Herbaria are natural history collections that host a vast amount of information on plant taxonomy, biology, distribution, and genetic diversity, and are therefore are a key resource for scientific research. However, changes in environmental conditions can make these collections highly susceptible to pest infestations. Maintaining relative humidity (RH) and temperature control within herbaria can help preserve plant specimens. The role of these variables has not been properly studied in tropical regions, especially in relation to the abundance of invertebrates that can infest collections. In this study we use daily temperature and RH measurements, and data from invertebrate pest traps collected quarterly between 2017-2021 in the CDS herbarium of the Charles Darwin Research Station. With these data, we test for 1) the effect of ambient conditions on invertebrate abundance in the herbarium, 2) the effect of surpassing the recommended temperature and RH thresholds on invertebrate abundance, and 3) the correlation between herbarium ambient conditions and outdoor weather data, in order to evaluate the effectiveness of environmental controls. Our results show a significant positive correlation between periods of high temperature and the abundance of invertebrates, increasing the number of individuals by 32.4% per 1ºC (±12.7 S.E., p = 0.02), but no significant effects on potential pests. We also found a significant correlation between outdoor and indoor environmental conditions. These results suggest that despite imperfect environmental controls, best practice recommendations of 40-55% humidity and temperature of 21-23ºC are most appropriate for maintaining invertebrate pest control. In this case, work is needed to ensure temperature is maintained below 23ºC to prevent growth and spread of invertebrates in collections. Altogether, this study shows the direct relationship between environmental conditions and the abundance of invertebrates, and stresses the importance of maintaining ambient control in natural history collections in tropical climactic regions.
