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References Addison, B. A., Kitaysky, A. S. & Hipfner, J. M. 2008. Sex allocation in a monomorphic seabird with a single-egg clutch: test of the environment, mate quality, and female condition hypotheses. - Behavioral Ecology and Sociobiology 63: 135-141. Bradbury, R. B. & Blakey, J. K. 1998. Diet, maternal condition, and offspring sex ratio in the Zebra finch, Poephila guttata . - Proceedings of the Royal Society of London B 265: 895-899. Burley, N. 1981. Sex ratio manipulation and selection for attractiveness. - Science 211: 721-722. Burley, N. 1986. Sex-ratio

References Box G.E.P., G.M. Jenkins, 1983, Analiza szeregów czasowych: prognozowanie i sterowanie , PWN, Warszawa. Byrne J., D. Warburton, 1987, Male excess among anatomically normal fetuses in spontaneous abortions , Am. J. Med. Genet. , 26 , 605-611. Cagnacci A., A. Renzi, S. Arangino, C. Alessandrini, A. Volpe, 2004, Influences of maternal weight on the secondary sex ratio of human offspring , Hum. Reprod. , 19 , 442-444. Catalano R., 2003, Sex ratios in the two Germanies: a test of the economic stress hypothesis , Hum. Reprod. , 18 , 1972

Dioecy, the separation between male and female individual plants, is a relatively uncommon reproductive system in flowering plants (only ~5% of angiosperms; Charlesworth 2002 ). Sex ratio is measured as the ratio of the number of individuals of one sex relative to the other sex, or the ratio of allocation in each ( Sapir et al. 2008 ). An equal number of males and females is an evolutionarily stable strategy, led by frequency-dependent natural selection due to competition for mates among individuals of the same sex ( Fisher 1930 ). The mechanisms governing sex

J. Perinat. Med. 38 (2010) 209–213 • Copyright by Walter de Gruyter • Berlin • New York. DOI 10.1515/JPM.2010.024 2010/70 Article in press - uncorrected proof Original articles – Newborn Recent dramatic increase in the male-to-female sex ratio of babies born in Hong Kong Grace Ying Wong1,*, Wing Cheong Leung2 and Robert Kien Howe Chin3 1 Department of Obstetrics and Gynecology, Princess Margaret Hospital, Kowloon, Hong Kong 2 Department of Obstetrics and Gynecology, Kwong Wah Hospital, Kowloon, Hong Kong 3 Department of Obstetrics and Gynecology, Kowloon West

References Ainsworth C (2000): Boys and girls come out to play: themolecular biology of dioecious plants. Ann Bot 86: 211-221. Bell G (1991): The ecology and genetics of fitness in Chlamydomonas. 4. The properties of mixtures of genotypes ofthe same species. Evolution 45: 1036-1046. Bogen R, Wool D, Shmida A (1997): Host tree sex ratio and herbivores gall abundance: Pistacia trees and galling aphids. Ecol Environ 4: 3-10. Dawson TE, Bliss LC (1989): Intraspecific variation in the water relations of Salix arctica, an arctic-alpine dwarf willow. Oecologia 79: 322

-6): 251-254. Abstract. EL-ABDULLAH, F. ‒ MOCHIDA, O. ‒ ARIDA, G. ‒ BASILIO, R. P. (1984): Monitoring the adult densities of the striped rice borer, Chilo suppressalis Walker, and laboratory evaluation of certain insecticides against it’s larvae in the Philippines. J. Agric. Res. Tanta Univ. 10 (3): 1055-1062. EL-DEEB, M. A. (1992): Sex ratio, mating ability and oogenesis for three species of corn borer moths caught in light traps at Sharkia Region. Annals of Agricultural Sciense, Moshtohor. 30 (1): 555-564. ELLIOTT, W. M. ‒ DIRKS, V. A. (1979): Postmating age estimates

Evolution 14: 255-268. DOI: 10.1080/08927014.2002.9522744 Tepedino V. J., Torchio P. F. (1982) Phenotypic variability in nesting success among Osmia lignaria propinqua females in a glasshouse environment: (Hymenoptera: Megachilidae). Ecological Entomology 7(4): 453-462. DOI: 10.1111/j.1365-2311.1982. tb00688.x Tepedino V. J.; Torchio P. F. (1989) Influence of Nest Hole Selection on Sex Ratio and Progeny Size in Osmia lignaria propinqua (Hymenoptera: Megachilidae). Annals of the Entomological Society of America 82: 355-360. Ulbrich K., Seidelmann K. (2001) Modeling

J. Perinat. Med. 39 (2011) 99–102 • Copyright by Walter de Gruyter • Berlin • New York. DOI 10.1515/JPM.2010.134 2010/024 Article in press - uncorrected proof Letter to the Editor Human sex ratio at birth and related factors* Fatemeh Emamghorashi1,**, Seyed Taghi Heydari2, Narjes Seddigh3, Maryam Vahdat3 and Atieh Mohtashami4 1 Department of Pediatrics, Jahrom, Iran 2 Health Policy Research Center, Shiraz University of Medical Sciences, Shiraz, Iran 3 Department of Obstetrics, Motahari Hospital, Jahrom, Iran 4 Department of Obstetrics, Peymanieh Hospital, Jahrom

Mammalia 75 (2011): 243–248 2011 by Walter de Gruyter • Berlin • Boston. DOI 10.1515/MAMM.2011.026 2010/103 Article in press - uncorrected proof Sex ratios of Arabian Sand Gazelle Gazella marica Thomas, 1897 in the Mahazat as-Sayd Protected Area, Saudi Arabia Peter Low Cunningham1,2,* and Torsten Wronski1,2 1 King Khalid Wildlife Research Centre, Thumamah, P.O. Box 61681, Riyadh, Kingdom of Saudi Arabia, e-mail: pckkwrc@yahoo.co.uk 2 Zoological Society of London, Conservation Programmes, Regent’s Park, London, NW1 4RY, UK *Corresponding author Abstract The sex

Introduction The relationship between secondary sexual dimorphism and unequal sex ratios is critical to a few evolutionary theories ( Emlen and Oring 1977 ), ( Daly and Wilson 1978 ). In bats, both male-biased and female-biased size dimorphism have been documented (Myers 1978 , Willig and Hollander 1995 ), although the underlying causes of sex-limited selection pressures have not been demonstrated for any species. Similarly, the direction and magnitude of sex ratio deviating from parity is most often related to polygamous mating systems. When the number of