Biology subjects

Nietlisbach, P.

Publications and source records attributed to Nietlisbach, P..

2 recordsLinked to original sources

bioRxiv2021

The genetics of assisted gene flow: immediate costs and long-term benefits

Plant and animal populations are facing several novel risks such as human-mediated habitat fragmentation and climate change that threaten their long-term productivity and persistence. With the genetic health of many populations deteriorating due to climate change outpacing physiological adaptation, human interventions in the form of assisted gene flow (AGF) may provide genetic variation to adapt populations to predicted climate change scenarios and result in more robust and productive populations. We ran genetic simulations to mimic a variety of AGF scenarios and measured their outcomes on population-level fitness to answer the question: in which circumstances is it worthwhile to perform AGF? Based on the parameters we explored, AGF may be harmful in certain situations over the short term (e.g., the first [~]10-20 generations), due to outbreeding depression and introducing deleterious genetic variation. Moreover, under many parameter sets, the benefits of AGF were relatively weak or took many generations to accrue. In general, when the adaptive trait is controlled by many loci of small effect, the benefits of assisted gene flow take much longer to realize-potentially too long for most climate-related management decisions. We also show that when translocation effort is divided across several generations and outbreeding depression is strong, the recipient population experiences a smaller decrease in fitness as compared to moving all individuals in a single effort. Importantly, in most cases, we show that the genomic integrity of the recipient population remains relatively intact following AGF; the amount of genetic material from the donor population typically ends up constituting no more of the recipient populations genome than the fraction introduced. Our results will be useful for conservation practitioners and silviculturists, for instance, aiming to intervene and adaptively manage so that populations maintain a robust genetic health and maintain productivity into the future given anthropogenic climate change.

evolutionary biology↗

bioRxiv2019

Individuals' expected genetic contributions to future generations, reproductive value, and short-term metrics of fitness in free-living song sparrows (Melospiza melodia)

Appropriately defining and enumerating fitness is fundamental to explaining and predicting evolutionary dynamics. Yet theoretical concepts of fitness are often hard to translate into quantities that can be quantified in wild populations experiencing complex environmental, demographic, genetic and selective variation. While the fittest entities might be widely understood to be those that ultimately leave most descendants at some future time, such long-term legacies are hard to measure, impeding evaluation of how well more tractable short-term metrics of individual fitness directly predict longer-term outcomes. One opportunity for conceptual and empirical convergence stems from the principle of individual reproductive value (Vi), defined as the number of copies of each of an individuals alleles that is expected to be present in future generations given the individuals realised pedigree of descendants. Since Vi tightly predicts an individuals longer-term genetic contribution, quantifying Vi provides a tractable route to quantifying what, to date, has been an abstract fitness concept. We used complete pedigree data from free-living song sparrows (Melospiza melodia) to demonstrate that individuals expected genetic contributions stabilise within an observed 20-year time period, allowing individual Vi to be evaluated. Considerable among-individual variation in Vi was evident in both sexes. However, standard short-term metrics of individual fitness, comprising lifespan, lifetime reproductive success and projected growth rate, typically explained less than half the variation. Given these results, we discuss what evolutionary inferences can and cannot be directly drawn from short-term versus longer-term fitness metrics observed on individuals, and highlight that analyses of pedigree structure may provide useful complementary insights into evolutionary processes and outcomes.

evolutionary biology↗