Species

2018 ◽  
Author(s):  
Kim Sterelny
Keyword(s):  
Homo Sapiens ◽  
Evolutionary Process ◽  
Biological Species ◽  
Biological Species Concept ◽  
Temporal Perspective ◽  
As Species ◽  
History Of ◽  
Diversity Of Life ◽  
Species Taxon ◽  
Species Definitions

The diversity of life is not seamless but comes in relatively discrete packages, species. Is that packaging real, or an artefact of our limited temporal perspective on the history of life? If all living forms are descended from one or a few ancestors, there may be no real distinction between living and ancestral forms, or between closely related living animals. Received wisdom holds that species are the ’units of evolution’, for it is they that evolve. They are the upshot of evolutionary processes, but, if species and not just their component organisms compete with one another, they are also important agents in the evolutionary process. If so, species are real units in nature, not arbitrary segmentations of seamless variation. The ’species problem’ has been approached from two angles. One focus has been on specific taxa of the tree of life. What would settle whether some arbitrarily chosen organism is a member of homo sapiens or canis familiaris? This is sometimes known as the ’species taxon’ problem. An alternate way of approaching diversity has been to ask what all species have in common. What do all the populations we think of as species share? This is the ’species category’ problem. One idea is to group organisms into species by appealing to the overall similarity. This ’phenetic’ conception is in retreat. Most contemporary species definitions are relational, the animals that compose pan troglodytes are a species, not because they are all very similar (they are very like the pygmy chimps as well) but because of their relations amongst themselves and with their ancestors. The most famous relational definition is the ’biological species concept’, according to which conspecific organisms are organisms that can interbreed, however different they look. Relational species definitions aim to define a category of theoretical and explanatory interest to evolutionary and ecological theory. Given that there are many explanatory interests, one problem in evaluating these accounts is to determine whether they are genuinely rivals.

scholarly journals Recent Evolutionary History of the Fox Sparrows (Genus: Passerella)

The Auk ◽  
2003 ◽  
Vol 120 (2) ◽  
pp. 522-527
Author(s):  
Robert M. Zink ◽  
Jason D. Weckstein
Keyword(s):  
Control Region ◽  
Evolutionary History ◽  
Biological Species ◽  
Biological Species Concept ◽  
Base Pairs ◽  
Dna Variation ◽  
As Species ◽  
History Of ◽  
Passerella Iliaca ◽  
And Control

Abstract On the basis of plumage coloration and mitochondrial DNA variation, four main groups are recognized within the Fox Sparrow (Passerella iliaca): the red group (iliaca, RE), sooty group (unalaschcensis, SO), thick-billed (megarhyncha, TB), and slate-colored (schistacea, SC). To establish phylogenetic relationships among those four groups, we analyzed 2119 base pairs of sequence from four mitochondrial regions: ND2, ND3, cytochrome b, and control region. The control region is less variable than the coding genes surveyed. Both maximum parsimony and maximum likelihood resolved the same ingroup relationships (RE(SC(TB,SO))). However, placement of the root could not be established, even with four outgroups. Lack of resolution of the root is due to the nearest living relative of the Fox Sparrow being over 11% divergent. Despite lacking a clear root, the data suggest that the two taxa connected by a hybrid zone (TB, SC) are not sister species, which has implications for species limits because under the biological species concept they should be lumped. We recommend that all four main groups be recognized as species.

scholarly journals Molecular Systematics and the Role of The “Várzea”–“Terra-Firme” Ecotone in the Diversification of Xiphorhynchus Woodcreepers (Aves: Dendrocolaptidae)

The Auk ◽  
2002 ◽  
Vol 119 (3) ◽  
pp. 621-640 ◽  
Author(s):  
Alexandre Aleixo
Keyword(s):  
Strong Support ◽  
Sequence Divergence ◽  
Decisive Role ◽  
Biological Species ◽  
Habitat Specialization ◽  
Terra Firme ◽  
Sister Relationship ◽  
As Species ◽  
History Of ◽  
Distinct Lineage

Abstract The phylogeny of all known Xiphorhynchus (Dendrocolaptidae) species and many of its subspecies was reconstructed to evaluate species limits in this taxonomically challenging genus and investigate the possible role played by the Amazonian “várzea” (floodplain forest)–“terra-firme” (upland forest) ecotone in its diversification. Phylogenies were inferred based on 2,430 bp of the mitochondrial DNA genes ND2, ND3, and cytochrome b. All phylogeny estimates supported the monophyly of all extant Xiphorhynchus species to the exclusion of the sibling species pair Straight-billed (X. picus) and Zimmer's (X. kienerii) woodcreeper. Confirming findings of previous molecular and anatomical studies, strong support was found to include the Lesser Woodcreeper (Lepidocolaptes fuscus) in Xiphorhynchus. Levels of sequence divergence among some subspecies of Buff-throated (X. guttatus), Ocellated (X. ocellatus), and Spix's (X. spixii) woodcreepers reached or exceeded those found between closely related, undisputed biological species of Xiphorhynchus. High levels of sequence differentiation and the paraphyly of some Xiphorhynchus species indicated that the following taxa should be recognized as species: Lafresnaye's (X. guttatoides), Tschudi's (X. chunchotambo), and Elegant (X. elegans) woodcreepers. All Xiphorhynchus species restricted to terra-firme forest in lowland Amazonia formed a well supported monophyletic group, whereas species restricted to várzea forest were either basal to a clade containing species found in a wide variety of habitats (Striped Woodcreeper [X. obsoletus]) or belonged to a distinct lineage likely to be regarded as a separate genus (X. kienerii). These findings falsified an anticipated sister relationship between várzea and terra-firme species, as expected if the várzea–terra-firme ecotone had played a decisive role in population differentiation and speciation within Xiphorhynchus. Instead, phylogeny estimates suggested that the várzea–terra-firme habitat specialization evolved early on in the evolutionary history of Xiphorhynchus and that subsequent differentiation occurred mostly within the terra-firme habitat.

scholarly journals Untangling systematics of the Paramacrobiotus areolatus species complex by an integrative redescription of the nominal species for the group, with multilocus phylogeny and species delineation in the genus Paramacrobiotus

2020 ◽  
Vol 188 (3) ◽  
pp. 694-716 ◽  
Author(s):  
Daniel Stec ◽  
Łukasz Krzywański ◽  
Krzysztof Zawierucha ◽  
Łukasz Michalczyk
Keyword(s):  
Dna Sequences ◽  
Integrative Taxonomy ◽  
Genetic Distances ◽  
Biological Species ◽  
Biological Species Concept ◽  
Nominal Species ◽  
Species Delineation ◽  
F1 Hybrid ◽  
Complex Species ◽  
History Of

Abstract Incomplete descriptions of nominal taxa are one of the most significant obstacles in modern taxonomy, including the taxonomy of Tardigrada. Another major problem in tardigrade systematics is the lack of tests for the reliability of genetic markers in species delineation. Here, we employ an integrative taxonomy approach to redescribe the nominal taxon for the P. areolatus complex, Paramacrobiotus areolatus. Moreover, we obtained multilocus DNA sequences for another 16 populations representing 9–12 Paramacrobiotus species collected from Europe, North America, Africa and Australia, enabling us to reconstruct the most extensive phylogeny of the genus to date. The identification of a pair of potentially cryptic dioecious P. areolatus complex species with divergent genetic distances in ITS2 (1.4%) and COI (13.8%) provided an opportunity to test the biological species concept for the first time in the history of tardigrade taxonomy. Intra- and interpopulation crosses did not differ in reproductive success in terms of F1 offspring. However, because of the low F1 family sizes, we were unfortunately unable to test F1 hybrid fertility. Although our results are only partially conclusive, they offer a baseline not only for further taxonomic and phylogenetic research on the areolatus complex, but also for studies on species delineation in tardigrades in general.

scholarly journals Different Stages of Evolution of Humankind

2017 ◽  
pp. 46-77
Author(s):  
Slaven Jozic
Keyword(s):  
Human Evolution ◽  
Homo Sapiens ◽  
Evolutionary Process ◽  
Great Apes ◽  
Distinct Species ◽  
Scientific Disciplines ◽  
Late Cretaceous Period ◽  
Anatomically Modern Humans ◽  
Gradual Development ◽  
History Of

Human evolution is the evolutionary process that led to the emergence of anatomically modern humans, beginning with the evolutionary history of primates—in particular genus Homo—and leading to the emergence of Homo sapiens as a distinct species of the hominid family, the great apes. This process involved the gradual development of traits such as human bipedalism and language, as well as interbreeding with other hominines, which indicate that human evolution was not linear but a web. The study of human evolution involves several scientific disciplines, including physical anthropology, primatology, archaeology, paleontology, neurobiology, ethology, linguistics, evolutionary psychology, embryology and genetics. Genetic studies show that primates diverged from other mammals about 85 million years ago, in the Late Cretaceous period, and the earliest fossils appear in the Paleocene, around 55 million years ago. Within the Hominoidea (apes) superfamily, the Hominidae family diverged from the Hylobatidae (gibbon) family some 15–20 million years ago; African great apes (subfamily Homininae) diverged from orangutans (Ponginae) about 14 million years ago; the Hominini tribe (humans, Australopithecines and other extinct biped genera, and chimpanzee) parted from the Gorillini tribe (gorillas) between 8–9 million years ago; and, in turn, the subtribes Hominina (humans and biped ancestors) and Panina (chimps) separated 4–7.5 million years ago.

Is the taxonomy appropriate? Delineating species for conservation purposes

2017 ◽  
Author(s):  
Richard Frankham ◽  
Jonathan D. Ballou ◽  
Katherine Ralls ◽  
Mark D. B. Eldridge ◽  
Michele R. Dudash ◽  
...  
Keyword(s):  
Species Concept ◽  
Conservation Management ◽  
Biological Species ◽  
Species Concepts ◽  
Outbreeding Depression ◽  
Biological Species Concept ◽  
Genetic Rescue ◽  
Low Genetic Diversity ◽  
Inbred Populations ◽  
Species Definitions

The first step in conservation management is to delineate groups for separate versus combined management. However, there are many problems with species delineation, including diverse species definitions, lack of standardized protocols, and poor repeatability of delineations. Definitions that are too broad will lead to outbreeding depression if populations are crossed, while those that split excessively may preclude genetic rescue of small inbred populations with low genetic diversity. To minimize these problems, we recommend the use of species concepts based upon reproductive isolation (such as the biological species concept) and advise against the use of phylogenetic and general lineage species concepts. We provide guidelines as to when taxonomy requires revision and outline protocols for robust species delineations.

Appropriate delineation of species for conservation purposes

2019 ◽  
pp. 85-96
Author(s):  
Richard Frankham ◽  
Jonathan D. Ballou ◽  
Katherine Ralls ◽  
Mark D. B. Eldridge ◽  
Michele R. Dudash ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Reproductive Isolation ◽  
Biological Species ◽  
Species Concepts ◽  
Outbreeding Depression ◽  
Biological Species Concept ◽  
Genetic Rescue ◽  
Low Genetic Diversity ◽  
Inbred Populations ◽  
Species Definitions

The first step in conservation management is to delineate groups for separate versus combined management. However, there are many problems with species delineation, including diverse species definitions, lack of standardized protocols, and poor repeatability of delineations. Definitions that are too broad will lead to outbreeding depression if populations are crossed, while those that split excessively may preclude genetic rescue of small inbred populations with low genetic diversity. To minimize these problems, we recommend the use of species concepts based upon reproductive isolation (such as the Biological Species Concept) and advise against the use of Phylogenetic and General Lineage Species Concepts. We provide guidelines as to when taxonomy requires revision and outline protocols for robust species delineations.

Hierarchic Interactions: The Evolutionary Process

1986 ◽  
Author(s):  
Niles Eldredge
Keyword(s):  
Homo Sapiens ◽  
Evolutionary Process ◽  
Point Of View ◽  
Unique Problem ◽  
Economic Implications ◽  
Present Context ◽  
History Of ◽  
The One ◽  
Multicellular Organisms

Organisms—biology begins with organisms, and indeed a great deal of the history of biology is a trek through progressively finer subdivisions of organisms. When “forefronts” of biology are listed these days, nearly all concern the molecular biology of intracellular (and intraorganelle) physicochemical processes—and quite rightly so. But the ontology of units larger than organisms, while not wholly neglected, is at least as difficult a problem. Organisms are by far the easiest of biological units for us to see, to probe, to conceptualize as “individuals.” But, in the present context, organisms pose a unique problem all their own: they constitute the only class of individuals to be found in both the genealogical and ecological hierarchies. Consider the confusion that permeates even the recent explicitly hierarchical literature: ecology and evolution (as in the quote from Valentine that stands at this chapter’s head) are generally seen as separate areas of inquiry, but the choice of the higher-level individuals to be incorporated into one’s hierarchy very much depends upon one’s point of view. Below the organism level, of course, the distinction between the somatic and germ lines (i.e., in multicellular organisms) once again ensures a clean separation of the elements of the two hierarchies. Hence the conclusion (Eldredge and Salthe 1984) that there must in fact be two independent, yet parallel and interacting, process hierarchies that together combine to yield evolution. Organisms, as members of both hierarchies, threaten to muddy the picture. It is possible, of course, to distinguish between the economic and reproductive functions of organisms, as I have done at length in the preceding chapter. Physiologists, after all, have long been telling their students that reproduction is the one physiological process not essential to the survival of an organism; thus, it is no surprise that it is invariably the first such process to be dispensed with when the organism is stressed. It is easy to distinguish the economic from the reproductive functions of the vast majority of organisms, but in many vertebrates, most especially Homo sapiens, sexuality has clear economic implications, obscuring the distinction between the two hierarchies perhaps even more.

scholarly journals Harmonizing hybridization dissonance in conservation

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Claudio S. Quilodrán ◽  
Juan I. Montoya-Burgos ◽  
Mathias Currat
Keyword(s):  
Species Concept ◽  
Evolutionary Process ◽  
Intrinsic Property ◽  
Biodiversity Loss ◽  
Biological Species ◽  
Biological Species Concept ◽  
Conservation Units ◽  
Conservation Implications ◽  
First Case ◽  
The Impact

AbstractA dramatic increase in the hybridization between historically allopatric species has been induced by human activities. However, the notion of hybridization seems to lack consistency in two respects. On the one hand, it is inconsistent with the biological species concept, which does not allow for interbreeding between species, and on the other hand, it is considered either as an evolutionary process leading to the emergence of new biodiversity or as a cause of biodiversity loss, with conservation implications. In the first case, we argue that conservation biology should avoid the discussion around the species concept and delimit priorities of conservation units based on the impact on biodiversity if taxa are lost. In the second case, we show that this is not a paradox but an intrinsic property of hybridization, which should be considered in conservation programmes. We propose a novel view of conservation guidelines, in which human-induced hybridization may also be a tool to enhance the likelihood of adaptation to changing environmental conditions or to increase the genetic diversity of taxa affected by inbreeding depression. The conservation guidelines presented here represent a guide for the development of programmes aimed at protecting biodiversity as a dynamic evolutionary system.

Homo canis

2017 ◽  
Author(s):  
Raymond Pierotti ◽  
Brandy R. Fogg
Keyword(s):  
Human Evolution ◽  
Homo Sapiens ◽  
Social Groups ◽  
Modern Human ◽  
Biological Species ◽  
Shared Experience ◽  
Nuclear Families ◽  
Religious Traditions ◽  
Wide Range ◽  
History Of

This chapter examines what it means to be human, a member of the biological species Homo sapiens. Comparing humans to a wide range of primates, it shows that no other species has a similar social structure, with social groups of varying sizes built around nuclear families. Moreover, it explores how these traits may have been shaped by humans' shared experience with Canis lupus. Humans are indeed unique, but their adaptations emerge from a set of unusual events, and a considerable amount of the history of modern human evolution seems to be influenced by their association with wolves and their dog descendants. The chapter then demonstrates how modern attitudes toward predators result from religious traditions rather than scientific understanding.

Biogeography and taxonomy of racket-tail hummingbirds (Aves: Trochilidae: Ocreatus): evidence for species delimitation from morphology and display behavior

Zootaxa ◽  
2016 ◽  
Vol 4200 (1) ◽  
pp. 83 ◽  
Author(s):  
KARL-L. SCHUCHMANN ◽  
ANDRÉ-A. WELLER ◽  
DIETMAR JÜRGENS
Keyword(s):  
Geographic Variation ◽  
Endemic Species ◽  
Species Delimitation ◽  
Evolutionary History ◽  
Species Concept ◽  
Molecular Data ◽  
Biological Species ◽  
Biological Species Concept ◽  
Taxonomic History ◽  
History Of

We analyzed geographic variation, biogeography, and intrageneric relationships of racket-tail hummingbirds Ocreatus (Aves, Trochilidae). Presently, the genus is usually considered monospecific, with O. underwoodii including eight subspecies (polystictus, discifer, underwoodii, incommodus, melanantherus, peruanus, annae, addae), although up to three species have been recognized by some authors. In order to evaluate the current taxonomy we studied geographic variation in coloration, mensural characters, and behavioral data of all Ocreatus taxa. We briefly review the taxonomic history of the genus. Applying the Biological Species Concept, species delimitation was based on a qualitative-quantitative criteria analysis including an evaluation of character states. Our results indicate that the genus should be considered a superspecies with four species, the monotypic Ocreatus addae, O. annae, and O. peruanus, and the polytypic O. underwoodii (including the subspecies underwoodii, discifer, incommodus, melanantherus, polystictus). In this taxonomic treatment, O. annae becomes an endemic species to Peru and O. addae is endemic to Bolivia. We recommend additional sampling of distributional, ethological, and molecular data for an improved resolution of the evolutionary history of Ocreatus. 

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