Plenary Session 7: Fifty Years of Anole Censuses at Barro Colorado Island: Density Decline and Biodiversity2021-07-23 16:15 - 16:45 |
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1. 16:15 VIRTUAL Fifty Years of Anole Censuses at Barro Colorado Island: Density Decline and Biodiversity. Robin Andrews*, Virginia Tech randrews@vt.edu
Our fifty years of censusing Anolis apletophallus (formerly A. limifrons) has had two conceptual motivations. In the early 1970’s, our motivation was to test the then paradigm that populations of tropical plants and animals were more stable than those of the temperate zone. Dramatic fluctuations in abundance of A. apletophallus during the first three decades of censusing documented, as did other contemporary studies, that tropical populations fluctuate every bit as much as populations at north latitudes. The conceptual motivation is now climate change. Since 1971, rainfall events BCI have become shorter and more intense (while annual rainfall has not changed) and nighttime temperature has increased. Overall, abundance of A. apletophallus has declined. The three best predictors of abundance and population growth rate are the Southern Oscillation Index (SOI) (positive), theminimum value of mean monthly minimum temperature(negative), andannual rainfall (negative). Of these predictors, annual rainfall has a mechanistic link to lizard abundance; annual rainfall alters the interaction between A. apletophallus eggs and their major predator, Solenopsis ants. High rainfall negatively affects egg survival because high moisture enhances foraging by Solenopsis in the litter where eggs are laid and hence increases predation on eggs. Overall, the positive association between abundance and SOI indicates that abundance is higher after the cooler and wetter La Niña years and lower after the warmer and drier El Niño years. The prediction of more extreme El Niño events in the future implies that abundance of A. apletophallus at BCI will continue to decline. |