《微生物生物学》课程书籍文献：《Molecular Identification of Fungi》真菌的分子鉴定PDF电子书（Youssuf Gherbawy l Kerstin Voigt Editors）.pdf_P16-P20

Chapter 1 Fungal Pathogens of Plants in the Homogocene George Newcombe and Frank M. Dugan Abstract As the pace of biotic homogenization has accelerated over time, the threat of novel phytopathogens has become a question of growing importance for mycologists and plant pathologists. Meanwhile, this question is but one of a whole set of related questions that invasion biologists are attempting to answer. Pathogen release is of interest to both sets of scientists because it provides a measure of the extent to which previously isolated mycobiotas have undergone cryptic homogenization, and at the same time it is the basis for a promising hypothesis to explain plant invasions. We argue that only a fraction of all first encounters between novel pathogens and evolutionarily naive plants could result in susceptible outcomes. This is analogous to the fact that only a fraction of all plant introductions result in plant invasions. 1.1 Introduction Geologists define the last 10,000 years, or our current epoch, as the Holocene (Bishop 2003). What has been described as the “Neolithic Revolution” also dates from 10,000 years ago (Wells 2007). Spurred by early developments in crop domestication in regions such as the Fertile Crescent (Wells 2007), Neolithic farmers began to move to and settle in new areas with their crops ten millennia ago (Vaughan et al. 2007). What was no doubt at first gradual and local ultimately became global. Human migrations and population expansions during the Holocene are mixing the previously isolated biotas of the world at an accelerating pace (Mooney and Cleland 2001). Organisms outside their native ranges bear many G. Newcombe Department of Forest Resources, and Center for Research on Invasive Species and Small Populations, University of Idaho, Moscow, ID 83844-1133, USA e-mail: georgen@uidaho.edu F.M. Dugan USDA-ARS, Washington State University, Pullman, WA 99163-6402, USA Y. Gherbawy and K. Voigt (eds.), Molecular Identification of Fungi, DOI 10.1007/978-3-642-05042-8_1, # Springer-Verlag Berlin Heidelberg 2010 3

G.Newcombe and F.M.Dugan descriptors:non-native,nonindigenous,exotic,introduced,or alien. Non-native pathogens are additionally called"novel."Some non-native organisms have proven invasive,and invasion biologists have begun to describe the latter part of our epoch as the Homogocene a term coined by Gordon Orians (Rosenzweig 2001a).This term invokes the global scope and increasing rate of anthropogenic,biotic homoge nization that is defined as the "gradual replacement of native biotas by locally expanding non-natives"(Olden et al.2004).The consequences of homogenization for biotic the subject t of a growing t;here we foc ingly,most of the literature of inva on plants and animals (Pysek et al.2006),leaving mycologically oriented ecologists to wonder about fungi.Crop pathogens are of course exceptional in this regard as they are often discussed in the phytopathological literature (Rossman 2009:Stukenbrock and MeDonald 2008)and lists of such pathogens that are thought to be non-native are frequently compiled (Madden 2001).The most famous historical example is arguably the pseudo-fungus (myce)with therish potato famine. and oger ated from the Ande (Gomez-Alpi r),and thei reu d prove r examples i clude b Sigatoka and yellow Sigatoka of banana (causal agents Mycosphaerella musicol and M.fijiensis,respectively).In these cases,the host is from Southeast Asia,and this may also be true for these fungi that were nevertheless first documented in Fiji: both diseases now constitute global epidemics on banana(Marin et al.2003).Other instances from agriculture are concisely mentioned here and there in what follows. However,this review emphasizes examples of plants from natural plant com munities (i.e cultural settings).Chestnut blight and w ite p ine wide other scientific publ we pr the behavior of funga al phytopathogens in the Homogocer e reveals ecologically significant patterns.These patterns should be of as much interest to invasion biologists and ecologists as they are to mycologists and plant pathologists.because fungi influence plants even while going unnoticed. Voyaging peoples have likely always brought useful and favored plants and animals with them to be deliberately introduced to new lands that they encountered. Before Captain Cook landed in Hawaii in 1778,Polynesian seafa ers had alre red these islands and intr ad aced such Coloca plants as ,aro ulenta).swee potato (Ipomoea bal um),and perhaps twe dozen other species(Carlquist 1980).Such early plant introductions were certainly not limited to Polynesia,or to plants brought with European colonists to the New World.Plant-hunting expeditions were probably initiated as early as 3.000 vears before Columbus,as hieroglyphs appear to show that the Queen of Egypt sent out collectors of exotic plants for her gardens(Baskin 2003).Mycologists know that at least some endophytic and phyt pathogenic fungi must have quietly accompanied these plant ctions (Palm 1999.2001：Palm nd Ros an 2003).But what can we say today about these co-introductions nd their effects on Hawaiiar

descriptors: non-native, nonindigenous, exotic, introduced, or alien. Non-native pathogens are additionally called “novel.” Some non-native organisms have proven invasive, and invasion biologists have begun to describe the latter part of our epoch as the Homogocene a term coined by Gordon Orians (Rosenzweig 2001a). This term invokes the global scope and increasing rate of anthropogenic, biotic homogenization that is defined as the “gradual replacement of native biotas by locally expanding non-natives” (Olden et al. 2004). The consequences of homogenization for biotic communities and ecosystem processes are the subject of a growing research effort; here we focus on fungal pathogens in the Homogocene. Unsurprisingly, most of the literature of invasion biology focuses on plants and animals (Pysˇek et al. 2006), leaving mycologically oriented ecologists to wonder about fungi. Crop pathogens are of course exceptional in this regard as they are often discussed in the phytopathological literature (Rossman 2009; Stukenbrock and McDonald 2008) and lists of such pathogens that are thought to be non-native are frequently compiled (Madden 2001). The most famous historical example is arguably the pseudo-fungus (oomycete) associated with the Irish potato famine, Phytophthora infestans. Both the host and pathogen probably originated from the Andes (Go´mez-Alpizar et al. 2007), and their reunion in Ireland proved disastrous both for the crop and the people who depended on it. Other examples include black Sigatoka and yellow Sigatoka of banana (causal agents Mycosphaerella musicola and M. fijiensis, respectively). In these cases, the host is from Southeast Asia, and this may also be true for these fungi that were nevertheless first documented in Fiji; both diseases now constitute global epidemics on banana (Marı´n et al. 2003). Other instances from agriculture are concisely mentioned here and there in what follows. However, this review emphasizes examples of plants from natural plant communities (i.e., nonagricultural settings). Chestnut blight and white pine blister rust (discussed below) are widely investigated, but we present many other instances much less familiar to the scientific public. We believe that a careful examination of the behavior of fungal phytopathogens in the Homogocene reveals ecologically significant patterns. These patterns should be of as much interest to invasion biologists and ecologists as they are to mycologists and plant pathologists, because fungi influence plants even while going unnoticed. Voyaging peoples have likely always brought useful and favored plants and animals with them to be deliberately introduced to new lands that they encountered. Before Captain Cook landed in Hawaii in 1778, Polynesian seafarers had already discovered these remote, volcanic islands and introduced such plants as candlenut (Aleurites moluccana), ti (Cordyline fruticosa), taro (Colocasia esculenta), sweet potato (Ipomoea batatas), sugarcane (Saccharum officinarum), and perhaps two dozen other species (Carlquist 1980). Such early plant introductions were certainly not limited to Polynesia, or to plants brought with European colonists to the New World. Plant-hunting expeditions were probably initiated as early as 3,000 years before Columbus, as hieroglyphs appear to show that the Queen of Egypt sent out collectors of exotic plants for her gardens (Baskin 2003). Mycologists know that at least some endophytic and phytopathogenic fungi must have quietly accompanied these plant introductions (Palm 1999, 2001; Palm and Rossman 2003). But what can we say today about these co-introductions and their effects on Hawaiian 4 G. Newcombe and F.M. Dugan

1 Fungal Pathogens of Plants in the Homogocene and other ecosystems around the world?Were those co-introduced endophytes so host-specific that we can be sure that they remained exclusive to their original hosts?If they jumped to other hosts,presumably related ones(Gilbert and Webb 2007).what ecological effects might they have had,and how can we distinguish today from volved inte The Europeans wai.and inude all fungi globally.Maritime began in the e early hfteenth century (Love 2006)were initially restricted in scope,but they gradually became global and much more ambitious.Scientific travelers such as Alexander von Humboldt,Charles Darwin,and Alfred Russell Wallace began in the nineteenth century to discover how life's diversity was distributed around the world.At the same time,plant explorers of many nationalities were seeking to deliberately introduce desirable plants to their home countries (Reichard and White 2001).Crop plants had already beer ntroduced alm everywhere thathe bly Columbus for e ple,wasted no tim on the m an New World domes maize.into Europe in 1493 (Rebourg et al. 2003);during the same year Columbus introduced orange trees of Asian origin to Hispaniola(Haughton 1978). Ten thousand years ago,homogenization was undoubtedly not occurring at modern rates,although it had probably been initiated on local or regional scales So,the Homogocene cannot be said to have begun with the Holocene.Instead,1500 social historian titles or subtitles a ordingly include ive of worldwide m nt of oods and Accumulation on a Wo peoples be Scal on of F ope System, etc.(Amin 1974;Crosby 2004; Wallerstein 1974.1980.1989).Five hundred and nine years ago,the"Age of Discovery"was under way,and today, deliberate plant introductions are so common that the"maiority of woody invasive plants in the United States were introduced for horticultural purposes- one study found that 82%of 235 woody plant species identified as colonizing outside of cultivation had been used in landscaping"(Reichard and White 2001).The “Homogocene” may not yet be a seriou s term in science but it does simply and evoke global c the last half a millenni vas on biol gling d in E a divide alier nts (Pysek et al.2004)into those th at are called"archaeophytes if introduce before 1500,and"neophytes"if introduced later.However,we hasten to make explicit what we have already hinted at:migration or purposeful import of plant materials well prior to 1500 probably made important contributions to homogeni- zation on a regional,and sometimes even continental or oceanic,scale.In addition to the example of Polynesia above,expansion of Neolithic farming cultures such as the Arawak(from the upper Amazon and Orinoco basins to the West Indies).Bantu (fron tern to south Indo-Eu ean(from a still dis on,perhaps r the Europe steppes eventual through and mu ste cen a)moved pla ma tances(Diamond and Bellwood 2003).Pronounced effects have been postulated for movement of plant pests and diseases in these distant times,e.g.,the "honeymoon

and other ecosystems around the world? Were those co-introduced endophytes so host-specific that we can be sure that they remained exclusive to their original hosts? If they jumped to other hosts, presumably related ones (Gilbert and Webb 2007), what ecological effects might they have had, and how can we distinguish them today from co-evolved interactions? These questions go well beyond Hawaii, and include all fungi globally. Maritime explorations by western Europeans that began in the early fifteenth century (Love 2006) were initially restricted in scope, but they gradually became global and much more ambitious. Scientific travelers such as Alexander von Humboldt, Charles Darwin, and Alfred Russell Wallace began in the nineteenth century to discover how life’s diversity was distributed around the world. At the same time, plant explorers of many nationalities were seeking to deliberately introduce desirable plants to their home countries (Reichard and White 2001). Crop plants had already been introduced almost everywhere that they would grow profitably; Columbus, for example, wasted no time in introducing one of the most important New World domesticates, maize, into Europe in 1493 (Rebourg et al. 2003); during the same year Columbus introduced orange trees of Asian origin to Hispaniola (Haughton 1978). Ten thousand years ago, homogenization was undoubtedly not occurring at modern rates, although it had probably been initiated on local or regional scales. So, the Homogocene cannot be said to have begun with the Holocene. Instead, 1500 would appear to be a good year to choose for the beginning of the Homogocene. This date is also in agreement with the judgment of ecological, economic, and social historians, whose titles or subtitles accordingly include phraseology suggestive of worldwide movement of goods and peoples beginning at this time, e.g., “Accumulation on a World Scale,” “Expansion of Europe,” “Modern WorldSystem,” etc. (Amin 1974; Crosby 2004; Wallerstein 1974, 1980, 1989). Five hundred and nine years ago, the “Age of Discovery” was under way, and today, deliberate plant introductions are so common that the “majority of woody invasive plants in the United States were introduced for horticultural purposes – one study found that 82% of 235 woody plant species identified as colonizing outside of cultivation had been used in landscaping” (Reichard and White 2001). The “Homogocene” may not yet be a serious term in science but it does simply and directly evoke global commingling during the last half a millennium. Plant-oriented invasion biologists in Europe already use 1500 to divide alien plants (Pysˇek et al. 2004) into those that are called “archaeophytes” if introduced before 1500, and “neophytes” if introduced later. However, we hasten to make explicit what we have already hinted at: migration or purposeful import of plant materials well prior to 1500 probably made important contributions to homogenization on a regional, and sometimes even continental or oceanic, scale. In addition to the example of Polynesia above, expansion of Neolithic farming cultures such as the Arawak (from the upper Amazon and Orinoco basins to the West Indies), Bantu (from western to southern Africa), and Indo-European (from a still disputed location, perhaps Anatolia or the European steppes, but eventually throughout Europe and much of western and central Asia) moved plant materials considerable distances (Diamond and Bellwood 2003). Pronounced effects have been postulated for movement of plant pests and diseases in these distant times, e.g., the “honeymoon 1 Fungal Pathogens of Plants in the Homogocene 5