Extinction in Random Environments
An important currency for individuals is their lifetime reproductive success (LRS), which is random simply due to demographic stochasticity. That randomness determines extinction probability. However, the distribution of LRS is also significantly affected by environmental variation. Previously we have shown (for a random environment that follows a Markov chain) how LRS is affected by an…
Individuals' lifetime reproductive success is crucial to their survival, but it is subject to randomness due to demographic fluctuations. This unpredictability directly influences a species' probability of extinction. However, environmental fluctuations also play a significant role in shaping reproductive outcomes. Our previous research focused on how an individual's birth environment impacts their lifetime reproductive success within a random environment that follows a Markov chain.
Yet, our previous study failed to consider the temporal connection between a parent's birth environment and the environments their offspring are born into. In this work, we aim to calculate the precise joint probability distribution of lifetime reproductive success for lineages spanning multiple environmental states, assuming a Markovian environment.
With this joint distribution in hand, we derive exact lineage extinction probabilities that take into account demographic stochasticity, environmental frequency, and temporal autocorrelation. To illustrate the practical applications of our framework, we apply it to two species: the Pacific Chinook salmon, which is semelparous with high early mortality, and the European roe deer, which is iteroparous with delayed maturity.
Our findings reveal that the initial birth state of a lineage can permanently determine its fate. For the salmon, an unfavorable birth state leads to near-certain extinction, regardless of future environmental changes. Conversely, for the roe deer, we uncover an unexpected phenomenon where prolonged poor conditions can inadvertently rescue vulnerable individuals by extending the upper range of their reproductive potential.
Moreover, our exact calculations demonstrate that simplified one-dimensional lifetime reproductive success distributions can create a misleadingly homogeneous reproductive landscape, inadvertently overstating extinction risks for lineages that started in poor environments while understating risks for those that began in favorable conditions.
By preserving the environmental covariance, we can more accurately predict evolutionary viability and the emergence of advantageous mutations. As global climate change intensifies environmental volatility, adopting exact joint demographic models becomes essential for accurately assessing true extinction risks for various species.
Written by urgent.news from bioRxiv's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
