File Name: biological systematics principles and applications .zip
The evidence for hypothesized relationships is typically shared derived characteristics synapomorphies that are not present in more distant groups and ancestors. Theoretically, a common ancestor and all its descendants are part of the clade, however, from an empirical perspective, common ancestors are inferences based on a cladistic hypothesis of relationships of taxa whose character states can be observed.
John D. Photograph: Courtship behavior in Linsleya Coleoptera: Meloidae. Sytematics is commonly defined as the study of biological diversity and the relationships among organisms. Taxonomy, that component of systematics specifically focusing on the theory and practice of classification, is not clearly separable and both are frequently used interchangeably by biologists.
John D. Photograph: Courtship behavior in Linsleya Coleoptera: Meloidae. Sytematics is commonly defined as the study of biological diversity and the relationships among organisms.
Taxonomy, that component of systematics specifically focusing on the theory and practice of classification, is not clearly separable and both are frequently used interchangeably by biologists. This chapter will first briefly review the importance of systematics to the pest management enterprise and then summarize the use of biological characteristics in systematic research. Entomophagous insects will be stressed due to their significant role in pest management and because the systematics of these groups have frequently employed biological characteristics.
A distinction is often made in systematics between higher classification and species classification. It will also be useful here to discuss the role of biological characters at these two levels. Systematics plays a central role in biology by providing the means for characterizing the organisms that we study.
Through the production of classifications that reflect evolutionary relationships it also allows predictions and testable hypotheses. By allowing taxa taxonomic groups to be correctly identified classifications provide a key to the literature and a means for organizing information Danks Our ability to predict biological characteristics is a particularly valuable product of classifications that often is taken for granted.
For example, it is only because of robust classifications that we can assume with reasonable assurance that any wasp of the families Trichogrammatidae or Scelionidae is an insect egg parasite, that a species of Pipunculidae Diptera is a parasite of Homoptera, that a wasp identified as a Signiphoridae is likely to be a hyperparasite via another species of chalcidoid, and that an adult blister beetle of the genus Epicauta is phytophagous but has a larval stage which feeds on grasshopper eggs.
The importance of sound systematics in pest management is obvious. Pest species and their natural enemies must be correctly identified before adequate control measures can be contemplated. Armed with an identification we automatically know something about the biology and distribution of the pest organism.
If the species has previously been studied the literature can be tapped for information. If it has not been studied some preliminary measures can be taken based on knowledge accumulated on related species. If it is an exotic pest and biological control is contemplated, the identification can help us determine the original home of the species and the area where foreign exploration for parasites, predators or pathogens is likely to be most productive.
Similarly, identification of the natural enemies already in place allows some estimate of the importance of natural control and the likelihood that the introduction of exotics will be required. Pest management entomologists must always keep in mind that systematics, like all scientific endeavors, is not a static field. Consequently classifications, which in the final analysis are hypotheses of relationship, as well as the identifications that they allow, are provisional and subject to change, particularly as new taxa and characters are discovered.
In many cases, identifications are required and made before a group has been adequately studied taxonomically. For example, Trichogramma, a genus of insect egg parasites commonly used in augmentative release programs against pestiferous Lepidoptera, has been of interest to entomologists for over a century.
These minute wasps are extremely difficult to identify and their diversity was vastly underestimated until only recently. Whereas only six species were considered identifiable as late as , well over species are now known Pinto and Stouthamer Needless to say, most of the species names used in the vast Trichogramma literature for the past years are incorrect or at least suspect.
Because the specimens on which these published data are based were rarely preserved, we are unable to verify the original identifications or determine the correct new names based on current knowledge. As a result very little of this considerable literature is useful to modern researchers. For this reason it is absolutely imperative that investigators safeguard the results of their research by depositing voucher specimens in a prominent collection.
This is particularly important for entomophagous insects, a group which because of small body size and morphological homogeneity, are more poorly known taxonomically than most. Taxonomic characters have been variously defined, but for our purpose we can consider them as attributes of a taxon that allow its differentiation or potential differentiation from others. Characters or traits used in taxonomy are hypothesized as being under genetic control although this is rarely tested directly.
Characters are used to construct classifications and to identify the taxa which classifications recognize. A character useful for identification is not necessarily useful for constructing a classification, and vice-versa. Taxonomic characters can be conveniently categorized as morphological, physiological, molecular, ecological, reproductive and behavioral. For our purposes "biological characters" will specifically refer to the last three categories. Reproductive characters are herein restricted to mode of reproduction and reproductive compatibility.
The vast majority of classifications and keys for identification are based on morphological characters. This is not because they are inherently better for systematics but because they are more easily observed and evaluated for variation. The other kinds of characters often require expensive equipment, live material and they are more difficult to voucher.
Estimating variation in particular is not a trivial matter with non-morphological characters. Given reasonably complete collections in museums, it is relatively straightforward to determine if a morphological character occurs throughout the range of a species, in all or only a subset of the known species of a genus, in all or only a subset of the known genera in a family, etc. The equivalent documentation for consistency of biological characters such as host preference, or reproductive incompatibility requires far more energy and resources.
Consequently the danger of basing taxonomic hypotheses on insufficient data generally is greater when non-morphological characters are emphasized. This is not to discourage the use of non-traditional character sources in systematics, indeed they are often indispensable, but simply to stress the importance of adequate sampling. Certainly, classifications and species concepts are most robust when based on and supported by a variety of character sources.
Biological traits have frequently been used at all levels in higher classification, i. Behavioral and ecological characters have been particularly popular. For obvious reasons, reproductive characters are most commonly employed in the formulation of species concepts.
In many cases, taxa are grouped informally on the basis of biological traits simply for convenience or heuristic reasons. For example, dividing the parasitic Hymenoptera into idiobionts host killed immediately or soon after oviposition and koinobionts host allowed to develop a period of time after oviposition are useful artificial groupings not intended to imply relationship.
In other cases, however, biological traits have inappropriately been considered of special importance and weighted as indicators of natural groupings without attention to contradictory evidence from other characters. Thus the parasitoid families Rhipiphoridae and Meloidae Coleoptera , and in some cases the Strepsiptera as well, have been placed together primarily because of behavioral and developmental similarities all have phoretic first instar larvae and hypermetamorphic development.
These groupings cannot be justified once other features are considered and the similarities must be attributed to convergent evolution rather than homology similarities derived from a common ancestor. Ideally, the testing of the relative reliability of behavioral and ecological traits for natural groupings relies on their incorporation with other characters for phylogenetic analysis using cladistic methodology, or subsequently mapping them onto previously established cladograms.
Obviously those traits showing the least convergence or homoplasy are the most useful for classification. Although the utilization of behavior and ecology clearly is a developing field, the concern that these features are more homoplastic than morphological traits and thus less reliable for estimating phylogenetic relationships seems to be unfounded Wenzel , Miller and Wenzel These conclusions are based on phylogenetic or cladistic character analysis using principles developed by the German systematist Willi Hennig.
Phylogenetic classifications can be of value for predicting life history data for groups with incompletely known biologies. Gauld has outlined such an application of classifications for the ichneumonid subfamily Labeninae.
Cladistic analysis based on morphological features recognized four lineages: Labenini, Groteini, Poecilocryptini and Brachycyrtini. Armed with this analysis and meagre knowledge on labenine biology, Gauld hypothesized a scenario for the evolution of biological characteristics in the subfamily.
He also noted that general biological characteristics of a poorly studied group can often be predicted on the basis of data from a sister group phylogenetically most closely related taxon for which such traits are known. Shaw provides an excellent example of how a biological character, in this case host utilization in the Braconidae and in the Euphorinae in particular, can be evaluated phylogenetically.
For this he first constructed phylogenetic trees based on morphology alone. Host associations in the various tribes were then mapped on the resultant trees. The Euphorinae utilize the adult stage of various insect taxa as hosts.
Adult parasitism is uncommon in the Braconidae but also is known in the Neoneurinae and Aphidiinae. Some might be tempted to weight this trait and suggest that this important feature, so uncommon in the family, indicates the relationship of these three subfamilies.
However, phylogenetic analysis shows this not to be the case at all. Adult parasitism correlates poorly with other characters suggesting that it is not a homologous character but has evolved independently in each subfamily. Shaw also shows that among the numerous groups of insects attacked by euphorines, the origin of adult parasitism in the subfamily was probably via the Chrysomelidae, and presents hypotheses for the sequence of host shifts in the various tribes. He finds evidence that these host shifts are to closely related taxa in some cases, and in other cases to unrelated taxa occurring in the same microhabitat.
The taxonomic use of biological characters is more common at the species level. Rather than being used to show relationship, the search at this level is for species-specific traits that allow separation or identification. Such characters are employed quite frequently in entomophagous groups of insects because 1 such data often accumulate in the process of biological control studies, and 2 many taxa are morphologically conservative, requiring other character sources for optimal characterization and identification.
Most modern hypotheses of species in bisexual animal groups follow the biological species concept and carry the assumption of reproductive isolation from closely related species. Species that are reproductively isolated but morphologically identical or nearly so are referred to as cryptic species.
Biological characters most frequently used to help distinguish cryptic species of entomophagous insects are ecological, behavioral and reproductive. Ecological data. Host or habitat disjunction among morphologically similar forms often provide clues that cryptic species are involved.
Numerous species of entomophagous insects were recognized only after ecological differences were found. In some cases, these differences increased the systematist's confidence that previously detected but minor morphological traits were significant at the species level; in other cases, they facilitated their discovery. Although relatively little biological information has accumulated for entomophagous insects, it appears that microhabitat preference is more likely to be species specific than is host preference.
For example in the genus Trichogramma all species studied to any extent are known to parasitize the eggs of a variety of hosts Pinto and Stouthamer Yet there appears to be considerable habitat specificity in this genus. Some species prefer field habitats, other are found most frequently in arboreal situations, others prefer marshes, and some are common in disturbed habitats but absent from adjacent natural areas.
Even within a particular habitat there may be considerable preference. Norlund cites examples showing that for certain species parasitization of a host egg depends on the crop plant it is laid on, and Pinto and Stouthamer note that in southern California different Trichogramma are associated with different species of chaparral plants growing side by side. Similar microhabitat preferences occur in the Ichneumonidae, one of the largest groups of insects. Again, these are considered to be of much greater significance than host preferences.
This is not to negate the potential importance of host differences in signaling species differences. There are several cases of cryptic species associated with different hosts. For example, Trioxys utilis Muesebeck, an aphidiine Braconidae introduced into California against the spotted alfalfa aphid, Therioaphis maculata Bucktron , is very similar morphologically to T. Both species were considered conspecific for a time Rosen Cases are also known with closely related species of the same genus occupying different trophic levels as parasite and hyperparasite of the same host and in the same habitat.
Although host preference may initially suggest distinct species are involved, as in the case of Trioxys, habitat differences, reproductive incompatibility and minor morphological differences are usually also found once the taxa become well studied.
Embed Size px x x x x Schuh, , , Cornell University Press, Most students who take a course in biological systematics do so to learn how to construct a data matrix and generate and evaluate a tree of phylogenetic relationships. Schuh, provides a welcome tool for these students and their instructors: it is a comprehensive and completely new textbook, the first of its kind since Systematics, the study of the reconstruction of the history of life, forms the underlying basis for organizing the knowledge of biology; cladistics is the diagrammatic method of charting phylogenetic relationships over time among evolving life forms. Cladistics analysis, the key tool used in this book, is also of great use outside pure systematic studies, and interests many students of population biology, ecology, epidemiology, and natural resources. Suitable for both graduate and advanced undergraduate students, Biological Systematics: Principles and Applications covers the core material for courses in biological systematics, with equal emphasis on both botany and zoology.
Editorial Board. Systematic Biology is the bimonthly journal of the Society of Systematic Biologists. Papers for the journal are original contributions to the theory, principles, and methods of systematics as well as phylogeny, evolution …. The society offers special rates for students, options for multi-year memberships, and affordable lifetime memberships. Find out more Read past winners of the Publisher's Award. Joyce C.
It was written by the following authors: Andrew V. Brower , Randall T. Book Biological Systematics: Principles and Applications, which can be read online, published by the company: Cornell University Press. Other books on similar topics can be found in sections: Medicine , Science , Technology. The book was published on
Schuh, Andrew V. Brower Biological Systematics: Principles and Applications draws equally from examples in botany and zoology to provide a modern account of cladistic principles and techniques. It is a core systematics textbook with a focus on parsimony-based approaches for students and biologists interested in systematics and comparative biology. In this new and thoroughly revised edition, Randall T.
Department of Chemistry Prepare for employment, post-graduate education, or life-long learning. We keep the library up-to-date, so you may find new or improved material here over time. The ancient Egyptians first identified, studied, and applied the principles of chemistry to extract metal from ores, make alcoholic beverages, glaze pottery, turn fat into soap, and much more. Do You Know Edujournal - October 13, Literature Notes.
Most students who take a course in biological systematics do so to learn how to construct a data matrix and generate and evaluate a tree of phylogenetic relationships. Schuh, providesMoreMost students who take a course in biological systematics do so to learn how to construct a data matrix and generate and evaluate a tree of phylogenetic relationships. Schuh, provides a welcome tool for these students and their instructors: it is a comprehensive and completely new textbook, the first of its kind since Systematics, the study of the reconstruction of the history of life, forms the underlying basis for organizing the knowledge of biology- cladistics is the diagrammatic method of charting phylogenetic relationships over time among evolving life forms. Cladistics analysis, the key tool used in this book, is also of great use outside pure systematic studies, and interests many students of population biology, ecology, epidemiology, and natural resources. Suitable for both graduate and advanced undergraduate students, Biological Systematics: Principles and Applications covers the core material for courses in biological systematics, with equal emphasis on both botany and zoology.
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Biological Systematics: Principles and Applicationsdraws equally from examples in botany and zoology to provide a modern account of cladistic principles and.Tilly G. 18.12.2020 at 20:04
About This Book. Biological Systematics: Principles and Applications draws equally from examples in botany and zoology to provide a modern account of cladistic.