Copper Content and Resistance Mechanisms in the Terrestrial Moss Ptychostomum capillare: A Case Study in an Abandoned Copper Mine in Central Spain.

We present a case study on the tissue absorption of copper of a widely distributed moss species, Ptychostomum capillare in the polluted soil of an abandoned copper mine in central Spain. We studied the soil properties in a copper soil pollution gradient and sampled the moss tufts growing on them in four plots with contrasted soil copper levels. We determined the copper content in the soil and in the moss tissues. On these moss samples, we also performed histochemical tests and X-ray dispersive spectrometry coupled with scanning electron microscopy (SEM-EDX), both in untreated shoots and in samples where surface waxes were removed. We checked the behavior of this species using a metallophillous moss, Scopelophila cataractae, for comparative purposes. Copper contents in P. capillare seem to depend more on available, rather than total soil copper contents. Our results indicate that this moss is able to concentrate 12-fold the available soil copper in soil with low available copper content, whereas in the most polluted soil the concentration of Cu in the moss was only half those levels. Both histochemical and SEM-EDX tests show no surface copper in the mosses from the least polluted plot, whereas in samples from the soil with highest copper content, the removal of surface waxes also reduces or removes copper from the moss shoots. Our observations point at a mixed strategy in P. capillare in this copper mine, with metal accumulation behavior in the lowest Cu plot, and an exclusion mechanism involving wax-like substances acting as a barrier in the most polluted plots. These distortions impede the estimation of environmental levels and thus compromise the value of this moss in biomonitoring. We highlight the need of extending these studies to other moss species, especially those used in biomonitoring programs.

Phylogenetic and paleobotanical evidence for late Miocene diversification of the Tertiary subtropical lineage of ivies (Hedera L., Araliaceae).

BACKGROUND: Hedera (ivies) is one of the few temperate genera of the primarily tropical Asian Palmate group of the Araliaceae, which extends its range out of Asia to Europe and the Mediterranean basin. Phylogenetic and phylogeographic results suggested Asia as the center of origin and the western Mediterranean region as one of the secondary centers of diversification. The bird-dispersed fleshy fruits of ivies suggest frequent dispersal over long distances (e.g. Macaronesian archipelagos), although reducing the impact of geographic barriers to gene flow in mainland species. Genetic isolation associated with geographic barriers and independent polyploidization events have been postulated as the main driving forces of diversification. In this study we aim to evaluate past and present diversification patterns in Hedera within a geographic and temporal framework to clarify the biogeographic history of the genus. RESULTS: Phylogenetic (biogeographic, time divergence and diversification) and phylogeographic (coalescence) analyses using four DNA regions (nrITS, trnH-psbA, trnT-trnL, rpl32) revealed a complex spatial pattern of lineage divergence. Scarce geographic limitation to gene flow and limited diversification are observed during the early-mid Miocene, followed by a diversification rate increase related to geographic divergence from the Tortonian/Messinian. Genetic and palaeobotanical evidence points the origin of the Hedera clade in Asia, followed by a gradual E-W Asian extinction and the progressive E-W Mediterranean colonization. The temporal framework for the E Asia - W Mediterranean westward colonization herein reported is congruent with the fossil record. Subsequent range expansion in Europe and back colonization to Asia is also inferred. Uneven diversification among geographic areas occurred from the Tortonian/Messinian onwards with limited diversification in the newly colonized European and Asian regions. Eastern and western Mediterranean regions acted as refugia for Miocene and post-Miocene lineages, with a similar role as consecutive centers of centrifugal dispersal (including islands) and speciation. CONCLUSIONS: The Miocene Asian extinction and European survival of Hedera question the general pattern of Tertiary regional extinction of temperate angiosperms in Europe while they survived in Asia. The Tortonian/Messinian diversification increase of ivies in the Mediterranean challenges the idea that this aridity period was responsible for the extinction of the Mediterranean subtropical Tertiary flora. Differential responses of Hedera to geographic barriers throughout its evolutionary history, linked to spatial isolation related to historical geologic and climatic constraints may have shaped diversification of ivies in concert with recurrent polyploidy.

Downed woody debris carbon emissions in a European temperate virgin forest as driven by species, decay classes, diameter and microclimate.

Downed woody debris (DWD) plays an important role as regulator of nutrient and carbon (C) cycling in forests, accounting for up to the 20 % of the total C stocks in primary forests. DWD persistence is highly influenced by microbial decomposition, which is determined by various environmental factors, including fluctuations in temperature and moisture, as well as in intrinsic DWD properties determined by species, diameter, or decay classes (DCs). The relative importance of these different drivers, as well as their interactions, remains largely unknown. Moreover, the importance of DWD for C cycling in virgin forests remains poorly understood, due to their scarcity and poor accessibility. To address this research gap, we conducted a study on DWD respiration (RDWD), in a temperate virgin forest dominated by European beech and silver fir. Our investigation analysed the correlation between RDWD of these two dominant tree species and the seasonal changes in climate (temperature and moisture), considering other intrinsic DWD traits such as DCs (1, 2 and 4) and diameters (1, 10 and 25 cm). As anticipated, RDWD (normalized per gram of dry DWD) increased with air temperature. Surprisingly, DWD diameter also had a strong positive correlation with RDWD. Nonetheless, the sensitivity to both variables and other intrinsic traits (DC and density) was greatly modulated by the species. On the contrary, water content, which exhibited a considerable spatial variation, had an overall negative effect on RDWD. Virgin forests are generally seen as ineffective C sinks due to their lack of net productivity and high respiration and nutrient turnover. However, the rates of RDWD in this virgin forest were significantly lower than those previously estimated for managed forests. This suggests that DWD in virgin forests may be buffering forest CO2 emissions to the atmosphere more than previously thought.