Benjamin Carroll Tharp

Future climate change will have severe impacts on the geographic distribution of species, likely leading to shifts in their suitable habitat and eventually to the extinction of some species whose distribution areas are restricted. However, some species may respond differently to climate change. In this study we model the current and future potential habitats of three Juniperus species with different population trends: J. jaliscana , J. monticola and J. pinchotii . Occurrence records were collected across their distribution, combined with environmental and topographical variables to generate a MaxEnt model of the potential distributions in the years 2050 and 2070. The most important environmental variables were precipitation of wettest quarter for J. jaliscana , maximum temperature of warmest month for J. monticola , and mean temperature of coldest quarter for J. pinchotii . Our results showed that the habitat suitability of these three Juniperus species decreased overall by more than 50% under the climate change scenarios. These findings contributed to a better understanding of the impacts of climate change on ecological distribution of these species and could inform decisions regarding to their conservation, and management, and sustainable use strategies, as well as to implement active ex situ conservation strategies.

Premise Glacial/interglacial cycles and topographic complexity are both considered to have shaped today's diverse phylogeographic patterns of taxa from unglaciated eastern North America (ENA). However, few studies have focused on the phylogeography and population dynamics of wide‐ranging ENA herbaceous species occurring in forest understory habitat. We examined the phylogeographic pattern and evolutionary history of Podophyllum peltatum L., a widely distributed herb inhabiting deciduous forests of ENA.MethodsUsing chloroplast DNA (cpDNA) sequences and nuclear microsatellite loci, we investigated the population structure and genetic diversity of the species. Molecular dating, demographic history analyses, and ecological niche modeling were also performed to illustrate the phylogeographic patterns.ResultsOur cpDNA results identified three main groups that are largely congruent with boundaries along the Appalachian Mountains and the Mississippi River, two major geographic barriers in ENA. Populations located to the east of the Appalachians and along the central Appalachians exhibited relatively higher levels of genetic diversity. Extant lineages may have diverged during the late Miocene, and range expansions of different groups may have happened during the Pleistocene glacial/interglacial cycles.ConclusionsOur findings indicate that geographic barriers may have started to facilitate the population divergence in P. peltatum before the Pleistocene. Persistence in multiple refugia, including areas around the central Appalachians during the Quaternary glacial period, and subsequent expansions under hospitable climatic condition, especially westward expansion, are likely responsible for the species’ contemporary genetic structure and phylogeographic pattern.

Understanding how, and from where, invasive species were introduced is critical for revealing the invasive mechanism, explaining the invasion success, and providing crucial insights for effective management. Here, we combined a phylogeographic approach with ecological niche modeling comparisons to elucidate the introduction mode and source of Nicotiana glauca , a native South American species that is now invasive worldwide. We tested three different scenarios based on the invasion source—random native, restricted native, and bridgehead invasive—considering genetic diversity and climatic niche comparisons among native and invaded areas. We found three genetic lineages geographically and climatically differentiated within the native range. Only one of these genetic groups contained the invasive haplotypes, but showed no climatic niche overlap with any invaded area. Conversely, one invaded area located in western South America, with more genetic diversity than other invaded areas but less than the native range, showed climatic niche overlap with almost all other invaded areas worldwide. These findings indicate that N. glauca first likely invaded the southernmost areas beyond its native range, forming a bridgehead invasive source, from which the species subsequently invaded other regions around the world. Invasiveness would have been fostered by changes in the environmental preferences of the species in the bridgehead area, towards drier, colder and less seasonal climates, becoming the actual source of invasion to areas climatically similar throughout the world. The fine scale resolution analyses combining genetic and climatic approaches within the native range were essential to illuminating the introduction scenario of this invasive species.

Ambrosia trifida L. (Asteraceae) – североамериканское однолетнее растение, включенное в перечень карантинных объектов в Европе, в том числе в Российской Федерации и сопредельных странах. Об- суждаются результаты исследований 2017–2021 гг. по выявлению современного распространения и особенностей натурализации этого вида на европейской части России. Центрами массовой натура- лизации А. trifida на исследуемой территории являются Заволжье (Самарская область, юг Татарста- на), Предуралье (Оренбургская область, Башкортостан), Предволжье (запад Саратовской области), Хоперско-Бузулукская равнина (северо-запад Волгоградской области), юго-запад Окско-Донского плоскоместья и Калачская возвышенность (центр и юг Воронежской области). Анклавы в виде на- турализовавшихся популяций отмечены в Брянской и Владимирской областях, а также в городах Казань и Уфа. В дальнейшем можно ожидать распространение A. trifida на большой части европей- ской территории России.

The identification of future refugia for endangered species from the effects of global warming is crucial for improving their conservation. Because climate-driven shifts in ranges and local extinctions can result in a spatial mismatch with their symbiotic organisms, however, it is important to incorporate in niche modelling the ecological partners of the species studied. The aim of this study was to evaluate the effect of climate change on the distribution of suitable niches for the ghost orchid ( Dendrophylax lindenii ) and its phorophytes and pollinators. Thus, its five species of host trees and three pollen vectors were included in the analysis. Climatic preferences of all the species studied were evaluated. The modelling was based on three different climate change projections and four Shared Socio-economic Pathway trajectories. All the species analysed are characterized by narrow temperature tolerances, which with global warming are likely to result in local extinctions and range shifts. D. lindenii is likely to be subjected to a significant loss of suitable niches, but within a reduced geographical range, both host trees and pollen vectors will be available in the future. Future conservation of this orchid should focus on areas that are likely be suitable for it and its ecological partners.

The expansion of many wetland species is a function of both clonal propagation and sexual reproduction. The production of ramets through clonal propagation enables plants to move and occupy space near parent ramets, while seeds produced by sexual reproduction enable species to disperse and colonize open or disturbed sites both near and far from parents. The balance between clonal propagation and sexual reproduction is known to vary with plant density but few studies have focused on reproductive allocation with density changes in response to global climate change. Schoenoplectus americanus is a widespread clonal wetland species in North America and a dominant species in Chesapeake Bay brackish tidal wetlands. Long-term experiments on responses of S . americanus to global change provided the opportunity to compare the two modes of propagation under different treatments. Seed production increased with increasing shoot density, supporting the hypothesis that factors causing increased clonal reproduction (e.g., higher shoot density) stimulate sexual reproduction and dispersal of genets. The increase in allocation to sexual reproduction was mainly the result of an increase in the number of ramets that flowered and not an increase in the number of seeds per reproductive shoot, or the ratio between the number of flowers produced per inflorescence and the number of flowers that developed into seeds. Seed production increased in response to increasing temperatures and decreased or did not change in response to increased CO 2 or nitrogen. Results from this comparative study demonstrate that plant responses to global change treatments affect resource allocation and can alter the ability of species to produce seeds.

Invasive plant species cause massive ecosystem damage globally yet represent powerful case studies in population genetics and rapid adaptation to new habitats. The availability of digitized herbarium collections data, and the ubiquity of invasive species across the landscape make them highly accessible for studies of invasion history and population dynamics associated with their introduction, establishment, spread, and ecological interactions. Here we focus on Lonicera japonica, one of the most damaging invasive vine species in North America. We leveraged digitized collections data and contemporary field collections to reconstruct the invasion history and characterize patterns of genomic variation in the eastern USA, using a straightforward method for generating nucleotide polymorphism data and a recently published, chromosome-level genome for the species. We found an overall lack of population structure among sites in northern West Virginia, USA, as well as across sites in the central and eastern USA. Heterozygosity and population differentiation were both low based on FST analysis of molecular variance, principal components analysis, and cluster-based analyses. We also found evidence of high inbreeding coefficients and significant linkage disequilibrium, in line with the ability of this otherwise outcrossing, perennial species to propagate vegetatively. Our findings corroborate earlier studies based on allozyme data, and suggest that intentional, human-assisted spread explains the lack of population structure, as this species was planted for erosion control and as an ornamental, escaping cultivation repeatedly across the USA.

Predicting the likelihood that non-native species will be introduced into new areas remains one of conservation’s greatest challenges and, consequently, it is necessary to adopt adequate management measures to mitigate the effects of future biological invasions. At present, not much information is available on the areas in which non-native aquatic plant species could establish themselves in the Iberian Peninsula. Species distribution models were used to predict the potential invasion risk of (1) non-native aquatic plant species already established in the peninsula (32 species) and (2) those with the potential to invade the peninsula (40 species). The results revealed that the Iberian Peninsula contains a number of areas capable of hosting non-native aquatic plant species. Areas under anthropogenic pressure are at the greatest risk of invasion, and the variable most related to invasion risk is temperature. The results of this work were used to create the Invasion Risk Atlas for Alien Aquatic Plants in the Iberian Peninsula, a novel online resource that provides information about the potential distribution of non-native aquatic plant species. The atlas and this article are intended to serve as reference tools for the development of public policies, management regimes, and control strategies aimed at the prevention, mitigation, and eradication of non-native aquatic plant species.

Premise: Cacti are characteristic elements of the Neotropical flora and of major interest for biogeographic, evolutionary, and ecological studies. Here we test global biogeographic boundaries for Neotropical Cactaceae using specimen‐based occurrences coupled with data from visual observations, as a means to tackle the known collection biases in the family.MethodsSpecies richness and record density were assessed for preserved specimens and human observations and a bioregional scheme tailored to Cactaceae was produced using the interactive web application Infomap Bioregions based on data from 261,272 point records cleaned through automated and manual steps.Key ResultsWe find that areas in Mexico and southwestern USA, Eastern Brazil and along the Andean region have the greatest density of records and the highest species richness. Human observations complement information from preserved specimens substantially, especially along the Andes. We propose 24 cacti bioregions, among which the most species‐rich are: northern Mexico/southwestern USA, central Mexico, southern central Mexico, Central America, Mexican Pacific coast, central and southern Andes, northwestern Mexico/extreme southwestern USA, southwestern Bolivia, northeastern Brazil, Mexico/Baja California.ConclusionsThe bioregionalization proposed shows biogeographical boundaries specific to cacti, and can thereby aid further evolutionary, biogeographic, and ecological studies by providing a validated framework for further analyses. This classification builds upon, and is distinctive from, other expert‐derived regionalization schemes for other taxa. Our results showcase how observation data, including citizen‐science records, can complement traditional specimen‐based data for biogeographic research, particularly for taxa with specific specimen collection and preservation challenges and those that are threatened or internationally protected.This article is protected by copyright. All rights reserved.

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