1. Bitterlings are small freshwater fish that use long ovipositors to place eggs in host mussels and have morphological adaptations to increase larval survival. The most well-known adaptations are the minute tubercles on the skin surface of larvae, which are developed in early-stage larvae with weak swimming ability and disappear in free-swimming larvae before they leave the host mussel. 2. In the present study, a comprehensive analysis of the developmental stages of Rhodeus pseudosericeus larvae, their morphological and physiological characteristics, their migration inside mussels, and the development of minute tubercle are presented as direct evidence of the morphological function of the minute tubercles. These tubercles began to develop 1 day after hatching (formation stage), grew for 2–5 days (growth stage), reached the peak height after 6–7 days (peak stage), abruptly reduced in height after 8–10 days (abrupt reduction stage), and went through a final gradual reduction (reduction stage) until completely disappearing 27 days after hatching (disappearance stage). 3. The larvae remained in the mussels’ interlamellar space of the gill demibranchs until 10 days after hatching, and began to migrate to mussels’ suprabranchial cavity 11 days after hatching. At this time, the larvae had clear components of heart rate and caudal fin began to develop. At 24 days after hatching, the minute tubercles had almost disappeared, and some individuals were observed swimming out of the mussels. 4. The experiment results herein presented prove that the minute tubercles are a first direct evidence that the bitterling larvae are morphologically adapted to prevent premature ejection from the mussel.
Resource polymorphism is a ubiquitous phenomenon in vertebrates and may represent a critical intermediate stage in speciation. Freshwater lakes in high-altitude areas represent a natural system for understanding resource polymorphism in fishes in diverse lacustrine environments and a few co-distributed species. We report resource polymorphism in a cyprinid fish, Schizopygopsis thermalis, in Lake Amdo Tsonak Co, a headwater lake in the upper Salween River system. Two morphs, planktivorous and benthivorous, were identified according to geometric morphological and traditional linear traits. The planktivorous morph exhibits a longer head and lower jaw, larger asymptotic standard length (L∞), lower growth rate (k) and higher growth performance index (φ) than the benthivorous morph. With respect to descriptive traits, the planktivorous morph possesses a terminal mouth and a highly developed mucus cavity in the cheek and chin, while the benthivorous morph is characterized by an inferiorly positioned mouth with a sharpened horny edge on the lower jaw. Our results indicate that distinct pelagic-benthic resources and low interspecific competition in the lake drove the initial differentiation of the two morphs and that partial spatial reproductive isolation might maintain and reinforce the differences between them.
Maintenance of a portfolio of adaptive alleles may provide resilience of populations to natural environmental variability. We used Pacific ocean perch (POP; Sebastes alutus) to test for the maintenance of adaptive variation across overlapping generations. POP are a long-lived species characterized by widespread larval dispersal in their first year and a longevity of over 100 years. In order to understand how early marine dispersal affects POP survival and population structure, we used Restriction Site Associated DNA sequencing (RADseq) to obtain 11,146 single-nucleotide polymorphisms (SNPs) from 401 young-of-the-year (YOY) POP collected during surveys conducted in 2014 (19 stations) and 2015 (4 stations) in the eastern Gulf of Alaska. Population clustering analysis showed that the POP samples represented four distinct ancestral populations mixed throughout the sampling area. Based on prior work on larval dispersal of POP, these larvae are most likely from distinct parturition locations that are mixing during their pelagic dispersal life stage. Latent factor mixed models revealed that POP larvae face significant selection during their first year at sea, which were specific to the year of their birth. Thus each adult cohort’s genetic composition is heavily influenced by the environmental conditions experienced during their first year at sea. Long-lived species relying on broadcast spawning strategies may therefore be uniquely resilient to environmental variability by maintaining a portfolio of cohort-specific adaptive genotypes, and age truncation due to overfishing of older cohorts may have detrimental effect on the population viability.
Cerasus serrulata (Rosaceae) is an important flowering cherry resource. It is almost the most widely distributed species in the genus, mainly included in the subtropical and temperate China, which enables the geographic evolutionary pattern to be a representative. Besides, the morphological traits are greatly varied especially in ornamental characters. All of these makes Cerrasus serrulata a valuable research object. Thus, phylogeographic analysis was conducted to apprehend the spatial pattern and evolutionary history, which can also add insights into the phylogeography of the genus Cerasus and plants in subtropical and temperate China, as well as to deeper understand the genetic diversity and structure of the germplasm to make better and more effective utilization. A total of 327 individuals of 18 populations were collected. Three cpDNA fragments (matK, trnD-E, trnS-G) and the nuclear internal transcribed spacer (ITS) were utilized. The result showed a high genetic diversity both in species level and population level of Cerrasus serrulata. The high genetic differentiation among populations and the existence of phylogeographic structure in whole were detected. In addition, no bottleneck was identified. The the distribution pattern and center were formed before the LGM. Two geographical lineages were inferred. One was confined to Qingling Mountain and Taihang Mt. The other was from the Wuling Mt to Lu-Huang Mt, and then went northeast to the coast of Asia. Besides, taxonomic treatments of the Cerasus serrulata complex were reconsidered.
Plants employ a diverse set of defense mechanisms to mediate interactions with insects and fungi. These relationships can leave lasting impacts on host plant genome structure such as rapid expansion of gene families through tandem duplication. These genomic signatures provide important clues about the complexities of plant/biotic stress interactions and evolution. We used a pseudo-backcross hybrid family to identify Quantitative Trait Loci (QTL) controlling associations between Populus trees and several common Populus diseases and insects. Using whole genome sequences from each parent, we identified candidate genes that may mediate these interactions. Candidates were partially validated using mass spectrometry to identify corresponding QTL for defensive compounds. We detected significant QTL for two interacting fungal pathogens and three insects. The QTL intervals contained candidate genes potentially involved in physical and chemical mechanisms of host-plant resistance and susceptibility. In particular, we identified overlapping QTLs for a phenolic glycoside and Phyllocolpa sawfly abundance. There was also significant enrichment of recent tandem duplications in the genomic intervals of the native parent, but not the exotic parent. Tandem gene duplication may be an important mechanism for rapid response to biotic stressors, enabling trees with long juvenile periods to reach maturity despite many coevolving biotic stressors.
Aim: We aim to document the extent to which climate oscillation and rat infestation on islands affect the distribution of seabirds at sea. Location: The Chagos Archipelago, British Indian Ocean Territory, Central Indian Ocean Methods: At sea observations of seabirds (n = 425) were collected from 2012 to 2017 during the breeding season. We used generalized additive models to identify relationships between dominant seabird families (Laridae, Sulidae, and Procellariidae), geomorphology, oceanographic variability, and climate oscillation. We built boosted regression trees to quantify the effects of proximity to both rat-free and rat-infested islands on seabird distribution, identifying breaking point thresholds in distribution. Results: We identified oceanic hotspots and common geomorphic and oceanographic drivers for all seabird families. We documented positive relationships between Sulidae and Procellariidae abundance and the Indian Ocean Dipole, as represented by the Dipole Mode Index. The abundance of Laridae and Sulidae declined abruptly with greater distance to island. Both families aggregated more densely (1.08 and 1.25 times higher respectively) and in greater proximity (distribution thresholds at 16 and 44 km closer to islands, respectively) next to rat-free island compared with to rat-infested islands. In contrast, Procellariidae increased in abundance with greater distance to islands, plateauing at 83 km and were not significantly influenced by rat presence on nearby islands. We identified areas of increased abundance at sea under a scenario where rats are eradicated from infested islands with subsequent seabird recolonization. Main conclusions: Climate oscillations may cause shifts in seabird distribution, possibly through changes in regional productivity and prey distribution. Invasive species eradications and subsequent island recolonization can lead to predictable distribution gains and increased competition. Our analysis predicting range extension after successful eradications enables anticipatory threat-mitigation in these areas, minimising competition between colonies and thereby maximising the risk of success and the conservation impact of eradication programmes.
Correlative evidence suggests that high problem-solving and foraging abilities in a mate are associated with direct fitness advantages, so it would benefit females to prefer problem-solving males. Recent work has also shown that females of several bird species who directly observe males prefer those that can solve a novel foraging task over those that cannot. In addition to or instead of direct observation of cognitive skills, many species utilize assessment signals when choosing a mate. Here we test whether females can select a problem-solving male over a non-solving male when presented only with a signal known to be used in mate assessment: song. Using an operant conditioning assay, we compared female zebra finch (Taeniopygia guttata) preference for the songs of males that could quickly solve a novel foraging task to the songs of males that could not solve the task. Females were never housed with the test subject males whose song they heard, and the only information provided about the males was their song. We found that females elicited more songs of problem-solving males than of non-solvers, indicating that song can contain information about a male’s ability to solve a novel foraging task and that naïve females prefer the songs of problem-solving males.
Phenotypic plasticity can allow animals to adapt their behaviour, such as their mating effort, to their social and sexual environment. However, this relies on the individual receiving accurate and reliable cues of the environmental conditions. This can be achieved via the receipt of multi-component cues, which may provide redundancy and robustness. Male Drosophila melanogaster detect presence of rivals via combinations of any two or more redundant cue components (sound, smell and touch) and respond by extending their subsequent mating duration, which is associated with higher reproductive success. Although alternative combinations of cues of rival presence have previously been found to elicit equivalent increases in mating duration and offspring production, their redundancy in securing success under sperm competition has not previously been tested. Here, we explicitly test this by exposing male D. melanogaster to alternative combinations of rival cues and examining reproductive success in both the presence and absence of sperm competition. The results supported previous findings of redundancy of cues in terms of behavioural responses. However, there was no evidence of reproductive benefits accrued by extending mating duration in response to rivals. The lack of identifiable fitness benefits of longer mating under these conditions, both in the presence and absence of sperm competition, contrasted with some previous results, but could be explained by: 1) damage sustained from aggressive interactions with rivals leading to reduced ability to increase ejaculate investment, 2) presence of features of the social environment, such as male and female mating status, that obscured the fitness benefits of longer mating, 3) decoupling of behavioural investment with fitness benefits.
Recently diverged population in the early stages of speciation offer an opportunity to understand mechanisms of isolation and their relative contribution. Drosophila willistoni is a tropical species with broad distribution from Argentina to the southern United States, including the Caribbean islands. We have recently documented a postzygotic barrier between Central America, North America, and the northern Caribbean islands (D. w. willistoni) from South American and the southern Caribbean islands (D. w. winge). Here we identify premating isolation between strains regardless of their subspecies status, with the effect being dependent on environment. We find no evidence of postmating prezygotic isolation and proceed to characterize hybrid male sterility among the subspecies. Sterile male hybrids transfer an ejaculate that is devoid of sperm but causes elongation and expansion of the female uterus. In sterile male hybrids, bulging of the seminal vesicle appears to impede the movement of the sperm towards the sperm pump, where sperm normally mixes with accessory glands products. Our results highlight a unique form of hybrid male sterility in Drosophila that is driven by a mechanical impediment to transfer sperm rather than by an abnormality of the sperm itself. Interestingly, this form of sterility is reminiscent of a form of infertility (azoospermia) that is caused by lack of sperm in the semen due to blockages that impede the sperm from reaching the ejaculate.
Plant adaptation to high altitudes has long been a substantial focus of ecological and evolutionary research. However, the genetic mechanisms underlying such adaptation remain poorly understood. Here, we address this issue by sampling, genotyping, and comparing populations of Tibetan poplar, Populus szechuanica var. tibetica, distributed from low (~2000 m) to high altitudes (~3000 m) of Sejila Mountain on the Qinghai-Tibet Plateau. Population structure analyses allow clear classification of two groups according to their altitudinal distributions. However, in contrast to the genetic variation within each population, differences between the two populations only explain a small portion of the total genetic variation (3.64%). We identified asymmetrical gene flow from high- to low-altitude populations. Integrating with population genomic and landscape genomic manner, we detected a hot spot region containing ten genes under natural selection and associated with five environmental factors. These genes participate in abiotic stress resistance and regulating the reproductive process. Our results provide insight into the genetic mechanisms underlying high-altitude adaptation in Tibetan poplar.
Glyphosate is the world’s most widely used herbicide. The commercial success of this molecule is due to its non-selectivity and its action, which would supposedly target specific biosynthetic pathways found mainly in plants. Multiple studies have however provided evidence for high sensitivity of many non-target species to glyphosate and/or to formulations (glyphosate mixed with surfactants). This herbicide, found at significant levels in aquatic systems through surface runoffs, impacts life history traits and immune parameters of several aquatic invertebrates’ species. Some of these species are vectors of diseases, one of the most important of which is the mosquito. Mosquitoes, from hatching to emergence, are exposed to aquatic chemical contaminants. In this study, we first compared the toxicity of pure glyphosate to the toxicity of glyphosate-based formulations for the main vector of avian malaria in Europe, Culex pipiens mosquito. Then we evaluated, for the first time, how field realistic dose of glyphosate interacts with larval nutritional stress to alter mosquito life history traits and susceptibility to avian malaria parasite infection. Our results show that exposure of larvae to field-realistic doses of glyphosate, pure or in formulation, did not affect larval survival rate, adult size and female fecundity. One of our two experimental blocks showed, however, that exposure to glyphosate decreased development time and reduced mosquito infection probability by malaria parasite. Interestingly the effect on malaria infection was lost when the larvae were also subjected to a nutritional stress, probably due to a lower ingestion of glyphosate.
Environmental DNA (eDNA) is used for monitoring the occurrence of freshwater organisms. Various studies show a relation between the amount of eDNA detected and target organism abundance, thus providing a potential proxy for reconstructing population densities. However, environmental factors such as water temperature and microbial activity are known to affect the amount of eDNA present as well In this study, we use controlled aquarium experiments using Gammarus pulex L. (Amphipoda) to investigate the relationship between the amount of detectable eDNA through time, pH, and levels of organic material. We found eDNA to degrade faster when organic material was added to the aquarium water, but that pH had no significant effect. We infer that eDNA contained inside cells and mitochondria is extra resilient against degradation, though this may not reflect actual presence of target species. These results indicate that, although estimation of population density might be possible using eDNA, measured eDNA concentration could, in the future, be corrected for local environmental conditions in order to ensure accurate comparisons.
1. Terrestrial plant populations located at the margins of species’ distributions often display reduced sexual reproduction and an increased reliance on asexual reproduction. One hypothesis to explain this phenomenon is that the decline is associated with environmental effects on the energetic costs to produce reproductive organs. 2. In order to clarify the changing processes of sexual reproduction along an altitudinal gradient, we investigated the sexual reproductive parameters, such as the number of sporophytes and gametangia, in Racomitrium lanuginosum, a dioicous moss found on Mt. Fuji. Matured sporophytes were present only below 3000 m, and the number of sporophytes per shoot tended to be lower at higher altitudes. 3. The numbers of male inflorescences per shoot and antheridia per inflorescence and shoot significantly decreased with increasing altitude. In contrast, the numbers of female inflorescences per shoot and archegonia per inflorescence and shoot varied little across altitudes. 4. Synthesis. Our results suggest that the success of sexual reproduction in R. lanuginosum is restricted at higher altitudes on Mt. Fuji by decreases in male gametangia and the subsequent chance of fertilization. These differences between males and females may be caused by differences in the cost of production and development of gametangia, sensitivity to environmental stresses (low air temperature, shortened growth period, and environmental conditions in winter), and phenological patterns at higher altitudes.
Aim: Threats faced by narrowly distributed endemic plant species in the face of the Earth’s sixth mass extinction and climate change exposure are especially severe for taxa on islands. We investigated the current and projected distribution and range changes of Cochemiea halei, an island endemic cactus. This taxon is of conservation concern, currently listed as vulnerable on the International Union for the Conservation of Nature Red List and as a species of special concern under Mexican federal law. The goals of this study are to 1). identify the correlations between climate variables and current suitable habitat for C. halei; 2). determine if the species is a serpentine endemic or has a facultative relationship with ultramafic soils; 3). predict range changes of the species based on climate change scenarios. Location: The island archipelago in Bahía Magdalena on the Pacific coast, Baja California Sur, Mexico. Methods: We used temperature and precipitation variables at 30 arcsecond resolution and soil type, employing multiple species distribution modeling methods, to identify important climate and soil conditions driving current habitat suitability. The best model of current suitability is used to predict possible effects of four climate change scenarios based on best case to worst case representative concentration pathways, with projected climate data from two general circulation models, over two time periods. Main conclusions: The occurrence of the species is found to be strongly correlated with ultramafic soils. The most important climate predictor for habitat suitability is annual temperature range. The species is predicted to undergo range contractions from 21% to 53%, depending on the severity and duration of exposure to climate change. The broader implications for a wide range of narrowly adapted, threatened and endemic plant species indicate an urgent need for threat assessment based on habitat suitability and climate change modeling.
Functional traits are becoming more common in the analysis of marine zooplankton community dynamics associated with environmental change. We use zooplankton groups with common functional properties to assess long-term trends in the zooplankton caused by certain environmental conditions in a highly eutrophicated gulf. Time series of zooplankton traits were collected since 1960 in the Gulf of Riga, Baltic Sea and were analysed using general additive model, principal component analysis, and multivariate model. One of the most significant changes was the considerable increase in the amount of the zooplankton functional groups (FGR) in coastal springtime communities, and dominance shifts from more complex to simpler organism groups – cladocerans and rotifers. The results also show that the functional trait organism complexity (body size) decreased considerably due to cladoceran and rotifer increase following elevated water temperature. Salinity and oxygen had negligible effects on the zooplankton community.
Reconstructing ecological niche evolution can provide insight into the biogeography and diversification of evolving lineages. However, comparative phylogenetic methods can infer the history of ecological niche evolution inaccurately because (1) species’ niches are often poorly characterized; and (2) phylogenetic comparative methods rely on niche summary statistics rather than full estimates of species’ environmental tolerances. Here we propose a new framework for coding ecological niches and reconstructing their evolution that explicitly acknowledges and incorporates the uncertainty introduced by incomplete niche characterization. Then, we modify existing ancestral state inference methods to leverage full estimates of environmental tolerances. We provide a worked empirical example of our method, investigating ecological niche evolution in the New World orioles (Aves: Passeriformes: Icterus spp.). Temperature and precipitation tolerances were generally broad and conserved among orioles, with niche reduction and specialization limited to a few terminal branches. Tools for performing these reconstructions are available in a new R package called nichevol.
In this study, we used two common ant species (Lasius niger and L. neoniger) to assay how they translate variation in the diet (both in composition and frequency) into growth. We measured colony development for over 8 months and measured several phenotypic traits of the worker caste, and examined whether forager preference corresponded with diet quality. Individuals (workers) and colonies (superorganisms) increased in size with increasing amounts of protein in the diet, and as a function of how much food was available. Optimal colony growth was a balance between survival and growth, and each of these were maximized with different nutrient regimes. Interestingly, forager preference was not totally aligned with the diet that maximized colony growth. Our results highlight that: 1) organism and superorganism size are controlled by the same nutrients, and this may reflect a common molecular basis for size across life’s organizational levels, 2) there are nutrient trade-offs that are associated with life-history trade-offs, likely leading to selection for a balanced diet, and 3) the connection between the preference of foragers for different nutrients and how nutrient combinations affect colony success and demographics are complex and only beginning to be understood.
Understanding spatiotemporal population trends and their drivers is a key aim in population ecology. We further need to be able to predict how the dynamics and sizes of populations are affected in the long term by changing landscapes and climate. However, predictions of future population trends are sensitive to a range of modelling assumptions. Deadwood-dependent fungi are an excellent system for testing the performance of different predictive models of sessile species as these species have different rarity and spatial population dynamics, the populations are structured at different spatial scales and they utilize distinct substrates. We tested how the projected large scale occupancies of species with differing landscape-scale occupancies are affected over the coming century by different modelling assumptions. We compared projections based on occupancy models against colonization-extinction models, conducting the modelling at alternative spatial scales, and using fine or coarse resolution deadwood data. We also tested effects of key explanatory variables on species occurrence and colonization-extinction dynamics. The hierarchical Bayesian models applied were fitted to an extensive repeated survey of deadwood and fungi at 174 patches. We projected higher occurrence probabilities and more positive trends using the occupancy models compared to the colonisation-extinction models, with greater difference for the species with lower occupancy, colonization rate and colonization:extinction ratio than for the species with higher estimates of these statistics. The magnitude of future increase in occupancy depended strongly on the spatial modelling scale and resource resolution. We encourage using colonisation-extinction models over occupancy models, modelling the process at the finest resource-unit resolution that is utilizable by the species, and conducting projections for the same spatial scale and resource resolution at which the model fitting is conducted. Further, the models applied should include key variables driving the metapopulation dynamics, such as the availability of suitable resource units, habitat quality and spatial connectivity.