Glacial biodiversity of the southernmost glaciers of the European Alps(Clapier and Peirabroc,Italy)

We applied a multi-taxa approach integrating the co-occurrence of plants,ground beetles,spiders and springtails with soil parameters(temperatures and chemical characteristics)in order to describe the primary succession along two glacier forelands in the Maritime Alps(Italy),a hotspot of Mediterranean biodiversity.We compared these successions to those from Central Alps:Maritime glacier forelands markedly differ for their higher values of species richness and species turnover.Contrary to our expectation,Maritime glacier forelands follow a‘replacement change model’,like continental succession of Inner Alps and differently from other peripheral successions.We propose that the temperatures along these Mediterranean glacier forelands are warmer than those along other Alpine glacier forelands,which promote the faster species turnover.Furthermore,we found that early and mid successional stages of the investigated glaciers are richer in cold-adapted and endemic species than the later ones:we confirmed that the‘replacement change’model disadvantages pioneer,cold-adapted species.Given the overall correspondence among coldadapted and endemic species,the most threatened in this climate phase,our results raise new concerns about the extinction risk of these species.We also describe supraglacial habitat of Maritime glaciers demonstrating that supraglacial debris represents an environment decoupled from the regional climate and may have an important role as refugium for coldadapted and hygrophilous plant and animal species,whose survival can be threatened by climate change and by a rapid ecological succession in the adjacent forelands.

Microtubule Depolymerization Affects Endocytosis and Exocytosis in the Tip and Influences Endosome Movement in Tobacco Pollen Tubes

Polarized organization of the cytoplasm of growing pollen tubes is maintained by coordinated function of actin filaments （AFs） and microtubules （MTs）. AFs convey post-Golgi secretory vesicles to the tip where some fuse with specific domains of the plasma membrane （PM）. Secretory activity is balanced by PM retrieval that maintains cell mem- brane economy and regulates the polarized composition of the PM, by dividing lipids/proteins between the shank and the tip. Although AFs play a key role in PM internalization in the shank, the role of MTs in exo-endocytosis needs to be characterized. The present results show that integrity of the MT cytoskeleton is necessary to control exo-endocytosis events in the tip. MT polymerization plays a role in promoting PM invagination in the apex of tobacco pollen tubes since nocodazole affected PM internalization in the tip and subsequent migration of endocytic vesicles from the apex for degradation. MT depolymerization in the apex and shank was associated with misallocation of a significantly greater amount of internalized PM to the Golgi apparatus and its early recycling to the secretory pathway. Fluorescence Recovery After Photobleaching （FRAP） experiments also showed that MT depolymerization in the tip region influenced the rate of exocytosis in the central domain of the apical PM.

STORIA DEL GHIACCIAIO DEL TROBIO(Aipi Orobie,Bergamo)E COLONIZZAZIONE DELLA VEGETAZIONE NELLE AREE LIBERATE DOPO LA PICCOLA ETGLACIALE

RIASSUNTO-Nella presente nota viene esaminata la storia olocenica del Ghiacciaio del Trobio(AlpiOrobie)e la morfogenesi glaciale della valle omonima.Le evidenze geomorfologiche indicano che,duran-te l’Olocene,la lingua del ghiacciaio non ha mai superato i margini dell’anfiteatro deposto alla culmina-zione della Piccola Età Glaciale.All’inferno dell’anfiteatro sono stati individuati due sistemi morenici,deposti a seguito di due modeste avanzate alla fine del XIX secolo e intorno al 1920.La vegetazione pioniera è rappresentata da formazioni pioniere delle morene silicee(Androsacionalpinae Br.-Bl.et Jenny’26),arricchita da numerosi elementi basifili.In base ad un confronto con areeproglaciali situate alia stessa quota nelle Alpi,la dinamica vegetazionale nell’anfiteatro del Gleno apparelenta.Probabilmente ciò dipende dall’abbassamento dei piani altitudinali nelle Alpi Orobie e dall’esposi-zione sfavorevole dell’area in studio.History of the Trobio Glacier(Orobian Alps,Bergamo)and pioneering by vegetationin the areas cleared after Little Ice Age.The present study carries out an outline of the Holocene glacialhistory of the Trobio Glacier.Reconstruction is based on a comparison between geomorphological surveyand historical documents.During the whole Holocene the Trobio Glacier tongue did not exceed the deposits of the Maximumof the Little Ice Age.Two weak advance phases are documented by morains and photographs at thebeginning of the 1920’s.During the last century the ice volume was reduced more strongly and productionof glacial deposits was smaller than for the other glaciers of the Orobie chain.This seems to be dueto the particular setting of the glacial basin.Investigations on vegetation dynamics lead to the identification of three main types of lithophilousvegetation:Oxyrietum dyginae Br.-Bl.’26,Luzuletum alpino-pilosae Br.-Bl.’26(Androsacion alpinaeBr.-Bl.et Jenny’26)and one type dominated by Cirsium spinosissimum and Achillea nana.They arewell developed only on the older deposits of the Little Ice Age.A comparison with some others proglacialareas at the same altitude was made.A depression of altitudinal belts in Orobie chain is observed.This,in combination with the northern exposition of the Trobio Basin,probably explains the strong decreaseof the pioneering activity of the vegetation.