It’s immediately clear to anyone visiting the Greater Antilles that humans have had a dramatic impact on natural environments. Even in those areas that remain forested and seemingly pristine, it isn’t difficult to find the stray coffee bush or mango tree. Indeed, some understory crops, such as coffee and cacao, have traditionally been grown under an intact canopy. These traditional practices have been changing over the past few decades, however, as large commercial operations have favored the efficiency of clear-cutting and subsequent cultivation in open sun. The impacts of this shift from shade to sun cultivation on biodiversity have been debated for decades, with most studies indicating overall losses in biodiversity and super-abundance of a few common species in sun plantations.
In spite of the prevalence of agriculture in the Greater Antilles, relatively few studies have investigated the abundance of anoles and other lizards in different types of agriculturally disturbed habits (but see my first first authored paper!). A new study by Borkhataria et al. (2012) conducts a comparative analysis of species abundance of birds, anoles, and invertebrates in shade versus sun coffee on Puerto Rico. This study is a welcome addition to the literature because the portion of coffee on Puerto Rico grown in sun plantations has doubled in recent years, although overall coffee production has declined.
Borkhataria et al. (2012) use Heckel and Roughgarden’s classic mark-resight approach involving tree-marking spray paint guns and latex paint. Using this technique, an observer sprays anoles in a pre-defined area with paint over a period of three or four days, using a different color paint each day. By counting the number of lizards painted, or repainted, across the study, one can obtain reasonable estimates of anole density.
Borkhataria et al.’s (2012) results won’t surprise anyone who’s familiar with the Puerto Rican anole fuana: “Anolis cristatellus and A. stratulus were significantly more abundant in sun plantations whereas A. gundlachi and A. evermanni were detected more frequently in shade plantations.” You need to look at their Table 2, however, to get a better since for what exactly is going on. Three species are relatively common in both types of coffee: Anolis cristatellus is the most common anole in both shade (0.04/m2) and sun (0.06/m2) coffee, A. krugi is present at similar densities in both types of coffee (0.01/m2), and A. stratulus is twice as common in sun (0.2/m2) as in shade (0.01/m2). Thus, even those species that appear to do better in sun plantations are still relatively abundant in shade. The same cannot be said in the opposite direction: A. gundlachi and A. evermanni are all but eliminated from sun coffee with the number of observed individuals dropping from 525 to 2 and 241 to 6, respectively.
Borkhataria et al. (2012) conclude their abstract by stating that their “findings confirmed that shade plantations harbor a wide array of elements of biodiversity; but sun plantations may also harbor many elements of biodiversity, and in some cases, in higher abundance than in shade plantations.” For the anoles, however, the results seem to rather unambiguously support the notion that diversity will be lost in association with a transition from shade to sun cultivation of coffee.