Solving the puzzle of Pringleophaga – threatened, keystone detritivores in the sub‐Antarctic

Abstract

1. In the globally significant, lowland terrestrial systems of the subAntarctic's South Indian Ocean Province Islands, caterpillars of the flightless moth genus Pringleophaga (Lepidoptera: Tineidae) are typically responsible for much nutrient turnover.2. On Marion Island, Pringleophaga marioni is a keystone species for this reason.3. Rising temperatures have led to increasing populations of introduced house mice, which, in turn, feed extensively on Pringleophaga caterpillars.4. Because of the caterpillars' keystone role, predation by mice is leading to changes in the functioning of the terrestrial system. 5. Given the estimates of an extended life cycle duration for P. marioni (and its congeners), that is, two to more than 5 years, an ongoing puzzle is why the species has not shown greater population declines on Marion Island than have been recorded (in some habitats 40-97% in 20 years), given extremely high estimates of predation (c. 1% of standing biomass per day). 6. One reason may be inaccurate previous estimates of life cycle duration for the species.7. Here, we provide a new, quantitative estimate, by rearing caterpillars at different temperature regimes (5, 10, 15 and 5-15°C), and combining these results with additional data from a prior study, to demonstrate that the life cycle duration for this species is approximately 1 year -half the previous minimum estimate.8. The new quantitative data provide grounds for improved models for estimating population persistence of this species, and information for models assessing the costs and benefits of conservation interventions such as the eradication of invasive house mice.

Thermal preference and performance in a sub-Antarctic caterpillar: A test of the coadaptation hypothesis and its alternatives

“…Pringleophaga marioni Viette (Tineidae) is a flightless moth, the caterpillars of which occur in virtually all habitats on the sub-Antarctic Marion and Prince Edward islands (46.9°S, 36.7°E) (Crafford et al, 1986;Haupt et al, 2014aHaupt et al, , 2016. The caterpillars are detritivores and take nearly a year to progress through this stage (Haupt et al 2014a). Field collected caterpillars have a critical thermal minimum (CT min ) between -1.6 and 0.1°C, and a critical thermal maximum (CT max ) range of 37.7 to 38.7°C (Klok and Chown, 1997).…”

“…Caterpillars were collected from abandoned wandering albatross nests (Diomedea exulans), where they occur in high numbers (Haupt et al, 2016), and returned to the laboratory within six hours of collection. Individuals were placed in petri dishes filled with albatross nest material, which served as both refuge and food (Haupt et al, 2014a). Maintaining individuals separately was necessary to avoid cannibalism (French and Smith, 1983).…”

“…The strong inference approach (Platt, 1964) adopts joint exploration of alternative explanations for variations in thermal performance (Huey et al, 1999). Here, we apply this approach to caterpillars of the flightless sub-Antarctic moth, Pringleophaga marioni, for which the thermal biology is well-known (Klok and Chown, 1997;Sinclair and Chown, 2003;Sinclair et al, 2004;Chown, 2005, 2006;Haupt et al, 2014aHaupt et al, ,b, 2016Chown et al, 2016). Specifically, we examine the relationship between thermal preference (T pref ) and the thermal optimum (T opt ) for locomotion.…”

“…), thus testing the 'thermodynamic effect' hypothesis. Finally, we determine whether or not thermal preference aligns with performance measures other than locomotion, and specifically those that may be significant for a relatively long-lived (ca 1 year) detritivorous caterpillar (Haupt et al, 2014a).…”

Expanding horizons and widening participation in Insect Conservation and Diversity

“…The success of L. dispar in parts of its range due to high host and habitat flexibility, can, without stretching the analogy too far reflect the success of (Leather et al, 2008), our geographical range has expanded from 17 different countries in 2008 to 38 countries in 2014 (based on addresses of submitting authors). We have increased our number of issues from four per year to six, and in 2014 published papers dealing with insects from habitats as far removed as the sub-Antarctic (Haupt et al, 2014) and Sweden (Koch et al, 2014). Although beetles, wasps and butterflies feature prominently in our pages, as benefits their high relative diversity, understudied groups such as the Plecoptera remain highly sought-after (Bojkkov a et al, 2014).…”