MFWB_A - Evolutionary Transitions in Lizards

key life history traits

low-energy, variable thermal regulation

snakes key evolution

limb loss and trunk elongation, often fossorial

sex determination

genotypic sex determination, temperature dependent sex determination

genotypic sex determination

2 sex chromosomes, differ in size and composition, can be single locus or full chromosome

temperature dependent sex determination

depends on incubation temperature, still made to male/female due to developmental triggers

reptile sex determination examples

turtles - mostly TSD, some GSD, crocodiles - TSD, tuatara - TSD, squamates - TSD, GSD, parthenogenesis

lecithotrophy

all nutrients are in the egg when ovulated (oviparous), all nutrients from yolk but embryo in uterus (viviparous)

matrotrophy

minimal nutrient transfer to primarily lecithotrophic embryos (viviparity), e.g., horned lizard, all boas

placentotrophy

active and passive transfer of nutrients and oxygen from mother to foetus, transfer of waste from foetus to maternal blood supply (viviparity), e.g, South American skink

viviparity costs

condition while in pregnancy, increased predation as decreased speed, increased basking, limited number of clutches a year, decrease female performance

cold climate hypothesis

viviparity associated with cold climate as it’s costly, many squamates in tropics, allows for better regulation of embryonic temperature and potentially accelerates development

viviparity benefits

gives female more control over development, internal incubation faster and steadier, offspring have higher hatching success, decreases cost of predation on nest, improved neonate survival

common lizard

bimodal reproductive mode, 6 mitochondrial lineages - 2 egg laying and 4 live birth, hybrids intermediate between ovi and vivi, more advanced developmental stage when hatching, shorter incubation time, thinner eggshell

admixture mapping

evolution of viviparity, QTL mapping in wild, makes use of natural hybrid zones, identifies genetic markers associated with a phenotype - e.g, in Austria - collect pregnant females, record way of birth