Analyzing evolutionary patterns in amniote embryonic development*

Abstract

SUMMARY Heterochrony (differences in developmental timing between species) is a major mechanism of evolutionary change. However, the dynamic nature of development and the lack of a universal time frame makes heterochrony difficult to analyze. This has important repercussions in any developmental study that compares patterns of morphogenesis and gene expression across species. We describe a method that makes it possible to quantify timing shifts in embryonic development and to map their evolutionary history. By removing a direct dependence on traditional staging series, through the use of a relative time frame, it allows the analysis of developmental sequences across species boundaries. Applying our method to published data on vertebrate development, we identified clear patterns of heterochrony. For example, an early onset of various heart characters occurs throughout amniote evolution. This suggests that advanced (precocious) heart development arose in evolutionary history before endothermy. Our approach can be adapted to analyze other forms of comparative dynamic data, including patterns of developmental gene expression.

Developmental stages until hatching of the Lake Victoria cichlid Haplochromis piceatus (Teleostei: Cichlidae)

“…Heterochrony and its biological implications have been considered extensively elsewhere (Gould, 1977;Richardson, 1995;Klingenberg, 1998;Richardson, 1999;Mabee et al, 2000;Smith, 2001;Jeffery et al, 2002;Richardson and Oelschä ger, 2002). Jones (1974) noted that heterochrony causes problems in comparison between different substrate brooding cichlid species and species hybrids.…”

Comparative patterns of postcranial ontogeny in therian Mammals: An analysis of relative timing of ossification events

“…As I write this, only three parsimony analyses based exclusively on event pairs as characters have been published (Velhagen, '97;Jeffery et al, 2001Jeffery et al, , 2002a. Velhagen ('97) studied the Pairs followed by an asterisk are unique to the group in question, those that have no asterisk evolved independently in some other studied taxon or taxa.…”

Mammalian organogenesis in deep time: tools for teaching and outreach

“…In fishes generally (e.g., zebrafish: Richardson et al 1997) the heart has not yet formed at stages in which in amniotes the heart has complete looping (Jeffery et al 2002). This reflects the higher complexity of the amniote heart, which needs more time to differentiate and hence starts to develop earlier (Starck 1979(Starck -1982.…”