Sexual signals are important in speciation, but understanding their evolution is complex as these signals are often composed of multiple, genetically interdependent components. To understand how signals evolve, we thus need to consider selection responses in multiple components and account for the genetic correlations among components. One intriguing possibility is that selection changes the genetic covariance structure of a multicomponent signal in a way that facilitates a response to selection. However, this hypothesis remains largely untested empirically. In this study, we investigate the evolutionary response of the multicomponent female sex pheromone blend of the moth Heliothis subflexa to 10 generations of artificial selection. We observed a selection response of about 3/4s of a phenotypic standard deviation in the components under selection. Interestingly, other pheromone components that are biochemically and genetically linked to the components under selection did not change. We also found that after the onset of selection, the genetic covariance structure diverged, resulting in the disassociation of components under selection and components not under selection across the first two genetic principle components. Our findings provide rare empirical support for an intriguing mechanism by which a sexual signal can respond to selection without possible constraints from indirect selection responses.
Metabolic rate is a trait that may evolve in response to the direct and indirect effects of predator-induced mortality. Predators may indirectly alter selection by lowering prey densities and increasing resource availability or by intensifying resource limitation through changes in prey behaviour (e.g. use of less productive areas). In the current study we quantify evolution of metabolic rate in the zooplankton Daphnia pulicaria following an invasive event by the predator Bythotrephes longimanus in Lake Mendota, Wisconsin, US. This invasion has been shown to dramatically impact D. pulicaria, causing a ~60% decline in their biomass. Using a resurrection ecology approach, we compared the metabolic rate of D. pulicaria clones originating from prior to the Bythotrephes invasion with that of clones having evolved in the presence of Bythotrephes. We observed a 7.4% reduction in metabolic rate among post-invasive clones compared to pre-invasive clones, and discuss the potential roles of direct and indirect selection in driving this change.
Plant phenology is manifested in the seasonal timing of vegetative and reproductive processes, but also has ontogenetic aspects. The adaptive basis of seasonal phenology has been considered mainly in terms of climatic drivers. However, some biotic factors as likely evolutionary influences on plants’ phenology appear to have been under-researched. Several specific cases of putative biotic factors driving plant phenology are outlined, involving both herbivores and pathogens. These illustrate the diversity of likely interactions rather than any systematic coverage or review. Emphasis is on woody perennials, in which phenology is often most multi-faceted and complicated by the ontogenetic aspect. The complete seasonal leaf fall that characterises deciduous plants may be a very important defence against some pathogens. Whether biotic influences drive acquisition or long-term persistence of deciduousness is considered. In one case; of leaf rusts in poplars, countervailing influences of the rusts and climate suggest persistence. Often, however, biotic and environmental influences likely reinforce each other. The timing and duration of shoot flushing may in at least some cases contribute to defences against herbivores, largely through brief periods of ‘predator satiation’ when plant tissues have highest food value. Wide re-examination of plant phenology, accommodating the roles of biotic factors and their interplays with environments as additional adaptive drivers, is advocated, towards developing and applying hypotheses that are observationally or experimentally testable.
The subfamily Typhlocybinae is a ubiquitous, highly diverse group of mostly tiny, delicate leafhoppers. The tribal classification has long been controversial and phylogenetic methods have only recently begun to test the phylogenetic status and relationships of tribes. To shed light on the evolution of Typhlocybinae, we performed phylogenetic analyses based on 28 newly sequenced and 19 previously sequenced mitochondrial genomes representing all currently recognized tribes. The results support the monophyly of the subfamily and its sister group relationship to Mileewinae. The tribe Zyginellini is polyphyletic with some included genera derived independently within Typhlocybini. Ancestral character state reconstruction suggests that some morphological characters traditionally considered important for diagnosing tribes (presence/absence of ocelli, development of hind wing submarginal vein) are homoplastic. Divergence time estimates indicate that the subfamily arose during the Middle Cretaceous and that the extant tribes arose during the Late Cretaceous. Phylogenetic results support establishment of a new genus, Subtilissimia Yan & Yang gen. nov., with two new species, Subtilissimia fulva Yan & Yang sp. nov. and Subtilissimia pellicula Yan & Yang sp. nov. (Typhlocybinae: Typhlocybini); but indicate that two previously recognized species of Farynala distinguished only by the direction of curvature of the processes of the aedeagus are synonyms, i.e., Farynala dextra Yan & Yang, 2017 equals Farynala sinistra Yan & Yang, 2017 syn. nov. A key to tribes of Typhlocybinae is provided.
The horned gall aphid Schlechtendalia chinensis, is an economically important insect that induces galls valuable for medicinal and chemical industries. S. chinensis manipulates its host plant to form well-organized horned galls during feeding. So far, more than twenty aphid genomes have been reported; however, all of those are derived from free-living aphids. Here we generated a high-quality genome assembly of S. chinensis, representing the first genome sequence of a galling aphid. The final genome assembly was 280.43 Mb, with 97% of the assembled sequences anchored into thirteen chromosomes. S. chinensis presents the smallest aphid genome size among available aphid genomes to date. The contig and scaffold N50 values were 3.39 Mb and 20.58 Mb, respectively. The assembly included 96.4% of conserved arthropod and 97.8% of conserved Hemiptera single-copy orthologous genes based on BUSCO analysis. A total of 13,437 protein-coding genes were predicted. Phylogenomic analysis showed that S. chinensis formed a single clade between the Eriosoma lanigerum clade and the Aphidini+Macrosiphini aphid clades. In addition, salivary proteins were found to be differentially expressed when S. chinensis underwent host alternation, indicating their potential roles in gall formation and plant defense suppression. A total of 36 cytochrome P450 genes were identified in S. chinensis, considerably fewer compared to other aphids, probably due to its small host plant range. The high-quality S. chinensis genome assembly and annotation provide an essential genetic background for future studies to reveal the mechanism of gall formation and to explore the interaction between aphids and their host plants.
Metabarcoding has improved the way we understand plants within our environment, from their ecology and conservation to invasive species management. The notion of identifying plant taxa within environmental samples relies on the ability to match unknown sequences to known reference libraries. Without comprehensive reference databases, species can go undetected or be incorrectly assigned, leading to false positive and negative detections. To improve our ability to generate reference sequence databases we developed a targeted capture approach using the OZBaits_CP V1.0 set, designed to capture chloroplast gene regions across the entirety of flowering plant diversity. We focused on generating a reference database for coastal temperate plant species given the lack of reference sequences for these taxa. Our approach was successful across all specimens with a target gene recovery rate of 92% which was achieved in a single assay (i.e., samples were pooled), thus making this approach much faster and more efficient than standard barcoding. Further testing of this database highlighted 80% of all samples could be discriminated to family level across all gene regions with some genes achieving greater resolution than others – which was also dependant on the taxon of interest. Thus, we demonstrate the importance of generating reference sequences across multiple chloroplast gene regions as no single loci is sufficient to discriminate across all plant groups. The targeted capture approach outlined in this study provides a way forward to achieve this.
Climate change and fisheries exploitation are dramatically changing the species composition, abundances, and size spectra of fish communities. We explore whether variation in abundance-size spectra, a widely studied ecosystem feature, is influenced by a critical parameter thought to govern the shape of size-structured ecosystems—the relationship between the sizes of predators and their prey (predator-prey mass ratios, or PPMRs). PPMR estimates are lacking for vast numbers of fish species, including at the broader trophic guild scale. Using measurements of 8,128 prey items in gut contents of 97 reef fish species, we established PPMRs for four major trophic guilds (piscivores, invertivores, planktivores and herbivores) using linear mixed effects models. To assess theoretical predictions that higher mean community-level PPMR leads to shallower size spectrum slopes, we compared observations of mean community-level PPMR with size spectrum slopes for coastal reef sites distributed around Australia. PPMRs of individual fishes were remarkably high (median ~71,000), with significant variation between different trophic guilds (~890 for piscivores; ~83,000 for planktivores), and ~8,700 for whole communities. Community-level PPMRs were positively related to size spectrum slopes, broadly consistent with theory, however, this pattern was also influenced by the latitudinal temperature gradient. Tropical reefs showed a stronger relationship between community-level PPMRs and community size spectrum slopes than temperate reefs. The extent that these patterns apply outside Australia, and consequences for community structure and dynamics, are key areas for future investigation.
Adaptive habitat construction is a process by which individuals alter their environment so as to increase their (inclusive) fitness. Such alterations are a subset of the myriad ways that individuals condition their environment. We present an individual-based model of habitat construction to explore what factors might favor selection when the benefits of environmental alterations are shared by individuals of the same species. Our results confirm the predictions of inclusive fitness and group selection theory and expectations based on previous models that construction will be more favored when its benefits are more likely to be directed to self or near kin. We found that temporal variation had no effect on the evolution of construction. For spatial heterogeneity, construction was disfavored when the spatial pattern of movement did not match the spatial pattern of environmental heterogeneity, especially when there was spatial heterogeneity in the optimal amount of construction. Under those conditions, very strong selection was necessary to favor genetic differentiation of construction propensity among demes. We put forth a constitutive theory for the evolution of adaptive habitat construction that unifies our model with previous verbal and quantitative models into a formal conceptual framework.
1. The recovery of terrestrial carnivores in Europe is a conservation success story. Initiatives focused on restoring top predators, require information on how resident species may interact with the re-introduced species as their interactions have the potential to alter food webs, yet such data are scarce for Europe. 2. In this study, we assessed patterns of occupancy and interactions between three carnivore species in the Romanian Carpathians. Romania houses one of the few intact carnivore guilds in Europe, making it an ideal system to assess intraguild interactions, and serve as a guide for reintroductions elsewhere. 3. We used camera trap data from two seasons in Transylvanian forests to assess occupancy and co-occurrence of carnivores using multispecies occupancy models. 4. Mean occupancy in the study area was highest for lynx ( winter= 0.76 95% CI: 0.42-0.92; autumn= 0.71 CI: 0.38-0.84) and wolf (winter= 0.60 CI: 0.34-0.78; autumn= 0.81 CI: 0.25-0.95) and lowest for wildcat (winter= 0.40 CI: 0.19-0.63; autumn= 0.52 CI: 0.17-0.78) 5. We found that marginal occupancy predictors for carnivores varied between seasons. We also found differences in predictors of co-occupancy between seasons for both lynx-wolf and wildcat-wolf co-occupancy. For both seasons, we found that conditional occupancy probabilities of all three species were higher when another species was present. 6. Our results indicate that while there are seasonal differences in predictors of occupancy and co-occupancy of the three species, co-occurrence in our study area is high, and is dependent on the existence of continuous, relatively undisturbed forests. 7. Terrestrial carnivore recovery efforts are ongoing worldwide. Insights into interspecific relations between carnivore species are critical when considering the depauperate communities they are introduced in. Our work showcases that apex carnivore coexistence is possible, but dependent on protection afforded to forest habitats and their prey base.
Explaining food web dynamics, stability, and functioning depend substantially on understanding of feeding relations within a community. Bulk stable isotope ratios (SIRs) in natural abundance are well-established tools to express direct and indirect feeding relations as continuous variables across time and space. Along with bulk SIRs, the SIRs of individual amino acids (AAs) are now emerging as a promising and complementary method to characterize the flow and transformation of resources across a diversity of organisms, from microbial domains to macroscopic consumers. This significant AA-SIR capacity is based on empirical evidence that a consumer’s SIR, specific to an individual AA, reflects its diet SIR coupled with a certain degree of isotopic differences between the consumer and its diet. However, many empirical ecologists are still unfamiliar with the scope of applicability and the interpretative power of AA-SIR. To fill these knowledge gaps, we here describe a comprehensive approach to both carbon and nitrogen AA-SIR assessment focusing on two key topics: pattern in AA-isotope composition across spatial and temporal scales, and a certain variability of AA-specific isotope differences between the diet and the consumer. On this basis we review the versatile applicability of AA-SIR to improve our understanding of physiological processes as well as food web functioning, allowing us to reconstruct dominant basal dietary sources and trace their trophic transfers at the specimen and community levels. Given the insightful and opportunities of AA-SIR, we suggest future applications for the dual use of carbon and nitrogen AA-SIR to study more realistic food web structures and robust consumer niches, which are often very difficult to explain in nature.
Heterogeneity in riverine habitats acts as a template for species evolution that influences river communities at different spatio-temporal scales. Although birds are conspicuous elements of these communities, the roles of phylogeny, functional traits and habitat character in their niche-use or species’ assembly have seldom been investigated. We explored these themes by surveying multiple headwaters over 3000 m of elevation in the Himalayan Mountains of India where specialist river birds reach their greatest diversity on Earth. After ordinating community composition, species traits and habitat character, we investigated whether river-bird traits varied with elevation in ways that were constrained or independent of phylogeny, hypothesising that trait patterns reflect environmental filtering. Community composition and trait representation varied strongly with elevation and river naturalness as species that foraged in the river/riparian ecotone gave way to small insectivores with obligate links to the river channel. These trends were influenced strongly by phylogeny as communities became more clustered by functional traits at higher elevation. Phylogenetic signals varied among traits, however, and were reflected in body mass, bill size and tarsus length more than in body size, tail length and breeding strategy. These variations imply that community assembly in high altitude river birds reflects a blend of phylogenetic constraint and habitat filtering coupled with some proximate niche-based moulding of trait character. We suggest that the regional co-existence of river birds in the Himalaya is facilitated by the same array of factors that together reflect the highly heterogeneous template of river habitats provided by these mountain headwaters.
High-throughput DNA sequencing technologies make it possible now to sequence entire genomes relatively easily. Complete genomic information obtained by whole genome resequencing (WGS) can aid in identifying and delineating species even if they are extremely young, cryptic or morphologically difficult to discern and closely related. Yet for taxonomic or conservation biology purposes WGS can remain cost-prohibitive, too time-consuming, and often constitute a “data overkill”. Rapid and reliable identification of species (and populations) that is also cost-effective is possible based on species-specific markers that can be discovered by WGS. Based on WGS data we designed a PCR restriction fragment length polymorphism (PCR-RFLP) assay for 19 Neotropical Midas cichlid populations (Amphilophus cf. citrinellus), that includes all 13 described species of this species complex. Our work illustrates that identification of species and populations (i.e., fish from different lakes) can be greatly improved by designing genetic markers using available “high resolution” genomic information. Yet, our work also shows that even in the best-case scenario, when whole-genome resequencing information is available, unequivocal assignments remain challenging when species or populations diverged very recently, or gene flow persists. In summary, we provide a comprehensive workflow on how to design RFPL markers based on genome re-sequencing data, how to test and evaluate their reliability, and discuss the benefits and pitfalls of our approach.
Crustaceans comprise an ecologically and morphologically diverse taxonomic group. They are typically considered resilient to many environmental perturbations found in marine and coastal environments, due to effective physiological regulation of ions and hemolymph pH, and a robust exoskeleton. Ocean acidification can affect the ability of marine calcifying organisms to build and maintain mineralized tissue and poses a threat for all marine calcifying taxa. Currently, there is no consensus on how ocean acidification will alter the ecologically-relevant exoskeletal properties of crustaceans. Here, we present a systematic review and meta-analysis on the effects of ocean acidification on the crustacean exoskeleton, assessing both exoskeletal ion content (calcium and magnesium) and functional properties (biomechanical resistance and cuticle thickness). Our results suggest that the effect of ocean acidification on crustacean exoskeletal properties varies based upon seawater pCO2 and species identity, with significant levels of heterogeneity for all analyses. Calcium and magnesium content were significantly lower in animals held at pCO2 levels of 1500-1999 μatm as compared to those under ambient pCO2. At lower pCO2 levels, however, statistically significant relationships between changes in calcium and magnesium content within the same experiment were observed: a negative relationship between calcium and magnesium content at pCO2 of 500-999 μatm and a positive relationship at 1000-1499 μatm. Exoskeleton biomechanics, such as resistance to deformation (microhardness) and shell strength, also significantly decreased under pCO2 regimes of 500-999 μatm and 1500-1999 μatm, indicating functional exoskeletal change coincident with decreases in calcification. Overall, these results suggest that the crustacean exoskeleton can be susceptible to ocean acidification at the biomechanical level, potentially predicated on changes in ion content, when exposed to high influxes of CO2. Future studies will need to accommodate the high variability of crustacean responses to ocean acidification, as well as ecologically-relevant ranges of pCO2 conditions, when designing experiments with conservation-level endpoints.
The neurotransmitter dopamine has been shown to play an important role in modulating behavioural, morphological and life-history responses to food abundance. However, costs of expressing high dopamine levels remain poorly studied and are essential for understanding the evolution of the dopamine system. Negative maternal effects on offspring size from enhanced maternal dopamine levels have previously been documented in Daphnia. Here, we tested whether this translates into fitness costs in terms of lower starvation resistance in offspring. We exposed Daphnia magna mothers to aqueous dopamine (2.3 mg/L or 0 mg/L for the control) at two food levels (ad libitum versus 30% ad libitum) and recorded a range of maternal life history traits. The longevity of their offspring was then quantified in the absence of food. In both control and dopamine treatments, mothers that experienced restricted food ration had lower somatic growth rates and higher age at maturation. Maternal food restriction also resulted in production of larger offspring that had a superior starvation resistance, compared to ad libitum groups. However, although dopamine exposed mothers produced smaller offspring than controls at restricted food ration, these smaller offspring survived longer under starvation. Hence, maternal dopamine exposure provided an improved offspring starvation resistance. We discuss the relative importance of proximate and ultimate causes for why D. magna may not evolve towards higher endogenous dopamine levels despite the fitness benefits this appears to have.
1. Cattle grazing profoundly affects abiotic and biotic characteristics of ecosystems. While most research has been performed on grasslands, the effect of large managed ungulates on forest ecosystems has largely been neglected. 2. Compared to a baseline semi-natural state, we investigated how long-term cattle grazing of birch forest patches affected the abiotic state and the ecological community (microbes and invertebrates) of the soil subsystem. 3. Grazing strongly modified the soil abiotic environment by increasing phosphorus content, pH and bulk density, while reducing the C:N ratio. The reduced C:N-ratio was strongly associated with a lower microbial biomass, mainly caused by a reduction of fungal biomass. This was linked to a decrease in fungivorous nematode abundance and the nematode channel index, indicating a relative uplift in the importance of the bacterial energy-channel in the nematode assemblages. 4. Cattle grazing highly modified invertebrate community composition producing distinct assemblages from the semi-natural situation. Richness and abundance of microarthropods was consistently reduced by grazing (excepting collembolan richness) and grazing-associated changes in soil pH, Olsen P and reduced soil pore volume (bulk density) limiting niche space and refuge from physical disturbance. Anecic earthworm species predominated in grazed patches, but were absent from ungrazed forest, and may benefit from manure inputs, while their deep vertical burrowing behaviour protects them from physical disturbance. 5. Perturbation of birch forest habitat by long-term ungulate grazing profoundly modified soil biodiversity, either directly through increased physical disturbance and manure input or indirectly by modifying soil abiotic conditions. Comparative analyses revealed the ecosystem engineering potential of large ungulate grazers in forest systems through major shifts in the composition and structure of microbial and invertebrate assemblages, including the potential for reduced energy flow through the fungal decomposition pathway. The precise consequences for trophic interactions and biodiversity-ecosystem function relationships remains to be established, however.
Indiscriminate fire is rampant throughout subtropical South and Southeast Asian grasslands. However, very little is known about the role of fire and pyric herbivory on the functioning of highly productive subtropical monsoon grasslands lying within Cwa-climatic region. We collected grass samples from 60 m x 60 m plots and determined vegetation physical and chemical properties at regular 30-day intervals from April to July 2020, starting from 30 days after fire to assess post-fire regrowth forage quality. We counted pellet groups for the same four months from 2 m x 2 m quadrats that were permanently marked with pegs along the diagonal of each 60 m x 60 m plot to estimate grazing intensity to the progression of post-fire regrowth. We observed strong and significant reductions in crude protein (mean value 9.1 to 4.1 [55% decrease]) and phosphorus (mean value 0.2 to 0.11 [45% decrease]) in forage collected during different time intervals i.e., from 30 days to 120 days after fire. Mesofaunal deer utilised the burned areas extensively for a short period, i.e., up to two months after fire when the burned areas contained short grasses with a higher level of crude protein and phosphorus. Grazing intensity of chital (Axis axis) to post-fire regrowth differed significantly over time since fire, with higher intensity of use at 30 days after fire. Grazing intensity of swamp deer (Rucervus duvaucelii) did not differ significantly until 90 days after fire, however, decreased significantly after 90 days since fire. Large-scale indiscriminate single event fires thus may not fulfil nutritional requirements of all species in mesofaunal deer community in these subtropical monsoon grasslands. We recommend for a spatio-temporal manipulation of fire to reinforce grazing feedback and to yield for the longest possible period a reasonably good food supply for the conservation of mesofaunal deer.
In many cases, understanding species level responses to climate change requires understanding variation among individuals in response to such change. For species with strong symbiotic relationships, such as many coral reef species, genetic variation in symbiont responses to temperature may affect the response to increased ocean temperatures. To assess variation among symbiont genotypes, we examined the population dynamics and physiological responses of genotypes of Breviolum antillogorgium in response to increased temperature. We found broad temperature tolerance across genotypes, with all genotypes showing positive growth at 26, 30, and 32 C. Genotypes differed in the magnitude of the response of growth rate and carrying capacity to increasing temperature, suggesting that natural selection could favor different genotypes at different temperatures. However, the historical temperature at which genotypes were reared was not a good predictor of temperature response, suggesting a lack of adaptation to temperature over hundreds of generations. We found increased photosynthetic rates and decreased respiration rates with increasing temperature, and differences in physiology among genotypes, but found no significant differences in the response of different genotypes to temperature. In species with such broad thermal tolerance, selection experiments on symbionts outside of the host may not yield results sufficient for evolutionary rescue from climate change.
Gut microbiome is vertically transmitted by maternal lactation at birth in mammals. In this study, we investigated the gut microbiome and diet compositions of muskox, a large herbivore in the high Arctic. From muskox feces in Ella Island, East Greenland, we compared the microbiota composition using bacterial 16S rRNA gene sequencing and the dietary compositions of six female adults and four calves have been compared. Firmicutes was the most abundant bacterial phylum in both adults and calves, comprising 94.36% and 94.03%, respectively. There were significant differences in the relative abundance of two Firmicutes families: the adults were mainly dominated by Ruminococcaceae (73.90%), while the calves were dominated by both Ruminococcaceae (56.25%) and Lachnospiraceae (24.00%). Stable isotope analysis on the feces and eight referential plant samples in the study area showed that both adults and calves had similar ranges of 13C and 15N, possibly derived from the dominant diet plants of Empetrum nigrum and Salix glauca. Despite the similar diets, the different gut microbiome compositions in muskox adults and calves indicate that the gut microbiome of the calves may not be fully colonized yet as much as the one of the adults.