The evolutionary potential of an insect invader under climate change.

Although the impacts of climate change and invasive species are typically studied in isolation, they likely interact to reduce the viability of plant and animal populations. Indeed, invasive species, by definition, have succeeded in areas outside of their native range and may therefore have higher adaptive capacity relative to native species. Nevertheless, the genetic architecture of the thermal niche, which sets a limit to the potential for populations to evolve rapidly under climate change, has never been measured in an invasive species in its introduced range. Here, we estimate the genetic architecture of thermal performance in the harlequin beetle (Harmonia axyridis), a Central Asian species that has invaded four continents. We measured thermal performance curves in more than 400 third-generation offspring from a paternal half-sib breeding experiment and analyzed the genetic variance-covariance matrix. We show that while the critical thermal limits in this species have an additive genetic basis, most components of the thermal performance curve have low heritability. Moreover, we found evidence that genetic correlations may constrain the evolution of beetles under climate change. Our results suggest that some invasive species may have limited evolutionary capacity under climate change, despite their initial success in colonizing novel environments.

First finding of the parasitic fungus Hesperomyces virescens (Laboulbeniales) on native and invasive ladybirds (Coleoptera, Coccinellidae) in South Africa.

Hesperomyces virescens is a fungal ectoparasite (Laboulbeniales) that infects adult ladybirds. Research has recently focused on this parasite due to the discovery of its prevalence on the globally invasive harlequin ladybird Harmonia axyridis and for its potential use in studies of co-evolution and pathogen spread. We collected adults from ten species of ladybirds in the Western Cape Province, South Africa, and screened for the presence of H. virescens. Infections with H. virescens were found in the samples of two species, H. axyridis and the native Cheilomenes propinqua. This marks the first record of H. virescens on H. axyridis from the African continent and the first record on Cheilomenes worldwide.

Partitioning of evaporative water loss into respiratory and cutaneous pathways in Wahlberg's epauletted fruit bats (Epomophorus wahlbergi).

The relative contributions of respiratory and cutaneous evaporation to total evaporative water loss (TEWL) and how the partitioning of these two avenues varies with environmental temperature has received little attention in bats. We trained Wahlberg's epauletted fruit bats (Epomophorus wahlbergi) captured in Pretoria, South Africa, to wear latex masks while hanging in respirometry chambers, and we measured respiratory evaporative water loss (REWL) and cutaneous evaporative water loss (CEWL) over air temperatures (Ta) from 10° to 40°C. The bats' normothermic body temperature (Tb) was approximately 36°C, which increased at higher Ta to 40.5° ± 1.0°C at Ta ≈ 40°C. Both TEWL and resting metabolic rate (RMR) increased sharply at Ta >35°C, with a mean TEWL at 40°C equivalent to 411% of that at 30°C. The increase in TEWL was driven by large increases in both CEWL and REWL. CEWL comprised more than 50% of TEWL over the entire Ta range, with the exception of Ta ≈ 40°C, where REWL accounted for 58% of evaporative water loss. Surface area-specific CEWL increased approximately sixfold with increasing Ta. Thermoregulation at Ta approaching or exceeding Tb involved a considerable energetic cost, with RMR at Ta ≈ 40°C exceeding by 24% that measured at Ta ≈ 10°C. Our data do not support recent arguments that respiratory gas exchange across the wing membranes represents 5%-10% of the total in E. wahlbergi.

Summit metabolism and metabolic expansibility in Wahlberg's epauletted fruit bats (Epomophorus wahlbergi): seasonal acclimatisation and effects of captivity.

Summit metabolism (M sum), the maximum rate of resting metabolic thermogenesis, has been found to be broadly correlated with climatic variables and the use of heterothermy in some endotherms. Far less is known about M sum and metabolic expansibility [ME, the ratio of M sum to basal metabolic rate (BMR)] in bats compared with many other endotherm taxa. We measured BMR and M sum during winter and summer in captive and wild populations of a pteropodid from the southern subtropics, Wahlberg's epauletted fruit bat (Epomophorus wahlbergi) in Pretoria, South Africa. The M sum of fruit bats ranged from 5.178 ± 0.611 W (captive, summer) to 6.006 ± 0.890 W (captive, winter), and did not vary significantly between seasons. In contrast, BMR decreased by 17-25% in winter. The combination of seasonally stable M sum but flexible BMR resulted in ME being significantly higher in winter than in summer, ranging from 7.24 ± 1.49 (wild, summer) to 13.11 ± 2.14 (captive, winter). The latter value is well above the typical mammalian range. Moreover, both M sum and ME were significantly higher in captive bats than in wild individuals; we speculate this represents a phenotypic response to a reduction in exercise-associated heat production while in captivity. Our data for E. wahlbergi, combined with those currently available for other chiropterans, reveal that M sum in bats is highly variable compared with allometrically expected values for other mammals.