The importance of social dimension and maturation stage for the probabilistic maturation reaction norm in Poecilia reticulata

Abstract

Maturation is an important event in an organism's life history, with important implications on dynamics of both wild and captive populations. The probabilistic maturation reaction norm (PMRN) has emerged as an important method to describe variation in maturation in wild fish. Because most PMRNs are based on age and size only, it is important to understand limitations of these variables in explaining maturation. We experimentally assessed (i) the sensitivity of age-and size-based PMRNs to unaccounted sources of plasticity, (ii) the role of social environment on maturation and (iii) the significance of estimating PMRNs early and late in the maturation process (initiation and completion of maturation, respectively). We reared male guppies (Poecilia reticulata) under laboratory conditions, subjected to two food levels and three different social cues. We found that growth and social environment affected the maturation in a way that could not be accounted for by their effect on age and size. PMRNs estimated for the initiation stage were less plastic (growth differences and social cues influenced the PMRN shape only little) than those for completion. The initiation of maturation is probably closer to the maturation 'decision' and allows determining factors influencing maturation decision most accurately.

Reaction norm analysis reveals rapid shifts toward delayed maturation in harvested Lake Erie yellow perch (Perca flavescens)

“…It is important to acknowledge a general uncertainty about evolutionary inferences derived from changes in PMRNs involving natural populations. While the logic of PMRN analysis is compelling, maturation can be affected by factors other than size and age, such as growth history, body condition, thermal and even social aspects of the environment (Diaz Pauli & Heino, ; Grift, Heino, Rijnsdorp, Kraak, & Dieckmann, ; Morita & Fukuwaka, ; Morita, Tsuboi, & Nagasawa, ; Uusi‐Heikkilä et al, ). Consequently, shifting PMRNs in some cases could reflect contributions from phenotypic plasticity in response to unmeasured factors as opposed to being derived from underlying genetic change in response to harvest (Dieckmann & Heino, ; Kraak, ; Uusi‐Heikkilä et al, ).…”

Effects of ambient oxygen and size-selective mortality on growth and maturation in guppies

“…Males also had a higher investment in reproduction. Our estimates are comparable with earlier studies on guppies and other poeciliids for reproductive investment (Baatrup and Junge, 2001; Schlupp et al ., 2006) and size and age at maturation (Reznick and Bryga, 1987; Magurran, 2005); it should be noticed that most studies considered completion of maturation, rather than initiation of maturation (but see Diaz Pauli and Heino, 2013). Similar directional changes in maturation and reproductive investment have been observed in several exploited fish populations (Heino et al ., 2015) and in other selection experiments (van Wijk et al ., 2013; Uusi-Heikkilä et al ., 2015).…”

“…At the completion stage, there are several layers of spermagonial cysts, sperm cells and developed testicular ducts with enzyme activity, and spermatozeugmata (sperm bundles) are present (Schreibman et al ., 1982; Koya et al ., 2003). We consider the initiation of maturation to be a good representation of male maturation ‘decision’ in guppies; it is the time when they commit to maturation, reflecting more accurately the factors that affect maturation than the final maturation stage (Tobin et al ., 2010; Harney et al ., 2012; Diaz Pauli and Heino, 2013). Therefore, in the present study we assessed the effect of oxygen and size selection on the initiation of maturation, from now on referred to as maturation.…”

Probabilistic maturation reaction norms assessed from mark–recaptures of wild fish in their natural habitat

“…This is perhaps not surprising, because the allocation of energy to gonads starts months ahead of the actual spawning (Tyler and Sumpter 1996). While demographic maturation reaction norms are typically estimated from a retrospective approach (Grift et al 2003), our study speaks in favor of adding information about body size earlier in life (see also, Diaz Pauli and Heino 2013; Harney et al 2013). We acknowledge that information about the juvenile life history will often not be directly available from collected data.…”

“…This finding supports the long-held hypothesis that fishing may drive evolutionary changes in fish life histories (Miller 1957). However, the ability of probabilistic maturation reaction norms to detect evolution is still a matter of debate and investigation (Morita et al 2009; Uusi-Heikkilä et al 2011; Diaz Pauli and Heino 2013; Harney et al 2013). By specifically modeling the probability of maturing at combinations of age and body size, probabilistic maturation reaction norms should be insensitive to any environmental variation (e.g., temperature or food availability) affecting maturation through growth plasticity (Heino et al 2002).…”