Pre-adult mortality: should we care about it, and what can we do about it?

Area of Science:

• Evolutionary Biology
• Ecology
• Developmental Biology

Background:

• Pre-adult mortality is a widespread phenomenon, with 60-90% of offspring dying before reproduction across various taxa.
• Two primary hypotheses explain pre-adult mortality: stochastic events (chance) and selective disappearance (loss of low-quality individuals).

Purpose of the Study:

• To review current knowledge on early-life phenotypes and their role in pre-adult mortality.
• To explore whether these phenotypes are fixed or labile during development and act as targets of selection.
• To highlight the importance of pre-adult mortality in experimental studies.

Main Methods:

• Literature review and synthesis of existing research on pre-adult mortality and phenotypic selection.
• Analysis of hypotheses regarding stochasticity versus selective disappearance.
• Examination of developmental plasticity and its impact on survival.

Main Results:

• Pre-adult mortality is the norm, with significant variation in survival rates across taxa.
• Early-life phenotypic traits can be targets of selection, influencing who survives to reproduce.
• Laboratory conditions often minimize mortality, creating artificial populations that differ from natural settings.

Conclusions:

• Identifying traits determining survival is a key research gap.
• The composition of study populations (random vs. biased) impacts ecological and evolutionary interpretations.
• High pre-adult mortality in natural populations may explain the absence of detected fitness trade-offs in some studies.