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Life history and reproductive variation in the spotted skink, Niveoscincus ocellatus (Gray 1845)

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Wapstra, E (1997) Life history and reproductive variation in the spotted skink, Niveoscincus ocellatus (Gray 1845). PhD thesis, University of Tasmania.

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Abstract

The spotted skink, Niveoscincus ocellatus is a widely distributed small to
medium size skink (3-12 g) which occurs throughout eastern and central
Tasmania in a variety of climatic regimes. This thesis provides the first
major ecological study of this species and describes in detail the life
history and reproductive characteristics of two populations living at the
climatic extremes of the species' distribution: a site on the Central Plateau
represented the cold extreme and a site at Orford on the east coast
represented the warm extreme.
Niveoscincus ocellatus is a viviparous species that reproduces annually
across its range. It shows an asynchronous gonadal cycle, with maximum
male gonadal development in late summer and mating from April to
June and August to September. Vitellogenesis occurs predominantly in
autumn and continues through winter with ovulation in spring
(September to October). Parturition occurs in January in the temperate
Orford population, and in February in the subalpine Central Plateau
population. In addition to minor variations in the timing of
reproductive events between years at each site, N. ocellatus shows a
degree of flexibility in the timing of reproductive events between sites.
Ovulation and parturition occur approximately one month later at the
Central Plateau, but there is little difference in the length of the gestation
period between sites. An ability to show flexibility in the timing of
reproductive events is undoubtedly responsible, in part, for the
widespread distribution of Niveoscincus ocellatus in a range of climatic
conditions.
Niveoscincus ocellatus displays considerable geographic variation in life
history traits. Maturity is delayed at the Central Plateau (3 years) compared to Orford (2 years). As a result, indiv~duals from the Central
Plateau mature at a large size and have a larger maximum size.
Associated with their larger size and delayed maturity, Central Plateau
females produce larger (mass and number of young) clutches than those
from Orford. There is no trade-off between clutch size and size of
offspring between populations, and females from the Central Plateau
produce more (size adjusted) and larger offspring than females from
Orforct.
Through a series of experiments I show that life history traits of
N. ocellatus are phenotypically plastic, and that observed differences in
life history traits between sites, and annually within sites, may be
explained, at least in part, by phenotypic responses to environmental
variables. For example, growth rate of juveniles is positively correlated to
basking opportunities in the laboratory and to thermal conditions in field
enclosures, but is not influenced by any underlying genetic differences
between populations. Offspring growth rate and phenotype are also
influenced by other proximate factors, including the basking behaviour
of their mothers prior to parturition in the laboratory. Phenotypically
plastic responses allow a flexible approach to life history and
reproductive strategies and are of adaptive significance to species such as
N. ocellatus that occupy a wide geographic and/ or climatic range.

Item Type: Thesis (PhD)
Keywords: Skinks
Copyright Holders: The Author
Copyright Information:

Copyright 1997 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Additional Information:

Library has additional copy on microfiche. Thesis (Ph.D.)--University of Tasmania, 1998. Includes bibliographical references

Date Deposited: 04 Feb 2015 23:38
Last Modified: 11 Mar 2016 05:55
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