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Sex ratio variation in gynodioecious Lobelia siphilitica : effects of population size and geographic location
Author(s) -
CARUSO C. M.,
CASE A. L.
Publication year - 2007
Publication title -
journal of evolutionary biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.289
H-Index - 128
eISSN - 1420-9101
pISSN - 1010-061X
DOI - 10.1111/j.1420-9101.2007.01361.x
Subject(s) - gynodioecy , biology , sex ratio , inbreeding , natural selection , population , herbivore , natural population growth , genetic drift , sexual dimorphism , effective population size , ecology , small population size , population size , genetic variation , zoology , sex allocation , demography , dioecy , genetics , habitat , pollen , sociology , gene
Variation in population sex ratio can be influenced by natural selection on alternate sex phenotypes as well as nonselective mechanisms, such as genetic drift and founder effects. If natural selection contributes to variation in population sex ratio, then sex ratio should covary with resource availability or herbivory. With nonselective mechanisms, sex ratio should covary with population size. We estimated sex ratio, resource availability, herbivory and size of 53 populations of gynodioecious Lobelia siphilitica . Females were more common in populations with higher annual temperatures, lower soil moisture and lower predation on female fruits, consistent with sex‐specific selection. Females were also more common in small populations, consistent with drift, inbreeding or founder effects. However, small populations occurred in areas with higher temperatures than large populations, suggesting that female frequencies in small populations could be caused by sex‐specific selection. Both selective and nonselective mechanisms likely affect sex ratio variation in this gynodioecious species.