A central challenge in ecology and evolutionary biology is to understand how variation in abiotic and biotic factors combine to shape the distribution, abundance, and diversity of focal species. Environmental gradients, whether natural (e.g., latitude, elevation, ocean proximity) or anthropogenic (e.g., land use intensity, urbanization), provide compelling settings for addressing this challenge. However, not all organisms are amenable to the observational and experimental approaches required for untangling the factors that structure species along gradients. Here we highlight herbaceous plants in the genus Plantago as models for studying the ecology and evolution of species interactions along abiotic gradients. Plantago lanceolata and P. major are native to Europe and Asia but distributed globally, and are established models for studying population ecology and interactions with herbivores, pathogens, and soil microbes. Studying restricted range congeners in comparison to those cosmopolitan species can provide insight into abiotic and biotic determinants of range size and population structure. We highlight one such species, P. rugelii, which is endemic to eastern North America. We give an overview of literature on these focal Plantago species, and explain why they are logical candidates for studies of species interactions across environmental gradients. Finally, we emphasize collaborative and community science approaches that can facilitate such research, and note the amenability of Plantago for authentic research projects in science education.

We performed literature searches to quantify the number of published studies featuring each currently accepted Plantago species name, and to assess the relative number of those studies in ecology and evolutionary biology journals. On 19-20 February 2021, we queried the Web of Science Core Collection (Indexes: SCI-EXPANDED, SSCI, A&HCI, ESCI), all years, using search terms of this general format: "Plantago [species name]" OR ("Plantago" AND "P. [species name]"), for each of the 242 accepted Plantago species in the International Plant Names Index (IPNI 2021) plus two additional accepted species in the Integrated Taxonomic Information System (ITIS 2021) and three species names that are no longer accepted, but which we knew to be represented in the literature (Table S1). We retrieved the native range for each species from Plants of the World Online (POWO 2019; Table S1). For species with ten or more records returned, we then used the results analysis function in Web of Science to generate a list of records by subject category for each species, where subject categories are attributes of the journals in which the articles were published. For those species, we curated a list of the current geographic distribution and number of records in subject categories "Ecology", "Evolutionary Biology", and "Environmental Science" (Table S2). 

References

IPNI. 2021. International Plant Names Index. Published on the Internet http://www.ipni.org, The Royal Botanic Gardens, Kew, Harvard University Herbaria & Libraries and Australian National Botanic Gardens. Retrieved 19 February 2021.

ITIS. 2021. Integrated Taxonomic Information System, Published on the Internet http://www.itis.gov. Retrieved 19 February 2021.

POWO. 2019. Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; http://www.plantsoftheworldonline.org. Retrieved 19 February 2021.

Table S1. Native range and total number of Web of Science records returned for each of the 247 Plantago species names included in the literature search. Species names retrieved from POWO (http://powo.science.kew.org/) and ITIS (https://www.itis.gov/). Native range information is from https://npgsweb.ars-grin.gov/gringlobal/search, https://www.cabi.org/isc, and http://www.plantsoftheworldonline.org/.

Table S2. Native range, current distribution, and literature search results for the twenty-five Plantago species with the most Web of Science records (see Table S1 for the complete list of 247 species in the literature search). Species names retrieved from POWO (http://powo.science.kew.org/) and ITIS (https://www.itis.gov/). Native range information is from https://npgsweb.ars-grin.gov/gringlobal/search, https://www.cabi.org/isc, and http://www.plantsoftheworldonline.org/. Information on current distributions is from GBIF (https://www.gbif.org/) with "human observation" selected as the basis of record.