Habitat disturbance – Anole Annals

Dan Nicholson at SICB 2020

Evolution has long thought to be a slow process, taking thousands if not millions of years. Recently, there has been a paradigm shift in how scientists think about evolution. We now know that we can observe evolution on a contemporary timescale, observable to the human eye. Dan Nicholson, a Ph.D. Candidate at Queen Mary University of London in Rob Knell’s lab, is working with Mike Logan and others to observe the effects of habitat change on the evolutionary ecology of Anolis apletophallus.

Dan and his team transplanted anoles from the mainland of Panama to several islands around Barro Colorado Island in July of 2017. Before release, they recorded the anoles’ morphological characteristics, including hindlimb and forelimb length, toe pad size, and head depth, and well as characteristics of their perch location, including height and width. Tracking changes in these characteristics can detect natural selection at work. At SICB 2019, Dan reported the results of the first generation of island anoles.

At SICB 2020, Dan included the trends of the second generation of island anoles. The preliminary results indicate the island anoles have continued to use wider perches than the mainland anoles. However, the majority of the island anole morphological traits now align with the mainland anoles. The exception is that hindlimb length of the island anoles decreased, while the mainland anoles hindlimb length has increased.

Some potential causes of these results, Dan speculates, include genetic drift due to the small population size. The islands started with a robust number of anoles, but over the two years of this study, their numbers have rapidly dwindled. Another possibility is the island anoles are aligning with the mainland anoles morphologically due to gene flow. In the future, Dan wants to further analyze the preliminary results from a population angle, looking at changes in groups of traits instead of individual traits.

You can learn more about Dan’s research by following him on twitter.

Anolis antonii from the agricultural area

Habitat disturbance is considered one of the most important threats to biodiversity. Particularly, anthropogenic disturbance for agricultural practices alters the original structure of Anolis habitats and consequently negatively affects their health and survival. Because the body condition index (BCI) is an effective indicator to assess the health of animals, we hypothesized that the BCI of the Colombian endemic lizard Anolis antonii from an undisturbed habitat (natural area) would be higher than that from the disturbed habitat (agricultural area).

We studied two populations of Anolis antonii from the municipality of Ibague, Tolima, Colombia: (1) a population from an agricultural area cultivated with coffee (Coffea arabica) and plantains (Musa paradisiaca), and (2) a population from a secondary forest, an anthropogenic-free area. We measured the snout-vent length (SVL) and body mass (BM) of adult anoles (males and females)and calculated BCI from the residuals of a linear regression between BM and SVL.

Fig 2. A) Forest habitat and B) Agricultural habitat of Anolis antonii (Ibagué – Colombia)

We found that the BCI of the lizard population from the agricultural area was significantly lower than that of the secondary forest population. Consequently, A. antonii from the secondary forest, with a higher BCI, might have a greater ability to compete for available resources and survive than those from the cultivated area. Thus, this work shows that anthropogenic disturbance negatively decreases the body conditions of A. antonii lizards, which might represent a forthcoming threat for its conservation, especially due to the current habitat deterioration of this species by agriculture activities.

Read the paper:

Gallego-Carmona, C.A., Castro-Arango, J.A. and Bernal-Bautista, M.H., 2016. Effect of Habitat Disturbance on the Body Condition Index of the Colombian Endemic Lizard Anolis antonii (Squamata: Dactyloidae). South American Journal of Herpetology 11(3):183-187.