Mind the lag: understanding genetic extinction debt for conservation

Time lag refers to delayed genetic consequences after an environmental shift or population decline.Life-history traits such as long life span, vegetative propagation, overlapping generations, and mating by outcrossing, support the build-up of a time lag after an environmental shift; confounding factors include sampling strategy and marker choice.Time lags can be evaluated using temporal sampling, different estimates of effective and census population sizes, and choice of a reference population.The more widely recognized ‘extinction debt’ problem in community ecology depends on delayed genetic responses (‘genetic extinction debts’ = time lags) in the populations composing that community.Conservation strategies should account for time lags since actions taken today will impact future genetic composition, potentially mitigating negative effects before they become irreversible. The delay between disturbance events and genetic responses within populations is a common but surprisingly overlooked phenomenon in ecology and evolutionary and conservation genetics. If not accounted for when interpreting genetic data, this time lag problem can lead to erroneous conservation assessments. We (i) identify life-history traits related to longevity and reproductive strategies as the main determinants of time lags, (ii) evaluate potential confounding factors affecting genetic parameters during time lags, and (iii) propose approaches that allow controlling for time lags. Considering the current unprecedented rate of loss of genetic diversity and adaptive potential, we expect our novel interpretive and methodological framework for time lags to stimulate further research and discussion on the most appropriate approaches to analyse genetic diversity for conservation. The delay between disturbance events and genetic responses within populations is a common but surprisingly overlooked phenomenon in ecology and evolutionary and conservation genetics. If not accounted for when interpreting genetic data, this time lag problem can lead to erroneous conservation assessments. We (i) identify life-history traits related to longevity and reproductive strategies as the main determinants of time lags, (ii) evaluate potential confounding factors affecting genetic parameters during time lags, and (iii) propose approaches that allow controlling for time lags. Considering the current unprecedented rate of loss of genetic diversity and adaptive potential, we expect our novel interpretive and met