Altitudinal and environmental variation in lifespan in the Copper butterfly Lycaena tityrus

Abstract

Summary1. Variation in longevity within and between natural populations is widespread, and understanding the relative importance of environmental and genetic factors as well as their interactions in mediating such variation is crucial in longevity research. 2. In this study lifespan of adult copper butterflies was examined in relation to altitude, temperature (20 and 27°C), sex and adult feeding. 3. As expected, longevity increased with decreasing temperature, and sucrose-fed butterflies had longer lifespans compared to water-fed and finally non-fed individuals. The impact of feeding, especially of having access to water or not, was larger at the higher compared to the lower temperature. 4. Regarding altitudinal patterns, increased lifespan in high-altitude populations was largely restricted to beneficial feeding conditions, while under carbohydrate deprivation low-altitude animals lived longer, suggesting that low-altitude butterflies do better under food stress. 5. Differences in longevity between sexes were small at 20°C, while females lived substantially longer than males at the higher temperature. Consequently, females may be less susceptible to high temperature stress than males. Further, males suffered more from food stress than females, suggesting that females are generally more stress resistant than males. 6. Using a full factorial design, this study demonstrates that variation in longevity is caused by several factors, and additionally by substantial interactive effects. Consequently, patterns of variation in longevity are complex, and one needs to be cautious when neglecting this source of variation, by focussing on individual factors only.

Estimating reaction norms for predictive population parameters, age specific mortality, and mean longevity in temperature-dependent cohorts of Culex quinquefasciatus Say (Diptera: Culicidae)

“…For life span, the specific patterns were mostly as expected and thus in agreement with the general notion of pronounced differences between different rearing temperatures (Tatar 2001). Like many of the previous studies, the pattern of increasing life span of cohorts at low temperatures was evident in both mated and unmated cohorts as shown previously (Su and Mulla 2001, Norry and Loeschcke 2002, Gilles et al 2005, Kasap and Alten 2006, Aytekin et al 2009, Karl and Fisher 2009). This frequent pattern is related to increasing metabolic rates with increasing temperatures in ectotherms, with higher metabolic rates in turn being correlated with shorter life spans (Karl and Fisher 2009).…”

Temperature and humidity acclimation increase desiccation resistance in the butterfly Bicyclus anynana

“…A higher water loss in males is presumably linked to their smaller size and a concomitantly higher surface area-to-volume ratio. In such systems long lifespans in males will yield very little fitness returns, which may also explain the generally longer lifespans of females versus males in B. anynana and other butterflies (see also Bauerfeind & Fischer, 2005;Bauerfeind et al, 2009;Karl & Fischer, 2009). In addition, females may have been selected for more efficient strategies to avoid water loss, owing to (1) the need for water for egg production, (2) the loss of body water due to oviposition, and/or (3) a generally higher (desiccation) stress resistance, as females are expected to benefit more strongly from longer lifespans than males.…”

Exploring plastic and genetic responses to temperature variation using copper butterflies

“…The opposite trend found here is presumably related to nectar plant availability. While the flight period of the monovoltine high-altitude populations is very well synchronised with a period of high nectar flower abundance, bivoltine low-altitude butterflies, in particular in the (late) summer generation, may regularly be faced with a shortage of nectar plants (Karl & Fischer 2009 In Lycaena tityrus, high-altitude butterflies have substantially darker wings than low-altitude ones (Karl et al 2009c), thus showing the expected pattern of darker phenotypes being associated with cooler environments. This pattern, indicating directional thermal selection of pigmentation, has been described in variety of insects (e.g.…”

“…Regarding adult life span, there was a tendency towards a higher longevity in high-altitude butterflies (Karl & Fischer 2009). However, this increase in life span was largely restricted to beneficial feeding conditions, while under carbohydrate deprivation lowaltitude animals lived longer.…”

“…However, this increase in life span was largely restricted to beneficial feeding conditions, while under carbohydrate deprivation lowaltitude animals lived longer. Thus low-altitude butterflies do better under food stress, while the opposite is true under beneficial feeding conditions (Karl & Fischer 2009). Generally, a reduced longevity (often with a concomitantly increased early fecundity) is expected for high-altitude populations due to hazardous environmental conditions (Lencioni 2004.…”