Telomere fusions and translocations: a bridge too far?

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A bridge too far: cold and pathogen constraints to assisted migration of riparian forests

Assisted migration of warm‐adapted genotypes to currently cooler climates may reduce maladaptation from future climate change. Few assisted migration trials have considered limitations of the cooler climates and pathogens currently present at transplant sites. This is especially important to consider in riparian ecosystems that are priority targets for restoration in the western United States as they harbor diverse communities. In an effort to validate assisted migration as an effective strategy for mediating the negative impacts of climate change, we used a provenance trial with replicated genotypes from 19 populations of the foundation riparian tree species, Fremont cottonwood (Populus fremontii), transplanted to a cold site to test for genetic variation in growth, mortality, and resistance to shoot blight fungi (Venturia sp.). Populations from cool sites had up to 4 times faster growth, 3 times higher survival, and 8 times higher resistance to Venturia than populations from warm sites, providing evidence of local adaptation to both climate and pathogenic fungi. Budburst phenology and shoot blight were correlated with frost damage, subsequent shrub‐form architecture, and mortality. While climate change models predict 6°C increases, plants transferred distances of 6°C at this time would not perform well; an intermediate transfer distance of less than 3°C would avoid maladaptation to the current environment during assisted migration. Thus, multiple and intermediate transfer phases to supplement local genetic variation will likely be necessary for effective assisted migration to accommodate current environments and large changes in climate.     

Good from far,but far from good: The impact of a reference genome on evolutionary inference

Genomic diversity and past population histories are key considerations in the fields of conservation and evolutionary biology. In this issue of Molecular Ecology Resources, Prasad et al. (Mol. Ecol. Resour., 2021) examine how the quality and phylogenetic divergence of reference genomes influences the outcomes of downstream analyses such as diversity and demographic history inference. Using the beluga whale and rowi kiwi as examples (Figure 1), they systematically estimate heterozygosity, runs of homozygosity (ROH), and demographic history (PSMC) using reference genomes of varying quality and phylogenetic divergence from the target species. They show that demographic history analyses are impacted by phylogenetic distance, although this is not pronounced until divergence exceeds 3% from the target species. Similarly, their results imply that heterozygosity estimates are dependent on phylogenetic distance and the method used to perform the estimates, and ROHs are potentially undetectable when a nonconspecific reference is used. This investigation into the role of divergence and quality of reference genomes highlights the impact and potential biases generated by genome selection on downstream analyses, and provides a possible alternative in cross-species scaffolding in instances where a conspecific reference genome is not available.     

Links between genetic and functional diversity – a bridge too far?

The view that nutrient acquisition by most plants growing in natural ecosystems is mediated by mycorrhiza-forming symbiotic fungi is now largely accepted. With this perception comes the need to learn more about the identity of the organisms responsible for these key processes. Herein lies a challenge taken up by Vrålstad et al . on pp. 549–563 in this issue.     

Post blocking gone too far! Recovery of information and spatial analysis in field experiments

Federer (1998, Biometrics 54, 471-481) presents two analyses of field data in which high-order polynomials are fitted as random regressions to remove spatial variation. We challenge the justification of this approach and suggest some alternatives.     

Temporal regulation in the early embryo: is MBT too good to be true?

The question of how early embryonic events are temporally regulated has traditionally been tied to the mid-blastula transition (MBT). This concept has directed the studies in Xenopus and influenced the studies in other organisms. By examining the weaknesses in the concept of MBT, we hope to refocus the study of temporal regulation on the many developmental transitions that do exist and to clear the way for an alternative viewpoint that emphasizes the similarities between developmental processes in different organisms.     

Taxonomic and sensory biases in the mate-choice literature: there are far too few studies of chemical and multimodal communication

The sexual selection literature has grown rapidly in recent years. In an effort to elucidate biases in the focus of current mate-choice research here, I review 297 studies among 230 species. Among taxa, studies of birds were most common (40% of all studies), with insects, fishes, and anurans less well represented (20%, 18%, 14%, respectively). All other taxa were poorly represented in the literature (<3%). Across sensory modalities, studies of visual and acoustic signals were most common (46%, 30%, respectively), with relatively few studies investigating chemical, tactile, and electrical signals in mate choice (3%, 3%, <1%, respectively). Most mate-choice studies of birds and fishes investigated visual signals, while the majority of insect and anuran studies investigated acoustic signals. While these associations may reflect biological realities—birds and anurans tend not to emphasize chemical cues in mate choice; electric communication may indeed be quite uncommon—they may also be grossly misleading: chemical cues are likely critical for mate choice in millions of insect species. Moreover, I suggest that the particularly high vulnerability of chemical communication networks to anthropogenic fouling should provide immediate motivation for many more studies of chemical signals in mate choice. Finally, I find that despite widespread acceptance that male displays are often comprised of multiple elements produced across sensory modalities, studies simultaneously investigating the use of multiple cues in mate choice are rare. While not exhaustive, this review identifies biases in the focus of mate-choice studies, and should serve to identify fruitful directions for future mate-choice research.     

Allocating individuals to avoid inbreeding in ex situ conservation plantations: so far, so good

The only cost-effective way to control inbreeding in ex situ forest tree plantations is often to allocate trees in such a way that the possibility of close relatives mating is small and, consequently, inbreeding does not increase too much over time. The classical permutated neighbourhood methods look for the configuration in which no ramets of the same genet are planted in the surroundings (neighbourhoods) of a particular tree but deny the influence of more distant trees. Another limitation of these methods is that they cannot incorporate any other genetic (e.g. kinship) or ecological (e.g. phenology) information. We have developed a new method based on the minimisation of the global probability of generating inbred offspring for the whole population. Improvements of this method from the classical ones are: (i) it takes into account all the trees (whether near or far) and not only the neighbours; (ii) different pollen dispersal functions can be implemented, fitting the particularities of each species and population; (iii) it allows for the integration of all available information about the genetic relationship between trees; and (iv) it is flexible allowing for particular crosses to be banned or encouraged. The novel method showed a better performance than classical ones both for simulated data and a case study under a broad range of scenarios. Magnitude of the benefit depends on the actual and assumed parameters for the pollen dispersal function and the relationship between trees, but even in the simple case where only clone identity is considered some advantage can be obtained by implementing the new algorithm.