Projected range overlap between the predator Teretrius nigrescens and the invasive stored product pest Prostephanus truncatus expands under climate change

Authors: HARMAN, RACHEL - Orise Fellow; Morrison Iii, William; Gerken, Alison

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2025
Publication Date: 12/18/2025
Citation: Harman, R.R., Morrison Iii, W.R., Gerken, A.R. 2025. Projected range overlap between the predator Teretrius nigrescens and the invasive stored product pest Prostephanus truncatus expands under climate change. Biological Control. https://doi.org/10.1016/j.biocontrol.2024.105682.
DOI: https://doi.org/10.1016/j.biocontrol.2024.105682

Interpretive Summary: The larger grain borer is a destructive pest of stored corn and cassava that is native to Central America and has subsequently invaded Africa. In its native range, Teretrius nigrescens is a natural predator of larger grain borer. It was released in Africa as a biocontrol agent with some success in limiting population growth of larger grain borer and reducing its feeding damage to stored grains. Although the predator can currently survive in some of the same environments that larger grain borer was introduced into, climate change may impact the ranges of both species differently and, consequently, may alter the success of the predator as a biological control agent for larger grain borer. Thus, we modeled the potential distributions of both insects under current climate scenarios and future climate change scenarios. We found that 5.5% of the Americas (native range) and 8.2% of Africa (invaded range) are currently suitable for the predator and that the ranges partially overlap with larger grain borer. Under both low and high climate change scenarios, the range of both the larger grain borer and the predator are expected to expand in the Americas and Africa as is their overlap. However, we found lower overall and greater variability in temperatures and humidity limit the predator’s range, but not that of larger grain borer. Together, this suggests that the predator is not a singular effective measure to eradicate larger grain borer populations, particularly at northern latitudes where temperatures are more variable, and that additional pest management tactics should be explored.

Technical Abstract: The larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), is a forest-dwelling destructive pest of stored corn and cassava native to Central America and invasive in Africa. Its native predator, Teretrius nigrescens Lewis (Coleoptera: Histeridae), was released in Africa as a biocontrol agent with some success. However, responses to future changes in climate may impact insect species differently and, consequently, may alter the efficacy of biological control. Thus, we (1) used bioclimatic variables and known occurrences to model the potential distribution of T. nigrescens and P. truncatus in its native and introduced ranges, (2) projected future potential distribution out to the years 2050 and 2070 under low and high climate change scenarios (representative concentration pathways (RCP) 2.6 and 8.5, respectively), and (3) compared the ranges and important bioclimatic variables between the species. We used the platform Wallace, which employs an optimized maximum entropy (MaxEnt) model. Highly suitable areas (>75%) of T. nigrescens current distribution totaled 5.5% and 8.2% for the Americas and Africa, respectively. Areas of high suitability are estimated to double (RCP2.6) to triple (RCP8.5) by 2050 and increase again 1.3 times by 2070 under RCP8.5. Projected T. nigrescens distributions are much smaller in area and percentage expansion than prey. The overlap of current highly suitable distributions is lower in the native (4.5%) than the African range (22.2%); however, the overlap is expected to increase by 86% in the Americas and 63% in Africa under the 2070 RCP8.5. Bioclimatic variables important to the models show that low temperatures and variability in temperature and humidity limit the biocontrol agent’s distribution to a greater degree than the prey. These results suggest that biocontrol alone is not a singular effective measure to eradicate pest populations, particularly at northern latitudes.