The primary rationale for the use of phylogenetically based statistical methods is that phylogenetic signal, the tendency for related species to resemble each other, is ubiquitous. Whether this assertion is true for a given trait in a given lineage is an empirical question, but general tools for detecting and quantifying phylogenetic signal are inadequately developed. We present new methods for continuous-valued characters that can be implemented with either phylogenetically independent contrasts or generalized least-squares models. First, a simple randomization procedure allows one to test the null hypothesis of no pattern of similarity among relatives. The test demonstrates correct Type I error rate at a nominal α = 0.05 and good power (0.8) for simulated datasets with 20 or more species. Second, we derive a descriptive statistic, K, which allows valid comparisons of the amount of phylogenetic signal across traits and trees. Third, we provide two biologically motivated branch-length transformat...

/pdf/testing-for-phylogenetic-signal-in-comparative-data-3lvcin7t3t.pdf

Testing for phylogenetic signal in comparative data: behavioral traits are more labile.

1Department of Genetics, University of Georgia, Athens, Georgia 30602; 2NMFS/ CZES, Genetics, 2725 Montlake Boulevard East, Seattle, Washington 98112; 3Savannah River Ecology Laboratory, Drawer E, Aiken, South Carolina 29801; ~Department of Microbiology and Immunology, School of Medicine, University of California, Los Angeles, California 90024; -SSchool f Veterinary Medicine, Virginia Tech University, Blacksburg, Virginia 24046

/pdf/intraspecific-phylogeography-the-mitochondrial-dna-bridge-5e2au5n1qt.pdf

Intraspecific Phylogeography: The Mitochondrial DNA Bridge Between Population Genetics and Systematics

In a population of constant size the expected heterozygosity for a neutral locus when mutation and genetic drift are balanced is given by 4 Nv/(4Nv + 1) under the assumption that new mutations are always different from the pre-existing alleles in the population, where N is the effective population size and v the mutation rate per locus per generation (Kimura, 1968). The size of a natural population, however, often changes drastically in the evolutionary process. In an extreme case a single inseminated female from a large population may migrate to an unoccupied geographical or ecological territory and establish a new colony, followed by rapid population growth to form a new species. This process seems to have occurred repeatedly in the evolution of Hawaiian Drosophila species (Carson, 1970; 1971) and also in the establishment of the Bogota, Colombia, population of Drosophila pseudoobscura (Prakash, 1972). When population size is suddenly reduced, the average heterozygosity per locus is expected to decline, the rate of decline depending on the effective population size, while if population size increases the aver-

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1558-5646.1975.tb00807.x

The bottleneck effect and genetic variability in populations

There appears to be a general relationship between abundance and distribution that has two parts. First, within species, population density tends to be greatest in the center of the range and to decline gradually toward the boundaries. This pattern holds over a range of spatial scales from steep environmental gradients within local regions to the entire geographic range. Exceptions include: (1) abrupt changes in abundance that usually correspond to sharp, discontinuous changes in single environmental variables; and (2) multimodal patterns of abundance that are caused by environmental patchiness. The second general relationship is that among closely related, ecologically similar species spatial distribution is positively correlated with average abundance. Again this pattern holds over a variety of spatial scales from local regions to entire geographic ranges. These empirical patterns have already been reported in the literature, but their generality is demonstrated by analysis of additional data for divers...

On the Relationship between Abundance and Distribution of Species

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.

/pdf/the-ecology-of-individuals-incidence-and-implications-of-1qvkodaqfy.pdf

The Ecology of Individuals: Incidence and Implications of Individual Specialization

Animal species and evolution

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Animal species and evolution