Final answer:
Pollution reducing visibility in the water could hinder mate selection based on color, possibly leading to hybridization or changing selection pressures favoring non-visual mate recognition.
Step-by-step explanation:
In a scenario where sympatric speciation has occurred, resulting in two species with distinct male colorations for mating, pollution causing turbidity in the water would likely impede visual recognition, and thus the mating process that relies on color differentiation. If females cannot distinguish the coloration of males, they may be unable to select partners from their own species. This situation could lead to hybridization, where the two species might cross-fertilize, potentially producing hybrid offspring.
However, considering the specifics of reproductive mechanisms in sympatric species, such as unique mating behaviors, temporal separation in gamete maturation, or developmental barriers, hybrid offspring might be unviable or less fit, maintaining species separation. If courtship behaviors beyond visual cues are present, such as pheromones or behavioral displays, these species might still be able to successfully reproduce with conspecifics despite the visual impairment caused by the pollution. Conversely, the pollution may act as a selection pressure on these species, favoring individuals capable of recognizing mates through non-visual means or else mating randomly, which could have various evolutionary outcomes.