Plant competition experiments commonly suggest that larger species have an advantage, especially in light acquisition. However, within crowded natural vegetation, where competition evidently impacts fitness, most resident species are relatively small. It remains unclear, therefore, whether the size-advantage observed in controlled experiments is realized in habitats under intensive competition. We tested for evidence of a size-advantage in competition for light in an old-field plant community composed of herbaceous perennial species. We investigated whether larger species contributed to reduced light penetration (i.e., greater shading), and examined the impact of shade on smaller species by testing whether their abundance and richness were lower in plots with less light penetration. Light penetration in plots ranged from 0.3-72.4%. Plots with greater mean species height had significantly lower light penetration. Plots with lower light penetration had significantly lower small species abundance and richness. However, the impact of shade on small species abundance and richness was relatively small (R2 values between 8% and 15%) and depended on how we defined “small species”. Significant effects were more common when analyses focused on individuals that reached reproduction; focusing on only flowering plants can clarify patterns. Our results confirm that light penetration in herbaceous vegetation can be comparable to levels seen in forests, that plots with taller species cast more shade, and that smaller species are less abundant and diverse in plots where light penetration is low. However, variation in mean plot height explained less than 10% of variation in light penetration, and light penetration explained 5-15% of variation in small species abundance and richness. Coupled with the fact that reproductive small species were present even within the most heavily shaded plots, our results suggest that any advantage in light competition by large species is limited. One explanation is that some small species in these communities are shade tolerant.
Comparing genome scans among species is a powerful approach for investigating the patterns left by evolutionary processes. In particular, this offers a way to detect candidate genes that drive convergent evolution. We compared genome scan results to investigate if patterns of genetic diversity and divergence are shared among divergent species within the stickleback order (Gasterosteiformes): the threespine stickleback (Gasterosteus aculeatus), ninespine stickleback (Pungitius pungitus) and tubesnout (Aulorhynchus flavidus). Populations were sampled from the southern and northern edges of each species’ range, to identify patterns associated with latitudinal changes in genetic diversity. Weak correlations in genetic diversity (FST and expected heterozygosity) and three different patterns in the genomic landscape were found among these species. Additionally, no candidate genes for convergent evolution were detected. This is a counterexample to the growing number of studies that have shown overlapping genetic patterns, demonstrating that genome scan comparisons can be noisy due to the effects of several interacting evolutionary forces.
This paper aims to investigate the ecological role of Merlucicius merluccius, Linnaeus, 1758, in the southern and central Tyrrhenian Sea (GSA 10, Resolution GFCM/33/2009/2 General Fisheries Commission for the Mediterranean), analysing ontogenetic diet shift, geographical variations on prey composition and feeding habits. A sample of 734 hake specimens between 6 cm and 73 cm of total length (TL) were collected in 2018. To value the ontogenetic shifts in prey composition, five size-classes were created from the sample and for each class were calculated quantitative feeding indices. The cluster and MDS analysis, based on the % IRI, resulted in three trophic groups of hake size classes. The most abundant preys for small hake (size class I) were the Euphausiids, Stylocheiron longicorne and Mysidacea, while for hake with size over 10.5 cm of TL were crustaceans and fish. Engraulis encrasicolus was the most abundant prey fish for hake, followed by Boops boops and Myctophids. The mesopelagic fauna had a relevant role in the European hake diet in the southern zone. The high presence of Euphausiids, Mysids, Myctophidae and Sternoptychidae in the gut content of juvenile hakes (6-23 cm) showed the importance of organic matter and energy flowed from the mesopelagic environment to the epipelagic. Important is also the presence of decapod crustaceans in hake with size over 36 cm TL considering that our study area includes an important Gulf for the fishing of decapod crustacea.
Understanding the impacts and constraints of climate change on the potential geographic distribution of wild Akebia trifoliata is crucial for its sustainable management and economic development as a medicinal material or fruit. In this study, according to the first-hand information obtained on-the-spot investigation, the geographic distribution and response to climate factors of Akebia trifoliata were studied by the MaxEnt model and ArcGIS. The genetic diversity and population structure of 21 natural populations of Akebia trifoliata were studied by SSR markers. The results showed that precipitation and temperature were the two most important climatic factors that restrict the geographic distribution of Akebia trifoliata. Under the current climate scenario, the suitable growth regions of Akebia trifoliata in China were 91.7-121.9 °E and 21.6-37.5 °N. Combined with the evolutionary relationship and prediction results, 21 populations of Akebia trifoliata tended to migrate to the north. In the scenarios (SSP2-4.5, SSP3-7.0, and SSP5-8.5) of higher greenhouse gas emission concentration, the distribution area of Akebia trifoliata continued to expand, while in the low concentration greenhouse gas emission scenario (SSP1-2.6), the distribution area of Akebia trifoliata remained stable. The distribution center of Akebia trifoliata in China will shift to high latitude regions with the increase of temperature in the future. The results evaluated the impact of climate factors on the spatial distribution of wild Akebia trifoliata, displayed the possible changes of geographical distribution of Akebia trifoliata under different climate scenarios, and provided scientific evidence for durative protection and supervise of Akebia trifoliata.
Despite many studies showing biodiversity responses to warming, the generality of such responses across taxonomic groups remains unclear. Very few studies have tested for evidence of bryophyte community responses to warming, even though bryophytes are major contributors to diversity and functioning in many ecosystems. Here we report an empirical study comparing long-term change of bryophyte and vascular plant communities in two sites with contrasting long-term warming trends, using “legacy” botanical records as a baseline for comparison with contemporary resurveys. We hypothesized that ecological changes would be greater in sites with a stronger warming trend, and that vascular plant communities, with narrower climatic niches, would be more sensitive than bryophyte communities to climate warming. For each taxonomic group in each site, we quantified the magnitude of changes in species’ distributions along the elevation gradient, species richness, and community composition. We found contrasted temporal changes in bryophyte vs. vascular plant communities, which only partially supported the warming hypothesis. In the area with a stronger warming trend, we found a significant increase of local diversity and beta-diversity for vascular plants, but not for bryophytes. Presence absence data did not provide sufficient power to detect elevational shifts in species distributions. The patterns observed for bryophytes are in accordance with recent literature showing that local diversity can remain unchanged despite strong changes in composition. Regardless of whether one taxon is systematically more or less sensitive to environmental change than another, our results suggest that vascular plants cannot be used as a surrogate for bryophytes in terms of predicting the nature and magnitude of responses to warming. Thus, to assess overall biodiversity responses to global change, abundance data from different taxonomic groups and different community properties need to be synthesized.
Mammals around the world face serious threats and experience massive decline in their populations and geographic ranges. The sloth bear has become extinct from two of five range countries and the existing population face serious conservation threats. Despite being endangered in Nepal, decades of conservation obliviousness have hindered their conservation and management. We assessed the distribution and habitat use by sloth bears in relation to landscape, environmental, and anthropogenic factors in Chitwan National Park, Nepal. We conducted a sign survey from March-June 2020 in 4*4 km2 grids (n=45) in a checkerboard approach. An observation was spatially replicated four times by recording information in four continuous search trails of 1 km each. We recorded presence/absence of sloth bears, termites, fruits and disturbance in the field and extracted information on tree cover, terrain ruggedness and vegetation index from remotely sensed image of the study area. The data was analyzed using single species-single season occupancy method in PRESENCE software. By using repeated observations these models account for imperfect detectability of species to provide robust estimates of species occupancy. Averaged habitat occupancy estimate obtained from the best models was Ѱ = 0.53 ± 0.04SE with detection probability p = 0.44 ± 0.1SE. Selection of variable based on summed AIC weight from the top models (AIC<2) showed that presence of termites (ƩWi=0.66) significantly influenced sloth bear habitat occupancy. Habitat occupancy was positively influenced by termites followed by fruits, disturbance, terrain ruggedness and vegetation productivity, whereas, it was negatively influenced by tree cover. We suggest that future conservation interventions and action plans aimed at sloth bear management must adequately consider these requirements and issues.
The plant defence syndromes (PDSs) concept predicts host plants should develop diverse resistance profiles against their herbivores. We used Electrical Penetration Graphs (EPG) to investigate complex and genotype-specific penetration-barriers to Chaitophorous tremulae aphid feeding on Aspen (Populus tremula). Leaf condensed tannins were associated with enhanced probing activity and increased ingestion of xylem sap. Aphids probed less on Aspen genotypes low in tannins, suggesting other defence traits might be elicited. Our results support the idea of multi-layered PDS defence traits, and provide evidence of high plasticity in tannin profiles across temporal and spatial scales. We conclude that tannin plasticity may form a dynamically unpredictable aspect of the PDS defence arsenal that protects Aspen against piercing-sucking aphids.
Conspicuous female signals have recently received substantial scientific attention, but it remains unclear if their evolution is the result of selection acting on females independently of males or if mutual selection facilitates female change. Species that express female, but not male, phenotypic variation among populations represent a useful opportunity to address this knowledge gap. White-shouldered fairywrens (Malurus alboscapulatus) are tropical songbirds with a well-resolved phylogeny where female, but not male, coloration varies allopatrically across subspecies. We explored how four distinct signaling modalities, each putatively associated with increased social selection, are expressed in two populations that vary in competitive pressure on females. Females in a derived subspecies (M. a. moretoni) have evolved more ornamented plumage and have shorter tails (a signal of social dominance) relative to an ancestral subspecies (M. a. lorentzi) with drab females. In response to simulated territorial intrusions broadcasting female song, both sexes of M. a. moretoni are more aggressive and more coordinated with their mates in both movement and vocalizations. Finally, M. a. moretoni songs are more complex than M. a. lorentzi, but song complexity does not vary between sexes in either population. These results suggest that correlated phenotypic shifts in coloration and tail morphology in females as well as song complexity and aggression in both sexes may have occurred in response to changes in the intensity of social selection pressures. This highlights increased competitive pressures in both sexes can facilitate the evolution of complex multimodal signals.
Identifying and quantifying crop stressors interactions in agroecosystems is necessary to guide sustainable crop management strategies. Over the last 50 years, faba bean cropping area has been declining, partly due to yield instabilities associated to uneven insect pollination and herbivory. Yet, interactions between pollinators and a key pest, Bruchus rufimanus (florivorous and seed predating herbivore), on faba bean yield have not been investigated. Using a factorial cage experiment in the field we investigated how interactions between two potential stressors, lack of pollination from Bombus terrestris and herbivory by B. rufimanus, affect faba bean yield. Lack of insect pollination reduced bean weight per plant by 15%. Effects of B. rufimanus herbivory differed between the individual plant and the plant-stand scale (i.e. when averaging individual plant scale responses), likely due to high variation in the level of herbivory among individual plants. At the individual plant scale, B. rufimanus herbivory increased yield but only in the absence of pollinators, possibly due to plant over-compensation and/or pollination by B. rufimanus. At the plant-stand scale, we found no effect of B. rufimanus on yield. However, there was a tendency for heavier individual bean weight with insect pollination, but only when B. rufimanus herbivory was absent, possibly due to a negative effect of B. rufimanus on the proportion of legitimate flower visits by B. terrestris. This is the first experimental evidence of interactive effects of B. terrestris and B. rufimanus on faba bean yield. Our preliminary findings of negative and indirect associations between B. rufimanus and individual bean weight call for a better acknowledgment of these interactions in the field in order to understand drivers of crop yield variability in faba bean. This study showed that herbivory can increase yield, but this effect is only detectable when investigated in combination with lack of pollination.
The evolution of mimicry in similarly defended prey is well described by Müllerian mimicry theory, which predicts the convergence of warning patterns in order to gain the most protection from predators. However, despite this prediction, we can find great diversity of color patterns amongst Müllerian mimics such as Heliconius butterflies in the neotropics. Furthermore, some species have evolved the ability to maintain multiple distinct warning patterns in single populations, a phenomenon known as polymorphic mimicry. The adaptive benefit of these polymorphisms is questionable since variation from the most common warning patterns is expected to be disadvantageous as novel signals are punished by predators naive to them. In this study, we use artificial butterfly models throughout Central and South America to characterize the selective pressures maintaining polymorphic mimicry in Heliconius doris. Our results highlight the complexity of positive frequency-dependent selection, the principal selective pressure driving convergence amongst Müllerian mimics, and its impacts on interspecific variation of mimetic warning colouration. We further show how this selection regime can both limit and facilitate the diversification of mimetic traits.
Throughout the last century, climate change has altered the geographic distributions of many species. Insects, in particular, vary in their ability to track changing climates, and it is likely that phenology is an important determinant of how well expands can either expand or shift their geographic distributions in response to climate change. Grasshoppers are an ideal group to test this hypothesis, given that co-occurring confamilial, and even congeneric, species can differ in phenology. Here, I tested the hypothesis that early- and late-season species should possess different range expansion potentials, as estimated by habitat suitability from ecological niche models. I used nine different modeling techniques to estimate habitat suitability of six grasshopper species of varying phenology under two climate scenarios for the year 2050. My results support the hypothesis that phenology is an important determinant of range expansion potential. Early-season species might shift northward during the spring, while the modeled geographic distributions of late-season species were generally constant under climate change, likely because they were pre-adapted to hot and dry conditions. Phenology might therefore be a good predictor of how insect distributions might change in the future, and conservation efforts might focus most heavily on early-season species that are most impacted by climate change.
Simple sequence repeats (SSRs) are widely used genetic markers in ecology, evolution and conservation even in the genomics era, while a general limitation to their application is the difficulty of developing polymorphic SSR markers. Next-generation sequencing (NGS) offers the opportunity for the rapid development of SSRs; however, previous studies developing SSRs using genomic data from only one individual need redundant experiments to test the polymorphisms of SSRs. In this study, we designed a pipeline for the rapid development of polymorphic SSR markers from multi-sample genomic data. We used bioinformatic software to genotype multiple individuals using resequencing data, detected highly polymorphic SSRs prior to experimental validation, significantly improved the efficiency and reduced the experimental effort. The pipeline was successfully applied to a globally threatened species, the brown-eared pheasant (Crossoptilon mantchuricum), which showed very low genomic diversity. The 20 newly developed SSR markers were highly polymorphic, the average number of alleles was much higher than the genomic average. We also evaluated the effect of the number of individuals and sequencing depth on the SSR mining results, and we found that ten individuals and ~10X sequencing data were enough to obtain a sufficient number of polymorphic SSRs, even for species with low genetic diversity. Furthermore, the genome assembly of NGS data from the optimal number of individuals and sequencing depth can be used as an alternative reference genome if a high-quality genome is not available. Our pipeline provided a paradigm for the application of NGS technology to mining and developing molecular markers for ecological and evolutionary studies.
Division of labour occurs when cooperating individuals specialise to perform different tasks. In bacteria and other microorganisms, some species divide labour by random specialisation, where an individual’s role is determined by random fluctuations in biochemical reactions within the cell. Other species divide labour by coordinating across individuals to determine which cells will perform which task, using mechanisms such as between-cell signalling. However, previous theory, examining the evolution of mechanisms to divide labour between reproductives and sterile helpers, has only considered clonal populations, where there is no potential for conflict between individuals. We used a mixture of analytical and simulation models to examine non-clonal populations and found that: (1) intermediate levels of coordination can be favoured, between the extreme of no coordination (random) and full coordination; (2) as relatedness decreases, coordinated division of labour is less likely to be favoured. Our results can help explain why coordinated division of labour is relatively rare in bacteria, where groups may frequently be non-clonal.
Pairwise mutualisms are embedded within rich communities of co-occurring species. Mutualism by definition benefits partner species and theory predicts these effects can spill over into broader communities, with consequences for abundance, diversity, and composition. Specifically, positive feedbacks between partner species may shift competitive hierarchies and drive reductions in non-partner species. We used long-term monitoring data spanning 16 years to determine the ant partner species of tree cholla cacti (Cylindriopuntia imbricata), which reward ants with extrafloral nectar in exchange for anti-herbivore defense. We coupled these long-term data with short-term characterization of the ant community via pitfall trapping, which sampled partner and non-partner species across ten plots that varied naturally in cactus density. The long-term data revealed one dominant ant partner (Liometopum apiculatum) and two other less common partners (Crematogaster opuntiae and Forelius pruinosus). In the short-term census, the dominant ant partner occupied more cacti in plots of higher cactus density, and was also found at higher occurrence within the pitfall traps in the high cactus density plots, suggesting strong positive feedbacks that promote ant occurrence where plant partners are available. Despite the consistency of L. apiculatum partnership with cacti through time and the dominance of this partnership in areas of high cactus density, spillover effects from this mutualism appear limited. Of the common ant species, a single non-partner ant species showed a modest reduction in occurrence at high cactus density, possibly in response to increased presence of L. apiculatum. Additionally, the composition and diversity of the ant community in our plots were insensitive to cactus density variation, indicating that positive effects on the dominant ant partner did not have cascading impacts on the ant community. This study provides novel evidence that pairwise mutualisms, even those with strong positive feedbacks, may be limited in the scope of their community-level effects.
Anagrus nilaparvatae is an important egg parasitoid wasps of rice pests rice planthopper. Based on the powerful olfactory system of sensing chemical information in nature, A. nilaparvatae shows complicated life activities and behaviors, such as feeding, mating and hosting. In this study, we constructed a full-length transcriptome library and further to identify the characteristics of olfactory binding proteins, the first participant in the olfactory system. Through full-length transcriptome sequencing, splicing, assembly, and data correction by Illumina, we obtained 163.59Mb of transcriptome data and 501,179 items of annotation information, and performed GO functional classification of unigenes of the transcriptome. We analyzed the sequence characteristics of olfactory binding protein genes, and 8 genes (AnilOBP2, AnilOBP9 AnilOBP23, AnilOBP56, AnilOBP83, AnilCSP5, AnilCSP6 and AnilNPC2) were identified. After sequence alignment and conserved domain prediction, the 8 proteins were consistent with the typical characteristics of OBPs, CSPs and NPC2s in insects. The phylogenetic tree analysis showed that the 8 genes share low homology relationship with other species in Hymenopteran. Finally, RT-qPCR was used to analyze the expression responses of the 8 genes in different genders and stimulated by volatiles. The relative expression levels of AnilOBP9, AnilOBP26, AnilOBP83, AnilCSP5 and AnilNPC2 in males were significantly higher than those in female, while the relative expression levels of AnilCSP6 were opposite. The expression levels of AnilOBP9 and AnilCSP6 were significantly altered by the stimulation of β-caryophylene, suggesting the two genes may be related to host searching. In this study, the transcriptome data of parasitoid wasps A. nilaparvatae could provide a reference for the molecular biology research of the parasitoids, and the identification and analysis of olfactory binding proteins not only help us further clarify the physiological characteristics and parasitic mechanism of the parasitoids, but also promote the utilization of natural enemy resources.
Various species of freshwater fish regulate the expression of certain proteins in response to environmental contamination. Previous research has shown that CYP1A expression increases in response to contaminant levels, and can result in increased tumor formation. Fish in contaminated environments would thus benefit by downregulating the expression of CYP1A to reduce tumor prevalence as an adaptive strategy. Alternatively, regulation of the CYP1A protein in fish can serve as a bioindicator of the pollution level of an environment. This study evaluated CYP1A expression in twelve different species of freshwater fish from seven bodies of water throughout western NY including Cuba Lake, Genesee River, Hanging Bog, Love Canal, Moss Lake, Rushford Lake and Tifft Nature Preserve. Western blot analysis was used to measure CYP1A expression as a marker of site pollution and potential fish population adaptation. It was hypothesized that low CYP1A expression at a site with known contamination would suggest signs of adaptation to pollution levels present. Furthermore, if at least one sample from a species showed CYP1A expression, then the CYP1A antibody (Caymen Chemical, USA; 173132) had compatibility with that species, eliminating falsely suspected adaptation. The results from this study suggest possible adaptation of fish may be occurring in the polluted Tifft Nature Preserve and Genesee River. In contrast, CYP1A expression in fish from Cuba Lake, Hanging Bog, Love Canal, Moss Lake, and Rushford Lake appear to represent known pollution levels and adaptation is not likely occurring. Results from this study are preliminary and next steps include collection and analysis of sediment to provide a stronger correlation between pollution at sites and CYP1A expression.
Usually, adaptive phenotypic differentiation is paralleled by genetic divergence between locally adapted populations. However, adaptation can also happen in a scenario of non-significant genetic divergence due to intense gene flow and/or recent differentiation. While this phenomenon is rarely published, findings on incipient ecologically-driven divergence or isolation by adaptation are relatively common, which could confound our understanding about the frequency at which they actually occur in nature. Here, we explore genome-wide traces of divergence between two populations of the lacertid lizard Psammodromus algirus separated by a 600 m elevational gradient. These populations seem to be differentially adapted to their environments despite showing low levels of genetic differentiation (according to previously studies of mtDNA and microsatellite data). We performed a search for outliers (i.e. loci subject to selection) trying to identify specific loci with FST statistics significantly higher than those expected on the basis of overall, genome-wide estimates of genetic divergence. We find that local phenotypic adaptation (in terms of a wide diversity of characters) was not accompanied by genome-wide differentiation, even when we maximized the chances of unveiling such differentiation at particular loci with FST-based outlier detection tests. Instead, our analyses confirmed the lack of differentiation on the basis of more than 70,000 SNPs, which is concordant with a scenario of local adaptation without any degree of isolation by environment. Our results add evidence to previous studies in which local adaptation does not lead to any kind of isolation (or early stages of ecological speciation), but maintains phenotypic divergence despite the lack of a differentiated genomic background.
The fishing cat Prionailurus viverrinus is a wetland specialist endemic to South and Southeast Asia. Nepal represents the northern limit of its biogeographic range, but comprehensive information on fishing cat distribution in Nepal is lacking. We compiled fishing cat occurrence records (n=154) from Nepal, available in published literature and unpublished data (2009 – 2020), to assess their distribution. Bioclimatic and environmental variables associated with their occurrence were used to predict the potential fishing cat range using MaxEnt modeling. Fishing cat distribution was influenced by elevation, precipitation of the warmest quarter (18_bio), precipitation of the driest month (14_bio) and land cover. Wetlands and forest cover were the important predictors of fishing cat distribution. The model predicted an area of 4.4% (6,679 km2) of Nepal as potential habitat for the fishing cat. About two third of the predicted potentially suitable habitat lies outside protected areas, however a large part of the highly suitable habitat (67%) falls within protected areas. The predicted habitat map serves as a reference for future investigation into fishing cat distribution as well as formulating and implementing effective conservation programs for fishing cats in Nepal. Fishing cat conservation initiatives should include habitats both inside and outside the protected areas to ensure long-term survival. We recommend conservation of wetland sites, surveys of fishing cats in the identified potential habitats, and study of their genetic connectivity and population status.