Local adaptation mediated niche expansion in correlation with genetic richness

As a central issue in evolution and ecology, the quantitative relationship among the genome, adaptation and the niche was investigated. Local adaptation of five Escherichia coli strains carrying either the wild-type genome or reduced genomes was achieved by experimental evolution. A high-throughput fitness assay of the ancestor and evolved populations across an environmental gradient of eight niches resulted in a total of 80 fitness curves generated from 2,220 growth curves. Further analyses showed that the increases in both local adaptiveness and niche broadness were negatively correlated with genetic richness. Local adaptation caused common niche expansion, whereas niche expansion for generality or speciality was decided by genetic richness. The order of the mutations accumulated stepwise was correlated with the magnitude of the fitness increase attributed to mutation accumulation. Pre-adaptation probably participated in coordination among genetic richness, local adaptation and niche expansion.

Symbiont-driven niche expansion shaped the adaptive radiation of insects

For over 300 million years, insects have relied on symbiotic microbes for nutrition and defence1,2. However, it is unclear whether specific ecological conditions have repeatedly favoured the evolution of symbioses, and how this has influenced insect diversification1,3,4. Using data on 1844 microbe-insect symbioses across 400 insect families, we found that symbionts have allowed insects to radiate into a range of feeding niches deficient in B vitamins, including phloem, blood and wood. In some cases, such as herbivorous insects, the shift to a new niche has resulted in spectacular species proliferation. In other niches, such as strict blood feeding, diversification has been severely constrained. Symbioses therefore appear to solve universal nutrient deficiencies for insects, but the consequences for insect diversification depend on the feeding niche invaded.

The role of the gut microbiota in the dietary niche expansion of fishing bats

Background Due to its central role in animal nutrition, the gut microbiota is likely a relevant factor shaping dietary niche shifts. We analysed both the impact and contribution of the gut microbiota to the dietary niche expansion of the only four bat species that have incorporated fish into their primarily arthropodophage diet. Results We first compared the taxonomic and functional features of the gut microbiota of the four piscivorous bats to that of 11 strictly arthropodophagous species using 16S rRNA targeted amplicon sequencing. Second, we increased the resolution of our analyses for one of the piscivorous bat species, namely Myotis capaccinii, and analysed multiple populations combining targeted approaches with shotgun sequencing. To better understand the origin of gut microorganisms, we also analysed the gut microbiota of their fish prey (Gambusia holbrooki). Our analyses showed that piscivorous bats carry a characteristic gut microbiota that differs from that of their strict arthropodophagous counterparts, in which the most relevant bacteria have been directly acquired from their fish prey. This characteristic microbiota exhibits enrichment of genes involved in vitamin biosynthesis, as well as complex carbohydrate and lipid metabolism, likely providing their hosts with an enhanced capacity to metabolise the glycosphingolipids and long-chain fatty acids that are particularly abundant in fish. Conclusions Our results depict the gut microbiota as a relevant element in facilitating the dietary transition from arthropodophagy to piscivory.

Beyond tracking climate: niche evolution during native range expansion and its implications for novel invasions

Ecological niche models have been instrumental in understanding and forecasting the widespread shifts in species distributions under global change. However, growing evidence of evolution in spreading populations challenges their key assumption of niche conservatism, limiting model transferability in space and time. Climate niche evolution has been studied extensively in invasive species, but may also occur in native populations tracking climate change, when species encounter novel abiotic conditions that vary with latitude. We compared niche shifts during native range expansion and during invasion in Dittrichia graveolens, a Mediterranean annual plant species that is currently undergoing both types of spread. We asked whether the species' northward native range expansion in Eurasia matched climate change from 1901-1930 to 1990-2019, or if further range expansion was promoted by niche evolution. In addition, we asked how niche expansion in the native range affected forecasts of two ongoing invasions in Australia and California. We quantified niche shifts in environmental space using the analytical framework of niche centroid shift, overlap, unfilling, and expansion (COUE), and examined associated distribution changes in geographic space using Maximum Entropy modeling. Our results show that D. graveolens expanded its native range well beyond what would be sufficient to track climate change, a shift associated with a 5.5% niche expansion to include more temperate climates. In contrast, both invasions showed evidence of niche conservatism, with niche filling depending on invader residence time. Including the expanded native niche in invasion projections added new areas at risk of invasion, but none of these has been colonized at present. We conclude that native populations may track climate change and adapt to novel local conditions in parallel, causing an evolutionary expansion of the climate niche and more widespread range expansion than expected based on climate change alone.

Local adaptation mediated niche expansion in correlation with genetic richness

As a central issue in evolution and ecology, the quantitative relationship among the genome, adaptation and the niche was investigated. Local adaptation of five Escherichia coli strains carrying either the wild-type genome or reduced genomes was achieved by experimental evolution. A high-throughput fitness assay of the ancestor and evolved populations across an environmental gradient of eight niches resulted in a total of 80 fitness curves generated from 2,220 growth curves. Further analyses showed that the increases in both local adaptiveness and niche broadness were negatively correlated with genetic richness. Local adaptation caused common niche expansion, whereas niche expansion for generality or speciality was decided by genetic richness. The order of the mutations accumulated stepwise was correlated with the magnitude of the fitness increase attributed to mutation accumulation. Pre-adaptation probably participated in coordination among genetic richness, local adaptation and niche expansion.

Climatic-niche evolution with key morphological innovations across clades within Scutiger boulengeri (Anura: Megophryidae)

The studies of climatic-niche shifts over evolutionary time accompanied by key morphological innovations have attracted the interest of many researchers recently. We analyzed the realized niche dynamics across clades within Scutiger boulengeri using ecological niche models (ENMs), ordination method (environment principal component analysis; PCA-env), and correspondingly key morphological innovations combined phylogenetic comparative methods (PCMs) and phylogenetic generalized least squares (PGLS) regression methods throughout their distributions in Qinghai-Tibet Plateau (QTP) margins of China in Asia. Our analyses reveal that there is obvious niche divergence caused by niche expansion across S. boulengeri clades, especially in E. A, E. B and partial of E. C clades. Moreover, niche expansion is more popular than niche unfilling into novel environmental conditions. Annual mean temperature and Annual precipitation are the most important contributors in E. A and E. B clades, while Precipitation of driest month is most likely to be the leading limited factor in these two regions according to jackknife test of variable importance. In addition, we identified several key ecological and morphological traits that tend to be associated with niche expansion in S. boulengeri clades correspondingly. Specifically, we found that Elevation, Isothermality, Mean diurnal range and Max temperature of warmest month are significantly negative predictors of snout–vent length (SVL) under phylogenetic models, while the S. boulengeri toads from warmer and more arid environments tend to be larger. There seems to a trade-off strategy by trait covary of locomotor performance combined with enlarged SVL, which provide us a potential pattern of how a colonizing toad might seed a novel habit to begin the process of speciation and finally adaptive radiation. It is worth noting that we should not overlook that the Tibet continuously growing and moving northward over millions of years has laid the foundation for early divergence of clades within S. boulengeri.