Developmental plasticity and the evolution of animal complex life cycles

Abstract

Metazoan life cycles can be complex in different ways. A number of diverse phenotypes and reproductive events can sequentially occur along the cycle, and at certain stages a variety of developmental and reproductive options can be available to the animal, the choice among which depends on a combination of organismal and environmental conditions. We hypothesize that a diversity of phenotypes arranged in developmental sequence throughout an animal's life cycle may have evolved by genetic assimilation of alternative phenotypes originally triggered by environmental cues. This is supported by similarities between the developmental mechanisms mediating phenotype change and alternative phenotype determination during ontogeny and the common ecological condition that favour both forms of phenotypic variation. The comparison of transcription profiles from different developmental stages throughout a complex life cycle with those from alternative phenotypes in closely related polyphenic animals is expected to offer critical evidence upon which to evaluate our hypothesis.

Cheats as first propagules: A new hypothesis for the evolution of individuality during the transition from single cells to multicellularity

“…Despite their biological significance, the evolutionary origins of life cycles are unclear [15,19]. Here, informed by experimental studies, we draw attention to critical issues and mechanistic problems that lie at the heart of life cycle evolution.…”

Phenotypic plasticity in development and evolution: facts and concepts

“…For instance, the developmental switches producing the alternative phenotypes are mediated by the same endocrine factors (juvenile hormone and ecdysteroids) that control metamorphosis (Nijhout 1999). Evolutionary relationships between alternative and sequential polyphenism are further discussed by Minelli & Fusco (2010).…”

“…This is the case of the seasonal polyphenism in the bivoltine butterfly Bicyclus anynana, with two adult morphs adapted to the dry and wet season, respectively (Roskam & Brakefield 1998), and also the case of cyclomorphosis in many multivoltine species of rotifers, cladocerans and bryozoans (Greene 1999). Phenotypic variation in multivoltine species can involve morphology, life-history traits and modes of reproduction as well, resulting in a complex multi-generation life cycle (Minelli & Fusco 2010) as in the case of many aphids, with alternation of winged and wingless, amphigonic and parthenogenetic forms (Brisson 2010). -Coexisting morphs plasticity.…”

Drifting in the oceans: Isarachnanthus nocturnus (Cnidaria, Ceriantharia, Arachnactidae), an anthozoan with an extended planktonic stage

“…Also, morphological data may have limited distinguishing power for specific identification of larvae collected in the field, due to phenotypic plasticity in larval morphology as well as variation in life-cycle patterns, for species with complex life cycles (e.g., Boero et al 1992;Minelli and Fusco 2010). By contrast, DNA barcoding is very efficient for this and can be applied to virtually all taxonomic groups and in preserved specimens (Weeb et al 2006;Heimeier et al 2010).…”