. Annual catches have reached approximately 20,000 striped dolphins, and it is estimated that the population fished must number 400,000–600,000 animals. Recent variations in catch levels have resulted from economic and environmental fluctuations, not from a decrease in population size.

Environmental Fluctuations and Population Size

Nature ◽  
1971 ◽  
Vol 231 (5298) ◽  
pp. 112-114 ◽  
Author(s):  
FRANCISCO J. AYALA
Keyword(s):  
Population Size ◽  
Environmental Fluctuations

scholarly journals Environmental fluctuations can promote evolutionary rescue in high-extinction-risk scenarios

2020 ◽  
Vol 287 (1932) ◽  
pp. 20201144
Author(s):  
James H. Peniston ◽  
Michael Barfield ◽  
Andrew Gonzalez ◽  
Robert D. Holt
Keyword(s):  
High Risk ◽  
Environmental Change ◽  
Population Size ◽  
Extinction Risk ◽  
Environmental Variation ◽  
Stochastic Simulations ◽  
Initial Population ◽  
Risk Scenarios ◽  
Evolutionary Rescue ◽  
Environmental Fluctuations

Substantial environmental change can force a population onto a path towards extinction, but under some conditions, adaptation by natural selection can rescue the population and allow it to persist. This process, known as evolutionary rescue, is believed to be less likely to occur with greater magnitudes of random environmental fluctuations because environmental variation decreases expected population size, increases variance in population size and increases evolutionary lag. However, previous studies of evolutionary rescue in fluctuating environments have only considered scenarios in which evolutionary rescue was likely to occur. We extend these studies to assess how baseline extinction risk (which we manipulated via changes in the initial population size, degree of environmental change or mutation rate) influences the effects of environmental variation on evolutionary rescue following an abrupt environmental change. Using a combination of analytical models and stochastic simulations, we show that autocorrelated environmental variation hinders evolutionary rescue in low-extinction-risk scenarios but facilitates rescue in high-risk scenarios. In these high-risk cases, the chance of a run of good years counteracts the otherwise negative effects of environmental variation on evolutionary demography. These findings can inform the development of effective conservation practices that consider evolutionary responses to abrupt environmental changes.

Reduction of spermatogonia and testosterone in rat testes flown on space lab-3

1986 ◽  
Vol 44 ◽  
pp. 248-249
Author(s):  
Delbert E. Philpott ◽  
W. Sapp ◽  
C. Williams ◽  
T. Fast ◽  
J. Stevenson ◽  
...  
Keyword(s):  
Social Interaction ◽  
Social Status ◽  
Population Size ◽  
Physiological Response ◽  
Social Rank ◽  
Reproductive Function ◽  
Testicular Development ◽  
Organ Weights ◽  
Reproductive Maturation ◽  
Metabolic Activities

Space Lab 3 (SL-3) was flown on Shuttle Challenger providing an opportunity to measure the effect of spaceflight on rat testes. Cannon developed the idea that organisms react to unfavorable conditions with highly integrated metabolic activities. Selye summarized the manifestations of physiological response to nonspecific stress and he pointed out that atrophy of the gonads always occurred. Many papers have been published showing the effects of social interaction, crowding, peck order and confinement. Flickinger showed delayed testicular development in subordinate roosters influenced by group numbers, social rank and social status. Christian reported increasing population size in mice resulted in adrenal hypertrophy, inhibition of reproductive maturation and loss of reproductive function in adults. Sex organ weights also declined. Two male dogs were flown on Cosmos 110 for 22 days. Fedorova reported an increase of 30 to 70% atypical spermatozoa consisting of tail curling and/or the absence of a tail.

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