The distinct phenotypic signatures of dispersal and stress in an arthropod model: from physiology to life history

Abstract

Dispersing individuals are expected to encounter costs during transfer and in the novel environment, and may also have experienced stress in their natal patch. Given this, a non-random subset of the population should engage in dispersal and eventually show divergent stress-related responses towards new conditions. Dispersal allows escape from stress, but is equally subjecting individuals to it.Physiological shifts expressed in the metabolome form a major part of responses to stress exposure and are expected to be associated with the dispersal phenotype, thereby shaping physiological dispersal syndromes. We analyzed how metabolic profiles and life-history traits varied between dispersers and residents of the model two-spotted spider miteTetranychus urticae, and whether and how these syndromes varied with exposure to a stressful new host plant (tomato). Regardless of the effect of host plant, we found a physiological dispersal syndrome where, relative to philopatric individuals, dispersers were characterized by lower leaf consumption rates and a lower concentration of several amino acids, indicating a potential dispersal-foraging trade-off. As a possible consequence of this lower food intake, dispersers also showed a lower reproductive performance. Responses to tomato exposure were consistent with this plant being a stressor forTetranychus urticae, including reduced fecundity and reduced feeding by mites. Tomato-exposed mites laid larger eggs, which can be interpreted as a plastic response to food stress, increasing the likelihood of survival to maturity. Contrary to what could be expected from the costs of dispersal and stress resistance and from previous meta-population level studies, there was no interaction between dispersal status and host plant for any of the examined traits, indicating that the impacts of a new stressful host plant are equally incurred by residents and dispersers.We thus provide novel insights in the processes that shape dispersal and the putative feedbacks on ecological dynamics in spatially structured populations.

Individual heterogeneity and its importance for metapopulation dynamics

“…While phenotypic variation has been shown to explain patterns in biodiversity [23], [69] we here demonstrate its importance for metapopulation demography, and in extension metapopulation conservation. Our reshuffling treatment can be considered as an extreme case of hypermobility within the spatial network.…”

“…We quantified these dynamics in series of simulated and experimental metapopulations, and found variation in evolved dispersal rather than costs across metapopulations to match predictions on population size variability. Dispersal in general is phenotype-dependent [41], [42], leading to sorting of phenotypes in metapopulations [23], [43]. We provide experimental evidence that such a phenotypic self-organization is an additional and powerful driver of metapopulation dynamics.…”

“…An increased spatial genetic structure resulting from low levels of gene flow will elevate competitive interactions among kin, which is known to be an important driver of dispersal [21], thus potentially imposing negative feedbacks on the metapopulation dynamics [22]. Because dispersal is performed by a non-random subset of individuals from the population that share specific life history traits [18], [23], [24] and physiology [25], the phenotypic (kind) structure [26] will be altered by changes in connectedness. This has the potential to affect population dynamics through impacts on population growth.…”

Honest cues contribute to male choice for female guarding in a herbivorous spider mite

“…We quantified dispersal by the movement of mites across parafilm bridges to adjacent leaf discs (Dahirel et al, 2019) for adult females in the first batch of experiments. Spider mite movements were monitored 4 times/day.…”

The physiology of movement

“…Transcriptomic analyses hold great promise to find common underlying molecular pathways that relate to certain types of movement behaviors, but it remains difficult to connect different transcriptomic profiles to the exact levels of metabolite production [158]. In plant-feeding spider mites (Tetranychus urticae) that show genetic variation in dispersal along a latitudinal gradient, metabolomic profiling indicated that an allocation of energy could be linked to a dispersalforaging trade-off, with more dispersive mites evolving to cope with lower essential amino acid concentrations thereby allowing them to survive with lower amounts of food [159,160]. This finding is consistent with the theory that individuals of a population that forage on the same resources can differ on the genetic level in how these resources are metabolized and that these differences influence their movement behavior [137].…”