Biological individuality is a notoriously thorny topic for biologists and philosophers of biology. In this paper we argue that biological individuality presents multiple, interconnected questions for biologists and philosophers that together form a problem agenda. Using a case study of an interdisciplinary research group in ecology, behavioral and evolutionary biology, we claim that a debate on biological individuality that seeks to account for diverse practices in the biological sciences should be broadened to include and give prominence to questions about uniqueness (...) and temporality. We show that broadening the problem agenda of biological individuality draws attention to underrecognized philosophical issues and discussions and thereby organizes and enriches the existing debate. (shrink)

We here develop a concept of an individualized niche in analogy to Hutchison’s population-level concept of the ecological niche. We consider the individualized niche as the range of environmental conditions under which a particular individual has an expected lifetime reproductive success of ≥ 1. Our concept has primarily an ecological function, as it refers to the match of an individual phenotype to its contemporary environment while we discuss evolutionary fitness as an evaluative parameter of this fit. We address four specific (...) challenges that occur when scaling the niche down from populations to individuals. In particular, we discuss the consequences of uniqueness of individuals in a population and the corresponding lack of statistical replication, the dynamic nature of individualized niches and how they can be studied either as time-slice niches, as prospective niches or as trajectory-based niches, the dimensionality of the individualized niche, that is greater than the population niche due to the additional dimensions of intra-specific niche space, how the boundaries of individualized niche space can be defined by expected lifetime reproductive success and how expected reproductive success can be inferred by marginalizing fitness functions across phenotypes or environments. We frame our discussion in the context of recent interest in the causes and consequences of individual differences in animal behavior. (shrink)