© 2006 Society of Systematic Biologists
Taxonomic Inflation and the Stability of Species Lists: The Perils of Ostrich's Behavior
Edited by Adrian Paterson: Associate Editor
Department of Biodiversity and Evolutionary Biology, Museo Nacional de Ciencias Naturales–CSIC C/José Gutiérrez Abascal 2, 28006 Madrid, Spain E-mail: iriva{at}mncn.csic.es (I.D.l.R.)
Received February 2, 2006; Revised May 7, 2006; Accepted June 6, 2006 Finding a new species is amongst the most important discoveries a biologist can make (Wilson, 1998). The discovery of new species opens up countless research possibilities, because species are the primary objects of study in many research fields of biology, and the species is the taxonomic unit most commonly used for conservation planning and management (Margules and Pressey, 2000). The formal description of species is one of several major research themes of taxonomy (e.g., Cracraft, 2002) and, hence, a fundamental part of the science of biodiversity (Wilson, 1988, 1992, 2003, 2004; Wheeler, 1995, 2004; Butler, et al., 1998; Disney, 1998; Causey et al., 2004). Thousands of new species are described each year and many still await description (e.g., May, 1988; Purvis and Hector, 2000; Meier and Dikow, 2004). However, despite the increasing rate of discovery, we are in the course of a major biodiversity crisis (Wilson, 1988). This has caused taxonomy to undergo a revival (Wheeler et al., 2004). Nevertheless, funds for taxonomy remain scarce and it is not strongly encouraged or promoted by academics (Dubois, 2003). But taxonomy has evolved, acquiring a better understanding of what species are and finding new tools to infer their boundaries (Mayr, 1942; Wiley, 1978; Cracraft, 1983; De Queiroz, 2005a).
But there is still some confusion about the results of taxonomic science (Will et al., 2005). Isaac et al. (2004) and Mace (2004) (hereafter, IEA and MAC, respectively) have recently explored the consequences of taxonomic progress on macroecology and conservation biology. For example, they argue that the elevation of subspecies to species caused by the increasing use of phylogenetic species concepts (PSCs) is responsible for most growth in the number of species. IEA term this phenomenon "taxonomic inflation" (hereafter taxonomic inflation s. s.). They suggest that as a consequence of taxonomic inflation, taxonomy suffers from great uncertainty and species lists change too often, compromising current predictions in macroecology and conservation biology, two disciplines that heavily rely on species lists. They also argue that an increase in number of species would require a larger budget for conservation. Moreover, they accused taxonomic instability of being a potential cause of unfounded shifts in conservation priorities (i.e., the relocation of hotspots). As a partial solution to this problem, IEA and MAC advocate a broader application of the biological species concept (BSC). Further, they suggest that new additions to species lists should be controlled, standardized, and stabilized due to the necessity for macroecology and conservation of working with stable units.
A number of brief responses to IEA's arguments followed shortly after. Harris and Froufe (2005) identify geopolitical bias in the study of interspecific genetic divergences as the major cause of taxonomic inflation. Agapow and Sluys (2005) argue that taxonomic inflation reflects the nature of species. They suggest that stable species lists and an ideal species concept are both unattainable solutions. Knapp et al. (2005) assert that most new plant species are described following classical methods. These responses lead to the recognition that taxonomic inflation is a major cause of increase in species numbers only in "charismatic" vertebrates; that global taxonomic lists with full information on synonymies and other details will be more useful than stable species lists; and that it is necessary to correctly identify the causes of taxonomic inflation (Isaac et al., 2005; Mallet et al., 2005). The most detailed response was that of Köhler et al. (2005), who show evidence against taxonomic inflation in amphibians in general and demonstrate it to be unrelated to the steady increase in the discovery of amphibian diversity in Madagascar. Nevertheless, they did not intend to explain the causes and consequences of taxonomic inflation and did not explore the causes of other taxonomic changes involved in modifications of species lists. In summary, taxonomic inflation has been considered an indirect result of taxonomic procedures by most authors, but the origin and implications of taxonomic inflation as a result of development of taxonomy have not been explored. Moreover, apart from the point of view of IEA and MAC, the causes of taxonomic instability have still not been properly discussed.
In our view, IEA and MAC have highlighted a relevant scientific issue with both theoretical and practical implications. However, such a debate should be free of possible misconceptions about species concept, taxonomy, and taxonomic progress. Our discussion is based on five main arguments that need to be treated in detail and that in the best case have been only partially addressed: (1) taxonomic inflation is just the logical result of recent conceptual and methodological developments in taxonomic research; (2) taxonomic inflation, although widespread among taxa, is responsible for only a small fraction of the whole increase in species numbers; (3) changes in species lists are necessary to reflect the current state of biodiversity knowledge; (4) species lists divorced from taxonomic progress would have serious negative consequences on the veracity of macroecological hypotheses; (5) changes in species lists are pivotal to improve previous poorly based conservation planning.
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Species Concept in Taxonomy |
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The acceptance of a universal species concept has been problematic for more than 100 years (Mayr, 1942). Although most biologists probably hold a similar idea of what a species is (Mayr, 1942; Hey, 2001; Agapow et al., 2004; De Queiroz, 2005a, 2005b), usually, no particular concept is explicitly adopted in most publications and, certainly, not in the vast majority of taxonomic ones. The BSC has had broad acceptance among biologists during the last 60 years, despite its limited utility for many groups of organisms and situations (Mayr, 1942; Ghiselin, 1987; Claridge et al., 1997; Wheeler and Platnick, 2000a; Wilson, 2003; Bock, 2004; Wiens, 2004). The PSC (see redefinition in Wheeler and Platnick, 2000b) emerged within taxonomy with the development of modern phylogenetics, and it became popular because of the need for more operational (and more evolutionary) methods than those provided by the phenetic or the BSC (for a review, see Sites and Marshall, 2004). With the development of evolutionary biology, species were identified explicitly or implicitly as segments of population level lineages (Simpson, 1951; Mayr, 1969; Wiley, 1978; Cracraft, 1983; Bock, 2004; De Queiroz, 2005a, 2005b). Moreover, general adoption among taxonomists of a lineage-based species concept could be responsible for most taxonomic inflation (De Queiroz, 2005a). But some biologists (e. g., Helbig et al., 2002; Kelt and Brown, 2000; IEA; MAC) still consider morphological distinctiveness and/or absence of interbreeding as necessary criteria for recognizing species, although these are not sin equa non (e.g., see early writing of Mayr, 1942; but also Avise, 2000; Wheeler and Platnick, 2000a; Wilson, 2003; Agapow et al., 2004; Wiens, 2004).
In summary, taxonomic inflation could be a consequence of a better understanding of what species are. But considering different criteria for the recognition of species leads to more complex taxonomic research. Indeed, delimiting species is a complex task under the evolutionary scenario (Sites and Marshall, 2004). Nonetheless, a pluralistic taxonomic research program (Balakrishnan, 2005), recently termed "integrative taxonomy" (Dayrat, 2005; Will et al., 2005), should be able to provide the best inferences about species, based on multiple lines of evidence.
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The Relevance of Taxonomic Inflation |
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TopSpecies Concept in TaxonomyThe Relevance of Taxonomic...Stability of Species ListsConsequences of Taxonomic...Taxonomy and Biodiversity...ConclusionsReferences |
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If we extend taxonomic inflation to include the continuous increase in species diversity due to a recent shift toward evolutionary species criteria (taxonomic inflation s. l.), we can indeed see that taxonomic inflation seems to be an important cause of increase in species numbers. Agapow et al. (2004) detected an average increase of 48.7% in species numbers for a broad variety of organisms due to application of phylogenetic criteria. The greatest increase in species numbers was seen both in poorly known (e.g., fungi, with an increase of 300%) and well-known groups (primates, reptiles, or European freshwater fishes) due to recent taxonomic revisions applying new tools. Other examples clearly show that, when using only classical criteria and methods, we could be underestimating the true diversity of some groups (e.g., Woese, 1998; Wynn and Heyer, 2001; Fukami et al., 2004; Sáez and Lozano, 2005).
Whereas Agapow et al. (2004) and Agapow and Sluys (2005) considered the increase in number of species as a justified trend, IEA and MAC used such increase in mammalian species as a justification to propose stable lists. Nevertheless, the diversity of mammals has been growing continuously for more than 20 years before the adoption of PSC (e.g., fig. 1 of IEA and fig. 2 of MAC), and probably due to the noticeable amount of discoveries in tropical areas (i.e. Patterson, 2001; Brown 2004). But many other vertebrates not analyzed in detail by Agapow et al. (2004) have seen increases in species numbers both by taxonomic reassessments and through new discoveries, as exemplified by birds (Fjeldså, 2000) and, especially, amphibians.
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A third of amphibian species since Linnaeus to 1985 were described 20 years before the proposal of the PSC (Glaw and Köhler, 1998), and the current rate of increase resulting from new discoveries (i.e., not taxonomic inflation) is still remarkably high (Fig. 1), with a 25% increase in the last 11 years (Köhler et al., 2005). We reviewed the Amphibian Species of the World Database (Frost, 2004), and found 245 subspecies elevated to species since the founding of Linnaean nomenclature in 1758 (note that, contrary to Köhler et al. [2005], we did not include species resurrected from synonymy, which are a common cause of change in species lists but not of taxonomic inflation). Among 134 subspecies elevated to species rank between 1980 and 2004 (considered as the period of potential PSC influence), only 22 cases were due to explicit adoption of PSC and/or use of phylogenetic techniques (Fig. 2). Moreover, between 1950 and 1979, 87 subspecies were elevated to species, which reveals that elevation of subspecies was already a common result of taxonomic research rather than a trend exclusively promoted by the adoption of PSC (Fig. 3). Thus, increase in the number of amphibian species is due largely to new discoveries, with taxonomic inflation making only a minor contribution.
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The PSC could have inflated the number of species in taxa in which the BSC was taken seriously. The BSC allowed, and to some extent encouraged, different species to be lumped together under the argument that they have the potential to interbreed. In groups where the BSC was never really applied, such as most invertebrates or amphibians, there is very little evidence for any serious increase in numbers of species when the PSC is invoked. Moreover, elevation of subspecies is only possible for groups where previous taxonomic analyses have revealed polytypic species. That is more usual in well-known groups with conspicuous external characters that can be easily measured and quantified (i.e., birds, reptiles, and some mammals). Batrachologists, for example, seem not especially prone to rely on BSC or to describe subspecies to reflect morphological variation, whereas, in this respect, reptiles could have been more affected than amphibians; however, academic herpetologists and systematists do not necessarily agree with these species partitions. For example, when Collins (1991), proposed to apply the evolutionary species concept (as discussed by Frost and Hillis, 1990) to 55 allopatric subspecies of North American amphibians and reptiles and elevated them to full species category without further analyses, a plethora of criticisms followed (e. g., Frost et al., 1992; Lazell, 1992; Montanucci, 1992; Van Devender et al., 1992). Most critics strongly disagreed with Collins' approach, and they argued for a case-by-case study to ascertain the taxonomic status of all these taxa.
A real danger of inflation in numbers of "species" comes from molecular phylogenetics (Will et al., 2005). It has been suggested that the increase in number of molecular workers (not taxonomists) who simply want to obtain trees for reasons other than simply classification (i.e., detecting "evolutionarily significant units," as Collins [1991] probably did), could be creating a growing molecular phylogeny/classification gap (Franz, 2005). For example, there may be many evolutionarily significant units within a single, diverse, widespread species that do not correspond to species. If this line of molecular work is continued, it has the potential to vastly increase the number of named entities that would be treated as species, and hence be a major source of taxonomic inflation. But the same is applicable to any other approach that consider a single criterion. Therefore, it would be still necessary to test the result of any single criterion (i.e., molecular) by other methods (see above).
Taxonomic inflation does not appear to be due to an unfounded or fashionable shift in species concept by scientists working on higher vertebrates. Instead, it appears to be a consequence of having a greater amount of data in a new conceptual framework (a common cause of paradigm shift in other sciences). Indeed, we see a steady increase in species number due to taxonomists' intensive research on different groups of organisms. This is strong evidence that, in general, taxonomic research is increasingly working in the same way and with similar criteria for different taxa. Underestimation of species has the effect of confusing experiments and observations on more than one species in a way that is very difficult to later tease apart. There is no virtue in maintaining a "stable" list once it is known that what was previously taken as one species actually corresponds to two or more species. Assuming that we want to understand the products of evolution, if a better species concept is available—one that is more explicit, more testable—then it would be foolish to not adopt it, regardless of the consequences for numbers of species.
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Stability of Species Lists |
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Within-country or within-state species lists are of high relevance for conservation because biodiversity is managed at the political level. Country lists are proportionally more amenable to change than international lists of biodiversity due to local taxonomic discoveries, increase in range of species, extinction of populations, colonization, and reintroductions. In previously poorly known megadiverse countries such as Bolivia, Colombia, or Sri Lanka, the number of amphibian species has nearly doubled in a very short time (e.g., De la Riva et al., 2000; Köhler, 2000; Meegaskumbura et al., 2002; Rueda-Admonacid, 2004); this should have obvious and deep consequences on reserve planning and biodiversity management at the national level, although, unfortunately, this is not usually the outcome. The debate, and the use of amphibians as a case study, is not new. Dubois (1998) already pointed out that lists of amphibians, even in an area supposedly well studied such as Europe, are subject to many changes and that these changes are due to real taxonomic discoveries rather than to nomenclatural issues. As an illustrative example, the publication of the last "updated" taxonomic list of official names of amphibians and reptiles of Spain (CTAHE, 2005) was immediately followed by the publication of a paper in which a new genus of newt was recognized and a new species was described (Carranza and Amat, 2005).
The relevance of these changes is clearly exemplified by an overview of taxonomic research on amphibians from Bolivia, where we have worked for the past 15 years. We compiled a database of changes affecting the study of amphibian faunistics for Bolivia from 1800 onwards. The kinds of changes considered were those of taxonomic origin plus new records and description of new species (most of these changes were summarized by De la Riva et al., 2000). Moreover, we also considered the potential occurrence of species cited for adjacent regions belonging to surrounding countries (See Table 1 for summarized information). It is important to emphasize that all this taxonomic work proceeded by classical methods (i.e., external morphology, osteology), with only the incorporation of bioacoustics as a nonclassical tool, and within no particular conceptual shift or use of phylogenetic methods.
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Despite the privileged biogeographical position of Bolivia, where the Amazon, the Andes, Cerrado forest, and the Chaco meet, the first comprehensive list (De la Riva, 1990) included only 112 confirmed amphibian species (for the purposes of this analysis, we consider 117; see Table 1) and 47 likely to occur. Overall, 76% were lowland species, 30.7% were Andean, and 6.8% were Bolivian endemics. Following a remarkable boost of taxonomic research during the 1990s, only 10 years later these figures had changed dramatically (De la Riva et al., 2000) (Table 1), with a total number of 186 species (an increase of 66%). The current list (December 2005; our own data) is composed of 231 species (not including around 40 new species that are under description by the authors and colleagues), which represents a further increase of 24.2% in only 5 years. Bolivia currently harbors 48 endemics (six times the number of 1990), and most endemicity and a high diversity is concentrated in the Andes (46 spp.), particularly in humid paramos and montane forests (40 spp.). Moreover, almost all species under description are also Andean endemics restricted to Bolivia. The expected increase for the next five years is still astonishing, probably reaching 300 species (Table 1).
Evidently, these changes have deep conservation implications in the direction pointed by IEA and MAC, and we cannot envisage a point in which the ever-changing list of Bolivian amphibians could be currently stabilized or standardized without serious damage to both scientific knowledge and conservation prospects. The conservation budget in Bolivia will obviously require a substantial increase, in order to assess the conservation status and propose conservation measures for a number more than twofold the species known in 1990. Furthermore, it is necessary to redirect conservation priorities (i.e., hotspots). This panorama is applicable to other megadiverse countries because in tropical South America many areas remain unexplored or have been scarcely surveyed (Heyer, 1988; Kress et al., 1998). Fortunately, taxonomic changes are being considered in Bolivian conservation strategies and there is a continuous flow of information between conservation organizations and taxonomists (e.g., through the IUCN/SSC–CI/CABS Biodiversity Assessment Initiative).
This scenario is applicable to other groups as well. A recent review of the American species of Agathidium beetles (Wheeler and Miller, 2005a, 2005b) is also illustrative. This group was first revised in 1880. When next revised in 1933, it doubled in size. The next revision was in 2005 and again the group more than doubled in number of known species. In many hyperdiverse taxa where there are very few taxonomists in relation to numbers of species, it is not uncommon to see growth of knowledge occur like this, with major leaps in numbers once or twice a century.
Evidently, these kinds of steady changes in the panorama of biodiversity are what concern many scientists. But the discovery of new species and the better knowledge of taxonomic status (two main causes of changes in species lists) should not be a negative concern for any scientist. Of course, species lists change their numbers not only because of new discoveries, but also due to the correction of past mistakes. Some taxonomic actions (e.g., synonymies, resurrection of species names, elevation of subspecies to species rank, deletions, nomenclatural changes, etc.) may or may not alter the species number in a list, whereas other, "silent" changes (e.g., new combinations) never imply changes in species numbers. Under this perspective, because improved knowledge can lead to taxonomic changes, instability is an unavoidable property of species lists. Together with rather irrelevant, pure nomenclatural alterations, there are profound reanalyses of evolutionary hypotheses that in turn may represent broad taxonomic changes in the group studied (for recent examples with amphibians, see Faivovich et al.'s [2005] and Wiens et al.'s [2005] reviews of the family Hylidae, and Frost et al.'s [2006] new proposal of the "Amphibian tree of life"). Such well-supported rearrangements are necessary because they greatly improve our understanding of the natural world. The plea for standardized, stable lists that ignore this kind of progress is untenable and unrealistic. Fortunately, global organizations are working in the opposing direction. In this way, taxonomic research now has some additional support and is making substantial progress in providing first-hand species lists through electronic databases and linking all biodiversity disciplines (see Bisby, 2000; Edwards et al., 2000; Smith et al., 2000; Bisby et al., 2002; Godfray, 2002; Wilson, 2003). But no stable list has been proposed. Indeed, all electronic databases in all sectors are continuously updated because new species are described or synonymized each day, hypotheses on phylogenetic relationships are improved, and new organisms are added to collections (Edwards et al., 2000).
In conclusion, species lists are susceptible to change due to the current state of the art and the inherent properties of taxonomic research. If the inventory of living species is far from finished, then arresting any change in lists composition could only come from a similar arrest of taxonomic work. Dubois (1998) provided conclusive arguments regarding the danger for zoological sciences of accepting the requests from society about the necessity of an artificial stabilization of lists of taxon names: "... taxonomy should remain in the hands of taxonomists, not of administrators, authors of checklists or data-bases, or editors of journals. The request for stability of names is not a scientific demand, ..." and "In the long run, it may prove more interesting and useful to better understand the biodiversity on our planet than to have "final" and "stable," i.e. wrong and incomplete, lists of this biodiversity for the peace of mind of administrators and technocrats". We think that recommending stable, standardized lists is necessarily unrealistic. Proposing such lists is the same as ignoring discoveries and, like an ostrich, putting the head in the sand while, perhaps, many species become extinct. Nowadays, this behavior would be less justified than ever before, because modern data, online databases, and text-mining tools now allow a continuous updating that eliminates the past burden of chronic obsolescence of published species lists. The recent proposal by Polaszek et al. (2005) for a registry of animal names is an important step. If we are going to allow names to increase (or decrease) to better reflect patterns in nature, at least we should facilitate that users of names can easily find them all and to know when they have found them all (Patterson et al., 2006).
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Consequences of Taxonomic Changes for Macroecology |
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Following IEA, taxonomic instability affects macroecological hypotheses because it is not always clear how to study populations in relation to species names: "Tests of such [macroecological] patterns typically assume that species are discrete equivalent entities in a way that is unbiased relative to the hypothesis being examined." Thus, because species lists change so frequently, macroecology suffers from instability in its predictions. But macroecological hypotheses also change with the accumulation of data. Indeed, due to the poor level of knowledge we have on Earth's biodiversity, we are generalizing from the well-known groups to biodiversity as a whole (e.g., Purvis and Hector, 2000). In short, we are ignorant of the mere existence of most living beings, let alone their evolutionary relationships, even when phylogenetics is of high relevance for the study of the ecological and evolutionary processes that have originated biodiversity (Caldwell, 1996; Purvis and Hector, 2000; Gotelli, 2004; Wiens, 2004). Under this perspective, macroecological hypotheses on biodiversity are not only limited by lack of knowledge of how many species there are but also by how little we know about their relationships (Caldwell, 1996). We must assume that such hypotheses will probably always be in a state of flux. In fact, macroecologists face a problem that is widespread. The rapid output of gene sequences by the genomics projects means that anybody working in that field has to redo analyses constantly because the database keeps changing. Indeed, some ecologists have realized the parallels and are exploring ways of dealing with this problem (e.g., http://seek.ecoinformatics.org/).
IEA consider that it might be easier to test hypotheses if the species lists reflected the underlying reality, but they find it frustrating that the prevailing species concept often used by taxonomists differ from that assumed in the hypotheses. But unless the species are shown to be real (and complete), there can be no stability. In reality, this logical demand is exactly what taxonomy is trying to provide: the best concepts and criteria at hand (Wilson, 2003), and macroecologists should be able to re-test their hypotheses under the new vision of species (see Wiens [2004] for a similar proposal regarding the research program in speciation).
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Taxonomy and Biodiversity Conservation |
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Biodiversity research is becoming an increasingly large research enterprise (Wheeler et al., 2004) and conservation and management disciplines have to be flexible enough to cope with the amount of new discoveries. If the conservation goals are not met, it will be due mainly to lack of political interest and funding and not to increasing rates of discoveries. Moreover, that we have insufficient money to study and protect the currently known diversity is neither a reason to avoid species descriptions or to criticize taxonomy. This would be an unfounded and nonacademic position with serious implications for taxonomy and nature conservation.
Current taxonomic research is positive rather than negative (as pointed out by IEA) for hotspot conservation policy. For example, many hotspots that receive funds for conservation are in tropical and subtropical forests, where a large part of biodiversity is still awaiting description; thus, these protected hotspots, are already favoring the protection of undescribed species. The "hotter" the hotspots the better will be the current protection of these areas in the future (Sechrest et al., 2002). In a study on Andean birds, Fjeldså (2000) concluded that recognized hotspots only cover a small fraction of the distribution of endangered species, and hotspots of endemism match desirable conservation targets in a better way. Furthermore, hotspots of taxonomic richness were shown to be roughly the same using genera, biospecies, or phylogenetic species, and phylogenetic species revealed few new areas of endemism that were not apparent using "accepted" species (Fjeldså, 2000). In general, habitat loss, new discoveries, and updated information will contribute to change the number of hotspots and their limits (Margules and Pressey, 2000). However, we should keep in mind that protecting current hotspots is necessary but not sufficient (Pimm and Raven, 2000; Sechrest et al., 2002). If we find out that an established hotspot is not as diverse as some other places, this should not mean that we no longer must strive to preserve it. Society may well decide to prioritize areas based on more criteria than numbers of species. This is just one additional source of information on which such decisions might be made. Currently proposed hotspots are not and should not be static and unique priorities.
Taxonomy is helping conservation by providing new insights on what a species is and what to preserve; also, it is a useful tool for prioritizing regional conservation actions (Freitag and Van Jaarsveld, 1997; Kress et al., 1998; 2001; Young et al., 2000). Some previously largely neglected groups (e.g., amphibians) are now of great interest because they are helping to give more precise limits of hotspots and areas of endemism. However, these are only some of the reasons why conservationists should consider taxonomy as an ally and not as an enemy (see Dubois, 2003).
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Conclusions |
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TopSpecies Concept in TaxonomyThe Relevance of Taxonomic...Stability of Species ListsConsequences of Taxonomic...Taxonomy and Biodiversity...ConclusionsReferences |
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Taxonomic inflation does exist and is the result of the recent incorporation of evolutionary theory into taxonomic research. However, increase in biodiversity is caused mainly by continuous new discoveries and intense taxonomic work promoted by the biodiversity crisis, the use of modern technologies, and the growing access to different scientific resources and to poorly known areas. But, like any other branch of biology, taxonomy is more or less imperfect in its tools and procedures; in addition, the task that taxonomists have ahead is enormous. Thus, many of the products that taxonomy can offer will be, for the moment, necessarily provisional and unavoidably amenable to change. Nevertheless, we are undertaking revolutionary progresses in taxonomy and it is understandable that practitioners of the various branches of knowledge that somehow rely on taxonomy (e.g., conservationists and ecologists) are surprised when having to tackle the revolutions that these changes promote in their respective fields. The efforts of many biologists in developing and supporting taxonomic research and in updating and sharing biodiversity information represent a goal defended by many scientists (e.g., Blackmore, 1996; Butler et al., 1998; Disney, 1998; Bisby, 2000; Edwards et al., 2000; Smith et al., 2000; Bisby et al., 2002; Godfray, 2002; Hariharam and Balaji, 2002; Knapp et al., 2002; Wilson, 2003; 2004; Valdecasas and Camacho, 2003; Wheeler, 2004; Wheeler et al., 2004; Wheeler and Valdecasas, 2005). We think that any negative attitude towards taxonomic changes will in turn have serious negative effects on biodiversity conservation.
Taxonomic instability is merely a sign of our ignorance (Domínguez and Wheeler, 1997). Standardized, controlled, stable species lists are neither a logical nor realistic solution because they represent the neglect of the development of taxonomy as a relevant science. In other words, standardized stable lists that are not based on updated taxonomic information may be inaccurate and misleading. Furthermore, such lists could be counterproductive for conservation because they may ignore new discoveries. Thus, we should not standardize our lists, but rather, allow them as much empirical support, accessibility, and flexibility as possible. Taxonomic species lists should be based on the best taxonomic data at hand, and instability will reflect the continuous flux of taxonomic knowledge. It is pivotal that conservation and macroecology be consistent with taxonomic theory; taxonomy should not be subordinate to macroecology and conservation disciplines. Rigorous updated taxonomic lists should be the most important documents on which conservation policies and macroecology rely.
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Acknowledgements |
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We are especially indebted to John J. Wiens, Jörn Köhler, Kevin de Queiroz, and Quentin D. Wheeler for their valuable comments and encouraging discussion on earlier versions of the manuscript, and also to Santiago Castroviejo-Fisher and José M. Tierno de Figueroa. Further comments and critics by Adrian Paterson, Paul Agapow, Rob Cruickshank and Roderic Page considerably improved the final version of the manuscript. We appreciate Pru Hobson-West's help with the English. This work was partially funded by the projects REN/GLO 2001-1046 and CGL2005-03156 of the Spanish Ministry of Education and Science (I. De la Riva, Principal Investigator).
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References |
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Agapow P. M., Bininda–Emonds O. R. P., Crandall K. A., Gittleman J. L., Mace G. M., Marsahll J. C., Purvis A. The impact of species concept on biodiversity studies. Q. Rev. Biol. (2004) 79:161–179.[CrossRef][Medline]
Agapow P. M., Sluys R. The reality of taxonomic change. TREE (2005) 20:278–280.[Medline]
Avise J. C. Phylogeography. The history and formation of species (2000) Cambridge, Massachusetts: Harvard University Press.
Balakrishnan R. Species concepts, species boundaries and species identification: A view from the tropics. Syst. Biol. (2005) 54:689–693.
Bisby F. A. The quiet revolution: biodiversity informatics and the Internet. Science (2000) 289:2309–2312.
Bisby F. A., Shimura J., Ruggiero M., Edward J., Haeuser C. Taxonomy, at the click of a mouse. Nature (2002) 418:367.[Web of Science][Medline]
Blackmore S. Knowing the Earth's biodiversity: Challenges for the infrastructure of systematic biology. Science (1996) 274:63–64.
Bock W. J. Species: The concept, category and taxon. J. Zool. Syst. Evol. Res. (2004) 42:178–190.[CrossRef]
Brown B. E. Atlas of new world marsupials. Fieldiana Zool (2004) 102:1–308.
Butler D., Gee H., Macilwain C. Museum research comes on the endangered species list. Nature (1998) 394:115–119.[CrossRef][Web of Science]
Caldwell J. P. Diversity of Amazonian anurans: The role of systematics and phylogeny in identifying macroecological and evolutionary patterns. In: Neotropical biodiversity and conservation—Gibson A. C., ed. (1996) Los Angeles, California: Mildred E. Mathias Botanical Garden, University of California. 73–88.
Carranza S., Amat F. Taxonomy, biogeography and evolution of Euproctus (Amphibia: Salamandridae), with the resurrection of the genus Calotriton and the description of a new endemic species from the Iberian Peninsula. Zool. J. Linnean. Soc. (2005) 145:555–582.[CrossRef]
Causey D., Janzen D. H., Townsend A., Vieglais D., Krishtalka L., Beach J. H., Wiley E. O. Museum collections and taxonomy. Science (2004) 305:1106–1107.
Claridge M. F., Dawah H. A., Wilson M. R. Species. The units of biodiversity (1997) London: Chapman and Hall.
Collins J. T. Viewpoint: A new taxonomic arrangement for some North American amphibians and reptiles. Herp. Rev. (1991) 22:42–43.
Cracraft J. Species concept and speciation analysis. Curr. Ornithol. (1983) 1:159–187.
Cracraft J. The seven great questions of systematic biology: An essential foundation for conservation and the sustainable use of biodiversity. Ann. Missouri Bot. Garden (2002) 89:127–144.[CrossRef][Web of Science]
CTAHE. Lista patrón actualizada de la herpetofauna española. Conclusiones de nomenclatura y taxonomía para las especies de anfibios y reptiles de España. (2005) Barcelona: AHE. Comisión de Taxonomía de la Asociación Herpetológica Española.
Dayrat. Toward integrative taxonomy. Biol. J. Linn. Soc. (2005) 85:407–415.[CrossRef][Web of Science]
De la Riva I. Lista preliminar comentada de los anfibios de Bolivia con datos sobre su distribución. Boll. Mus. Reg. Sci. Nat. Torino (1990) 8:261–319.
De la Riva I., Köhler J., Lötters S., Reichle S. Ten years of research on Bolivian amphibians: updated checklist, distribution, taxonomic problems, literature and iconography. Rev. Esp. Herp. (2000) 14:19–164.
De Queiroz K. A unified concept of species and its consequences for the future of taxonomy. Proc. Cal. Acad. Sci. (2005a) In press.
De Queiroz K. Ernst Mayr and the modern concept of species. Proc. Natl. Acad. Sci. (2005b) 102:6600–6607.
Disney H. Rescue plan need for taxonomy. Nature (1998) 394:120.
Domínguez E., Wheeler Q. D. Taxonomic stability is ignorance. Cladistics (1997) 13:367–372.[CrossRef][Web of Science]
Dubois A. Lists of European species of amphibian and reptiles: will we soon be reaching "stability"? Amphibia-Reptilia (1998) 19:1–28.
Dubois A. The relationships between taxonomy and conservation biology in the century of extinctions. C. R. Biologies (2003) 326:9–21.[Medline]
Edwards J. L., Lane M. A., Nielsen E. S. Interoperability of biodiversity databases: biodiversity information on every desktop. Science (2000) 289:2312–2314.
Faivovich J., Haddad C. F. B., García P. C. A., Frost D. R., Campbell J. A., Wheeler W. C. Systematic revision of the frog family Hylidae, with special reference to Hylinae: Phylogenetic analysis and taxonomic revision. Bull. Am. Mus. Nat. Hist. (2005) 294:1–240.[CrossRef]
Fjeldså J. The relevance of systematics in choosing priority areas for global conservation. Environ. Conserv. (2000) 27:67–75.[CrossRef][Web of Science]
Franz N. M. On the lack of good scientific reasons for the growing phylogeny/classification gap. Cladistics (2005) 21:495–500.[CrossRef][Web of Science]
Frost D. R. Amphibian species of the world. A taxonomic and geographical reference (1985) Lawrence, Kansas, USA: Allen Press & ASC.
Frost D. R. Amphibian Species of the World: An online reference (2004) New York, USA: American Museum of Natural History. http://research.amnh.org/herpetology/amphibia/index.html.
Frost D. R., Grant T., Faivovich J., Bain R. H., Haas A., Haddad C. F. B., de Sá R. O., Channing A., Wilkinson M., Donnellan S. C., Raxworthy C. J., Campbell J. A., Blotto B. L., Moler P., Drewes R. C., Nussbaum R. A., Lynch J. D., Green D. M., Wheeler W. C. The amphibian tree of life. Bull. Am. Mus. Nat. Hist. (2006) 297:1–370.[CrossRef]
Frost D. R., Hillis D. M. Species in concept and practice: Herpetological applications. Herpetologica (1990) 46:87–104.[Web of Science]
Frost D. R., Kluge A. G., Hillis D. M. Species in contemporary herpetology: Comments on phylogenetic inference and taxonomy. Herp. Rev. (1992) 23:46–54.
Fukami H., Budd A. F., Paulay G., Solé-Cava A., Chen C. A., Iwao K., Knowlton N. Conventional taxonomy obscures deep divergence between Pacific and Atlantic corals. Nature (2004) 427:832–835.[CrossRef][Medline]
Ghiselin M. T. Species concepts, individuality, and objectivity. Biol. Phil. (1987) 2:127–143.[CrossRef]
Glaw F., Köhler J. Amphibian species diversity exceeds that of mammals. Herp. Rev. (1998) 29:11–12.
Godfray H. C. J. Challenges for taxonomy. Nature (2002) 417:17–19.[CrossRef][Medline]
Gotelli N. J. A taxonomic wish-list for community ecology. Phil. Trans. R. Soc. Lond. B (2004) 359:585–597.
Harding K. A. Catalogue of new world amphibians (1985) New York: Pergamon Press.
Hariharam G. N., Balaji P. Taxonomic research in India: Future prospects. Curr. Sci. (2002) 83:1068–1070.[Web of Science]
Harris D. J., Froufe E. Taxonomic inflation: Species concept or historical geopolitical bias? TREE (2005) 20:6–7.[Medline]
Helbig A. J., Knox A. G., Parkin D. T., Sangster G., Collison N. Guidelines for assigning species rank. TREE (2002) 144:518–525.
Hey J. The mind of the species problem. TREE (2001) 16:326–329.[Medline]
Heyer W. R. On frog distribution patterns east of the Andes. In: Proceedings of a workshop on neotropical distribution patterns—Vanzolini P. E., Heyer W. R., eds. (1988) Rio do Janeiro: Academia Brasileira de Ciências. 245–273.
Isaac N. J., Mallet J., Mace G. M. Taxonomic inflation: Its influence on macroecology and conservation. TREE (2004) 19:464–469.[Medline]
Isaac N. J., Mace G. M., Mallet J. Response to Agapow and Sluys: The reality of taxonomic change. TREE (2005) 20(6):280–281.
Kelt D. A., Brown J. H. Species as units in ecology and biogeography: Are the blind leading the blind? Global Ecol. and Biogeogr. (2000) 9:213–217.[CrossRef]
Knapp S., Bateman R. M., Chalmers N. R., Humphries C. J., Rainbow P. S., Smith A. B., Taylor P. D., Vane-Wright R. I., Wilkinson M. Taxonomy needs evolution, not revolution. Nature (2002) 419:559.[Web of Science][Medline]
Knapp S., Lughadha E. N., Paton A. Taxonomic inflation, species concepts and global species lists. TREE (2005) 20:7–8.[Medline]
Köhler J. Amphibian diversity in Bolivia: A study with special reference to montane forest regions. Bonn. zool. Monogr. (2000) 48:1–243.
Köhler J., Vieites D. R., Bonett R. M., Hita–García F., Glaw F., Steinke D., Vences M. Boost in species discoveries in a highly endangered vertebrate group: new amphibians and global conservation. BiosSci. (2005) 55:693–696.[CrossRef]
Kress W. J., Heyer W. R., Acevedo P., Coddington J., Cole D., Erwin T. L., Meggers B. J., Pogue M., Thorington R. W., Vari R. P., Weitzman M. J., Weitzman S. H. Amazonian biodiversity: Assessing conservation priorities with taxonomic data. Biodiv. Conserv. (1998) 7:1577–1587.[CrossRef]
Kress W. J., Miller S. E., Krupnick G. A., Lovejoy T. E. Museum collections and conservation efforts. Science (2001) 291:828–829.
Lazell J. Taxonomy tyranny and the exoteric. Herp. Rev. (1992) 23:14.
Mace G. The role of taxonomy in species conservation. Phil. Trans. R. Soc. Lond. B (2004) 359:711–719.
Mallet J., Isaac N. J. B., Mace G. M. Response to Harris and Froufe, and Knapp et al.: Taxonomic inflation. TREE (2005) 20:8–9.
Margules C. R., Pressey R. L. Systematic conservation planning. Nature (2000) 405:243–253.[CrossRef][Medline]
May R. M. How many species are there on Earth? Science (1988) 241:1441–1449.
Mayr E. Systematics and the origin of species from the viewpoint of a zoologist (1942) 3rd edition. Cambridge, Massachusetts: Harvard University Press. 1999.
Mayr E. The biological meaning of species. Biol. J. Linn. Soc. (1969) 1:311–320.[CrossRef]
Meegaskumbura M., Bossuyt F., Pethiyagoda R., Manamendra-Arachchi K., Bahir M., Milinkovitch M. C., Schneider C. J. Sri Lanka, an amphibian hot spot. Science (2002) 298:379.
Meier R., Dikow T. The significance of specimen databases from taxonomic revisions for estimating and mapping the global species diversity of invertebrates and repatriating reliable specimen data. Conserv. Biol. (2004) 18:478–488.[CrossRef][Web of Science]
Montanucci R. R. Commentary on a proposed taxonomic arrangement for some North American amphibians and reptiles. Herp. Rev. (1992) 23:9–10.
Morell V. New mammals discovered by biology's new explorers. Science (1996) 273:1491.[CrossRef][Web of Science][Medline]
Myers N., Mittermeier R. A., Mittermeier C. G., Da Fonseca G. A. B., Kent J. Biodiversity hotspots for conservation priorities. Nature (2000) 403:853–858.[CrossRef][Medline]
Patterson B. D. Fathoming tropical biodiversity: The continuing discovery of Neotropical mammals. Diver. Distrib. (2001) 7:191–196.[CrossRef]
Patterson D. J., Remsen D., Marino W. A., Norton C. Taxonomic indexing—extending the role of taxonomy. Syst. Biol. (2006) 55:367–373.
Pimm S. L., Raven P. Extinction by numbers. Nature (2000) 403:843–845.[CrossRef][Medline]
Polaszek A., Agosti D., Alonso–Zarazaga M., Beccaloni G., de Bjørn P. P., Bouchet P., Brothers D. J., Earl E. N., Godfray H. C. J., Johnson N. F., Krell F.-T., Lipscomb D., Lyal C. H. C., Mace G. M., Mawatari S., Miller S. E., Minelli A., Morris S., Ng P. K. L., Patterson D. J., Pyle R. L., Robinson N., Rogo L., Taverne J., Thompson F. C., Tol J., Wheeler Q. D., Wilson E. O. A Universal Register for animal names. Nature (2005) 437:477.[CrossRef][Medline]
Purvis A., Hector A. Getting the measure of biodiversity. Nature (2000) 405:212–219.[CrossRef][Medline]
Rueda-Almonacid J. V., Lynch J. D., Amézquita A. Libro Rojo de los Anfibios de Colombia. Serie Libros Rojos de Especies Amenazadas de Colombia (2004) Bogotá, Colombia: Conservación Internacional Colombia, Instituto de Ciencias Naturales–Universidad Nacional de Colombia, Ministerio del Medio Ambiente.
Sáez A. G., Lozano E. Body doubles. Nature (2005) 433:111.[CrossRef][Medline]
Sechrest W., Brooks T. M., Da Fonseca G. A. B., Konstant W. R., Mittermeier R. A., Purvis A., Rylands A. B., Gittleman J. L. Hotspots and the conservation of evolutionary history. Proc. Natl. Acad. Sci. USA (2002) 99:2067–2071.
Simpson G. G. The species concept. Evolution (1951) 5:285–298.[CrossRef][Web of Science]
Sites J. W. Jr., Marshall J. C. Operational criteria for delimiting species. Ann. Rev. Ecol. Evol. Syst. (1997) 35:199–227.[CrossRef]
Smith A. T., Boitani L., Bibby C., Brackett D., Corsi F., Da Fonseca G. A. B., Gascon C., Dixon M. G., Hilton–Taylor C., Mace G. M., Mittermier R. A., Rabinovich J., Richardson B. J., Rylands A., Stein B., Stuart S., Thomsen J., Wilson C. Databases tailored for biodiversity conservation. Science (2000) 290:2073.[Medline]
Valdecasas A. G., Camacho A. I. Conservation to the rescue of taxonomy. Biodiv. Conserv. (2003) 12:1113–1117.[CrossRef]
Van Devender T. R., Lowe C. H., McCrystal H. K., Lawler H. E. Viewpoint: Reconsider suggested systematic arrangements for some North American amphibians and reptiles. Herp. Rev. (1992) 23:10–14.
Wheeler Q. D. Systematics, the scientific basis for inventories. Biodiv. Cons. (1995) 4:476–489.[CrossRef]
Wheeler Q. D. Taxonomic triage and the poverty of phylogeny. Phil. Trans. R. Soc. Lond. B (2004) 359:571–583.
Wheeler Q. D. Losing the plot: DNA "barcodes" and taxonomy. Cladistics (2005) 21:405–407.[CrossRef][Web of Science]
Wheeler Q. D., Miller K. B. Slime–mold beetles of the genus Agathidium Panzer in North and Central America. Part 1, Coleoptera, Leiodidae. Bull. Am. Mus. Nat. Hist. (2005a) 290:1–95.[CrossRef]
Wheeler Q. D., Miller K. B. Slime–mold beetles of the genus Agathidium Panzer in North and Central America. Coleoptera, Leiodidae. Part 2. Bull. Am. Mus. Nat. Hist. (2005b) 291:1–167.[CrossRef]
Wheeler Q. D., Platnick N. I. A critique from the Wheeler and Platnick phylogenetic species concept perspective: Problems with alternative concepts of species. In: Species concepts and phylogenetic theory—Wheeler Q. D., Meier R., eds. (2000a) New York: Columbia University Press. 133–145.
Wheeler Q. D., Platnick N. I. The phylogenetic species concept (sensu Wheeler and Platnick). In: Species concepts and phylogenetic theory—Wheeler Q. D., Meier R., eds. (2000b) New York: Columbia University Press.
Wheeler Q. D., Raven P. H., Wilson E. O. Taxonomy: Impediment or expedient? Science (2004) 303:285.[Abstract]
Wheeler Q. D., Valdecasas A. G. Ten challenges to transform taxonomy. Graellsia (2005) 61:151–160.
Wiens J. J. What is speciation and how should we study it? Am. Nat. (2004) 163:914–923.[CrossRef][Web of Science][Medline]
Wiens J. J., Fetzner J. W., Parkinson C. L., Reeder T. W. Hylid frog phylogeny and sampling strategies for speciose clades. Syst. Biol. (2005) 54:719–748.
Wiley E. O. The evolutionary species concept reconsidered. Syst. Zool. (1978) 27:17–26.
Will K. W., Mishler B. D., Wheeler Q. D. The perils of DNA barcoding and the need for integrative taxonomy. Syst. Biol. (2005) 54:844–851.
Wilson E. O. The current status of biological diversity. In: Biodiversity—Wilson E. O., Peter F. M., eds. (1988) Washington, D.C.: National Academy Press. 3–18.
Wilson E. O. The diversity of life (1992) Cambridge, Massachusetts: Harvard University Press.
Wilson E. O. Consilience. The unity of knowledge (1998) London: Abacus Press.
Wilson E. O. The encyclopedia of life. TREE (2003) 18:77–80.
Wilson E. O. Taxonomy as a fundamental discipline. Phil. Trans. R. Soc. Lond. B (2004) 359:739.
Woese C. R. Default taxonomy: Ernst Mayr's view of the microbial world. Proc. Natl. Acad. Sci. USA (1998) 95:11043–11046.
Wynn A., Heyer W. R. Do geographically widespread species of tropical amphibians exist? An estimate of genetic relatedness within the Neotropical frog Leptodactylus fuscus (Schneider, 1799) (Anura: Leptodactylidae). Trop. Zool. (2001) 14:255–285.
Young B. E., Lips K. R., Reaser J. K., Ibáñez R., Salas A. W., Cedeño J. R., Coloma L. A., Ron S., La Marca E., Meyer J. R., Muñoz A., Bolaños F., Chaves G., Romo D. Population declines and priorities for amphibian conservation in Latin America. Conserv. Biol. (2000) 15:1213–1223.[Web of Science]
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