Stress resistance as a component of dispersal syndromes in the non-native Merizodus soledadinus on Kerguelen islands

Global changes and human activities have increased the likelihood of
transport of non-native insect species all around the globe. When
established, the spread of organisms leads to the spatial sorting of the
populations, progressively contributing to the selection of individuals
with enhanced dispersal performance at the edges of the invaded range.
During dispersal, propagules are also subjected to contrasting
environmental conditions that can be stressful. These include temperature
extremes and variations, desiccation and the quantity and quality of food,
which can impose physiological constraints. As a consequence, dispersal
syndrome may be promoted along invasion gradients with individuals being
characterized by higher stress tolerance in addition to higher dispersal
capacities. However, only few studies have examined the differences in
stress resistance of non-native insect populations along their invasion
gradient. Merizodus soledadinus (Guérin-Méneville, 1830) is a non-native
insect species invading the subantarctic Kerguelen Islands, where its
quick spread highly impacts the native fauna. On the Kerguelen Islands,
its invasion history is precisely known. This offers a unique opportunity
to study its stress resistance in relation to the residence time. In this
study, we investigated the effects of the residence time of populations of
M. soledadinus on its resistance to heat, desiccation, food deprivation
and the combination of these three stresses in the laboratory. We found
that desiccation and multiple stress treatments caused the highest
mortality rates. Range edge populations showed a longer survival compared
to core populations. However, the dynamics of survival were different:
core populations experienced a steady decline in survival, while range
edge populations initially experienced a slow mortality decline followed
by a rapid mortality. This suggests greater stress resistance for
individuals at the invasion front, potentially explaining the intense
expansion of M. soledadinus on Kerguelen Islands. Further research could
explore the bioenergetic consequences of these differences in stress
resistance.