Table 1 Three trait combinations could explain the lower mass-specific metabolic rate of viviparous species (a) and three other trait combinations could explain their lower mass-specific production (b).

From: Exceptional parallelisms characterize the evolutionary transition to live birth in phrynosomatid lizards

 

(a) Trait combinations resulting in a lower mass-specific metabolic rate

i

Body mass is similar among oviparous and viviparous species, but body temperature is lower in viviparous species.

ii

Body mass is higher and body temperature is lower in viviparous species.

iii

Body mass is higher in viviparous species, but body temperature is similar among oviparous and viviparous species.

 

(b) Trait combinations resulting in a lower mass-specific production

iv

Offspring size is similar among oviparous and viviparous species, but annual fecundity is lower in viviparous species.

v

Offspring size is smaller and annual fecundity is lower in viviparous species.

vi

Offspring size is smaller in viviparous species, but annual fecundity is similar between oviparous and viviparous species.

  1. Note that phrynosomatids are ancestrally oviparous and there are no back-transitions to oviparity. Therefore, our trait combinations are structured around explaining the transition to viviparity (rather than the other way around).
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