Reciprocal allopolyploid grasses (Festuca × Lolium) display stable patterns of genome dominance

Allopolyploidization entailing the merger of two distinct genomes in a single hybrid organism, is an important process in plant evolution and a valuable tool in breeding programs. Newly established hybrids often experience massive genomic perturbations, including karyotype reshuffling and gene expression modifications. These phenomena may be asymmetric with respect to the two progenitors, with one of the parental genomes being “dominant.” Such “genome dominance” can manifest in several ways, including biased homoeolog gene expression and expression level dominance. Here we employed a k-mer–based approach to study gene expression in reciprocal Festuca pratensis Huds. × Lolium multiflorum Lam. allopolyploid grasses. Our study revealed significantly more genes where expression mimicked that of the Lolium parent compared with the Festuca parent. This genome dominance was heritable to successive generation and its direction was only slightly modified by environmental conditions and plant age. Our results suggest that Lolium genome dominance was at least partially caused by its more efficient trans-acting gene expression regulatory factors. Unraveling the mechanisms responsible for propagation of parent-specific traits in hybrid crops contributes to our understanding of allopolyploid genome evolution and opens a way to targeted breeding strategies.     

Heterospecific recognition of referential alarm calls in two species of lemur

ABSTRACT

Alarm vocalizations are a common feature of the mammalian antipredator response. The meaning and function of these calls vary between species, with some species using calls to reference-specific categories of predators. Species can also use more than just the calls of conspecifics to detect threat, ‘eavesdropping’ on other species’ signalling to avoid predation. However, the evidence to date for both referential signalling and eavesdropping within primates is limited. We investigated two sympatric populations of wild lemur, the Coquerel’s sifaka Propithecus coquereli and the common brown lemur Eulemur fulvus, presenting them with playbacks of predator calls, conspecific alarm calls and heterospecific lemur alarm calls, and recorded their behavioural responses following the playbacks. Results suggest that the Coquerel’s sifaka may have functionally referential alarm calls with high specificity for aerial predators, but there was no evidence for any referential nature of the other call investigated. Brown lemurs appear to have a mixed alarm system, with one call being specific with respect to aerial predators. The other call investigated appeared to reference terrestrial predators. However, it was also used in other contexts, so does not meet the criteria for functional reference. Both species showed evidence for heterospecific alarm call recognition, with both the Coquerel’s sifaka and the brown lemurs responding appropriately to heterospecific aerial alarm calls.     

Glycoalkaloid Profile in Potato Haploids Derived from Solanum tuberosum–S. bulbocastanum Somatic Hybrids

Cultivated and wild potato species synthesize a wide variety of steroidal glycoalkaloids (GA) that may affect either human health or biotic stress resistance. Therefore, GA composition must be a major criterion in the evaluation of breeding products when species genomes are merged and/or manipulated. This work reports the results of GA analysis performed on unique haploid (2n=2x=24) plants obtained from tetraploid (2n=4x=48) Solanum bulbocastanum–S. tuberosum hybrids through in vitro anther culture. Glycoalkaloids were extracted from tubers and analyzed by HPLC. Haploids generally showed the occurrence of parental GA. However, in several cases loss of parental GA and gain of new GA lacking in the parents was observed. It may be hypothesized that new GA profiles of our haploids is the result of either genetic recombination or combinatorial biochemistry events. To highlight differences between haploids and parents, soluble proteins and antioxidant activities were also determined. Both were always higher in haploids compared to their parents. The nature of the newly formed GAs will be further investigated, because they may represent new metabolites that can be used against pest and diseases, or are useful for human health.     

Common alien plants are more competitive than rare natives but not than common natives

Success of alien plants is often attributed to high competitive ability. However, not all aliens become dominant, and not all natives are vulnerable to competitive exclusion. Here, we quantified competitive outcomes and their determinants, using response‐surface experiments, in 48 pairs of native and naturalised alien annuals that are common or rare in Germany. Overall, aliens were not more competitive than natives. However, common aliens (invasive) were, despite strong limitation by intraspecific competition, more competitive than rare natives. This is because alien species had higher intrinsic growth rates than natives, and common species had higher intrinsic growth rates than rare ones. Strength of interspecific competition was not related to status or commonness. Our work highlights the importance of including commonness in understanding invasion success. It suggests that variation among species in intrinsic growth rates is more important in competitive outcomes than inter‐ or intraspecific competition, and thus contributes to invasion success and rarity.     

Relative contribution of rainfall and coconut hybrids to the abundance and composition of the Auchenorrhyncha community as potential vectors of phytoplasmas in the state of Sergipe,Brazil

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Beyond trophic morphology: stable isotopes reveal ubiquitous versatility in marine turtle trophic ecology

The idea that interspecific variation in trophic morphology among closely related species effectively permits resource partitioning has driven research on ecological radiation since Darwin first described variation in beak morphology among Geospiza. Marine turtles comprise an ecological radiation in which interspecific differences in trophic morphology have similarly been implicated as a pathway to ecopartition the marine realm, in both extant and extinct species. Because marine turtles are charismatic flagship species of conservation concern, their trophic ecology has been studied intensively using stable isotope analyses to gain insights into habitat use and diet, principally to inform conservation management. This legion of studies provides an unparalleled opportunity to examine ecological partitioning across numerous hierarchical levels that heretofore has not been applied to any other ecological radiation. Our contribution aims to provide a quantitative analysis of interspecific variation and a comprehensive review of intraspecific variation in trophic ecology across different hierarchical levels marshalling insights about realised trophic ecology derived from stable isotopes. We reviewed 113 stable isotope studies, mostly involving single species, and conducted a meta‐analysis of data from adults to elucidate differences in trophic ecology among species. Our study reveals a more intricate hierarchy of ecopartitioning by marine turtles than previously recognised based on trophic morphology and dietary analyses. We found strong statistical support for interspecific partitioning, as well as a continuum of intraspecific trophic sub‐specialisation in most species across several hierarchical levels. This ubiquity of trophic specialisation across many hierarchical levels exposes a far more complex view of trophic ecology and resource‐axis exploitation than suggested by species diversity alone. Not only do species segregate along many widely understood axes such as body size, macrohabitat, and trophic morphology but the general pattern revealed by isotopic studies is one of microhabitat segregation and variation in foraging behaviour within species, within populations, and among individuals. These findings are highly relevant to conservation management because they imply ecological non‐exchangeability, which introduces a new dimension beyond that of genetic stocks which drives current conservation planning. Perhaps the most remarkable finding from our data synthesis is that four of six marine turtle species forage across several trophic levels. This pattern is unlike that seen in other large marine predators, which forage at a single trophic level according to stable isotopes. This finding affirms suggestions that marine turtles are robust sentinels of ocean health and likely stabilise marine food webs. This insight has broader significance for studies of marine food webs and trophic ecology of large marine predators. Beyond insights concerning marine turtle ecology and conservation, our findings also have broader implications for the study of ecological radiations. Particularly, the unrecognised complexity of ecopartitioning beyond that predicted by trophic morphology suggests that this dominant approach in adaptive radiation research likely underestimates the degree of resource overlap and that interspecific disparities in trophic morphology may often over‐predict the degree of realised ecopartitioning. Hence, our findings suggest that stable isotopes can profitably be applied to study other ecological radiations and may reveal trophic variation beyond that reflected by trophic morphology.     

A metabolome‐based core hybridisation strategy for the prediction of rice grain weight across environments

Marker‐based prediction holds great promise for improving current plant and animal breeding efficiencies. However, the predictabilities of complex traits are always severely affected by negative factors, including distant relatedness, environmental discrepancies, unknown population structures, and indeterminate numbers of predictive variables. In this study, we utilised two independent F₁ hybrid populations in the years 2012 and 2015 to predict rice thousand grain weight (TGW) using parental untargeted metabolite profiles with a partial least squares regression method. A stable predictive model for TGW was built based on hybrids from the population in 2012 (r = 0.75) but failed to properly predict TGW for hybrids from the population in 2015 (r = 0.27). After integrating hybrids from both populations into the training set, the TGW of hybrids could be predicted but was largely dependent on population structures. Then, core hybrids from each population were determined by principal component analysis and the TGW of hybrids in both environments were successfully predicted (r > 0.60). Moreover, adjusting the population structures and numbers of predictive analytes increased TGW predictability for hybrids in 2015 (r = 0.72). Our study demonstrates that the TGW of F₁ hybrids across environments can be accurately predicted based on parental untargeted metabolite profiles with a core hybridisation strategy in rice. Metabolic biomarkers identified from early developmental stage tissues, which are grown under experimental conditions, may represent a workable approach towards the robust prediction of major agronomic traits for climate‐adaptive varieties.