Guillaume Papuga

Abstract

Aims

Glacial retreat at the end of the Pleistocene epoch opened vast expanses of emergent habitat in the northern hemisphere that were colonized by opportunistic taxa. However, species that undergo post-glacial expansion may have originated from one or several glacial refugia. We inferred the post-glacial expansion history of the Eastern Red-backed Salamander (Plethodon cinereus), a fully terrestrial species with a vast distribution despite severe dispersal limitations. Previous studies indicated populations south of the glacial boundary at the eastern and western limits of the distribution were closely related, suggesting either multiple refugia or an extraordinary post-glacial expansion event.

Location

Eastern North America.

Taxon

Plethodon cinereus (Green, 1818), Caudata: Plethodontidae.

Methods

We collected ddRAD-seq data from 106 individuals throughout the distribution of P. cinereus. We estimated phylogeographic structure, including finer-scale structure among the post-glacial populations. To test the origins and routes of colonization, we used ecological niche modelling, population trees and analyses of directional range expansion.

Results

Analyses supported our hypothesis of a southeastern glacial refugium, with northward expansion along the Eastern Seaboard prior to westward invasion into the Great Lakes region, including southwestern expansion into unglaciated areas at the western end of the distribution. However, a distinct subgroup in the northwestern portion of the range raises the possibility of a second refugium near the ice-free Driftless Area.

Main Conclusions

Based on our results, we hypothesize a southeastern refugium from which most of today's northern populations undertook extensive post-glacial colonization. Our results indicate a geographically non-linear colonization history for P. cinereus.

Abstract

Two alien species in Europe, Impatiens glandulifera and I. balfourii, are closely related, have similar growth rates and reproductive capacities, and are very attractive to pollinators. Nevertheless, only I. glandulifera is a highly invasive alien species in Europe, while I. balfourii is non-invasive. We assumed that the varying levels of invasiveness are driven by differences in the floating ability of their seeds, which may determine the invasion success of riparian alien plants, such as the Impatiens species. By mimicking two types of aquatic conditions, we determined seed floating ability for each species from younger and older populations. We also analyzed four seed traits: seed viability, surface, shape and coat structure. Seeds of the non-invasive I. balfourii float less well than seeds of the invasive I. glandulifera. We also found that the seeds of I. balfourii from the younger population have a higher floating ability in comparison with that of the seeds from the older population. The results for I. glandulifera were the opposite, with decreased floating ability in the younger population. These differences were associated with seed surface, shape and coat structure. These results indicate that the floating ability of I. balfourii seeds may increase over time following its introduction into a given area, while in the case of I. glandulifera, this ability may gradually decrease. Therefore, the former species, currently regarded as a poor disperser, has the potential to become invasive in the future, whereas the latter does not seem to benefit from further investments in the floating ability of its seeds.

Membrane protein complexes are fundamental in many biological processes. Nevertheless, their structural details are difficult to resolve, especially in their cellular milieu. The combination of top-down (TD) mass spectrometry (MS), profiling post-translational modifications (PTMs) and sequence variants, and crosslinking (XL) MS for uncovering the spatial organization and interactors of protein complexes, provides a novel approach to study the structural behavior of protein complexes in their close to native environment.