Journal of Evolutionary Biology最新文献

A key selection pressure in most habitats is predation, and a common strategy adopted by prey is crypsis through background matching. Many marine blenny fishes are in the process of a dramatic transition across one of the world's most extreme ecotones: the invasion of land across the intertidal zone. We investigated the impact of this transition on body crypsis versus the conspicuousness of visual signals across 56 blenny taxa relative to 59 biologically relevant backgrounds, and as viewed by conspecifics and four representative fish and avian predators. We computed 33 colour and 23 pattern indices from standardised digital photographs of six individuals for each taxa (median sample). Six of these indices were selected for detailed analysis following phylogenetic Principal Component Analysis. While phylogenetic regressions revealed some aspects of body crypsis appeared to have changed adaptively with the progressive transition to land (specifically a reduction in body colour saturation), colonisation was primarily facilitated by a generalist form of crypsis. That is, the colours and patterns of aquatic blennies were already well matched to the range of terrestrial backgrounds where amphibious and terrestrial species were observed out of water. Predation appears to have been an important selection pressure constraining the colour and pattern of the dorsal fins used in social communication, which also matched visual backgrounds. Our data implies anti-predator strategies that translate well across habitats and different predator regimes will facilitate colonisation by either reducing predation risk or allowing species to persist long enough to respond adaptively to environmental change.

Cuticular hydrocarbons (CHCs) are key components of the insect cuticle and contribute to the wide geographical distribution of this taxon. Many studies have investigated sex and population differences in CHC profiles, with these investigations mostly focusing on latitudinal CHC variation, whereas CHC variation across altitudinal transects is less well-studied. Here, we tested whether CHC profiles vary along an altitudinal gradient in the cosmopolitan vinegar fly Drosophila melanogaster. We collected from three populations of D. melanogaster in the Western Himalayas at altitudes ranging from 760 to 2592 m above sea level and tested their CHC profiles for standing and plastic variation. We found quantitative differences in 25 CHCs across populations, and at higher elevations, males and females expressed higher amounts of particular long-chained hydrocarbons. We also found plastic-shifts in CHC profiles in all three populations when flies were exposed to desiccating conditions. Overall, our findings suggest that there is an altitudinal cline in CHCs. However, this does not mirror the well-established latitudinal clines in fly hydrocarbons.

Parthenogenetic wasps provide an ideal natural experiment to study the heritability, plasticity, and microevolutionary dynamics of body size. Dinocampus coccinellae (Hymenoptera:Braconidae, Euphorinae) is a solitary, generalist braconid parasitoid wasp that reproduces through thelytokous parthenogenesis, and parasitizes over fifty diverse species of coccinellid ladybeetles worldwide as hosts. Here we designed an experiment with parthenogenetic lines of D. coccinellae presented with three different host ladybeetle species of varying sizes, across multiple generations to investigate heritability, and plasticity of body size measured via a combination of morphometric variables such as thorax width, abdominal width, and wing length in D. coccinellae. We expected positively correlated parent-offspring parasitoid regressions, indicative of heritable size variation, from unilineal (parent and offspring reared on same host species) lines, since these restrict environmental variation in phenotypes. In contrast, because multilineal (parent and offspring reared on different host species) lines would induce phenotypic plasticity of clones reared in varying environments, we expected negatively correlated parent-offspring parasitoid regressions. Our results indicate (1) little heritable variation in body size, (2) strong independence of offspring size on the host environment, (3) small mothers produce larger offspring, and vice versa, independent of host. We then model the evolution of size and host-shifting under a constrained fecundity advantage model of Cope's Law using a Hidden Markov Model, showing that D. coccinellae likely has fitness advantages to maintain plasticity in body size despite parthenogenetic reproduction.

Ants exhibit many complex social organization strategies. One particularly elaborate strategy is supercoloniality, in which a colony consists of many interconnected nests (=polydomy) with many queens (=polygyny). In many species of Formica ants, an ancient queen number supergene determines whether a colony is monogyne (=headed by single queen) or polygyne. The presence of the rearranged P haplotype typically leads colonies to be polygyne. However, the presence and function of this supergene polymorphism have not been examined in supercolonial populations. Here, we use genomic data from species in the Formica rufa group to determine whether the P haplotype leads to supercoloniality. In a Formica paralugubris population, we find that nests are polygyne, despite the absence of the P haplotype in workers. We find spatial genetic ancestry patterns in nests consistent with supercolonial organization. Additionally, we find that the P haplotype is also absent in workers from supercolonial Formica aquilonia, and Formica aquilonia x polyctena hybrid populations, but is present in some Formica polyctena workers. We conclude that the P haplotype is not necessary for supercoloniality in the Formica rufa group, despite its longstanding association with non-supercolonial polygyny across the Formica genus.

Given their ubiquity in nature and their importance to human and agricultural health it is important to gain a better understanding of the drivers of the evolution of infectious disease. Across vertebrates, invertebrates and plants, defence mechanisms can be expressed either constitutively (always present and costly) or induced (activated and potentially costly only upon infection). Theory has shown that this distinction has important implications to the evolution of defence due to differences in their impact on both individual fitness and the feedback of the population level epidemiological outcomes such as prevalence. However, despite the fact that pathogens evolve in response to host immunity and that this can have important implications to the evolution of host defence, the implications of coevolution on constitutive and induced immunity have not been examined. Here we show theoretically how and when incorporating host-parasite coevolution between host defences and parasite growth strategies plays an important role in determining the optimum outcome. A key result is that whether the parasite affects host reproduction critically impacts host-parasite coevolution; when the parasite impacts fecundity, selection on the host is largely geared towards minimizing reproductive costs, through reducing investment in reproductively costly constitutive defense when the parasite prevalence is low, but also by investing in immunity to avoid infection or recover when prevalence is high. Our work emphasizes the importance of coevolution and epidemiological feedbacks to the coevolution of hosts and parasites and provides testable predictions of the determinants of constitutive verses induced defence.

Ageing of adult males could be accelerated by both high mating/reproductive effort and fighting for mates. Testing the relative importance of these factors is challenging, however, because males that win fights also tend to have more mates. We used a 2 x 2 experimental design to test how a prolonged (9 week) period of either winning or losing fights, and either high or low reproductive effort (manipulating by varying access to females) interact to affect male ageing and future reproduction allocation in the mosquitofish, Gambusia holbrooki. We measured telomere length and several life-history traits, including mating effort and ejaculates (sperm count and velocity). After 9 weeks there were significant differences between winners and losers in their mating effort, but not in their ejaculates. Males with a higher past reproductive effort (i.e. access to females) had significantly lower current mating effort and grew more slowly. Males with a higher past reproductive effort also had slower swimming sperm, but only if they were smaller than average in body size. Surprisingly, neither males with a higher past reproductive effort nor males that repeatedly lost fights had shorter telomeres. Our findings show that past social dynamics affect how males allocate resources to reproduction and somatic maintenance.

The study of mating systems, defined as the distribution of who mates with whom and how often in a sexually reproducing population, forms a core pillar of evolution research due to their effects on many evolutionary phenomena. Historically, the "mating system" has either been used to refer to the rate of self-fertilization or to the formation of mating pairs between individuals of distinct sexes. Consequently, these two types of mating systems have tended to be studied separately rather than jointly. This separation often means that mating systems are not necessarily researched in a coherent manner that might apply to different types of organisms (e.g., plants versus animals, or hermaphrodites versus dioecious species), even if similar mechanisms may drive the evolution of self-fertilization and mating pair formation. Here, we review the evolution of both plant and animal mating systems, highlighting where similar concepts underlie both these fields and also where differing mechanisms are at play. We particularly focus on the effects of inbreeding, but also discuss the influence of spatial dynamics on mating-system evolution. We end with a synthesis of these different ideas and propose ideas for which concepts can be considered together to move towards a more cohesive approach to studying mating-system evolution.

Individuals living in heterogeneous environments often choose microenvironments that provide benefits to their fitness. Theory predicts that such niche choice can promote rapid adaptation to novel environments and help maintain genetic diversity. An open question of large applied importance is how niche choice and niche choice evolution affect the evolution of insecticide resistance in phytophagous insects. We, therefore, developed an individual-based model based on phytophagous insects to examine the evolution of insecticide resistance and niche choice via oviposition preferences. To find biologically realistic parameter ranges, we performed an empirical literature survey on insecticide resistance in major agricultural pests and also conducted a density-dependent survival experiment using potato beetles. We find that, in comparison to a scenario where individuals randomly oviposit eggs on toxic or non-toxic plants, the evolution of niche choice generally leads to slower evolution of resistance and facilitates the coexistence of different phenotypes. Our simulations also reveal that recombination rate and dominance effects can influence the evolution of both niche choice and resistance. Thus, this study provides new insights into the effects of niche choice on resistance evolution and highlights the need for more studies on the genetic basis of resistance and choice.

Wing reduction is a common feature of upland insect communities. This phenomenon is thought to be primarily driven by selection against flight, which is typically unfavourable in upland environments due to high winds and cold temperatures. In some insect taxa, wing reduction has been directly linked to increased fecundity. However, few studies have directly tested for shifts in fecundity linked to flight musculature. Here, we test for dispersal-fecundity trade-offs in the widespread subalpine stonefly Zelandoperla fenestrata. Our analysis of 450 stoneflies across 81 localities reveals significant dispersal-fecundity trade-offs. Specifically, we identify a positive association between the size of their flight muscles and the length of their wings, and a negative association between wing length and ovarian mass. Furthermore, we found a significant negative relationship between flight musculature and ovary mass. These results represent a rare example of a dispersal-fecundity trade-off in the wild and illustrate that such trade-offs can potentially involve corresponding reductions in both flight musculature and wing development. Our findings suggest that widespread taxa subject to variable environmental conditions may benefit from flexible allocation of energetic resources.

Modularity and developmental (in)stability have the potential to influence phenotype production and, consequently, the evolutionary trajectories of species. Depending on the environmental factors involved and the buffering capacity of an organism, different developmental outcomes are expected. Cactophilic Drosophila species provide an established eco-evolutionary model with well-studied ecological conditions, making them ideal for studying these phenomena. Here, we investigated how variations in larval diet and exposure to alkaloids on primary and secondary host plants affect the degree of integration/modularity and fluctuating asymmetry (FA, a proxy for developmental instability) of wing shape in two sibling species with different degrees of specialisation: Drosophila buzzatii (generalist) and Drosophila koepferae (specialist). Additionally, we compared the anterior-posterior modular configuration with a recently proposed proximal-distal modular configuration. Our results revealed greater independence among proximal-distal modules compared to anterior-posterior modules. Moreover, we observed sex-specific responses, with males exhibiting greater susceptibility to stressful environments than females. Each species showed a particular trait pattern across treatments: D. buzzatii showed increased integration and FA when reared in a nutrient-poor, alkaloid-rich secondary host, while D. koepferae displayed similar responses in novel environments characterised by double doses of alkaloids on the secondary host plant. These findings align with the generalist-specialist paradigm, suggesting that specialists may be challenged by novel environments, whereas generalists may be more affected by stressful conditions. Our study highlights the importance of considering each part of the proximal-distal wing axis independently, and the need to consider ecological-evolutionary history when investigating the relationship between complex phenotypic traits and environmental stress.