Hybrid zones are, roughly speaking, narrow regions in which genetically distinct populations meet, mate, and produce hybrids. They are often only a few hundred meters wide and yet may be several hundred kilometers long. They are found in a wide variety of organisms: Tables 1 and 2 list about 150 reasonably clear examples, in which there is a spatial transition between two hybridizing forms. Such a widespread and striking phenomenon requires explanation; more importantly, it offers us several ways of understanding the nature and origin of species. First, hybrid zones pose interesting questions for the taxonomist, for they contrast two views of the species: as a set of populations delimited by genetic barriers to gene exchange; and as a set of populations maintained in a particular stable equilibrium by selection. Second, the wide range of genotypes found in a hybrid zone can be used to analyze the genetic differences and selective forces that separate the taxa involved. This may allow some inferences about the way these differences evolved and, by extrapolation, about the way fully isolated species diverge from each other. Finally, models of parapatric speciation, and of Wright's "shifting balance," involve the formation, move­ ment, and modification of hybrid zones. Hybrid zones must be understood before the plausibility of these models can be judged. After clarifying our terminology, we will summarize the relevant theory and then see how this can be used to make inferences from field data. A notable increase in the number of detailed genetic studies of hybrid zones occurred over

Analysis of Hybrid Zones

The principles of classification and a classification of mammals. Bulletin of the AMNH ; v. 85

This review compiles and evaluates existing scientific information on the use, limitations, and procedural considerations for EROD activity (a catalytic measurement of cytochrome P4501A induction) ...

Ethoxyresorufin-O-deethylase (EROD) activity in fish as a biomarker of chemical exposure.

We define a genetic species as a group of genetically compatible interbreeding natural populations that is genetically isolated from other such groups. This focus on genetic isolation rather than reproductive isolation distinguishes the Genetic Species Concept from the Biological Species Concept. Recognition of species that are genetically isolated (but not reproductively isolated) results in an enhanced understanding of biodiversity and the nature of speciation as well as speciation-based issues and evolution of mammals. We review criteria and methods for recognizing species of mammals and explore a theoretical scenario, the Bateson‐Dobzhansky‐ Muller (BDM) model, for understanding and predicting genetic diversity and speciation in mammals. If the BDM model is operating in mammals, then genetically defined phylogroups would be predicted to occur within species defined by morphology, and phylogroups experiencing stabilizing selection will evolve genetic isolation without concomitant morphological diversification. Such species will be undetectable using classical skin and skull morphology (Morphological Species Concept). Using cytochrome-b data from sister species of mammals recognized by classical morphological studies, we estimated the number of phylogroups that exist within mammalian species and hypothesize that there will be .2,000 currently unrecognized species of mammals. Such an underestimation significantly affects conclusions on the nature of speciation in mammals, barriers associated with evolution of genetic isolation, estimates of biodiversity, design of conservation initiatives, zoonoses, and so on. A paradigm shift relative to this and other speciation-based issues will be needed. Data that will be effective in detecting these ‘‘morphologically cryptic genetic species’’ are genetic, especially DNA-sequence data. Application of the Genetic Species Concept uses genetic data from mitochondrial and nuclear genomes to identify species and species boundaries, the extent to which the integrity of the gene pool is protected, nature of hybridization (if present), and introgression. Genetic data are unique in understanding species because the use of genetic data 1) can quantify genetic divergence from different aspects of the genome (mitochondrial and nuclear genes, protein coding genes, regulatory genes, mobile DNA, microsatellites, chromosomal rearrangements, heterochromatin, etc.); 2) can provide divergence values that increase with time, providing an estimate of time since divergence; 3) can provide a population genetics perspective; 4) is less subject to convergence and parallelism relative to other sets of characters; 5) can identify monophyly, sister taxa, and presence or absence of introgression; and 6) can accurately identify hybrid individuals (kinship and source of hybrid individuals, F1s, backcrosses, direction of hybridization, and in concert with other data identify which hybrids are sterile or fertile). The proposed definition of the Genetic Species Concept is more compatible with a description of biodiversity of mammals than is ‘‘reproductively isolated species.’’ Genetic profiles of mammalian species will result in a genetic description of species and mammalian diversity, and such studies are being accelerated by technological advances that reduce cost and increase speed and efficiency of generating genetic data. We propose that this genetic revolution remain museum- and voucher specimen‐based and that new names are based on a holotype (including associated tissues) deposited in an accredited museum.

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Speciation in mammals and the genetic species concept

This report describes the results of nonvolant mammal inventory fieldwork at Paracou, a lowland rainforest locality in northern French Guiana, and concludes the faunal analysis introduced by our previous monograph on the bats of Paracou (Simmons and Voss, 1998). Working within a 3–km radius over the course of 202 sampling dates from 1991 to 1994, we recorded a total of 64 nonvolant species by conventional trapping, arboreal platform trapping, pitfall trapping, diurnal and nocturnal hunting, and interviews with local residents. Included in this total species count are 12 marsupials, 9 xenarthrans, 6 primates, 10 carnivores, 5 ungulates, and 22 rodents. Systematic research with nonvolant mammal specimens collected as voucher material resulted in the discovery of new taxa, documented range extensions of previously described species, and helped resolve many longstanding taxonomic problems: (1) Gracilinanus emiliae (Thomas), herein reported for the first time from French Guiana, is redescribed and its...

The mammals of paracou, french guiana: a neotropical lowland rainforest fauna part 2. nonvolant species

Mammals of South America, Volume 1: Marsupials, Xenarthrans, Shrews, and Bats

The vast terrain between Panama and Tierra del Fuego contains some of the world's richest mammalian fauna, but until now it has lacked a comprehensive systematic reference to the identification, distribution, and taxonomy of its mammals. The first such book of its kind and the inaugural volume in a three-part series, "Mammals of South America" both summarizes existing information and encourages further research of the mammals indigenous to the region. Containing identification keys and brief descriptions of each order, family, and genus, the first volume of "Mammals of South America" covers marsupials, shrews, armadillos, sloths, anteaters, and bats. Species accounts include taxonomic descriptions, synonymies, keys to identification, distributions with maps and a gazetteer of marginal localities, lists of recognized subspecies, brief summaries of natural history information, and discussions of issues related to taxonomic interpretations. Highly anticipated and much needed, this book will be a landmark contribution to mammalogy, zoology, tropical biology, and conservation biology.

Mammals of South America

Handley, Charles O., Jr., Don E. Wilson, and Alfred L. Gardner, editors. Demography and Natural History of the Common Fruit Bat, Artibeus jamaicensis, on Barro Colorado Island, Panama. Smithsonian Contributions to Zoology, number 511, 173 pages, 69 figures, 62 tables, 1991.—Bats were marked and monitored on Barro Colorado Island, Panama, to study seasonal and annual variation in distribution, abundance, and natural history from 1975 through 1980. Data gathered advances our knowledge about flocking; abundance; feeding strategies; social behavior; species richness; population structure and stability; age and sex ratios; life expectancy and longevity; nightly, seasonal, and annual movements; synchrony within and between species in reproductive activity; timing of reproductive cycles; survival and dispersal of recruits; intra-and inter-specific relationships; and day and night roost selection. Barro Colorado Island (BCI) harbors large populations of bats that feed on the fruit of canopy trees, especially figs. These trees are abundant, and the individual asynchrony of their fruiting rhythms results in a fairly uniform abundance of fruit. When figs are scarce, a variety of other fruits is available to replace them. This relatively dependable food supply attracts a remarkably rich guild of bats. Although we marked all bats caught, we tried to maximize the number of Artibeus jamaicensis netted, because it is abundant Q-h of the total catch of bats on BCI), easily captured by conventional means (mist nets set at ground level), and responds well to handling and marking. An average Artibeus jamaicensis is a 45 g frugivore that eats roughly its weight in fruit every night. These bats prefer figs and often seek them out even when other types of fruit they might eat are far more abundant. They commute several hundred meters to feeding trees on the average, feeding on fruit from one to four trees each night, and returning to a single fruiting tree an average of four nights in succession. The bats tend to fly farther when fewer fig trees are bearing ripe fruit, and they feed from fewer trees, on the average, when the moon is nearly full. These bats, like their congeners, do not feed in the fruiting tree itself. Instead, they select a fruit and carry it to a feeding roost typically about 100 m away before eating it. We utilized radio telemetry to assess feeding rates from the number of "feeding passes"—transits between fruit tree and feeding roost. Bats are often netted while carrying fruit, revealing their diet. Feces also reveal dietary information. Adult female A. jamaicensis live in harems of three to 30 individuals with a single adult male. On BCI the harem groups roost during the day in hollow trees. There is presumably a large population of surplus males that roost together with nonadults of both sexes in foliage. Females commute an average of 600 m from their day roosts to feeding sites, and harem males travel less than 300 m. Twice a year most females give birth to a single young, once in March or April, and again in July or August; active gestation averages about 19 weeks. Juveniles are first netted when they are about ten weeks old, and females usually first bear young in March or April following their year of birth. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: The coral Montastrea cavernosa (Linnaeus). Library of Congress Caialoging-in-Publicalion Data Handley, Charles O. (Charles Overtoil), 1924Demography and natural history of the common fruit bat, Artibeus jamaicensis, on Barro Colorado Island, Panama / Charles O. Handley, Jr., Don E. Wilson, and Alfred L. Gardner. p. cm. — (Smithsonian contributions to zoology, no. 511) Includes bibliographical references (p. ). 1. Artibeus jamaicensis—Panama—Barro Colorado Island. I. Wilson, Don E. II. Gardner, Alfred L. III. Tide. IV. Series. QL1.S54 no. 511 [QL737.C57] 591 s-dc20 [599.4] 91-13449 @ The paper used in this publication meets the minimum requirements of the American National Standard for Permanence of Paper for Printed Library Materials Z39.48—1984.

Demography and natural history of the common fruit bat, Artibeus jamaicensis, on Barro Colorado Island, Panamá

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Karyotypic variation in oryzomyine rodents (Cricetinae) with comments on chromosomal evolution in the neotropical cricetine complex

Systematic studies of oryzomyine rodents (Muridae, Sigmodontinae) : diagnoses and distributions of species formerly assigned to Oryzomys "capito". Bulletin of the AMNH ; no. 236

Alfred L. Gardner

Papers

Mammals of South America, Volume 1: Marsupials, Xenarthrans, Shrews, and Bats

Mammals of South America

Demography and natural history of the common fruit bat, Artibeus jamaicensis, on Barro Colorado Island, Panamá

Karyotypic variation in oryzomyine rodents (Cricetinae) with comments on chromosomal evolution in the neotropical cricetine complex

Systematic studies of oryzomyine rodents (Muridae, Sigmodontinae) : diagnoses and distributions of species formerly assigned to Oryzomys "capito". Bulletin of the AMNH ; no. 236