Stephen I. Rothstein

Bio: Stephen I. Rothstein is an academic researcher from University of California, Santa Barbara. The author has contributed to research in topics: Cowbird & Brood parasite. The author has an hindex of 39, co-authored 114 publications receiving 6495 citations. Previous affiliations of Stephen I. Rothstein include University of California, Berkeley.

A Model System for Coevolution: Avian Brood Parasitism

Abstract: Many putative examples of coevolution do not stand up to critical analysis. A rigorous definition of coevolution requires that a trait in one species has evolved in response to a trait of another species, which trait was itself evolved in response to the first species (50, 69). This type of intimate, reciprocal evolutionary relationship is hard to demonstrate because most species interact with many other species, all of which may affect their evolution. For example, a host species is likely to be affected by many types of parasitic helminths and protozoans. Accordingly, some of its defenses will be fairly general and not attributable to any particular species of parasite. Such situations are termed diffuse coevolution, as opposed to pairwise coevolution in which adaptations have a stepwise, reciprocal nature. Unfortunately, diffuse coevolution is difficult to document because additional species may need to be considered. Also, adapting to many species may compromise adaptations to any one species so much that coevolutionary traits are weakly expressed and hard to identify. Systems in which the interacting species are few (optimally only two) provide the clearest examples of coevolution. Such systems include many mutualistic relationships and some parasite-host associations (51). Among the latter, brood parasitism provides some of the most persuasive examples of coevolution because it often involves small numbers of species.

An Experimental and Teleonomic Investigation of Avian Brood Parasitism

Abstract: The term “teleonomy” has been suggested by Williams (1966:258) to describe the scientific study of adaptations. Williams indicated that relatively few evolutionary studies deal primarily with teleonomy despite the fact that adaptation is the most basic feature of evolution and of all biology. Avian brood parasitism, the phenomenon in which certain birds, the parasites, deposit their eggs in the nests of other birds, their hosts, is especially well suited to teleonomic studies since it provides a system in which the presence or absence of relatively obvious adaptations can be examined in two interacting genetic lineages. Parasitism is typically detrimental to the host’ s reproductive efforts and selection favors defenses that reduce the impact of the parasite. These host defenses are in turn damaging to the parasite’ s reproductive efforts and selection favors counter-adaptations by the parasite. cause the death of all of the host’ s own young through competition for food (Friedmann 1963 ) . In certain cases, brood parasites seem to have extirpated or caused declines of local host populations (Schiermann in Southern 1954:221, Bond in Friedmann 1971:250, Mayfield 1961a). Thus, the adaptive value of host defenses is clearly very great.

Conserving migratory land birds in the new world: do we know enough?

Abstract: Migratory bird needs must be met during four phases of the year: breeding season, fall migration, wintering, and spring migration; thus, management may be needed during all four phases. The bulk of research and management has focused on the breeding season, although several issues remain unsettled, including the spatial extent of habitat influences on fitness and the importance of habitat on the breeding grounds used after breeding. Although detailed investigations have shed light on the ecology and population dynamics of a few avian species, knowledge is sketchy for most species. Replication of comprehensive studies is needed for multiple species across a range of areas, Information deficiencies are even greater during the wintering season, when birds require sites that provide security and food resources needed for survival and developing nutrient reserves for spring migration and, possibly, reproduction. Research is needed on many species simply to identify geographic distributions, wintering sites, habitat use, and basic ecology. Studies are complicated, however, by the mobility of birds and by sexual segregation during winter. Stable-isotope methodology has offered an opportunity to identify linkages between breeding and wintering sites, which facilitates understanding the complete annual cycle of birds. The twice-annual migrations are the poorest-understood events in a bird's life. Migration has always been a risky undertaking, with such anthropogenic features as tall buildings, towers, and wind generators adding to the risk. Species such as woodland specialists migrating through eastern North America have numerous options for pausing during migration to replenish nutrients, but some species depend on limited stopover locations. Research needs for migration include identifying pathways and timetables of migration, quality and distribution of habitats, threats posed by towers and other tall structures, and any bottlenecks for migration. Issues such as human population growth, acid deposition, climate change, and exotic diseases are global concerns with uncertain consequences to migratory birds and even less-certain remedies. Despite enormous gaps in our understanding of these birds, research, much of it occurring in the past 30 years, has provided sufficient information to make intelligent conservation efforts but needs to expand to handle future challenges.

Recent advances in understanding migration systems of New World land birds

Abstract: Our understanding of migratory birds' year-round ecology and evolution remains patchy despite recent fundamental advances. Periodic reviews focus future research and inform conservation and management; here, we take advantage of our combined experiences working on Western Hemisphere avian migration systems to highlight recent lessons and critical gaps in knowledge. Among topics discussed are: (1) The pipeline from pure to applied researchers leaves room for improvement. (2) Population limitation and regulation includes both seasonal and between-season interactions. (3) The study of movements of small-bodied species remains a major research frontier. (4) We must increase our understanding of population connectivity. (5) With few exceptions, population regulation has barely been investigated. (6) We have increasingly integrated landscape configuration of habitats, large-scale habitat disturbances, and habitat quality impacts into models of seasonal and overall demographic success. (7) The post-breeding seas...

Evolutionary Rates and Host Defenses Against Avian Brood Parasitism

Abstract: Experiments investigating host defenses against the brood parasitism of the brown-headed cowbird revealed that, within most species, nearly all individuals either accept or reject cowbird eggs. Therefore, species are easily designated as "accepters" or "rejecters". The results of these experiments differ somewhat from data on natural cowbird parasitism, where some species seem to be variable in their response. However, much of what appears in natural cowbird parasitism to be variable expressions of host defenses are probably not responses specific to cowbird parasitism but are manifestations of standard avian behavior patterns. I hypothesize that few intermediate species exist, because host defenses are selected so strongly that the time span over which any species shows an intermediate rejection rate is of short duration. Hence, the number of species in transition from accepter to rejecter is always low. Most accepters did show low rates (less than 20%) of apparent rejection to experimental cowbird paras...

Human biochemical genetics

Abstract: So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

The Ecology of Individuals: Incidence and Implications of Individual Specialization

Abstract: Most empirical and theoretical studies of resource use and population dynamics treat conspecific individuals as ecologically equivalent. This simplification is only justified if interindividual niche variation is rare, weak, or has a trivial effect on ecological processes. This article reviews the incidence, degree, causes, and implications of individual-level niche variation to challenge these simplifications. Evidence for individual specialization is available for 93 species dis- tributed across a broad range of taxonomic groups. Although few studies have quantified the degree to which individuals are specialized relative to their population, between-individual variation can some- times comprise the majority of the population's niche width. The degree of individual specialization varies widely among species and among populations, reflecting a diverse array of physiological, be- havioral, and ecological mechanisms that can generate intrapopu- lation variation. Finally, individual specialization has potentially im- portant ecological, evolutionary, and conservation implications. Theory suggests that niche variation facilitates frequency-dependent interactions that can profoundly affect the population's stability, the amount of intraspecific competition, fitness-function shapes, and the population's capacity to diversify and speciate rapidly. Our collection of case studies suggests that individual specialization is a widespread but underappreciated phenomenon that poses many important but unanswered questions.

Arms races between and within species.

Abstract: An adaptation in one lineage (e.g. predators) may change the selection pressure on another lineage (e.g. prey), giving rise to a counter-adaptation. If this occurs reciprocally, an unstable runaway escalation or 9arms race9 may result. We discuss various factors which might give one side an advantage in an arms race. For example, a lineage under strong selection may out-evolve a weakly selected one (9the life-dinner principle9). We then classify arms races in two independent ways. They may be symmetric or asymmetric, and they may be interspecific or intraspecific. Our example of an asymmetric interspecific arms race is that between brood parasites and their hosts. The arms race concept may help to reduce the mystery of why cuckoo hosts are so good at detecting cuckoo eggs, but so bad at detecting cuckoo nestlings. The evolutionary contest between queen and worker ants over relative parental investment is a good example of an intraspecific asymmetric arms race. Such cases raise special problems because the participants share the same gene pool. Interspecific symmetric arms races are unlikely to be important, because competitors tend to diverge rather than escalate competitive adaptations. Intraspecific symmetric arms races, exemplified by adaptations for male-male competition, may underlie Cope9s Rule and even the extinction of lineages. Finally we consider ways in which arms races can end. One lineage may drive the other to extinction; one may reach an optimum, thereby preventing the other from doing so; a particularly interesting possibility, exemplified by flower-bee coevolution, is that both sides may reach a mutual local optimum; lastly, arms races may have no stable end but may cycle continuously. We do not wish necessarily to suggest that all, or even most, evolutionary change results from arms races, but we do suggest that the arms race concept may help to resolve three long-standing questions in evolutionary theory. 9Wonderful and admirable as most instincts are, yet they cannot be considered as absolutely perfect: there is a constant struggle going on throughout nature between the instinct of the one to escape its enemy and of the other to secure its prey9 (Charles Darwin, in Romanes I883).