Long-term data reveal a population decline of the tropical lizard Anolis apletophallus, and a negative affect of el nino years on population growth rate

Abstract

Climate change threatens biodiversity worldwide, however predicting how particular species will respond is difficult because climate varies spatially, complex factors regulate population abundance, and species vary in their susceptibility to climate change. Studies need to incorporate these factors with long-term data in order to link climate change to population abundance. We used 40 years of lizard abundance data and local climate data from Barro Colorado Island to ask how climate, total lizard abundance and cohort-specific abundance have changed over time, and how total and cohort-specific abundance relate to climate variables including those predicted to make the species vulnerable to climate change (i.e. temperatures exceeding preferred body temperature). We documented a decrease in lizard abundance over the last 40 years, and changes in the local climate. Population growth rate was related to the previous years' southern oscillation index; increasing following cooler-wetter, la niña years, decreasing following warmer-drier, el nino years. Within-year recruitment was negatively related to rainfall and minimum temperature. This study simultaneously identified climatic factors driving long-term population fluctuations and climate variables influencing short-term annual recruitment, both of which may be contributing to the population decline and influence the population's future persistence.

Fig 1. Temporal trends in a) log abundance and b) population growth rate of Anolis apletophallus surveyed in an annual December census for 40 years.

Yellow shaded bars show strong (darker shading) and moderate (lighter shading) el nino events and blue bars show strong (darker shading) and moderate (lighter shading) la nina events (see http://ggweather.com/enso/oni.htm for description of strength ranking).

Fig 2. Temporal trends in a) log number of juveniles, b) log number of young, and c) log number of adults of Anolis apletophallus surveyed in an annual December census for 40 years.

Fig 3. Temporal trends in a) log abundance (solid line) and southern oscillation index (SOI) (dashed line) and b) population growth rate (solid line) with SOI (dashed line) on BCI over the last 40 years.

Yellow shaded bars show strong (darker shading) and moderate (lighter shading) el nino events and blue bars show strong (darker shading) and moderate (lighter shading) la nina events (see http://ggweather.com/enso/oni.htm for description of strength ranking).