For the following competitive exam question: A road is constructed through a tropical rain forest, following which a population of a species of butterflies declines. Which of the following is NOT a possible explanation for the road causing a decline in the forest butterfly population?

The answer: The Road facilitates immigration of gap-loving species which compete with the forest species

What is the defining characteristics of a 'gap' species?


2 Answers 2


The previous answer from @Ark Lomas is true to the extent that gap-loving refers to preference of an open habitat. It was found that these species e.g. have improved flight abilities and are in general geographically more wide-spread.

Here is prove:

Ecology of Tropical Butterflies in Rainforest Gaps J. K. Hill, K. C. Hamer, J. Tangah and M. Dawood Oecologia Vol. 128, No. 2 (Jul., 2001), pp. 294-302

Tropical forest gaps are ephemeral and patchily distributed within forest areas and have very different light environments compared with closed-canopy forest. We used fruit-baited traps to investigate if gaps are exploited by more opportunistic butterfly species compared with closed-canopy forest. Gaps supported a higher diversity of butterflies in terms of species evenness but closed-canopy sites contained species with more restricted geographical distributions. There was little similarity between the assemblages of butterflies trapped in the canopy and those in either gap or closed-canopy sites, but the greater similarity was with gaps, and increased diversity in gaps was partly due to canopy species turning up in gaps. Dispersal rates (as measured by recapture rates) were higher in gaps and there was evidence that butterflies in gaps had relatively larger and broader thoraxes, indicating a flight morphology adapted for faster flight. These results support the notion of a distinctive gap fauna comprising more widespread, mobile species. Habitat modification that opens up the canopy is likely to result in an increase in these widespread species and a decline in understorey species with restricted distributions.


a gap-loving species is a species that prefers existing in open spaces such as the gap that the road creates in the rain forest. I can't think of any organism native to rain forests that would be considered significantly gap-loving since most rain forest species rely on the trees and bushes etc... that the rain forest provides which therefore causes them to not prefer being exposed in the middle of a road.


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