Contrasting effects of ecological and evolutionary processes on range expansions and shifts

Mapping Intimacies ◽

10.22541/au.161217810.03338053/v1 ◽

2021 ◽

Author(s):

Christopher Weiss-Lehman ◽

Allison Shaw

Keyword(s):

Allee Effect ◽

Extinction Risk ◽

Range Shifts ◽

Evolutionary Processes ◽

Ecological Processes ◽

Mate Finding ◽

Factors Influencing ◽

Spatial Sorting ◽

And Shifts ◽

Dispersal Evolution

Research has conclusively demonstrated the potential for dispersal evolution in range expansions and shifts through a process termed spatial sorting. However, the degree of dispersal evolution observed has varied substantially among organisms. Further, it is unknown how the factors influencing dispersal evolution might impact other ecological processes at play. We use an individual-based model to investigate the effects of the underlying genetics of dispersal and mode of reproduction in range expansions and shifts. Spatial sorting behaves similarly to natural selection in that dispersal evolution increases with sexual selection and loci number. Contrary to our predictions, however, increased dispersal does not always improve a population’s ability to track changing conditions. The mate finding Allee effect inherent to sexual reproduction increases extinction risk during range shifts, counteracting the beneficial effect of increased dispersal evolution. Our results demonstrate the importance of considering both ecological and evolutionary processes for understanding range expansions and shifts.

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The hidden side of the Allee effect: correlated demographic traits and extinction risk in experimental populations

10.24072/pcjournal.41 ◽

2021 ◽

Vol 1 ◽

pp. 1-None

Author(s):

Elodie Vercken ◽

Géraldine Groussier ◽

Laurent Lamy ◽

Ludovic Mailleret

Keyword(s):

Allee Effect ◽

Extinction Risk ◽

Demographic Traits ◽

Experimental Populations

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A logistic two-sex model with mate-finding Allee effect

Involve a Journal of Mathematics ◽

10.2140/involve.2019.12.1343 ◽

2019 ◽

Vol 12 (8) ◽

pp. 1343-1355

Author(s):

Elizabeth Anderson ◽

Daniel Maxin ◽

Jared Ott ◽

Gwyneth Terrett

Keyword(s):

Allee Effect ◽

Mate Finding

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Using source-sink landscape theory to investigate factors influencing ecological processes in Kaiyang County, China

10.22541/au.159129026.69927744 ◽

2020 ◽

Author(s):

Shuang shuang Hou ◽

Li fei Yu ◽

Wei Yan ◽

Shu hong Gu ◽

Xiao ping Gu

Keyword(s):

Ecological Processes ◽

Factors Influencing ◽

Landscape Theory ◽

Source Sink

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Genetic Allee effects and their interaction with ecological Allee effects

10.1101/061549 ◽

2016 ◽

Author(s):

Meike J. Wittmann ◽

Hanna Stuis ◽

Dirk Metzler

Keyword(s):

Population Size ◽

Inbreeding Depression ◽

Survival Probability ◽

Allee Effect ◽

Extinction Risk ◽

List Type ◽

Small Populations ◽

Allee Effects ◽

Deleterious Mutations ◽

Lethal Equivalents

SummaryIt is now widely accepted that genetic processes such as inbreeding depression and loss of genetic variation can increase the extinction risk of small populations. However, it is generally unclear whether extinction risk from genetic causes gradually increases with decreasing population size or whether there is a sharp transition around a specific threshold population size. In the ecological literature, such threshold phenomena are called “strong Allee effects” and they can arise for example from mate limitation in small populations.In this study, we aim to a) develop a meaningful notion of a “strong genetic Allee effect”, b) explore whether and under what conditions such an effect can arise from inbreeding depression due to recessive deleterious mutations, and c) quantify the interaction of potential genetic Allee effects with the well-known mate-finding Allee effect.We define a strong genetic Allee effect as a genetic process that causes a population’s survival probability to be a sigmoid function of its initial size. The inflection point of this function defines the critical population size. To characterize survival-probability curves, we develop and analyze simple stochastic models for the ecology and genetics of small populations.Our results indicate that inbreeding depression can indeed cause a strong genetic Allee effect, but only if individuals carry sufficiently many deleterious mutations (lethal equivalents) on average and if these mutations are spread across sufficiently many loci. Populations suffering from a genetic Allee effect often first grow, then decline as inbreeding depression sets in, and then potentially recover as deleterious mutations are purged. Critical population sizes of ecological and genetic Allee effects appear to be often additive, but even superadditive interactions are possible.Many published estimates for the number of lethal equivalents in birds and mammals fall in the parameter range where strong genetic Allee effects are expected. Unfortunately, extinction risk due to genetic Allee effects can easily be underestimated as populations with genetic problems often grow initially, but then crash later. Also interactions between ecological and genetic Allee effects can be strong and should not be neglected when assessing the viability of endangered or introduced populations.

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Spatial Population Structure Determines Extinction Risk in Climate-Induced Range Shifts

The American Naturalist ◽

10.1086/706259 ◽

2020 ◽

Vol 195 (1) ◽

pp. 31-42 ◽

Cited By ~ 1

Author(s):

Christopher Weiss-Lehman ◽

Allison K. Shaw

Keyword(s):

Population Structure ◽

Extinction Risk ◽

Range Shifts ◽

Spatial Population ◽

Spatial Population Structure

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Climate change and other factors influencing the decline of the Tasmanian cider gum (Eucalyptus gunnii)

Australian Journal of Botany ◽

10.1071/bt08105 ◽

2008 ◽

Vol 56 (8) ◽

pp. 684 ◽

Cited By ~ 22

Author(s):

J. A. Calder ◽

J. B. Kirkpatrick

Keyword(s):

Climate Change ◽

Climatic Change ◽

Extinction Risk ◽

Spatial Relationship ◽

Good Health ◽

Aerial Photographs ◽

Severe Drought ◽

Tree Decline ◽

Factors Influencing ◽

The Relationship

Global climatic change has been strongly implicated in the decline of many species. However, other processes can contribute towards the extinction risk of these species. Could management of these processes arrest or slow climatically related decline? We test the relationship between climate change, and other potential threatening factors, and the decline of Eucalyptus gunnii, a tree endemic to the subalpine regions of Tasmania, Australia. Through observing the spatial patterns of both climatic change and dieback, we found there was a stronger pattern of increasing droughts in the eastern part of the species range, the region which also displayed the worst dieback. A time series of aerial photographs revealed that the most severe drought periods in the last several decades have coincided with the most rapid tree decline. However, the sites that suffered the worst dieback were also more heavily used for stock grazing, a factor which had a stronger spatial relationship with tree decline than climate. Other factors were also implicated in the decline, including possum browsing. The good health of some populations in the most climatically stressed areas suggests that the amelioration of non-climatic stresses could be effective in maintaining the health of the surviving populations.

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