New record in the Hawaiian Islands of Orasema minutissima (Hymenoptera: Eucharitidae), an ant-parasitic wasp and a potential biocontrol agent against the Little Fire Ant, Wasmannia auropunctata (Hymenoptera: Formicidae)

Orasema minutissima Howard (Hymenoptera: Eucharitidae) is recorded fromthe Hawaiian Islands for the first time. It has been established on the island of Hawai?isince at least 2019. The wasp is a parasitoid of the immature stages of Pheidole andWasmannia (Formicidae: Myrmicinae), both of which are significant pests on several ofthe Hawaiian Islands. Already found in substantial numbers, the wasp is a potential biological control agent for Wasmannia auropunctata, the Little Fire Ant.Fil: Heraty, John Michael. University of California; Estados UnidosFil: Rogers, Valle D.. University of California; Estados UnidosFil: Johnson, M. Tracy. Institute of Pacific Islands Forestry; Estados UnidosFil: Perreira, Williams D.. No especifíca;Fil: Baker, Austin J.. University of California; Estados UnidosFil: Bitume, Ellyn. Institute of Pacific Islands Forestry; Estados UnidosFil: Murray, Elizabeth. Washington State University; Estados UnidosFil: Varone, Laura. Fundación para el Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Eco-evolutionary dynamics in fragmented landscapes

Peer reviewedPostprin

Dispersal: a matter of scale

Population density around the natal site is often invoked as an explanation for variation in dispersal distance, with the expectation that competition for limiting resources, coupled with increased intra‐specific aggression at high densities, should drive changes in dispersal distances. However, tests of the density‐dependent dispersal hypothesis in long‐lived vertebrates have yielded mixed results. Furthermore, conclusions from dispersal studies may depend on the spatial and temporal scales at which density and dispersal patterns are examined, yet multi‐scale studies of dispersal are rare. Here, we present the findings of a long‐term study examining factors influencing natal dispersal distances for the non‐migratory population of Peregrine Falcons (Falco peregrinus) in the British Isles across distinct spatial and temporal scales. Our smallest scale study included Peregrines ringed as nestlings and subsequently recaptured alive in south Scotland–north England, an area that was intensively studied during the time periods 1974–1982 and 2002–2016. Second, we examined dispersal patterns of birds ringed as nestlings in south Scotland–north England, but subsequently recaptured alive or recovered dead anywhere in the British Isles. Finally, we examined the natal dispersal patterns for Peregrines ringed and recaptured or recovered anywhere in the British Isles from 1964 to 2016. Consistent with prior findings, females dispersed farther than males across all scales. However, the patterns of dispersal were strongly scale dependent. Specifically, we found a lack of a discernible relationship between index of density and dispersal distance in the limited study area, but when region‐wide recaptures and recoveries were included in the analyses, a negative relationship was revealed. Our results suggest that conclusions of dispersal studies may be scale dependent, highlighting the importance of spatial and temporal scales in examining and interpreting the relationship between population density and dispersal patterns

No behavioural response to kin competition in a lekking species

The processes of kin selection and competition may occur simultaneously if limited individual dispersal i.e. population viscosity, is the only cause of the interactions between kin. Therefore, the net indirect benefits of a specific behaviour may largely depend on the existence of mechanisms dampening the fitness costs of competing with kin. In lekking species, males may increase the mating success of their close relatives (and hence gain indirect fitness benefits) because female prefer large leks. At the same time, kin selection may also lead to the evolution of mechanisms that dampen the costs of kin competition. As this mechanism has largely been ignored to date, we used detailed behavioural and genetic data collected in the black grouse Lyrurus tetrix to test whether males mitigate the costs of kin competition through the modulation of their fighting behaviours according to kinship and the avoidance of close relatives when establishing a lek territory. We found that neighbouring males’ fighting behaviour was unrelated to kinship and males did not avoid settling down with close relatives on leks. As males’ current and future mating success are strongly related to their behaviour on the lek (including fighting behaviour and territory position), the costs of kin competition may be negligible relative to the direct benefits of successful male-male contests. As we previously showed that the indirect fitness benefits of group membership were very limited in this black grouse population, these behavioural data support the idea that direct fitness benefits gained by successful male-male encounters likely outbalance any indirect fitness benefits

Heritability and Artificial Selection on Ambulatory Dispersal Distance in Tetranychus urticae: Effects of Density and Maternal Effects

Dispersal distance is understudied although the evolution of dispersal distance affects the distribution of genetic diversity through space. Using the two-spotted spider mite, Tetranychus urticae, we tested the conditions under which dispersal distance could evolve. To this aim, we performed artificial selection based on dispersal distance by choosing 40 individuals (out of 150) that settled furthest from the home patch (high dispersal, HDIS) and 40 individuals that remained close to the home patch (low dispersal, LDIS) with three replicates per treatment. We did not observe a response to selection nor a difference between treatments in life-history traits (fecundity, survival, longevity, and sex-ratio) after ten generations of selection. However, we show that heritability for dispersal distance depends on density. Heritability for dispersal distance was low and non-significant when using the same density as the artificial selection experiments while heritability becomes significant at a lower density. Furthermore, we show that maternal effects may have influenced the dispersal behaviour of the mites. Our results suggest primarily that selection did not work because high density and maternal effects induced phenotypic plasticity for dispersal distance. Density and maternal effects may affect the evolution of dispersal distance and should be incorporated into future theoretical and empirical studies

Genetics of Dispersal

Dispersal is a process of central importance for the ecological and evolutionary dynamics of populations and communities, because of its diverse consequences for gene flow and demography. It is subject to evolutionary change, which begs the question, what is the genetic basis of this potentially complex trait? To address this question, we (i) review the empirical literature on the genetic basis of dispersal, (ii) explore how theoretical investigations of the evolution of dispersal have represented the genetics of dispersal, and (iii) discuss how the genetic basis of dispersal influences theoretical predictions of the evolution of dispersal and potential consequences. Dispersal has a detectable genetic basis in many organisms, from bacteria to plants and animals. Generally, there is evidence for significant genetic variation for dispersal or dispersal-related phenotypes or evidence for the micro-evolution of dispersal in natural populations. Dispersal is typically the outcome of several interacting traits, and this complexity is reflected in its genetic architecture: while some genes of moderate to large effect can influence certain aspects of dispersal, dispersal traits are typically polygenic. Correlations among dispersal traits as well as between dispersal traits and other traits under selection are common, and the genetic basis of dispersal can be highly environment-dependent. By contrast, models have historically considered a highly simplified genetic architecture of dispersal. It is only recently that models have started to consider multiple loci influencing dispersal, as well as non-additive effects such as dominance and epistasis, showing that the genetic basis of dispersal can influence evolutionary rates and outcomes, especially under non-equilibrium conditions. For example, the number of loci controlling dispersal can influence projected rates of dispersal evolution during range shifts and corresponding demographic impacts. Incorporating more realism in the genetic architecture of dispersal is thus necessary to enable models to move beyond the purely theoretical towards making more useful predictions of evolutionary and ecological dynamics under current and future environmental conditions. To inform these advances, empirical studies need to answer outstanding questions concerning whether specific genes underlie dispersal variation, the genetic architecture of context-dependent dispersal phenotypes and behaviours, and correlations among dispersal and other traits.Peer reviewe

Evolution of dispersal strategies and dispersal syndromes in fragmented landscapes

Funded by ERA-Net BiodivERsAPeer reviewedPostprin

Genetic and environmental contributions to dispersal distance in the two-spotted spider mite, Tetranychus urticae

Dispersal, the movement of individuals leading to gene flow, is a life-history trait found in virtually all organisms. Understanding the mechanisms behind why some individuals move when others remain is crucial to the study of population dynamics and conservation biology. Dispersal is comprised of three phases: emigration, transfer, and settlement. While emigration is well studied, the causes of differing dispersal distances resulting from decisions made at each of these phases are less well investigated. In this thesis, we attempted to distinguish genetic mechanisms of dispersal distance and to quantify plastic responses to different environmental and individual condition. To achieve this goal, we first attempted two different methods of artificial selection: one experiment on emigration and another on dispersal distance. While unable to produce differently dispersing lines in either of these experiments, the results revealed the importance of different environmental factors on dispersal decisions, i.e. the importance of phenotypic plasticity in the expression of this trait. We then performed experiments investigating the effects of population density, genetic relatedness, and maternal density on dispersal distance and the shape of the dispersal kernel. We found that increases in population density and relatedness increased dispersal distances, and that relatedness increased the distance traveled by the furthest moving 10% of individuals. We also found that in general, maternal and even grand-maternal density can influence the distance at which offspring will disperse, almost regardless of the offspring’s own environment. Our results contribute to the field of dispersal ecology by demonstrating that dispersal distance, in addition to emigration, can be affected by the interaction between external environmental factors (context-dependent dispersal) and the phenotypic condition of the individual (condition-dependent dispersal). We propose additional experiments to further clarify and augment the results of this thesis. Finally, we suggest that these results can be used in predictive modeling to know how a population might disperse when faced with differing environments. Thus, our results are useful in terms of predicting dispersal behavior by species undergoing range expansion, and for conservation biologists attempting to rescue populations that are affected by habitat fragmentation.(BIOL 3) -- UCL, 201

Dispersal distance is influenced by parental and grand-parental density

Non-genetic transmission of information across generations, so-called parental effects, can have significant impacts on offspring morphology, physiology, behaviour and life-history traits. In previous experimental work using the two-spotted spider mite Tetranychus urticae Koch, we demonstrated that dispersal distances increase with local density and levels of genetic relatedness. We here show that manipulation of parental and grand-parental density has a significant effect on offspring dispersal distance, of the same order of magnitude as manipulation of offspring density. We demonstrate that offspring exposed to the same density disperse further if they were born to parents exposed to higher density compared with parents exposed to low density. Offspring dispersal distance also increases when grand-parents were exposed to higher density, except for offspring exposed to lowdensities, which disperse at shorter distances whatever the grand-parental density. We also show that offspring from mothers exposed to higher densities were overall larger, which suggests that parents in high densities invest more in individual offspring, enabling them to disperse further. We propose that our findings should be included in models investigating the spread rate of invasive species or when predicting the success of conservation measures of species attempting to track changing climates. © 2014 The Author(s) Published by the Royal Society. All rights reserved