Changing environmental gradients over forty years alter ecomorphological variation in Guadalupe Bass Micropterus treculii throughout a river basin

Natural history collections are critical resources for contemporary and future studies of urban evolution

Urban environments are among the fastest changing habitats on the planet, and this change has evolutionary implications for the organisms inhabiting them. Herein, we demonstrate that natural history collections are critical resources for urban evolution studies. The specimens housed in these collections provide great potential for diverse types of urban evolution research, and strategic deposition of specimens and other materials from contemporary studies will determine the resources and research questions available to future urban evolutionary biologists. As natural history collections are windows into the past, they provide a crucial historical timescale for urban evolution research. While the importance of museum collections for research is generally appreciated, their utility in the study of urban evolution has not been explicitly evaluated. Here, we: (a) demonstrate that museum collections can greatly enhance urban evolution studies, (b) review patterns of specimen use and deposition in the urban evolution literature, (c) analyze how urban versus rural and native versus nonnative vertebrate species are being deposited in museum collections, and (d) make recommendations to researchers, museum professionals, scientific journal editors, funding agencies, permitting agencies, and professional societies to improve archiving policies. Our analyses of recent urban evolution studies reveal that museum specimens can be used for diverse research questions, but they are used infrequently. Further, although nearly all studies we analyzed generated resources that could be deposited in natural history collections (e.g., collected specimens), a minority (12%) of studies actually did so. Depositing such resources in collections is crucial to allow the scientific community to verify, replicate, and/or re-visit prior research. Therefore, to ensure that adequate museum resources are available for future urban evolutionary biology research, the research community-from practicing biologists to funding agencies and professional societies-must make adjustments that prioritize the collection and deposition of urban specimens.

Adaptive Evolution in Cities: Progress and Misconceptions

Current narratives suggest that urban adaptation - the adaptive evolution of organisms to cities - is pervasive across taxa and cities. However, in reviewing hundreds of studies, we find only six comprehensive examples of species adaptively evolving to urbanization. We discuss the utility and shortcomings of methods for studying urban adaptation. We then review diverse systems offering preliminary evidence for urban adaptation and outline a research program for advancing its study. Urban environments constitute diverse, interacting selective agents that test the limits of adaptation. Understanding urban adaptation therefore offers unique opportunities for addressing fundamental questions in evolutionary biology and for better conserving biodiversity in cities. However, capitalizing on these opportunities requires appropriate research methods and dissemination of accurate narratives.

Superfrogs in the city: 150 year impact of urbanization and agriculture on the European Common Frog

Despite growing pressure on biodiversity deriving from increasing anthropogenic disturbances, some species successfully persist in altered ecosystems. However, these species' characteristics and thresholds, as well as the environmental frame behind that process are usually unknown. We collected data on body size, fluctuating asymmetry (FA), as well as nitrogen stable isotopes (δ¹⁵ N) from museum specimens of the European Common Frog, Rana temporaria, all originating from the Berlin-Brandenburg area, Germany, in order to test: (a) if specimens have changed over the last 150 years (1868-2018); and (b) if changes could be attributed to increasing urbanization and agricultural intensity. We detected that after the Second World War, frogs were larger than in pre-war Berlin. In rural Brandenburg, we observed no such size change. FA analysis revealed a similar tendency with lower levels in Berlin after the war and higher levels in Brandenburg. Enrichment of δ¹⁵ N decreased over time in both regions but was generally higher and less variable in sites with agricultural land use. Frogs thus seem to encounter favorable habitat conditions after pollution in postwar Berlin improved, but no such tendencies were observable in the predominantly agricultural landscape of Brandenburg. Urbanization, characterized by the proportion of built-up area, was not the main associated factor for the observed trait changes. However, we detected a relationship with the amount of urban greenspace. Our study exemplifies that increasing urbanization must not necessarily worsen conditions for species living in urban habitats. The Berlin example demonstrates that public parks and other urban greenspaces have the potential to serve as suitable refuges for some species. These findings underline the urgency of establishing, maintaining, and connecting such habitats, and generally consider their importance for future urban planning.

Functional response of fish communities in a multistressed freshwater world

Freshwater fish communities are impacted by multiple pressures, determining loss of functional diversity and redundancy. Our aim was to disentangle the roles and relevancies of different pressures in shaping fish communities in small streams of the Po plain (North Italy). Long term trend (1998-2018) of functional diversity of 31 fish communities was assessed and modeled in respect to three potential pressures: temperature increase, intensity of exotic fish invasion, and habitat quality degradation. Ecological traits mostly influenced by the pressures were also identified. Reduction of functional richness mostly due to local extinction or contraction of cold adapted predators, such as salmonids, was linked to increasing temperatures. Warming probably also led to a shift of generalist and dominant species, which became more abundant in streams hosting mixed communities of salmonids and cyprinids, and determined the increase of functional dispersion and uniqueness. Reduction of functional redundancy and increasing functional dispersion were both also related to the introduction of new ecological traits brought by expanding exotic species. Low functional overlap was found among native and exotic species, indicating that the invasion process was mainly controlled by competitive interactions and/or resource opportunism. Functional response to habitat quality was not clearly evident. In conclusion, the impact of temperature increase and exotic species on fish functional diversity was effective, idiosyncratic and mediated by the scale of analysis and by the intensity of pressures.

Effect of preservation on fish morphology over time: Implications for morphological studies

It has long been recognized that the process of preserving biological specimens results in alterations of body shape, though detailed studies examining the degree to which morphological changes occur throughout the preservation process are lacking. We utilize geometric morphometric analyses, an increasingly common tool for examining shape variation in a wide variety of biological disciplines, to examine the effects of formalin and ethanol preservation on the body shape of 10 freshwater fish species over time: from fresh specimens to eight weeks after preservation. We found significant changes in body shape among fresh and formalin fixed specimens. Furthermore, changes in body shape continue to occur after subsequent ethanol preservation. Two fish species collected at multiple localities show significant morphological differences for a limited number of morphometric characters. However, the significance, or lack thereof, often changed inconsistently from one stage of preservation to another. We conclude that morphometric analyses would ideally be performed on fresh specimens. However, recognizing that this is not always feasible, it is important to be aware of the morphometric changes that can occur during preservation.