Early ontogeny shows the same interspecific variation as natural history parameters in the crested newt (Triturus cristatus superspecies) (Caudata, Salamandridae)

Abstract

When the phenotypic divergence within a monophyletic group is characterised by parallel variation of different phenotypic traits, it is very likely that the environment through constraints and/or selection has affected the developmental pathways simultaneously. Such patterns of phenotypic divergence characterise the phenotypic evolution of the crested newts (Triturus cristatus superspecies). In this study, we have examined interspecific variations in the embryonic development of four crested newt species. The species are similar with respect to some basic developmental traits, some morphologically defined developmental stages and the survival rate during early embryogenesis. However, there is significant variation in the developmental rate, as well as differences in the pattern of correlation amongst analysed life-history and developmental traits. Consistent with previous studies, T. dobrogicus appears to be an outlier species, with the longest embryonic period and a significantly different correlation pattern for early life-history and developmental traits. We suggest that the invasion of a novel aquatic environment by T. dobrogicus resulted in large-scale directional changes in development, which could explain parallel change in numerous phenotypic and life-history traits with a high rate of evolution.

Trunk elongation and ontogenetic changes in the axial skeleton of Triturus newts

“…Adults of T. anatolicus (a recently described species, previously subsumed in Triturus ivanbureschi ) (Wielstra & Arntzen, ) came from two locations in Turkey (Table ). Triturus ivanbureschi and T. dobrogicus juveniles were at the same developmental stage, after complete resorption of external gills (stage 56 according to Glaesner, ) and they were offspring from laboratory breeding experiments (details of the experimental setting are provided in Cvijanović, Ivanović, Tomašević Kolarov, Džukić, & Kalezić, ). In total, 148 specimens stored in the IBISS batrachological collection were analyzed (for a complete list of specimens and their collection numbers please see Supporting Information).…”

Ontogeny of body form and metamorphosis: insights from the crested newts

“…Larvae of different ages and juveniles were obtained from laboratory experiments in which newts were reared under controlled laboratory conditions in two separate experiments (for the experimental settings, see Cvijanović et al ., 2009). After hatching, the larvae were placed in 100 mL plastic cups filled with 50 mL of dechlorinated tap water.…”

“…Regarding morphological diversification in crested newts, a number of phenotypic traits (e.g. Ivanović et al ., 2007, 2008 ab ; Cvijanović et al ., 2009), including adult body shape and size (Arntzen & Wallis, 1999), vary according to the species' ecological requirements. Triturus dobrogicus appears to be the most divergent at one end of the ecophenotypical cline, with T. arntzeni and T. macedonicus at the opposite pole, and T. cristatus occupying an intermediate position (Arntzen, 2003; Litvinchuk, Rosanov & Borkin, 2007).…”

The ontogenetic origins of skull shape disparity in the Triturus cristatus group

“…Of these species, T. dobrogicus is the most aquatic, inhabiting permanent and/or long-lasting, large, stagnant bodies of water. For the investigation of the differences in skull shape, individuals just after metamorphosis (i.e., metamorphs) were obtained from laboratory experiments in which newts were reared under controlled laboratory conditions (for the experimental settings and origin of metamorphs see Cvijanović et al 2009;Ivanović et al 2011). For the investigation of the differences in skull shape, individuals just after metamorphosis (i.e., metamorphs) were obtained from laboratory experiments in which newts were reared under controlled laboratory conditions (for the experimental settings and origin of metamorphs see Cvijanović et al 2009;Ivanović et al 2011).…”