Abstract
Global climate change affects natural populations of many species by increasing the average temperature and the frequency of extreme weather events (e.g. summer heat waves). The ability of organisms to cope with these environmental changes can, however, depend on their genetic properties. For instance, genetic load owing to inbreeding could alter organisms’ responses to climate change-mediated environmental changes but such effects are often overlooked. We investigated the effects of an experimental heat wave (25°C versus 15°C) on life history (reproduction, size) and constitutive immune defence traits (phenoloxidase-like and antibacterial activity of haemolymph) in relation to inbreeding by manipulating the mating type (outcrossing, self-fertilization) in two populations of a hermaphroditic freshwater snail, Lymnaea stagnalis. High temperature increased reproduction and size of snails but impaired their immune function. In one of the two study populations, inbreeding reduced reproductive output of snails indicating inbreeding depression. Furthermore, this effect did not depend on the temperature snails were exposed to. Our results suggest that L. stagnalis snails can be negatively affected by inbreeding but it may not alter their responses to heat waves.
Highlights
Owing to global climate change, the average temperatures at the Earth’s surface, as well as the frequency and severity of extreme weather events, are increasing [1, 2]. Extreme weather conditions such as summer heat waves are suggested to be more significant to natural populations than the gradual increase in average temperatures [3, 4]
We investigated the combined effects of an experimental heat wave and inbreeding on life history traits and constitutive immune defence traits [phenoloxidase (PO)-like activity and antibacterial activity of haemolymph] in a simultaneously hermaphroditic freshwater snail, Lymnaea stagnalis
Exposure to high temperature increased their probability to reproduce (17.0% increase compared with 15 ̊C; generalized linear model (GLM): d.f. = 1, F = 30.045, p < 0.001; Fig 1), the number of laid eggs (123.1% increase; Table 1 and Fig 2), Inbreeding and the response to a heat wave and size (4.7% increase; Table 1 and Fig 2)
Summary
Owing to global climate change, the average temperatures at the Earth’s surface, as well as the frequency and severity of extreme weather events, are increasing [1, 2]. Extreme weather conditions such as summer heat waves are suggested to be more significant to natural populations than the gradual increase in average temperatures [3, 4]. This is because high temperatures can have strong effects on organismal physiology and even alter species interactions [5,6,7,8]. Such effects are largely due to changes in fitness-related traits such as reproduction [9, 10] and defence against natural enemies [11, 12]. The responses of organisms to environmental alterations can, vary across individuals and populations depending on their genetic properties such as allele composition and the level of inbreeding [13,14,15].
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