TY - JOUR
T1 - Taming fitness
T2 - organism-environment interdependencies preclude long-term fitness forecasting
AU - Doulcier, Guilhem
AU - Takacs, Peter
AU - Bourrat, Pierrick
PY - 2021/1
Y1 - 2021/1
N2 - Fitness is a central but notoriously vexing concept in evolutionary biology. The propensity interpretation of fitness is often regarded as the least problematic account for fitness. It ties an individual's fitness to a probabilistic capacity to produce offspring. Fitness has a clear causal role in evolutionary dynamics under this account. Nevertheless, the propensity interpretation faces its share of problems. We discuss three of these. We first show that a single scalar value is an incomplete summary of a propensity. Second, we argue that the widespread method of “abstracting away” environmental idiosyncrasies by averaging over reproductive output in different environments is not a valid approach when environmental changes are irreversible. Third, we point out that expanding the range of applicability for fitness measures by averaging over more environments or longer time scales (so as to ensure environmental reversibility) reduces one's ability to distinguish selectively relevant differences among individuals because of mutation and eco-evolutionary feedbacks. This series of problems leads us to conclude that a general value of fitness that is both explanatory and predictive cannot be attained. We advocate for the use of propensity-compatible methods, such as adaptive dynamics, which can accommodate these difficulties.
AB - Fitness is a central but notoriously vexing concept in evolutionary biology. The propensity interpretation of fitness is often regarded as the least problematic account for fitness. It ties an individual's fitness to a probabilistic capacity to produce offspring. Fitness has a clear causal role in evolutionary dynamics under this account. Nevertheless, the propensity interpretation faces its share of problems. We discuss three of these. We first show that a single scalar value is an incomplete summary of a propensity. Second, we argue that the widespread method of “abstracting away” environmental idiosyncrasies by averaging over reproductive output in different environments is not a valid approach when environmental changes are irreversible. Third, we point out that expanding the range of applicability for fitness measures by averaging over more environments or longer time scales (so as to ensure environmental reversibility) reduces one's ability to distinguish selectively relevant differences among individuals because of mutation and eco-evolutionary feedbacks. This series of problems leads us to conclude that a general value of fitness that is both explanatory and predictive cannot be attained. We advocate for the use of propensity-compatible methods, such as adaptive dynamics, which can accommodate these difficulties.
KW - eco-evolutionary feedbacks
KW - environment
KW - expected reproductive output
KW - fitness
KW - propensity
UR - http://www.scopus.com/inward/record.url?scp=85096635398&partnerID=8YFLogxK
UR - http://purl.org/au-research/grants/arc/FL170100160
U2 - 10.1002/bies.202000157
DO - 10.1002/bies.202000157
M3 - Article
C2 - 33236344
AN - SCOPUS:85096635398
VL - 43
SP - 1
EP - 13
JO - BioEssays
JF - BioEssays
SN - 0265-9247
IS - 1
M1 - 2000157
ER -