Things are not always what they seem: Climate change is driving population changes in Neotropical tiger moths, but few species are declining!
Understanding the causes and consequences of insect declines has become an important goal in ecology, particularly in the tropics, where most terrestrial diversity exists. Researchers from Entomology Institute Greg Lamarre, Nick Pardikes, and Yves Basset are pursuing efforts to understand how climate change affects arthropod communities and how these changes may influence trophic interactions in megadiverse tropical forests.
Fig.: The Glass wing species Xanthyda_cf._chalcosticta (Michel Laguerre)
Over the past 12 years, the ForestGEO Arthropod Initiative has systematically monitored multiple insect groups on Barro Colorado Island (BCI), Panama, providing baseline data for assessing long-term population trends. This time the team focused on the charismatic tiger moths of Barro Colorado Island!
We estimated the rates of change in abundance among 96 tiger moth species on BCI, and we found that the population trends of most species were stable or increasing, with few declining species. This article represents an essential contribution to the vivid debate on insect declines. Over 12 years of intense monitoring, we demonstrated that most species of a species-rich moth clade showed no decline, and some even substantially increased in numbers in a tropical lowland forest reserve. Our study contrasts drastically with recent findings indicating insect decline in tropical and temperate regions.
Sensitivity to average maximum temperatures predicted temporal trends, indicating that population abundances of tiger moth species that were twice as abundant in months with a one-degree increase in temperature have increased by 5% each year. Still, it highlights the potential future impact of climate change, as climatic sensitivity traits were the best predictors of population trends. Since 1981, BCI has experienced a 17.9% increase in mean annual precipitation, and we showed that moth populations that respond to increasing precipitation in Panama are also increasing. Arctiinae species that were more abundant in months with higher precipitation showed positive population trends. As recent models predict increased temperature and rainfall for tropical regions, this group of moths may be favored by future environmental conditions. However, future phenotypic responses and upper levels of thermal tolerance are hard to predict. Should the rate of warming exceed physiological response capacities, we can expect sharp declines in population density for many tropical insect species.
Lamarre G., Pardikes N., Segar S. T., Hackforth C. N., Laguerre M., Vincent B., Lopez Y., Perez F., Bobadilla R., Silva J. A. R., Basset Y. F. (2022) More winners than losers over 12 years of monitoring tiger moths (Erebidae: Arctiinae) on Barro Colorado Island, Panama. Biology Letters 18: 0210519. DOI: 10.1098/rsbl.2021.0519