Rainforest Ants Vs. Desert Ants

Meet Sophie Schofield, Dr. Tom Bishop, and Dr. Kate Parr:


These three ant researchers wanted to know how drastically different environments impact functional traits in ants. So, they found out, and published their discoveries in Myrmecological News in September of last year.

Specifically, Schofield and her two colleagues compared the ant community in a Costa Rican rainforest to the ant community in an Iranian desert, and predicted that the desert ants would have relatively longer legs, smaller eyes, smaller mandibles, and lighter color when compared to their rainforest counterparts. These expectations were motivated by several hypotheses:

  • The size grain hypothesis predicts that less open, more complex habitats like rainforests promote proportionally shorter legs to allow for greater efficiency of movement
  • The light level-eye size hypothesis predicts that tropical microhabitats occupied by ants tend to be significantly darker than those in the desert, thus promoting smaller eyes in rainforests.
  • The foraging specialism hypothesis predicts that rainforest habitats allow for a greater range of foraging options, leading to more specialist predators with larger mandibles
  • Lighter colors are better adapted to reflecting light in open environments like deserts.
An Odontomachus ant is hungry in Costa Rica. Photo: Alex Wild

Schofield and colleagues only found strong support for the size grain hypothesis, and only mild or no support for the other three hypotheses. The most surprising of these is coloration: ants in the Costa Rican rainforest were unexpectedly significantly lighter than their desert counterparts, contrary to expectations based on sun light levels. It is possible that, as suggested in the Discussion, pigmentation in ants may actually confer resistance to UV-B radiation. The researchers also find that traits of the desert ants represent a fairly small subset of variation found in rainforest ants – this is perhaps not too unexpected, as the desert had only 25 species compared to the rainforest’s 275 species.

Although this study is somewhat limited with several possible confounding factors in the comparison of only two habitat types in different biogeographic regions, the differences detected by Schofield and colleagues are interesting and warrant further investigation. In some ways, the overall similarity of traits between the two habitats is even more notable, given the apparent extreme differences between these two environments. It will be interesting to see what patterns emerge as these type of methods are applied across a wider range of habitats!