Richard F. Johnston

House Sparrows: Rapid Evolution of Races in North America

Conspicuous adaptive differentiation in color and size has occurred in the house sparrow (Passer domesticus) in North America and the Hawaiian Islands since its introduction in the middle of the 19th century. Patterns of geographic variation in North America parallel those shown by native polytypic species, in conformity with Glogers and Bergmanns ecogeographic rules. Racial differentiation of house sparrow populations may require no more than 50 years.

THE GRINNELLIAN NICHE OF THE WOOD THRUSH

Our results suggest that the limits of the breeding range of the wood thrush and its relative abundance within its range are not highly related to the presence of ecologically similar species. These parameters are better accounted for by variables such as species-specific nesting and foraging requirements, which in turn covary with the vegetation structure of the eastern deciduous forest. Studies of single-species geographical ecology should precede studies of assemblages. The Grinnellian model is more likely than the Hutchinsonian model to provide sound information on factors regulating the distribution and abundance of animals. Nevertheless, without controlled experiments both the Hutchinsonian and the Grinnellian models are descriptive, and inferences about processes underlying patterns will continue to be weak. The neo-Grinnellian approach uses some of the same analytical techniques as the Hutchinsonian approach, but it employs multiple comparisons to study the geographical ecology of single species, and it is cautious about interpretation. Comparisons with congeners and species of similar ecology are still of interest, including the extent to which species differences result from interspecific niche shifts. An important problem that will always plague niche analysis based an observational data is whether regional differences in resource use are a reflection of (1) biological differences among the populations; (2) measurement of resources that are irrelevant to the species; or (3) interspecific niche shifts. In cases in which controlled experiments are not possible, this problem can be addressed as single-species, large, multifactor studies in geographical ecology. These studies need not be cast in terms of community theory. Future studies should try to clarify the relationship between habitat selection and both Hutchinsonian and Grinnellian niche analysis. Careful design of sampling procedures with multiple comparisons could permit evaluation of the relative power of proposed mechanisms to explain observed patterns.

Synanthropic birds of North America

Biological synanthropy refers to human-mediated symbioses. Synanthropic birds are thus avian symbionts of humans. Such birds have a wide degree of relationship to humans, ranging from the almost obligate to the tangential. Avian synanthropy, which includes urbanized and urbanizing birds, is a common ecological relationship, to which at least 25% of North American birds can be referred. Species known to be specialists on early stages of ecological succession, as well as habitat generalists, may be predisposed to be synanthropic. This paper presents certain details on the scope of the behavior and discusses the taxonomic range of birds that can be judged to be synanthropic. Synanthropy may have demographic consequences, such as decreased longevity and increased fecundity.

Evolution in the House Sparrow. III. Variation in Size and Sexual Dimorphism in Europe and North and South America

Geographic variation in size of skin variables in house sparrows Passer domesticus parallels the known variation in skeletal variables; size varies from small to large with latitude in North America but from large to small with latitude in Europe; there is no clinal pattern in our South American samples. Secondary sexual size dimorphism is wholly characteristic of house sparrows of all three continents. For North American and European samples there is smoothly clinal variation in the degree to which the sexes differ in size, with the greatest differences occurring at more northerly localities. The degree of size dimorphism increases northerly irrespective of geographic trends in overall size in either sex. Differential sexual size dimorphism may reflect differences in dominance between the sexes at winter feeding sites. Almost all Western Hemisphere populations of house sparrows show differences in size variables relative to those of probable ancestral European populations, but these are not sufficient by rigorous taxonomic standards to warrant nomenclatural recognition.

EVOLUTION IN THE HOUSE SPARROW. I. INTRAPOPULATION VARIATION IN NORTH AMERICA

This paper, the first in a series on evolution in the House Sparrow (Passer domesticus) in North America and other regions in which it has been introduced since 1850, presents an analysis of individual, age, and sexual variation in external morphological characters undertaken in preparation for studies of geographic variation. A preliminary report on geographic variation in North American populations has appeared (Johnston and Selander, 1964), and a full account will be presented in the second paper of this series (Selander and Johnston, unpublished data).

POPULATION STRUCTURE IN SALT MARSH SONG SPARROWS PART I. ENVIRONMENT AND ANNUAL CYCLE

The Song Sparrows (Melospiza melodia) that live on the salt marshes of San Francisco Bay, California, have attracted the attention of students of birds for the past sixty years. The principal reason for this has been their morphological distinctness from all other Song Sparrows, including those that live in areas close to the salt marshes. Such a pattern of differentiation and distribution has always raised the problem of how the salt-marsh populations maintain themselves as distinct entities. The study reported now is a continuation of previous work on salt-marsh Song Sparrows; the questions asked were, what characteristics of salt-marsh populations influence or have some relationship to the maintenance of their morphologic and/or genetic integrity, and how do these characteristics express themselves? Certain details bearing on these questions that are supplied in this and a succeeding paper have been interpreted in the light of the theoretical and factual framework partly supplied by such authors as Wright (1940; 1943), Mayr (1942; 1953), Miller (1947), and Marshall (1948). The Song Sparrows studied exist partly isolated from other populations of Song Sparrows on San Pablo salt marsh, Richmond, Contra Costa County. They offered advantages not otherwise generally available to the worker in population ecology of birds: they were abundant and were situated in a discrete unit of salt marsh; they belonged to a group genetically distinctive to the extent of being accorded the taxonomic status of race (M. m. samuelis); they were non-migratory; they had been studied from a general ecological viewpoint by Marshall (loc. cit.); and they belonged to a widespread species for which Nice (1937; 1943) had compiled a definitive life history based on studies in Ohio. Thus, most of the effort in studying the birds was directed to the investigation of population structure. Since these Song Sparrows differ in certain respects from those in Ohio, a number of features of their life history that bear on population structure are included. I have not offered a comparison of these differences except where it has seemed to be particularly significant. Generous help and counsel in the preparation of this report have been given me by Alden H. Miller, Frank A. Pitelka and Ray F. Smith; their suggestions have applied to all parts of the study. Responsibility for validity at all levels remains mine, however. The habitat photographs were taken by Joseph G. Hall. My wife, Lora Lee Johnston, assisted with preparation of manuscript. It is a pleasure to acknowledge the aid of these people.

Nonrandom Mating in Feral Pigeons

Feral pigeons (Columba livia) showed two sorts of nonrandom mating: sizebased assortative mating and plumage-based disassortative mating. Size-based mating was evident in that individuals of like sizes were paired; such mating was presumably based on perception of size or a size-correlated variable, such as social dominance rank, by both sexes. Plumage-based pairing was evident in that individuals of unlike plumages were bonded; this was based on perception of unlike plumage patterns, probably by females. Both sizebased and plumage-based pairing influenced reproductive output.

A multifactorial study of variation in interclutch interval and annual reproductive success in the feral pigeon,Columba livia

SummaryWe examined the relative ability of multiple factors to explain variation in two interrelated life-history traits, interclutch interval and annual reproductive success, in feral pigeons. Seasonal influences, brood size, and female body mass and tarsus length explained significant amounts of variation in interclutch interval in this population, while female plumage phenotype was insignificant. These results are discussed in terms of resource allocation and responses to environmental heterogeneity. Multivariate selection analysis revealed strong directional fecundity selection on body mass, and correlated selection response on bill length. A prospective selection analysis based on estimates of the genetic variance-covariance matrix revealed that the mean change in a trait often differed in sign from the directional selection estimate. The relationship between annual reproductive success and these two traits was found only in melanic females, suggesting that selection differentials may covary with plumage pattern.

Geographic variation in size of female wild Rock Doves

The Rock Dove (Columba livia) was domesticated around 5,000 years ago in the eastern Mediterranean region generally called the Near East (Levi 1974). Escapes of domestics from confinement for thousands of years have provided stocks that developed into feral populations. Feral pigeons now have characteristics of both wild and domestic ancestry, frequently live essentially as though they are wholly wild, and are capable of broadscale genetic introgression in wild colonies (Johnston et al. 1988, Johnston and Janiga 1995). In western Europe, wild colonies are known to exist in the Outer Hebrides of Scotland and perhaps on the coastline of northern and western Ireland; in the Mediterranean basin, wild colonies are known from coastal Sardinia, northwestern Egypt, and perhaps Libya and montane sectors of the former Yugoslavia. Interior montane North Africa, the Near East, Afghanistan, Pakistan, northwestern montane India, southwestern China, Uzbekistan, and Russia probably have Rock Dove populations that are still isolated from feral pigeons, but recent information is fragmentary. No information exists on the degree to which wild Rock Doves are killed for food by humans living under high densities in politically and economically unstable regions, but the birds can be subjected to overharvesting when their nesting cliffs are discovered by people short of dietary protein. For these reasons, as well as of the difficulties in travelling to some of the regions just noted, specimen samples of wild Rock Doves are not likely to be significantly augmented in the near future. An earlier report (Johnston 1992) on size variation was restricted to samples of male specimens, although a display of sexual size dimorphism over the characters employed was provided. Here I provide comparable data for females.

Annual review of ecology and systematics

This book contains proceedings of the Annual Review of Ecology and Systematics. Topics covered include: global change, world environment, ecology, ecosystems, interactions, pollutants and climatic change. with Volume 23 the succession from the pioneers to the next seral stage has been completed. This seems an appropriate opportunity to renew the invitation to members of the ecology and systematics communities last issued in Volume 14 (1983) for suggestions for reviews that we might not think of soliciting ourselves. The names of the spine and title have changed, bust the objectives have not.