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Low‐temperature physiology of climatically distinct south African populations of the biological control agent Neochetina eichhorniae
Author(s) -
Rogers Daniel J.,
Terblanche John S.,
Owen Candice A.
Publication year - 2021
Publication title -
ecological entomology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.865
H-Index - 81
eISSN - 1365-2311
pISSN - 0307-6946
DOI - 10.1111/een.12935
Subject(s) - weevil , biology , biological pest control , population , host (biology) , zoology , ecology , botany , demography , sociology
Neochetina eichhorniae is the most widely established biocontrol agent on water hyacinth populations around South Africa. However, some N. eichhorniae populations have failed to adequately control their host population, specifically those exposed to cold conditions. The aim of this study was to determine whether two climatically distinct populations of N. eichhorniae in South Africa differ in their low‐temperature physiology, which tests whether local‐climate adaptation has occurred. We estimated weevil CT min , LLT 50 , SCP, and SCP mortality using standard approaches. Contrary to expectation based on climatic thermal profiles at the two sites, weevils from the warm locality ((mean ± SE) CT min = 5.0 °C ± 0.2, LLT 50 = −11.3 °C ± 0.03, SCP = −15.8 °C ± 0.6) were able to maintain activity and tolerate colder temperatures than the weevils from the colder site (CT min = 6.0 °C ± 0.5, LLT 50 = −10.1 °C ± 0.1, SCP = −12.9 °C ± 0.8). These contradictory outcomes are likely explained by the poor nutrient quality of the plants at the cold site, driving low‐temperature performance variation that overrode any macroclimate variation among sites. The cold site weevils may also have adapted to survive wide‐temperature variability, rather than perform well under very cold conditions. In contrast, the mass‐reared population of insects from the warm site has likely adapted to the consistent conditions that they experience over many years in confinement.