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  3. Scientists have long speculated as to the extent that inbreeding contributes to the decline and eventual extinction of la

Scientists have long speculated as to the extent that inbreeding contributes to the decline and eventual extinction of la

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问题            Scientists have long speculated as to the extent that inbreeding contributes
       to the decline and eventual extinction of large assimilated populations, most
       agreeing that in natural populations the impact of inbreeding depression on
Line    population survival is insignificant in comparison to that of demographic and
(5)     environmental variables. While there is ample evidence of fitness reduction due
       to inbreeding depression in captivity, no field studies on natural populations
       have been conducted to test the proposed effect on extinction.
           However, Saccheri recently found in his study of a large metapopulation of
       the Glanville .fritillary butterfly that extinction risk increased significantly
(10)    with decreasing heterozygosity, an indication of inbreeding, even after
       accounting for the effects of the relevant ecological factors. Rate of maturation,
       larval survival, adult longevity and egg-hatching rate were found to be adversely
       affected by inbreeding, and appear to be the fitness components underlying the
       relationship between inbreeding and extinction. One wonders, nevertheless,
(15)    how applicable these results would be to the increasing number of species with
       small isolated populations due to habitat loss and fragmentation.
If the phenomenon "extinction risk increased significantly with decreasing heterozygosity" (lines 9-10) agrees with the proposed effect on extinction, the passage assumes
选项 A、heterozygosity is an indicator of increasing inbreeding depression in assimilated metapopulations
B、heterozygosity is unrelated to the degree of inbreeding depression in assimilated metapopulations
C、heterozygosity is an indicator of decreasing inbreeding depression in isolated metapopulations
D、heterozygosity is an indicator of increasing inbreeding depression in isolated metapopulations
E、heterozygosity is an indicator of decreasing inbreeding depression in assimilated metapopulations
答案E
解析
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