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Abstract Phrynocephalus guinanensis has sexual dimorphism in abdominal coloration, but its ontogenetic development of sexual size dimorphism (SSD) is unknown. Using mark-recapture data during four days each year from August from 2014 to 2016, we investigated the development of sex ratios, SSD, sex-specific survivorship and growth rates in a population of P guinanensis. Our results indicated that the sex ratio of males to females was 1:2.8. Males had a lower survival rate (6%) than females (14%) across the age range from hatchling to adult, which supported the discovered female-biased sex ratio potentially associated with the low survival rate of males between hatchlings and juveniles. Male-biased SSD in tail length and head width existed in adults rather than in hatchling or juvenile lizards. The growth rates in body dimensions were undistinguishable between the sexes during the age from hatchling to juvenile, but the growth rate in head length from juvenile to adult was significantly larger in males than females. Average growth rate of all morphological measurements from hatchling to juvenile were larger compared with corresponding measurements from juvenile to adult, but only being significant in tail length, head width, abdomen length in females and snout-vent length in males. We provided a case study to strengthen our understanding of the important life history traits on how a viviparous lizard population can survive and develop their morphology in cold climates.
Keywords toad-headed lizard, mark-recapture, sexual size dimorphism, growth rate, survivorship, sex ratio
1.Introduction
Life history characteristics are associated with growth, reproduction, and survivorship that can affect the life table of an organism, which were thought to be strongly influenced by natural selection (Fox et al, 2001; Roff, 1992). Only populations with adaptive life history can survive, reproduce and evolve in an unstable environment (Stearns, 1992). Recently, there have been multiple ecological research about life history characteristics, which includes body size and growth pattern, sex ratio, age-specific survivorship (i.e., Galliard et al., 2005; Molinazuluaga et al, 2015; Wu et al., 2005; Zhao and Liu, 2014).
Sex ratio is an important topic in population demographic studies (Caswell, 2001; Jirotkul, 1999; Kvarnemo and Ahnesjo, 1996). Fluctuations in sex ratio are regulated (Pettersson et al., 2004), and mainly influenced by intrasexual competition and sex-specific mortality or emigration in a population (Cluttonbrock...