Phenetic Species Concepts Research Articles

Morphometric studies suggest taxonomic changes in a species complex in Chromolaena (Asteraceae, Eupatorieae, Praxelinae)

The Chromolaena congesta complex (Asteraceae, Eupatorieae) presents a difficult challenge for biodiversity researchers due to the intertwined connections of its species and the difficulty of establishing morphological boundaries. In this study, we aimed to use morphometric analyses to evaluate the delimitation of the taxa belonging to the C. congesta complex, identify informative morphological traits and to understand the identity of several “atypical” specimens morphologically related to the complex. To achieve this, we used cluster and principal component analysis to evaluate 50 morphological traits from a total of 210 specimens throughout the geographic distribution of the species complex. We found support for the recognition of at least six species - Chromolaena ascendens, C. gentianoides, C. hirsuta, C. latisquamulosa, C. rhinanthacea and C. squarrulosa - according to a phenetic species concept and to corroborate the restoration of three species from synonymy. Furthermore, our results provide a morphological recircumscription of C. congesta and C. elliptica and indicate two taxonomic novelties, including a new combination and a new species. Despite the answers provided by morphology, many taxonomic issues remain to be solved, and further studies with other types of evidence should be carried to contribute towards a more stable classification.

<strong>A revision of <em>Hierochloe</em> sect. <em>Monoecia</em> (Anthoxanthinae, Pooideae, Poaceae)</strong>

We propose a new taxonomic arrangement for the South American species of Hierochloe sect. Monoecia, based on a recently published study combining morphological, molecular and cytological data. Only four out of the eight commonly accepted species of this section (H. pusilla, H. juncifolia, H. quebrada and H. redolens pro parte) are recognised using both phylogenetic (apomorphic) and phenetic species concepts. The four remaining species (H. altissima, H. gunckelii, H. spicata and H. utriculata) are reduced to varieties of the widespread H. redolens due to weak molecular, macro- and micromorphological differentiation. These varieties are presented here as new taxonomical combinations: H. redolens var. gunckelii, H. redolens var. spicata, H. redolens var. utriculata and H. redolens var. altissima. Lectotypes are designated for the names H. pusilla, H. juncifolia, H. redolens var. utriculata, and H. redolens var. altissima.

Genetic and morphological variation in Chara contraria and a taxon morphologically resembling Chara connivens

ABSTRACT Charophyte species delineation is regularly based on a set of thallus morphological characteristics, but considering pronounced phenotypic plasticity, difficulties and doubts commonly occur in Chara species determination. DNA barcoding may contribute to solving these challenges. Here we characterize Chara contraria with an unusual set of morphological characteristics, and specimens morphologically resembling Chara connivens collected in Serbia, by describing their morphological traits and analysing matK barcoding results. Our results indicated that dioecious Chara specimens, tentatively determined as Chara “connivens” based on morphological traits, were genetically more closely related to C. globularis. These Chara “connivens” specimens formed a sister group to a monophyletic C. globularis cluster, suggesting that it may be neither C. connivens nor C. globularis. We strongly encourage further barcoding of C. “connivens” samples from freshwater, in order to find out if there are consistent genetic differences between the dioecious freshwater C. “connivens” and monoecious C. globularis. Barcoding of matK placed the monoecious Chara specimens, which based on morphological characteristics initially were determined as C. virgata, into the C. contraria group. This indicates that the microscopic traits which commonly are used for Chara species determination sometimes are misleading. In general, our study challenges the commonly used phenetic species concept in Charophyte taxonomy and illustrates the importance of molecular approaches to evaluate the validity of morphological characteristics of the plant thallus in species delineation.

The Extinction and De-Extinction of Species

In this paper, we discuss the following four alternative ways of understanding the outcomes of resurrection biology (also known as de-extinction). Implications of each of the ways are discussed with respect to concepts of species and extinction. (1) Replication: animals created by resurrection biology do not belong to the original species but are copies of it. The view is compatible with finality of extinction as well as with certain biological and ecological species concepts. (2) Re-creation: animals created are members of the original species but, despite their existence, the species remains extinct. The view is incompatible with all species concepts presented. (3) Non-extinction: animals produced belong to the original species which actually never went extinct. The view may be consistent with phenetic and phylogenetic species concepts as well as with finality of extinction. (4) According to literal resurrection, resurrection biology is successful in reversing extinction through the creation of new members of species that once went extinct. This view presupposes non-finality of extinction and it is compatible with phenetic species concepts. It is notable that no species or extinction concept is consistent with all possible views of resurrection biology nor is any view of resurrection biology consistent with all species or extinction concepts. Thus, one’s views regarding species and extinction determine which views one can adopt regarding resurrection biology and vice versa.

한반도내 당마가목의 실체와 근연종과의 관계-전형질분석을 중심으로

Subalpine species, Sorbus pohuashanensis in the Korean peninsula, which is assumed to be evolved from hybridization between S. commixta and an unknown species based on the flavonoids data. Morphometric analysis was conducted on the basis of 19 leaf and flower (or fruit) characters. A total of 721 samples in 13 pop- ulations of Sorbus pohuashanensis and S. commixta from Korea and additional specimens of S. commixta, S. pohuashanensis, and S. wilsoniana from Japan and China were examined to reveal the hybridization patterns and morphological differences. We found a preliminary evidence where Korean mountain rowan is more related to a Chinese inland taxon, S. wilsoniana, rather than Northeastern Chinese S. pohuashanensis in terms of fla- vonoids. The current morphological structure of the Korean mountaion rowan, however, which is more similar to S. commixta, was neither associated with that of S. wilsoniana nor that of S. pohuashanensis. This indicates that this morphological variation represents an intermediate of S. commixta and S. wilsoniana via a more ancient hybridization event in terms of qualitative characters, such as stipules, buds, and carpels. These morphometric differences together with other distinguishing characteristics suggest that the Korean mountain rowan should be considered as a conspecific species of S. commixta, although this demonstration of hybridization with the cur- rent phenetic species concept contradicts longstanding historical species concept.

Evolution without Species: The Case of Mosaic Bacteriophages

Recent work in viral genomics has shown that bacteriophages exhibit a high degree of mosaicism, which is most likely due to a long history of prolific horizontal gene transfer (HGT). Given these findings, we argue that each of the most plausible attempts to properly classify bacteriophages into distinct species fail. Mayr's biological species concept fails because there is no useful viral analog to sexual reproduction. Phenetic species concepts fail because they obscure the mosaicism and the rich reticulated viral histories. Phylogenetic species concepts, even when extended to take into account reticulation, fail because there is no non-arbitrary distinction between recombination events that create a new viral species and those that do not. There is good reason to think that bacteriophages, arguably the Earth's most abundant biological agent, evolve without forming species. 1. Introduction 2. The Biology of Viruses 2.1. Bacteriophage life cycles 2.2. Mechanisms of HGT 3. The Species Problem and Species Concepts 3.1. Phenetic species concepts 3.2. The biological species concept 3.3. Phylogenetic species concepts 3.4. The ecological species concept 3.5. Homeostatic property cluster species 4. Viruses and Species Taxonomy 5. Reticular Phylogenies 6. Conclusion

A checklist of the bryophytes of Corsica (France): new records and a review of the literature

Based on a thorough review of the literature as well as floristic surveys undertaken over 20 years, a checklist of the bryophytes of Corsica, a mountainous western Mediterranean island, is presented. The occurrence of 17 liverwort and 44 moss species is documented for the first time from Corsica. As a result, the Corsican bryoflora includes 540 species: 148 liverworts, three hornworts and 389 mosses. Among the species reported, seven liverwort and 17 moss species are red-listed in Europe. By contrast with angiosperms, no bryophyte is endemic to the island based on traditional, phenetic species concepts. The number of new species reported here indicates that Corsica is exceedingly under-recorded bryologically. A better knowledge of the distribution, frequency and ecology of bryophyte species on the island is thus an absolute prerequisite in order to propose appropriate conservation measures in this Mediterranean environment that is, at least locally, severely threatened.

Reply to Henderson: On Delimiting Species for Taxonomic Analyses

In a recent series of papers, Henderson (2004, 2005a,b) has described and employed a method for de limiting species for use in taxonomic analyses. Because his work has focused on phylogenetic analyses based on herbarium specimens, Henderson (2005b) has ar gued that some species concepts (e.g., the biological [BSC] and monophyletic species concepts) are simply not informative at this stage of research and that other concepts (e.g., the morphological [MSC] and taxonomic [TSC] species concepts) are unscientific. Having dis missed these and other species concepts as inappro priate, Henderson then adopts a modification of the phylogenetic species concept (PSC; Mayden's [1997] PSQ) as the justifiable approach for delimiting species in the context of herbarium-based revisionary or monographic studies. Henderson (2005b) cites Luckow (1995) and Mayden (1997) to provide support for his rejection of various species concepts. What Henderson fails to do is to put these comments in context or verify exactly what was presented in those papers. I have no quarrel with Luc kow's (1995) comments: her intent was clearly stated (Instead, I will review species concepts used in phy logenetics ) and she provided a thoughtful review. However, Luckow's discussion of the BSC, coupled with her failure to address the similarity of the PSC and the (PhSC) species does invite examination with respect to what follows. Mayden (1997), on the other hand, is careless with at least one species concept. He quotes Sneath (1976) to provide a definition of the PhSC: ... the species level is that at which distinct clusters can be observed/7 First, this is not a definition of a species and, second, what's more pertinent is what precedes the ellipsis in the Sneath (1976) quote: the present discussion we may consider... It is clear, at least to me, that Sneath was making no attempt to provide a definition of although his ideas were mirrored by Andersson (1990): ... the species is de fined as the category of clusters that are inwardly con tinuous and outwardly discrete,... . Later, Mayden (1997) implies that the species along with several others, is based on morphology alone, and identifies both the MSC and TSC as synonyms of the PhSC. May den (1997) is not alone in perpetuating this misrepresentation. For example, Claridge et al. (1997), commenting on Sokal and Crovello (1970; see below), state that critics of the BSC (i.e., Sokal and Crovello, among others) ... preferred either an overtly morpho species approach [my emphasis] or some sort of system/7 This view was stressed earlier by Doyen and Slobodchikoff (1974) who claimed that ... data are restricted to morphological and physiological characteristics'' as opposed to their approach which, like that of Sokal and Crovello (1970) begins with phe netic analyses, but then introduces both reproductive and ecological data to clarify putatively misleading results. Had Mayden (1997), Claridge et al. (1997), and Doy en and Slobodchikoff (1974) read Sokal (1973) and Sneath and Sokal (1973) more carefully, they would have realized that this is true of the classical species concept/' which Sokal (1973) described as that based on morphological differences. The phenetic species concept, as developed most fully by Sokal and Crovello (1970), who viewed it as a surrogate for the BSC, was dealt with by Sokal (1973) as the phenetic species concept advocated by the taxono mists, a concept that is, to quote Sokal (1973), only a quantification and refinement of the species of the orthodox taxonomist. But, what a refinement? taxonomists advocated the use of as many characters as possible, from as many data sources as possible (including chemical, behavioral, ecological and distributional characters; see Sneath and Sokal [1973], pages 90-96), for delimiting groups that could be equated with species and higher level taxa. There is nothing in Sokal and Crovello (1970), Sokal (1973), Sneath and Sokal (1973), or Sneath (1976) to suggest that the refined version of the species which Sokal (1973) referred to as the numerical phe netic species, is limited to morphological data. I have no real quarrel with much of what Henderson proposes. Additionally, I do not intend to engage in the debate over which species concept is to be pre ferred. Mayden (1997) presents a general overview of species concepts and any reader who has followed this literature knows that some of these concepts, such as

Species Concepts in Extant Scleractinian Corals: Considerations Based on Reproductive Biology and Genotypic Population Structures

Challenges to the biological species concept, arising primarily from studies of plants, continue to prompt discussion on the nature of species and on appropriate criteria for their definition. A review of techniques used to define species limits in scleractinian corals indicates that a phenetic species concept is generally adhered to, but that there is also a tacit acceptance of the biological species concept. The available information on asexual reproduction, breeding systems, and dispersal, relevant to discussions of interbreeding barriers and gene flow, is discussed to assess the applicability of the biological species concept for extant scleractinian corals. It is concluded from preliminary data that, although corals utilize many of the varied breeding strategies and modes of asexual reproduction described for plants, they differ in their lack of exclusively asexual species, their inability to hybridize successfully, and in the requirement of broadcast spawning corals for a minimum developmental period during the dispersive larval phase. At present, there is no evidence to discount gene flow as a cohesive force in maintaining scleractinian species nor to reject the biological species or recognition concepts as inappropriate for this group. However, presently described coral species are equally compatible with the evolutionary and phylogenetic species concepts. It will not be possible to resolve questions concerning the cohesive force(s) that bind species within the Scleractinia until further studies on the breeding systems, fertilization biology, hybridization, and genotypic population structures of extant corals, and on species persistence in the fossil record are undertaken.