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Title:Behavioral and genetic correlates of reproductive success in male addax (Addax nasomaculatus, De Blainville 1816)
Author(s):Spevak, Edward Martin
Director of Research:Paige, Kenneth
Doctoral Committee Chair(s):Paige, Kenneth
Doctoral Committee Member(s):Suarez, Andrew; Cheng, Christina; Roca, Alfred
Department / Program:School of Integrative Biology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Reproductive Success
Abstract:The addax (Addax nasomaculatus) is a critically endangered antelope whose range is now restricted to a few small populations in the Sahara and thus the focus of national and international conservation efforts. Very little is known about their general behavior and social structure, either in the wild or in captivity. This study examined the behavior of semi-free ranging herds of addax to establish the mating strategies male addax pursue to increase their reproductive success. This study demonstrates that addax have the ability to become territorial under certain conditions, possibly due to the high population density and constant resource base as seen in related oryx species. Two mating strategies were evident among male addax in this population: territorial and following or non-territorial. Resources and the behavior and density of females influenced the presence of these different mating strategies with male age and rank and available territory determining the strategy. Male reproductive success of addax was assessed using both behavioral observations and genetic paternity analysis using microsatellites and the second exon of Adna DR3 of the major histocompatibility complex (MHC). There was a significant relationship between the age of the male and the number of offspring sired (rs =.46, N = 66, p = .0002) and a male's rank and his reproductive success (rs = -.88, p = .0007). There was no difference between the total number of calves sired by territorial versus non-territorial males. However, individual territorial males sired on average significantly more calves than non-territorial males. Possession of a territory was a significant component of reproductive success (R2 = .27, F.05= 11.77, d.f. = 2, 63, p < .05). There was a significant difference between behavioral and genetic estimates with behavioral data overestimating the reproductive success of younger age classes (1-2 year olds and 2-3 year olds) and underestimated the 3 year olds and above. In this study, comparisons between genetic and behavioral estimates of reproductive success showed that behavioral estimates consistently underestimated the absolute reproductive success of successful males and overestimated the success of many unsuccessful males. However, in the absence of known paternity behavioral methods give an adequate estimate of male reproductive success for multi-male herds. This is the first study of addax in which territorial behavior was observed and where its benefits, in terms of reproductive success, were assessed. This study also demonstrates the usefulness of microsatellites and DRB3 of the MHC in helping to establish paternity and therefore reproductive success in addax. Additionally, a further examination of Adna DRB3 of the MHC found low levels of allelic diversity in addax. Despite low levels of allelic diversity, as measured by DR measures of heterozygosity within and among addax populations were found to be informative, correlating highly with infant survivorship and average heterozygosity across the genome as measured using microsatellite markers.
Issue Date:2015-12-01
Rights Information:Copyright 2015 Edward M. Spevak
Date Available in IDEALS:2016-03-02
Date Deposited:2015-12

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