Extreme plasticity in reproductive biology of an oviparous lizard

Abstract

Most oviparous squamate reptiles lay their eggs when embryos have completed less than one‐third of development, with the remaining two‐thirds spent in an external nest. Even when females facultatively retain eggs in dry or cold conditions, such retention generally causes only a minor (<10%) decrease in subsequent incubation periods. In contrast, we found that female sand lizards (Lacerta agilis) from an experimentally founded field population (established ca. 20 years ago on the southwest coast of Sweden) exhibited wide variation in incubation periods even when the eggs were kept at standard (25°C) conditions. Females that retained eggs in utero for longer based on the delay between capture and oviposition produced eggs that hatched sooner. In the extreme case, eggs hatched after only 55% of the “normal” incubation period. Although the proximate mechanisms underlying this flexibility remain unclear, our results from this first full field season at the new study site show that females within a single cold‐climate population of lizards can span a substantial proportion of the continuum from “normal” oviparity to viviparity.

Facultative oviparity in a viviparous skink ( Saiphos equalis )

“…15: 20180827 fine-scale control over neonate deposition within the uterus. The oviposition we observed (stage 33 versus 40) overlaps with oviposition of some oviparous species [22,24] and is close to the typical range for most oviparous squamates (embryonic stages 25-31; [22]). Hence, the oviposition observed here is likely to be biologically significant.…”

Understanding the evolution of viviparity using intraspecific variation in reproductive mode and transitional forms of pregnancy

“…Eggs of Lacerta agilis (L. 1758) from the northern (cold‐climate) extreme of the species' range have widely varying inter‐clutch incubation periods, with eggs that are laid later in the season hatching after briefer periods (Shine, Wapstra & Olsson, 2018). An experimental island population in this region has even more variable incubation periods, although embryonic stage at oviposition is not yet known (Olsson et al ., 2018). Oviparous populations of the bimodally reproductive H. angulatus may also exhibit a range of different incubation durations [from 17 (Rossman, 1973) to 40 (Ford & Ford, 2002) to 109 (Gorzula & Señaris, 1998) days].…”

Effects of male telomeres on probability of paternity in sand lizards

“…Wild-caught sand lizards were kept at facilities at the University of Gothenburg in the year 2000 for breeding experiments as outlined in [6][7][8]. Lizards were kept in individual cages (400 Â 600 Â 400 mm) containing a sand substrate and a flat rock over a moist patch of soil where females laid their eggs.…”