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Demographic origins of skewed operational and adult sex ratios: perturbation analyses of two‐sex models
Author(s) -
Veran Sophie,
Beissinger Steven R.
Publication year - 2009
Publication title -
ecology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.852
H-Index - 265
eISSN - 1461-0248
pISSN - 1461-023X
DOI - 10.1111/j.1461-0248.2008.01268.x
Subject(s) - biological dispersal , biology , juvenile , sex ratio , demography , operational sex ratio , philopatry , population , ecology , longevity , vital rates , population growth , genetics , sociology
Abstract Skewed sex ratios – operational (OSR) and Adult (ASR) ‐ arise from sexual differences in reproductive behaviours and adult survival rates due to the cost of reproduction. However, skewed sex‐ratio at birth, sex‐biased dispersal and immigration, and sexual differences in juvenile mortality may also contribute. We present a framework to decompose the roles of demographic traits on sex ratios using perturbation analyses of two‐sex matrix population models. Metrics of sensitivity are derived from analyses of sensitivity, elasticity, life‐table response experiments and life stage simulation analyses, and applied to the stable stage distribution instead of lambda. We use these approaches to examine causes of male‐biased sex ratios in two populations of green‐rumped parrotlets ( Forpus passerinus ) in Venezuela. Female local juvenile survival contributed the most to the unbalanced OSR and ASR due to a female‐biased dispersal rate, suggesting sexual differences in philopatry can influence sex ratios more strongly than the cost of reproduction.