Temperature is a key abiotic factor controlling population dynamics. In facultatively sexual animals inhabiting the temperate zone, temperature regulates the switch between asexual and sexual modes of reproduction, initiates growth or dormancy and acts together with photoperiod to mediate seasonal physiological transitions. Increasing temperature due to recent global warming is likely to disrupt population dynamics of facultatively sexual animals because of the strong temperature-dependence of multiple fitness components. However, the fitness consequences of warming in these animals are still poorly understood. This is unfortunate, since facultatively sexual animals – through their ability for asexual reproduction resulting in quick population growth and sexual reproduction enabling long-term persistence – are key components of freshwater ecosystems. Here, I studied the fitness effects of warming in Hydra oligactis, a freshwater cnidarian that reproduces asexually throughout most of the year but switches to sexual reproduction under decreasing temperatures. I exposed hydra polyps to simulated short summer heatwaves or long-term elevated winter temperatures. Since sexual development in this species is dependent on low temperature, I predicted reduced sexual investment (gonad production) and elevated asexual fitness (budding) in polyps exposed to higher temperatures. The results show a complex effect of warming on sexual fitness: while gonad number decreased in response to warming, polyps exposed to high winter temperature were capable of multiple rounds of gamete production. Asexual reproduction and survival rate, on the other hand, clearly increased in response to higher temperatures, especially in males. These results predict increased population growth of H. oligactis in temperate freshwater habitats, which will likely affect the population dynamics of its’ main prey (freshwater zooplankton), and through that, the whole food web.
Insect decline is a major threat for ecosystems around the world as they provide many important functions, such as pollination or pest control. Pollution is one of the main reasons for the decline, besides changes in land use, global warming, and invasive species. While negative impacts of pesticides are well studied, there is still a lack of knowledge about the effects of other anthropogenic pollutants, such as airborne particulate matter, on insects. To address this, we exposed workers of the bumblebee Bombus terrestris to sublethal doses of diesel exhaust particles (DEPs) and brake dust, orally or via air. After seven days, we looked at the composition of the gut microbiome and tracked changes in gene expression. While there were no changes in the other treatments, oral DEP exposure significantly altered the structure of the gut microbiome. In particular, the core bacterium Snodgrassella had a decreased abundance in the DEP treatment. Similarly, transcriptome analysis revealed changes in gene expression after oral DEP exposure, but not in the other treatments. The changes are related to metabolism and signal transduction which indicates a general stress response. Taken together, our results suggest potential health effects of DEP exposure on insects, here shown in bumblebees, as gut dysbiosis may increase the susceptibility of bumblebees to pathogens, while a general stress response may lower available energy resources. However, experiments with multiple stressors and on colony level are needed to provide a more comprehensive understanding of the impact of DEPs on insects.
Forage fishes are a critical food web link in marine ecosystems, aggregating in a hierarchical patch structure over multiple spatial and temporal scales. Surface-level forage fish aggregations (FFAs) represent a concentrated source of available prey for surface- and shallow-foraging marine predators. Existing survey and analysis methods are often imperfect for studying forage fishes at scales appropriate to foraging predators, making it difficult to quantify predator-prey interactions. In many cases, general distributions of forage fish species are known; however, these may not represent surface-level prey availability to predators. Likewise, we lack an understanding of the oceanographic drivers of spatial patterns of prey aggregation and availability or forage fish community patterns, generally. Specifically, we applied Bayesian joint species distribution models to bottom trawl survey data to assess species- and community-level forage fish distribution patterns across the US Northeast Continental Shelf (NES) ecosystem. Aerial digital surveys gathered data on surface FFAs at two project sites within the NES, which we used in a spatially explicit hierarchical Bayesian model to estimate the abundance and size of surface FFAs. We used these models to examine the oceanographic drivers of forage fish distributions and aggregations. Our results suggest that, in the NES, regions of high community species richness are spatially consistent with regions of high surface FFA abundance. Bathymetric depth drove both patterns, while subsurface features, such as mixed layer depth, primarily influenced aggregation behavior and surface features, such as sea surface temperature, sub-mesoscale eddies, and fronts influenced forage fish diversity. In combination, these models help quantify the availability of forage fishes to marine predators and represent a novel application of spatial models to aerial digital survey data.
Strong theory exists regarding population sex ratio evolution that predicts equal sex ratio (when parental investment is equal). In most animals, sex chromosomes determine the sex of offspring, and this fixed genotype for sex has made theory difficult to test since genotypic variance for the trait (sex) is lacking. It has long been argued that the genotype has become fixed in most animals due to the strong selection for equal sex ratios. The marine copepod Tigriopus californicus has no sex chromosomes, multiple genes affecting female brood sex ratio and a brood sex ratio that responds to selection. The species thus provides an opportune system in which to test established sex ratio theory. In this paper we further our exploration on the possibility that T. californicus has polygenic sex determination using an incomplete diallel crossing design and the “animal model” for analysis of the variance components of sex determination in the species. Our data confirm the presence of extra-binomial variance for sex, further confirming that sex is not determined through simple Mendelian trait inheritance. In addition, our crosses and backcrosses of isofemale lines selected for biased brood sex ratios show intermediate phenotypic means, as expected if sex is a threshold trait determined by an underlying “liability” trait controlled by many genes of small effects. Finally, we estimate heritability of an individual to be male or female on the observed binary scale as 0.09 (95% CI: 0.034-0.14). This work furthers our accumulating evidence for polygenic sex determination in T. californicus.
Trophic networks describe interactions between species at a given location and time. Due to environmental changes, anthropogenic perturbations or sampling effects, trophic networks may vary in space and time. The collection of network time series or networks in different sites thus constitutes a metanetwork. A crucial step toward the understanding of those metanetworks is to build appropriate tools to handle and represent them. We present here the R package metanetwork, which will ease the exploration and the analysis of trophic metanetwork datasets that are increasingly available. Our main methodological advance consists in suitable layout algorithm for trophic networks, which is based on trophic levels and dimension reduction of a graph diffusion kernel. In particular, it highlights relevant features of trophic networks (trophic levels, energetic channels). In addition, we developed graphical tools to handle, compare and aggregate those networks. Static and dynamic visualisation functions have been developed to represent large networks. We apply our package workflow to several trophic network data sets.
Upon uptake of toxins, insects launch a detoxification program. This program is deployed in multiple organs and cells to raise their tolerance against the toxin. The molecular mechanisms of this program inside the insect body have been studied and understood in detail. Here, we report on a yet unexplored extra-corporeal detoxification of insecticides in Drosophila melanogaster. Wild-type D. melanogaster incubated with DDT, a contact insecticide, in a closed environment die as expected. However, incubation of a second cohort in the same environment after removal of the dead flies was not lethal. Consistent to the kin selection theory, the effect is significantly lower if the flies of the two cohorts are unrelated. Incubation assays with Chlorpyrifos, another contact insecticide, yielded identical results, while incubation assays with Chlorantraniliprole, again a contact insecticide, was toxic for the second cohort of flies. A cohort of flies incubated in a DDT environment after an initial incubation of a honeybee survived treatment. Together, our data suggest that insects including Apis mellifera and D. melanogaster have the capacity to modify their proximate environment. Consequently, in their ecological niche, following individuals might be saved from intoxication thereby facilitating colonisation of an attractive site.
Ecology is broad and relies on several complementary approaches to study the mechanisms driving the distribution and abundance of organisms and their interactions. One of them is citizen science, the co-production of scientific data and knowledge by non-professional scientists, in collaboration with or under the direction of professional scientists. Citizen science has bloomed in the scientific literature over the last decade and is being incrasingly popular. We used a bibliometric analysis to study whether associating the public to ecological research changes the making of ecology and the nature of questions it asks. We analysed keywords and abstracts of 41,105 articles published the last ten years, disentangling CitSci articles (those explicitly referring to citizen science) and non-CitSci articles. Keyword co-occurrence and thematic map analyses revealed that CitSci articles primarily focused on biodiversity and climate change in a more descriptive way than non-CitSci articles which were more likely to address theoretical questions in ecology. Roughly, citizen science in ecology addressed patterns, whereas non participatory research dug further into mechanisms. Biodiversity also appeared as a more central theme in the CitSci corpus, where it was more systematically associated with other keywords. Our study indicates that should the surge of citizen science approaches in ecological scientific literature have change the type of ecological inquiry, this thematic change is marginal. Still, we provide evidence that specific research questions individualized from ecological CitSci thus supporting the view that citizen science is becoming an independent field of investigation, and not only a peculiar methodological approach to ecological research.
Animals show among-individual variation in behaviours, including migration behaviours, which are often repeatable across time periods and contexts, commonly termed “personality”. These behaviours can be correlated, forming a behavioural syndrome. In this study, we assessed the repeatability and correlation of different behavioural traits i.e., boldness, exploration and sociality and the link to migration patterns in Atlantic cod juveniles. To do so, we collected repeated measurements within two short-term (three days) and two long-term (two months) intervals of these traits and genotypes of the Pan I locus, which is indirectly correlated to feeding migration patterns in this species. We found that mainly exploration behaviour was repeatable in the short- and long-term intervals, and a trend for the relationship between exploration and the Pan I locus. Boldness and sociality were only repeatable in the second short-term interval indicating a possible development of stability over time and did not show a relation with the Pan I locus. We found no indication of behavioural syndromes among the studied traits. Although we were unable to identify the existence of a migration syndrome for the migratory genotype (Pan IBB), this study is the first one to highlight the existence of a possible link between the personality trait exploration and the migration-linked Pan I locus. This supports the need for further research that should focus on the effect of exploration tendency and other personality traits on cod movement, including the migratory (frontal) ecotype, to develop management strategies based on behavioural units, rather than treating the population as a single homogeneous stock.
Interference competition has the potential to alter avian assemblages at long-lasting arid zone waterholes, particularly in a warming world, as more potentially aggressive species frequent these sites to drink. We used camera traps and observational surveys to investigate interference competition between terrestrial avian species at six long-lasting waterholes across three sampling seasons (two summers and one winter) within the MacDonnell Ranges Bioregion in central Australia. The proportion of individuals drinking for each of four dietary classes (granivores, nectarivores, omnivores, and insectivores) was modelled in relation to their abundance in the immediate waterhole habitat, which informed the potential for competition in each season. We then used the temporal overlap estimators to quantify the degree of competition between species at waterholes with species grouped into families (Meliphagidae, Ptilonorhynchidae, Estrildidae, and Rhipiduridae). We found the proportion of individuals drinking at waterholes was greatest during hot and dry periods, suggesting the potential for interference competition is greatest during these times. This was particularly the case for nectarivores where, in hot and dry conditions, the proportion of drinking individuals increased significantly as their abundance also increased in the waterhole habitat. We predicted that subordinate species would alter their activity periods to avoid competitive interactions with meliphagids (honeyeaters), however, we found there was a high degree of temporal overlap between all families sampled across all seasons. These results suggest subordinate species are unlikely to be excluded from long-lasting waterholes by potentially aggressive species, such as honeyeaters. However, some species may face trade-offs between foraging and accessing waterholes to stay hydrated as they shift their activity to avoid the hottest parts of the day during the summer months. Under global warming, extended hot and dry periods will likely create conditions where balancing energy and hydration requirements becomes increasing difficult and results in the loss of body condition.
The fan mussel Pinna nobilis is currently on the brink of extinction due to a multifactorial disease mainly caused to the highly pathogenic parasite Haplosporidium pinnae, meaning that the selection pressure outweighs the adaptive potential of the species. Hopefully, rare specimens have been observed somehow resistant to the parasite, stretching the need to identify the traits underlying this better fitness. Among the candidate to explore at first intention are fast evolving immune genes, of which toll-like receptor (TLR). In this study, we examined the genetic diversity at 14 TLR loci across Pinna nobilis, Pinna rudis and Pinna nobilis x Pinna rudis hybrid genomes, collected at four physically distant regions, that were found to be either resistant or sensitive to the parasite Haplosporidium pinnae. We report a high genetic diversity, mainly observed at cell surface TLRs compared to that of endosomal TLRs. However, the TLR-7 and TLR-1 exhibited unexpected level of diversity and haplotype phylogeny, respectively. The lack of population structure, associated with a high genetic diversity and elevated dN/dS ratio were interpreted as balancing selection, though both directional and purifying selection were detected. Overall, we observed small contributions of putatively selected SNPs involved in the resistance. However, the most contributing SNPs were carried by two TLR-6 loci and might be used as potent biomarkers of distinguish between resistant and sensitive P. nobilis individuals. Moreover, more than 10% of P. nobilis individuals were found introgressed with P. rudis. Noteworthy, all introgressed P. nobilis observed as resistant to H. pinnae carried a TLR-7 of P. rudis origin. This study contributes to the ongoing efforts towards conservation carried out to prevent from extinction this Mediterranean endemic species.
The evolution of body size, both within and between species, has been long predicted to be influenced by multifarious environmental factors. However, the specific drivers of body size variation have remained difficult to understand because of the wide range of proximate factors that consistently covary with ectotherm body sizes across populations with varying local environmental conditions. Here, we used a widely distributed lizard (Eremias argus) collected from different populations situated across China to assess how climatic conditions and/or available resources at different altitudes shape the geographical patterns of lizard body size across populations. We used body size data from locations differing in altitudes across China to construct linear mixed models to test the relationship between lizard body size and ecological and climate conditions across altitudes. Lizard populations showed significant differences in body size across altitudes. Furthermore, we found that variation in body size among populations was also explained by climatic and seasonal changes along the altitudinal gradient. Specifically, body size decreased with colder and drier environmental conditions at high altitudes, resulting in a reversal of Bergmann’s rule. Limited resources at high altitudes, as measured by net primary productivity, may also constrain body size. Therefore, our study demonstrates that the intraspecific variation in female lizards’ body size may be strongly influenced by multifarious local environments as adaptive plasticity for female organisms to possibly maximise reproductive ecology along geographic clines.
Texas horned lizards (Phrynosoma cornutum) have disappeared from many areas in Texas, especially from urbanized areas, probably in large part due to loss of suitable habitat. Our previous studies have found that horned lizards persist and occur at high densities in some small towns in southern Texas. Nevertheless, this species has continued to decline and disappear from these towns. Long-term data from Kenedy and Karnes City indicate that when study sites experienced significant shrub and vegetation removal horned lizards declined by 79%. We hypothesize this may in part be due to the degradation of the thermal landscape for these lizards. We determined the preferred temperature range (Tset25 −Tset75) of lizards at our study sites and took field measurements of body temperature (Tb). Temperature loggers were also placed in three microhabitats across our study sites. Shrubs and vegetation provided the highest quality thermal environment, especially for about 5 hours midday when temperatures in the open and buried under the surface exceeded the lizards’ critical maximum temperature (CTmax) or were above their preferred temperature range. Horned lizard density was positively related to the thermal quality of the habitat across our sites. Texas horned lizards in these towns require a heterogenous mix of closely spaced microhabitats and especially thermal refugia, such as shrubs and vegetation along fence lines and in open fields. Maintaining thermal refugia is one of the most important and practical conservation actions that can be taken to help small ectotherms persist in human modified landscapes and cope with increasing temperatures due to climate change.
In the Flora of China account (Pan et al. 2001) of Saxifraga mengtzeana Engl. & Irmsch., eight synonyms were attributed to it and one variant, recognised as S. epiphylla Gornall & Ohba, was split from it. This study re-evaluates the taxonomic status of some of the synonyms and of the segregated species in the light of new evidence presented here. Morphological and molecular evidence demonstrate that populations from north-western Yunnan and Sichuan are genetically differentiated from those in south-eastern Yunnan and neighbouring Guangxi. Observations in the field and in cultivation show that the peltate petiole attachment diagnostic of S. mengtzeana var. peltifolia Engl. & Irmsch. is developmentally labile. Similar observations combined with molecular data show that viviparous phenotypes, formerly treated as S. epiphylla, although largely under genetic control, occur sporadically throughout the ranges of both northern and southern taxa. Populations from north-western Yunnan and Sichuan are best recognised as S. geifolia Balf.f., whereas those from south-eastern Yunnan and neighbouring Guangxi are S. mengtzeana. Peltate-leaved variants of the latter are given no status and are relegated to complete synonymy. Viviparous phenotypes of S. mengtzeana are demoted to the rank of forma, as f. epiphylla; analogous phenotypes of S. geifolia are newly described as f. vivipara. Keywords China, Saxifragaceae, Phylogeny, Morphology, Taxonomy
Increased access to genome-wide data provides new opportunities for plant conservation. However, information on neutral genetic diversity in a small number of marker loci can still be valuable because genomic data are not available to most rare plant species. In the hope of bridging the gap between conservation science and practice, we outline how conservation practitioners can more efficiently employ population genetic information in plant conservation. We first review the current knowledge about the within-population genetic variation and among-population differentiation in neutral genetic variation (NGV) and adaptive genetic variation (AGV) in seed plants. We then introduce the estimates of among-population genetic differentiation in quantitative traits (QST) and neutral markers (FST) to plant biology and summarize conservation applications derived from QST–FST comparisons, particularly on how to capture most AGV and NGV on both in-situ and ex-situ programs. Based on a review of published studies, we found that, on average, two and four populations would be needed for woody perennials (n = 18) to capture 99% of neutral and adaptive genetic variation, respectively, whereas four populations would be needed in case of herbaceous perennials (n = 14). On average, QST is about 3.6, 1.5, and 1.1 times greater than FST in woody plants, annuals, and herbaceous perennials, respectively. We suggest using maximum QST rather than average QST among trait comparisons. Hence, conservation and management policies or suggestions based solely on inference on FST could be misleading, particularly in woody species. We recommend conservation managers and practitioners consider this when formulating further conservation and restoration plans for plant species, and for woody species in particular.
Conversion of the North American prairies to cropland remains a prominent threat to grassland bird populations. Yet, a few species nest in these vastly modified systems. The thick-billed longspur (Rhynchophanes mccownii) is an obligate grassland bird whose populations have declined 4% annually during the past 50 years. Thick-billed longspurs historically nested in recently disturbed or sparsely vegetated patches within native mixed-grass prairie, but observations of longspurs in crop fields during the breeding season suggest such fields also provide cues for habitat selection. Maladaptive selection for poor quality habitat may contribute to ongoing declines in longspur populations, but information on thick-billed longspur breeding ecology in crop fields is lacking. We hypothesized that crop fields may function as ecological traps; specifically, we expected that crop fields may provide cues for territory selection but frequent human disturbance and increased exposure to weather and predators would have negative consequences for reproduction. To address this hypothesis, we compared measures of habitat selection (settlement patterns and trends in abundance) and productivity (nest density, nest survival, and number of young fledged) between crop fields and native sites in northeastern Montana, USA. Settlement patterns were similar across site types and occupancy ranged from 0.52 ± 0.17SE to 0.99 ± 0.01 on April 7 and 30, respectively. Early season abundance differed by year and changes in abundance during the breeding season were associated with precipitation-driven vegetation conditions, rather than habitat type. Standardized nest density (0.19 ± 0.27SD nests/plot/hour), the number of young fledged per successful nest (2.9 ± 0.18SE), and nest survival (0.24 ± 0.03 SE; n=222 nests) were similar for crop and native sites. Collectively, the data did not support our hypothesis that crop fields are ecological traps: longspurs did not exhibit a clear preference for cropland and reproductive output was not significantly reduced. Our results indicate that crop fields provide alternative breeding habitat within a human-dominated landscape.
The Philippine native pig (PhNP) is a unique genetic resource with complex genetics due to multiple ancestries and hybridizations with wild pigs. No prior study has determined the population structure and genetic diversity of PhNPs on multiple islands and provinces, which is essential for establishing conservation priorities. In this study, we explore the population structure and genetic diversity of various PhNP populations in Luzon and the Visayas, Philippines, to identify conservation priorities. We analyzed 157 native pigs representing 7 populations (Benguet (B), Kalinga (K), Nueva Vizcaya, Isabela (I), Quezon (Q), Marinduque (M), and Samar (S)) and 39 pigs of transboundary distribution (Duroc, Large White, Landrace, and Berkshire). The pigs were compared against a panel of 21 ISAG–FAO recommended microsatellite markers. We tested for population structure at the island, administrative region and province levels. Strong genetic differentiation between native and transboundary breeds was confirmed by analysis of molecular variance (Frt: 0.08; F’st: 0.288-0.728), Bayesian clustering (k = 2) and Nei’s DA genetic distance (98% bootstrap support for the PhNP cluster). PhNP exhibited high heterozygosity (Ho: 0.72), a high allele count (Na: 9.24) and a low inbreeding coefficient (Fis: -0.022 to 0.150). Bayesian clustering supported genetic differentiation at the island (k = 2; North Luzon and South Luzon-Visayas cluster), administrative region (k = 4) and population (k= 9) levels. The pairwise F’st between PhNP populations ranged from 0.130 (Q and M) to 0.427 (Q and K), confirming that PhNP populations exhibited sufficient genetic distance to be considered separate populations. This study shows that the seven previously assigned PhNP populations, roughly delimited by provincial origin, are unique genetic units for conservation. Furthermore, the small effective population sizes of B, Q, I, and S (Ne: 5, 17, 24, and 26, respectively) necessitate immediate conservation actions, such as incentivizing the farming of PhNP.
The study of the eukaryotic fraction of the microbiota using a metabarcoding approach is usually hindered by the high host to eukaryotic microbiota DNA ratio in samples. Indeed, the 18S rRNA gene is very similar for both the host and its eukaryotic communities, leading to a preferential amplification of the predominant host DNA when using universal primers. Multiple approaches have been developed to reduce host DNA amplification. One method is based on elongation arrest blocking primers, oligonucleotides modified with a C3 Spacer that stops the advancement of the DNA polymerase at non-conserved regions of a target gene. In this paper, we successfully developed and tested species-specific elongation arrest blocking primers to block the Flag cichlid, Mesonauta festivus, 18S rRNA SSU. Our elongation arrest blocking primers significantly reduced the amount of host DNA amplicons by 66 %. In addition to reducing the amount of sequencing wasted, the blocking primers increased the detectability of potentially dangerous parasitic taxa in fish gut, highlighting the potential of the method for parasitic screening. For instance, we discovered a case of infection by the parasitic ciliate Nyctotherus sp. and detected the presence of a parasitic Trematode and an Amoebae. While our data support the possibility of achieving a complete inhibition of host DNA amplification using elongation arrest blocking primers, more research is still required. Still, there is a need for the development and additional testing of protocols to study the eukaryotic diversity present in fish gut, a slow-growing field of study in comparison to its prokaryotic counterpart.
Cynanchum pingtaoi sp. nov. (Apocynaceae), from Yunnan Province, China, is described and illustrated based on molecular and morphological evidence. Its deeply cordate to reniform leaves, campanulate and large flowers show that it is a member of former Raphistemma which has been included in Cynanchum now. It is different from the all former Raphistemma species (C. hooperianum,C. longhushanense and C. pulchellum) by the broadly ovate corolla lobe, purple-red corolla, and connivent corona tip slightly exceeding corolla throat. Its detailed morphological description and illustrations are provided. Meanwhile, Cynanchum longhushanense (Y. Wan) G.D.Tang & Miao Liao nom. nov. is proposed as the replacement name of Raphistemma brevipedunculatum Y. Wan which is reinstated from a synonym of C. hooperianum (Blume) Decne because of their significant morphological differences.