Contemporary changes in phenotypic variation, and the potential consequences for eco-evolutionary dynamics

Most studies assessing rates of phenotypic change focus on population mean trait values, whereas a largely overlooked additional component is changes in population trait variation. Theoretically, eco-evolutionary dynamics mediated by such changes in trait variation could be as important as those mediated by changes in trait means. To date, however, no study has comprehensively summarised how phenotypic variation is changing in contemporary populations. Here, we explore four questions using a large database: How do changes in trait variances compare to changes in trait means? Do different human disturbances have different effects on trait variance? Do different trait types have different effects on changes in trait variance? Do studies that established a genetic basis for trait change show different patterns from those that did not? We find that changes in variation are typically small; yet we also see some very large changes associated with particular disturbances or trait types. We close by interpreting and discussing the implications of our findings in the context of eco-evolutionary studies.

Phenotypic variation in urban environments: mechanisms and implications

In the past decade, numerous studies have explored how urbanisation affects the mean phenotypes of populations, but it remains unknown how urbanisation impacts phenotypic variation, a key target of selection that shapes, and is shaped by, eco-evolutionary processes. Our review suggests that urbanisation may often increase intraspecific phenotypic variation through several processes; a conclusion aligned with results from our illustrative analysis on tit morphology across 13 European city/forest population pairs. Urban-driven changes in phenotypic variation will have immense implications for urban populations and communities, particularly through urbanisation's effects on individual fitness, species interactions, and conservation. We call here for studies that incorporate phenotypic variation in urban eco-evolutionary research alongside advances in theory.

Ontogenetic diversity buffers communities against consequences of species loss

Biodiversity can be measured at multiple organizational scales. While traditional studies have focused at taxonomic diversity, recent studies have emphasized the ecological importance of diversity within populations. However, it is unclear how these different scales of diversity interact to determine the consequence of species loss. Here we asked how predator diversity and presence of ontogenetic diversity within predator populations influences community structure. Ontogenetic diversity arises from shifts in the traits and ecology of individuals during ontogeny and it is one of the biggest sources of intraspecific diversity. However, whether it dampens or strengthens the negative consequences of with species loss is poorly understood. To study the interaction of species diversity and ontogenetic diversity, we experimentally manipulated predator species diversity and diversity of developmental stages within focal predator species and analysed their joint effect on predator and prey survival, biomass and prey community structure in experimental pond systems. While individual effects of ontogenetic diversity were often species specific, losing predator species from the community often had a much smaller or no effect on prey survival, biomass or community structure when all predator populations had high ontogenetic diversity. Thus, ontogenetic diversity within populations buffered against some of the consequences of biodiversity loss at higher organizational levels. Because the experiment controlled mean per capita size and biomass across structured versus unstructured populations, this pattern was not driven by differences in biomass of predators. Instead, results suggest that effects were driven by changes in the functional roles and indirect interactions across and within species. This indicates that even if all environmental conditions are similar, differences in the intrinsic structure of populations can modify the consequences of biodiversity loss. Together, these results revealed the importance of ontogenetic diversity within species for strengthening the resilience of natural communities to consequences of biodiversity loss and emphasize the need to integrate biodiversity patterns across organizational scales.

Changes in the Fluctuating Asymmetry of the Leaf and Reproductive Capacity of Betula pendula Roth Reflect Pessimization of Anthropogenically Transformed Environment

We have estimated the reproductive capacity of Betulapendula Roth and its relationship with an integrated measure of developmental stability, i.e., fluctuating asymmetry (FA) of the leaf. On the territory of a city with moderate anthropogenic pollution, a change has been detected in the integrated fluctuating asymmetry (IFA) of the morphology of the female reproductive sphere and reproductive capacity of Betula pendula. In conditions of anthropogenic stress, the birch is observed to produce a large yield of fruits annually, which is not subject to year-to-year fluctuations. Morphological variety of size and shape of fruit-producing organs increases along the gradient of industrial and transport pollution; part of morphotypes of infructescences and seeds is characterized by lowered or zero capacity for reproduction determined by seed quality (germination energy and germination capacity). The statistical data processing involved correlation, Shapiro–Wilk test, Levene’s test, factorial ANOVA, Scheffe test, Kruskal–Wallis ANOVA, Mann–Whitney test, χ2 method. Analysis of IFA has allowed us to reasonably well assess the state of the plant organism and to characterize environmental quality. A negative correlation between IFA and quantitative parameters of the functions of the reproductive sphere of B. pendula (infructescence diameter, seed quality) has been found, and positive correlation with qualitative parameters (the number of morphs of infructescences and seeds, the share of rare morphs of infructescences). Pessimization of urban environment creates the conditions for an increase in the share of defective infructescences and non-germinating seeds; a compensatory mechanism for this is an increase in reproductive effort of B. pendula. The consistency of responses in the vegetative and reproductive spheres reflects the disturbances in developmental stability of plants in urban communities.

The Evolution of 'Ecological Release' into the 21st Century

Ecological release, originally conceived as niche expansion following a reduction in interspecific competition, may prompt invasion success, morphological evolution, speciation, and other ecological and evolutionary outcomes. However, the concept has not been recently reviewed. Here, we trace the study of 'ecological release' from its inception through the present day and find that current definitions are broad and highly varied. Viewing this development as a potential impediment to clear communication and hypothesis testing, we suggest a consensus definition for ecological release: niche expansions and shifts when a constraining interspecific interaction is reduced or removed. In rationalizing this definition, we highlight the various ways ecological release can unfold and address its potential evolutionary consequences.

Phylogeny, taxonomic reassessment and ‘ecomorph’ relationship of the Orientallactaga sibirica complex (Rodentia: Dipodidae: Allactaginae)

The ecological gradient–morphological variation (‘ecomorph’) relationship has long interested ecologists and evolutionary biologists, but it is applied far less frequently than genetic differentiation in cryptic species detection and species identification. With integrative methods, we revise taxonomic uncertainties in the Orientallactaga sibirica complex (OSC), with 298 sequence specimens and 469 voucher specimens from 138 localities covering nearly the entire distribution of the OSC. Phylogenetic relationships are assessed by Bayesian inference and maximum likelihood using two mitochondrial and nine nuclear genes. We use species-delimitation approaches to divide and validate the ‘candidate species’. We evaluate correlations between ecological divergence and phylogenetic splits, and visualize geographical patterns of morphological variation. The OSC is divided into four phylogenetic groups, the Ognevi, Altay, Bogda and Sibirica groups, and the OSC exhibits a significant ecomorph relationship and ecological divergence pattern. Morphological variations not only follow the general regularity under a large gradient of ecological factors, but are also closely related to the local environment/habitat. We suggest considering the comprehensive ecomorph relationship to identify species. Molecular analyses reveal that the OSC more easily forms deeply divergent lineages in the foothills and this differentiation depth may be related to mountain system size.