Reproductive barriers between populations of the cereal rust mite <Emphasis Type="Italic">Abacarus hystrix</Emphasis> confirm their host specialization |
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Authors: | Anna Skoracka |
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Institution: | (1) Department of Animal Taxonomy and Ecology, Institute of Environmental Biology, Adam Mickiewicz University, Umultowska 89, Poznan, 61-614, Poland |
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Abstract: | Recent studies have shown that certain host populations of the cereal rust mite Abacarus hystrix are highly specialized in their host use and it is likely that reproductive isolation exists between them. Here I verified
this expectation by testing for reproductive barriers between ryegrass and quackgrass populations of A. hystrix. I performed reciprocal crosses between individuals from both populations and observed results of crosses. Leaves of the
three grass species, ryegrass, quackgrass and wheat, were used as mating arenas. I used two criteria to determine reproductive
barriers between strains: the proportion of female progeny and viability of progeny. If studied populations of this haplodiploid
species are reproductively isolated a male-biased sex ratio and/or hybrid progeny of reduced viability would be expected.
I found that in the presence of quackgrass and ryegrass pre-zygotic barriers between studied populations exists. On wheat
I observed asymmetry in reproductive barriers. Between females from quackgrass and males from ryegrass a pre-zygotic barrier
existed (only males obtained). However, the opposite reciprocal cross (females from ryegrass and males from quackgrass) produced
progeny of both sexes. A male-biased sex ratio and low adult emergence suggests that post-zygotic mechanisms acted here. Low
viability of progeny obtained from crosses in which females from ryegrass were engaged suggests that the origin of the female
nymph acted as a predictor of hybrid inviability. The pattern of sterility observed in the cereal rust mite indicates that
in the presence of three hosts (ryegrass, quackgrass and wheat) pre- and post-zygotic reproductive barriers between quackgrass
and ryegrass populations of this mite exist. In addition to host fidelity (which acts as pre-zygotic barrier) there are post-zygotic
barriers to gene flow. |
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Keywords: | Acari Eriophyidae Hybrids Reproductive isolation Host races Asymmetric gene flow |
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