Urban Environments Aid Invasion of Brown Widows (Theridiidae: Latrodectus geometricus) in North America, Constraining Regions of Overlap and Mitigating Potential Impact on Native Widows

Urbanization is a major cause of biotic homogenization and habitat fragmentation for native communities. However, the role of urbanization on the success of biological invasions on a continental scale has yet to be explored. Urbanization may facilitate the establishment success of invasive species by minimizing niche differentiation between native and invaded ranges. In such cases, we might expect anthropogenic variables to have stronger influence on the geographic distribution of invasive compared to native populations. In this study, we use ecological niche modeling to define the distribution of non-native brown widow spider (Latrodectus geometricus) and three native black widows (L. hespersus, L. mactans, L. variolus) in North America and gauge the importance of urbanization on the geographic ranges of widows at a continental scale. We also quantify the geographic overlap of L. geometricus with each native widow to assess potential species and regions at risk of ecological impact. Consistent with our hypothesis, we find that the distribution of L. geometricus is strongly constrained to urban environments, while native widow distributions are more strongly driven by climatic factors. These results show that urbanization plays a significant role in facilitating the success of invasion, weakening the significance of climate on the realized niche in its invaded range.This research was supported by funding from the OU Graduate Adams Research Scholarship. Open Access fees paid for in whole or in part by the University of Oklahoma Libraries.Ye

Population demography maintains biogeographic boundaries

Funding Information: This manuscript was the result of a working group funded by a Quebec Center for Biodiversity Science grant to JPL and KEM. We thank Ben Holt and the Center for Macroecology, Evolution and Climate for sharing their map of mammal biogeographic regions. We thank Laura Pollock, Isaac Eckert and Federico Riva for comments on the written document and discussion of the topic. We also thank Anna Hargreaves, Brian Leung, Jonathan Belmaker, Lilian Sales and Shahar Chaikin for additional discussions. We are also grateful to the authors whose work provided the raw data for this synthesis. KEM is supported by a NSERC Discovery Grant. GM and JPL were supported by the Concordia University Research Chair in Biodiversity and Ecosystem Functioning. GM is additionally supported by a Concordia Graduate Fellowship. CS and CJG were supported by a Natural Sciences and Engineering Research Council of Canada Discovery Grant to CJG. CS was also supported by a U. Manitoba Graduate Fellowship, and a U. Manitoba Graduate Enhancement of Tri‐council funding grant to CJG. The authors declare no conflict of interest.Peer reviewedPostprin

Niche dynamics of Palaeolithic modern humans during the settlement of the Palaearctic

Aim During the Late Pleistocene (c. 126–10 ka), modern humans (Homo sapiens) expanded their geographical range across Eurasia and eventually colonized the Americas. Although the routes by which they migrated have been intensively analysed, the dynamics of their realized climatic niche are still largely unknown. We assess temporal changes in the climatic niche of modern humans, the geographical distribution of their climatic niche and whether niche dynamics correlate with the magnitude of climate change and cultural advances, between 46 and 11 ka. Location Palaearctic. Methods Using the radiocarbon dated archaeological record and spatial palaeoclimatic simulations, we quantify different parameters of the realized climatic niche of modern humans (niche overlap, niche breadth and climatic marginality) between consecutive 1000–2000 year intervals. Moreover, using climate envelope models, we map the potential distributions of modern humans for each time interval and identify the regions that remained more climatically suitable and stable for modern humans through time. Results Between 46 and 22 ka the climatic niche of modern humans expanded, including periods of intense growth in niche breadth at 40 and 30 ka. Changes in seasonal water availability and technological innovations partly correlate with dynamics in niche parameters. We document a persistent climatically suitable mid-latitude belt in south Siberia linking western Europe to the Far East that may have facilitated human migration, and a potential climatic refugium in Beringia. Main conclusions The climatic niche of modern humans changed across the Late Pleistocene, as the result of both climatic and cultural changes. These populations of hunter-gatherers occupied novel climatic conditions but also remained in previously occupied areas under changing climates during the settlement of the Palaearctic. Our approach can provide clues as to where early modern humans may have overlapped in geographical and environmental space with Neanderthals or Denisovans, as evidenced by their contribution to the genetic heritage of some current population

Family shapes microbiome differences in Oklahoma salamanders

IntroductionGiven the role of microbiomes in promoting host health and homeostasis, understanding the factors shaping skin microbial communities in wild vertebrates has become increasingly important in conservation. This goal is even more pressing for amphibians, for which the skin has multiple critical functions, and pathogens currently decimating populations are linked to significant changes in skin microbiomes. However, because microbiomes are also shaped by environmental and ecological influences, as well as by host phylogeny, it is important to quantify these contributions to microbiome structure in the presence of infection.MethodsTo understand the joint influence of these diverse factors shaping microbiomes, we used 16S rRNA sequencing to characterize the skin microbial communities of six salamander species (families Plethodontidae and Salamandridae) found in Oklahoma and contrasted the effects of infection status, phylogeny, host ecology, and host environment (i.e., climate) on skin microbiomes.ResultsDifferences at the level of host family were the main factor influencing microbiome diversity; however, we did not detect a substantial phylogenetic signal. Instead, host ecology and environment were more important in driving microbiome differences among species and genera. Salamanders that tested positive for the skin fungal parasite Batrachochytrium dendrobatidis (Bd) also had slightly less diverse microbiomes than Bd-free animals, but no such differences were associated with the systemic pathogen ranavirus (RV).DiscussionTogether, these results indicate a nuanced relationship between the number and type of microbes present on salamander skin and the factors influencing them. By developing a baseline assessment of the microbiome diversity and richness present on the skin of these focal species, this work also provides a foundation for monitoring and evaluating changes in skin microbiomes as populations continue to experience stressors and diseases

Species-specific responses of Late Quaternary megafauna to climate and humans

Despite decades of research, the roles of climate and humans in driving the dramatic extinctions of large-bodied mammals during the Late Quaternary remain contentious. We use ancient DNA, species distribution models and the human fossil record to elucidate how climate and humans shaped the demographic history of woolly rhinoceros, woolly mammoth, wild horse, reindeer, bison and musk ox. We show that climate has been a major driver of population change over the past 50,000 years. However, each species responds differently to the effects of climatic shifts, habitat redistribution and human encroachment. Although climate change alone can explain the extinction of some species, such as Eurasian musk ox and woolly rhinoceros, a combination of climatic and anthropogenic effects appears to be responsible for the extinction of others, including Eurasian steppe bison and wild horse. We find no genetic signature or any distinctive range dynamics distinguishing extinct from surviving species, underscoring the challenges associated with predicting future responses of extant mammals to climate and human-mediated habitat change.This paper is in the memory of our friend and colleague Dr. Andrei Sher, who was a major contributor of this study. Dr Sher died unexpectedly, but his major contributions to the field of Quaternary science will be remembered and appreciated for many years to come. We are grateful to Dr. Adrian Lister and Dr. Tony Stuart for guides and discussions. Thanks to Tina B. Brandt, Dr. Bryan Hockett and Alice Telka for laboratory help and samples and to L. Malik R. Thrane for his work on the megafauna locality database. Data taken from the Stage 3 project was partly funded by Grant #F/757/A from the Leverhulme Trust, together with a grant from the McDonald Grants and Awards Fund. We acknowledge the Danish National Research Foundation, the Lundbeck Foundation, the Danish Council for Independent Research and the US National Science Foundation for financial suppor

Climatic niche overlap models reveal niche partitioning among black widow spiders and potential ecological impacts of invasive brown widows in North America

The introduction of new species can have unpredictable effects on native communities. Understanding the potential for competitive interactions between widow spiders (Theridiidae: Latrodectus), and how they may have shaped species’ geographic distributions, is critical for predicting the impacts of biological invasions in this historically cryptic group. North America is home to three native widows (L. hesperus, L. mactans, L. variolus) and one invasive widow (L. geometricus) with distributions that are at least partly sympatric. Given the relative novelty of L. geometricus in native communities as they expand their range, it is unclear if and how they share resources with their congeners, and competition for climatic resources (space) could result in ecological impacts to native widows. Here we aim to model niche differentiation and niche dynamics between native widows, that have coevolved over time, and between native and brown widows to assess the potential for ecological impact. We investigated the potential for climatic niche partitioning to shape sympatric geographic distributions of native widows compared to each other and to L. geometricus. We aggregated photographed occurrences from social media communities and online repositories to quantify climatic niche overlap for all four species on a continental scale, to assess niche dynamics among native species and between invasive and nativespecies. We found that native species had distributions that were more strongly partitioned, showing weaker niche overlap, except for the two eastern widows, which showed strong overlap and niche equivalency. Conversely, we found greater niche overlap between L. geometricus and native widows, possibly because it is too soon to see the effect of competition on species’ geographic distributions, or because differences in diet or partitioning of urban versus nonurban microhabitats promote coexistence