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American Naturalist

Mohamed Abdelaziz, Mohammed Bakkali, José M Gómez, Enrica Olivieri, Francisco Perfectti
Self-fertilization has recurrently evolved in plants, involving different strategies and traits and often loss of attractive functions, collectively known as the selfing syndrome. However, few traits that actively promote self-fertilization have been described. Here we describe a novel mechanism promoting self-fertilization in the Brassicaceae species Erysimum incanum. This mechanism, which we called "anther rubbing," consists of autonomous, repeated, and coordinated movements of the stamens over the stigma during flower opening...
January 2019: American Naturalist
Pia Backmann, Volker Grimm, Gottfried Jetschke, Yue Lin, Matthijs Vos, Ian T Baldwin, Nicole M van Dam
Time delays in plant responses to insect herbivory are thought to be the principal disadvantage of induced over constitutive defenses, suggesting that there should be strong selection for rapid responses. However, observed time delays between the onset of herbivory and defense induction vary considerably among plants. We postulate that strong competition with conspecifics is an important codeterminant of the cost-benefit balance for induced responses. There may be a benefit to the plant to delay mounting a full defense response until the herbivore larvae are mobile enough to leave and large enough to cause severe damage to neighboring plants...
January 2019: American Naturalist
Alison M Wardlaw, Aneil F Agrawal
In many taxa, there is a conflict between the sexes over mating rate. The outcome of sexually antagonistic coevolution depends on the costs of mating and natural selection against sexually antagonistic traits. A sexually transmitted infection (STI) changes the relative strength of these costs. We study the three-way evolutionary interaction among male persistence, female resistance, and STI virulence for two types of STIs: a viability-reducing STI and a reproduction-reducing STI. A viability-reducing STI escalates conflict between the sexes...
January 2019: American Naturalist
Manuela Ferrari, Anna K Lindholm, Barbara König
Alternative reproductive tactics (ARTs) are defined as discrete differences in morphological, physiological, and/or behavioral traits associated with reproduction that occur within the same sex and population. House mice provide a rare example of ARTs in females, which can rear their young either solitarily or together with one or several other females in a communal nest. We assessed the fitness consequences of communal and solitary breeding in a wild population to understand how the two tactics can be evolutionarily stable...
January 2019: American Naturalist
Sidney F Gouveia, Rafael P Bovo, Juan G Rubalcaba, Fernando Rodrigues Da Silva, Natan M Maciel, Denis V Andrade, Pablo Ariel Martinez
Geographical gradients of body size express climate-driven constraints on animals, but whether they exist and what causes them in ectotherms remains contentious. For amphibians, the water conservation hypothesis posits that larger bodies reduce evaporative water loss (EWL) along dehydrating gradients. To address this hypothesis mechanistically, we build on well-established biophysical equations of water exchange in anurans to propose a state-transition model that predicts an increase of either body size or resistance to EWL as alternative specialization along dehydrating gradients...
January 2019: American Naturalist
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January 2019: American Naturalist
Philip G Hahn, Anurag A Agrawal, Kira I Sussman, John L Maron
A central tenet of plant defense theory is that adaptation to the abiotic environment sets the template for defense strategies, imposing a trade-off between plant growth and defense. Yet this trade-off, commonly found among species occupying divergent resource environments, may not occur across populations of single species. We hypothesized that more favorable climates and higher levels of herbivory would lead to increases in growth and defense across plant populations. We evaluated whether plant growth and defense traits covaried across 18 populations of showy milkweed (Asclepias speciosa) inhabiting an east-west climate gradient spanning 25° of longitude...
January 2019: American Naturalist
Rémi Patin, Daniel Fortin, Cédric Sueur, Simon Chamaillé-Jammes
Dilution of predation risk within groups allows individuals to be less vigilant and forage more while still facing lower risk than if they were alone. How group size influences vigilance when individuals can also adjust their space use and whether this relationship differs among individuals contributing differently to space use decisions remain unknown. We present a model-based study of how dilution affects the optimal antipredator behavior of group members in groups where all individuals determine their vigilance level while group leaders also determine space use...
January 2019: American Naturalist
Matthew H Webb, Robert Heinsohn, William J Sutherland, Dejan Stojanovic, Aleks Terauds
The positive abundance-occupancy relationship (AOR) is a pervasive pattern in macroecology. Similarly, the association between occupancy (or probability of occurrence) and abundance is also usually assumed to be positive and in most cases constant. Examples of AORs for nomadic species with variable distributions are extremely rare. Here we examined temporal and spatial trends in the AOR over 7 years for a critically endangered nomadic migrant that relies on dynamic pulses in food availability to breed. We predicted a negative temporal relationship, where local mean abundances increase when the number of occupied sites decreases, and a positive relationship between local abundances and the probability of occurrence...
January 2019: American Naturalist
Olof Leimar, Sasha R X Dall, John M McNamara, Bram Kuijper, Peter Hammerstein
Genetic polymorphism can contribute to local adaptation in heterogeneous habitats, for instance, as a single locus with alleles adapted to different habitats. Phenotypic plasticity can also contribute to trait variation across habitats, through developmental responses to habitat-specific cues. We show that the genetic architecture of genetically polymorphic and plasticity loci may influence the balance between local adaptation and phenotypic plasticity. These effects of genetic architecture are instances of ecological genetic conflict...
January 2019: American Naturalist
D Justin Yeh
The effect of learned culture (e.g., birdsong dialects and human languages) on genetic divergence is unclear. Previous theoretical research suggests that because oblique learning allows phenotype transmission from individuals with no offspring to an unrelated individual in the next generation, the effect of sexual selection on the learned trait is masked. However, I propose that migration and spatially constrained learning can form statistical associations between cultural and genetic traits, which may allow selection on the cultural traits to indirectly affect the genetic traits...
January 2019: American Naturalist
Tim Connallon, Shefali Sharma, Colin Olito
The evolutionary trajectories of species with separate sexes depend on the effects of genetic variation on female and male traits as well as the direction and alignment of selection between the sexes. Classical theory has shown that evolution is equally responsive to selection on females and males, with natural selection increasing the product of the average relative fitness of each sex over time. This simple rule underlies several important predictions regarding the maintenance of genetic variation, the genetic basis of adaptation, and the dynamics of "sexually antagonistic" alleles...
January 2019: American Naturalist
Yoel E Stuart
The mechanistic link between natural selection and parallel evolution is well established. Natural selection is the only known deterministic process that can regularly overcome chance and historical contingency to generate the evolution of similar characteristics in independent populations inhabiting similar environments. However, the ready inference of natural selection from parallel evolution has been established only relatively recently. Here, I review the use of "parallel evolution" in the first 125 years of The American Naturalist and show that there were other well-accepted definitions of the term through the history of the field...
January 2019: American Naturalist
Ruth G Shaw
The complex interplay of the multiple genetic processes of evolution and the ecological contexts in which they proceed frustrates detailed identification of many of the states of populations, both past and future, that may be of interest. Prediction of rates of adaptation, in the sense of change in mean fitness, into the future would, however, valuably inform expectations for persistence of populations, especially in our era of rapid environmental change. Heavy investment in genomics and other molecular tools has fueled belief that those approaches can effectively predict adaptation into the future...
January 2019: American Naturalist
Nils Gülzow, Yanis Wahlen, Helmut Hillebrand
Metaecosystem theory addresses the link between local (within habitats) and regional (between habitats) dynamics by simultaneously analyzing spatial community ecology and abiotic matter flow. Here we experimentally address how spatial resource gradients and connectivity affect resource use efficiency (RUE) and stoichiometry in marine phytoplankton as well as the community composition at local and regional scales. We created gradostat metaecosystems consisting of five linearly interconnected patches, which were arranged either in countercurrent gradients of nitrogen (N) and phosphorus (P) supply or with a uniform spatial distribution of nutrients and which had either low or high connectivity...
January 2019: American Naturalist
Charles Mullon, Laurent Lehmann
Understanding selection on intra- and interspecific interactions that take place in dispersal-limited communities is a challenge for ecology and evolutionary biology. The problem is that local demographic stochasticity generates eco-evolutionary dynamics that are generally too complicated to make tractable analytical investigations. Here we circumvent this problem by approximating the selection gradient on a quantitative trait that influences local community dynamics, assuming that such dynamics are deterministic with a stable fixed point...
December 2018: American Naturalist
Thomas Holding, John Joseph Valletta, Mario Recker
Antigenic diversity is commonly used by pathogens to enhance their transmission success. Within-host clonal antigenic variation helps to maintain long infectious periods, whereas high levels of allelic diversity at the population level significantly expand the pool of susceptible individuals. Diversity, however, is not necessarily a static property of a pathogen population but in many cases is generated by the very act of infection and transmission, and it is therefore expected to respond dynamically to changes in transmission and immune selection...
December 2018: American Naturalist
Patrick T Rohner, Wolf U Blanckenhorn
Sexual selection can displace traits acting as ornaments or armaments from their viability optimum in one sex, ultimately giving rise to sexual dimorphism. The degree of dimorphism should not only mirror the strength of sexual selection but also the net viability costs of trait maintenance at equilibrium. As the ability of organisms to bear exaggerated traits will depend on their condition, more sexually dimorphic traits should also exhibit greater sex differences in condition dependence. While this has been demonstrated among traits within species, similar patterns are expected across the phylogeny...
December 2018: American Naturalist
María Rebolleda-Gómez, Michael Travisano
Multicellularity provides multiple benefits. Nonetheless, unicellularity is ubiquitous, and there have been multiple cases of evolutionary reversal to a unicellular organization. In this article, we explore some of the costs of multicellularity as well as the possibility and dynamics of evolutionary reversals to unicellularity. We hypothesize that recently evolved multicellular organisms would face a high cost of increased competition for local resources in spatially structured environments because of larger size and increased cell densities...
December 2018: American Naturalist
Susana M Wadgymar, Rachel M Mactavish, Jill T Anderson
Parental environmental effects-or transgenerational plasticity-can influence an individual's phenotype or fitness yet remain underexplored in the context of global change. Using the perennial self-pollinating plant Boechera stricta, we explored the effects of climate change on transgenerational and within-generation plasticity in dormancy, germination, growth, and survival. We first conducted a snow removal experiment in the field, in which we transplanted 16 families of known origin into three common gardens at different elevations and exposed half of the siblings to contemporary snow dynamics and half to early snow removal...
December 2018: American Naturalist
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