Question

geologic events such as mountain building can directly affect biodiversity. the sino-himalayan fern, lepisorus clathratus is widely distributed on the qinghai-tibetan plateau.

if geologic events lead to a series of new mountain ranges that divide the plateau into several discrete valleys, which of the following best describes how the l. clathratus population would be affected?

a) geographic isolation will create separate gene pools, leading to speciation over time.

b) gene flow will be reduced by sexual selection and polyploidy.

c) chance events will cause allele frequencies to fluctuate unpredictably from one generation to the next.

d) ferns reproduce asexually, so there will be no impact on the gene pool of the species.

Explanation:

• Option A: When new mountain ranges divide the plateau, the fern populations in different valleys become geographically isolated. This isolation creates separate gene pools (as gene flow between them is reduced/stopped). Over time, genetic differences accumulate, leading to speciation. This matches the scenario of geographic isolation and its evolutionary impact.
• Option B: Sexual selection and polyploidy are not the main factors reducing gene flow here; the key is geographic isolation from mountain building, so B is incorrect.
• Option C: The description refers to genetic drift, but the scenario here is about geographic isolation leading to speciation, not random chance events causing allele frequency fluctuations (genetic drift), so C is incorrect.
• Option D: Ferns can reproduce sexually (e.g., via spores with sexual reproduction stages) and asexually. Also, geographic isolation would still impact gene pools even if asexual, so D is incorrect.

Answer:

A. Geographic isolation will create separate gene pools, leading to speciation over time.