The positive correlation between maternal size and offspring size: fitting pieces of a life‐history puzzle

Abstract

The evolution of investment per offspring (I) is often viewed through the lens of the classic theory, in which variation among individuals in a population is not expected. A substantial departure from this prediction arises in the form of correlations between maternal body size and I, which are observed within populations in virtually all taxonomic groups. Based on the generality of this observation, we suggest it is caused by a common underlying mechanism. We pursue a unifying explanation for this pattern by reviewing all theoretical models that attempt to explain it. We assess the generality of the mechanism upon which each model is based, and the extent to which data support its predictions. Two classes of adaptive models are identified: models that assume that the correlation arises from maternal influences on the relationship between I and offspring fitness [w(I)], and those that assume that maternal size influences the relationship between I and maternal fitness [W(I)]. The weight of evidence suggests that maternal influences on w(I) are probably not very general, and even for taxa where maternal influences on w(I) are likely, experiments fail to support model predictions. Models that assume that W(I) varies with maternal size appear to offer more generality, but the current challenge is to identify a specific and general mechanism upon which W(I) varies predictably with maternal size. Recent theory suggests the exciting possibility that a yet unknown mechanism modifies the offspring size-number trade-off function in a manner that is predictable with respect to maternal size, such that W(I) varies with size. We identify two promising avenues of inquiry. First, the trade-off might be modified by energetic costs that are associated with the initiation of reproduction ('overhead costs') and that scale with I, and future work could investigate what specific overhead costs are generally associated with reproduction and whether these costs scale with I. Second, the trade-off might be modified by virtue of condition-dependent offspring provisioning coupled with metabolic factors, and future work could investigate the proximate cause of, and generality of, condition-dependent offspring provisioning. Finally, drawing on the existing literature, we suggest that maternal size per se is not causatively related to variation in I, and the mechanism involved in the correlation is instead linked to maternal nutritional status or maternal condition, which is usually correlated with maternal size. Using manipulative experiments to elucidate why females with high nutritional status typically produce large offspring might help explain what specific mechanism underlies the maternal-size correlation.

Plant and Animal Reproductive Strategies: Lessons from Offspring Size and Number Tradeoffs

“…Both fecundity and offspring size generally increase with the size of the mother (Parsons, 1964;Roff, 1992;Honěk, 1993;Fox and Czesak, 2000;Shanbhag et al, 2003;Kolm et al, 2006a;Rollinson and Rowe, 2016), although exceptions exist (e.g., Fischer and Fiedler, 2001). Species for which no size-number tradeoff has been found typically show considerable variation in reproductive effort (Fox and Czesak, 2000).…”

“…Thus far, experimental evidence for the adaptive significance of variation in egg size across different conditions is limited, possibly because experimental conditions do not adequately mimic the complexity of natural environments. Other biotic factors that strongly select for large or small differential offspring size include food quality (e.g., Brody and Lawlor, 1984;Braby, 1994), competition (e.g., Parker and Begon, 1986), inbreeding (e.g., Duthie et al, 2016), limited dispersal (e.g., Kuijper and Johnstone, 2012) and predation (e.g., Kerfoot, 1974;Ernsting and Isaaks, 1997) (see also Table 2 in Rollinson and Rowe, 2016). In particular, increased competition generally selects for larger offspring size, while sizedependent predation may select for either smaller or larger offspring.…”

“…Reviews focused on animal reproductive strategies already exist (e.g., Fox and Czesak, 2000 for arthropods; Godfray et al, 1991;Monaghan and Nager, 1997 for birds;Einum et al, 2004 for fishes; Bernardo, 1996;Roff, 2002 for animals in general). The animal section aims to distill information from these reviews and from more recent literature, and synthesize the salient points.…”

Maternal effects on offspring size in a natural population of the viviparous tsetse fly

“…Across a great diversity of species, there is a common trend that -within species or populations -larger mothers tend to produce larger offspring (Fox & Czesak, 2000;Roff, 2002;Marshall et al, 2010;Rollinson & Rowe, 2015). This is because the per-brood reproductive effort is equivalent to offspring size.…”

食物限制对密点麻蜥繁殖投入和幼体表型的影响

“…Two kinds of trade-offs regarding energy allocation are faced by a mother when the energy available to her is limited. First, a mother has to decide on energy allocation for multiple tasks, such as maintenance, growth, and reproduction, leading to important life-history trade-offs (e.g., maintenance vs. reproduction) (Hegemann et al, 2013; Rollinson & Rowe, 2016); for instance, the tropical house wren ( Troglodytes aedon ) decreases parental reproductive investment (i.e. nestling feeding frequency), but does not alter self-maintenance (metabolic rate and body condition) when the cost of activity increases during reproduction (Tieleman et al, 2008).…”