Question

Species that co-occur in space and time tend to be similar to each other in traits such as tolerance to heat or to drought. This is most likely because of _________.

• A. Limiting similarity
• B. Divergent evolution
• C. Environmental filtering
• D. Competitive exclusion

Hint:

Ask whether the pattern is driven by the physical habitat screening out unsuited species, or by competition between species; a shared abiotic stress producing shared traits points to filtering, not competition.

Answer 1

The Correct Option is C

This question tests whether you can tell apart four community ecology ideas that all sound similar: environmental filtering, limiting similarity, divergent evolution and competitive exclusion. The clue given is that species found together at the same place and time share similar heat and drought tolerance.

1. Limiting similarity: this idea is about competition, not about the physical environment. It says species sharing a site should differ in their niche traits so they do not compete too hard for the same resources. That predicts species becoming different from each other, not similar, so it does not fit.
2. Divergent evolution: this describes lineages splitting apart and becoming more different from a shared ancestor over evolutionary time. It talks about how species change through history, and says nothing about why species living in the same place right now share similar stress tolerance.
3. Environmental filtering: a harsh or specific local condition, like high heat or low water, works like a sieve. Any species that cannot handle that condition simply does not persist there. So the pool of species that remains at that site is stacked with similar tolerance traits. This matches the pattern in the question exactly.
4. Competitive exclusion: this is the rule that two species fighting for one limiting resource cannot both survive together forever. It leads toward one species disappearing or the pair separating along a resource axis, not toward shared trait values.

Only environmental filtering explains why co-occurring species end up looking alike in a stress-tolerance trait: the shared environment lets through only the individuals or species that can already handle it, so what is left behind is a similar-trait subset.

Let's summarize:

• Environmental filtering produces trait convergence among species sharing a site because the abiotic stress acts as a common screen.
• Limiting similarity and competitive exclusion are both about competition, and both push toward trait divergence or exclusion, the opposite pattern.

So the process behind the shared heat and drought tolerance among co-occurring species is environmental filtering.