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Diploid organisms manipulate the extent to which their haploid gametes experience selection. Animals typically produce sperm with a diploid complement of most proteins and RNA, limiting selection on the haploid genotype. Plants, however, exhibit extensive expression in pollen, with actively transcribed haploid genomes. Here we analyze models that track the evolution of genes that modify the strength of haploid selection to predict when evolution intensifies and when it dampens the "selective arena" within which male gametes compete for fertilization. Considering deleterious mutations, evolution leads diploid mothers to strengthen selection among haploid sperm/pollen, because this reduces themutation load inherited by their diploid offspring. If, however, selection acts in opposite directions in haploids and diploids ("ploidally antagonistic selection"), mothers evolve to reduce haploid selection to avoid selectively amplifying alleles harmful to their offspring. Consequently, with maternal control, selection in the haploid phase either is maximized or reaches an intermediate state, depending on the deleterious mutation rate relative to the extent of ploidally antagonistic selection. By contrast, evolution generally leads diploid fathers to mask mutations in their gametes to the maximum extent possible, whenever masking (e.g., through transcript sharing) increases the average fitness of a father's gametes. We discuss the implications of this maternal-paternal conflict over the extent of haploid selection and describe empirical studies needed to refine our understanding of haploid selection among seemingly diploid organisms. [ABSTRACT FROM AUTHOR]

The author discusses the concerns raised by Soltis and colleagues regarding a study which used likelihood methods to estimate the impact of polyploidization events on diversification rates in plants. Topics discussed include the definition of polyploid lineage, the philosophical criticism about reticulate evolution, which is common among polyploid lineages, and the effects on polyploidy.

Females vary in the size of offspring that they produce, often in a manner that depends on maternal age or stage. This is puzzling, given that offspring size is predicted to evolve to a single optimal value where the gain in fitness from being larger exactly offsets the fitness lost to the mother by producing fewer offspring. We used a stage-structured life-history model to determine the optimal offspring size for females in different stages. We found that optimal offspring size does not vary with maternal stage when offspring fitness depends only on its size and not on the stage of the mother. This negative result holds even with density dependence, when larger offspring compete better. However, a trade-off between offspring size and maternal survival affects the optimal offspring size. The future reproductive value of the female, coupled with the costs and benefits of offspring investment, drives the evolution of stage-dependent offspring size. If producing larger offspring is riskier for mothers, females produce smaller offspring when their reproductive value in the next time step is large relative to current reproductive prospects. These analyses provide a novel framework for understanding why offspring size varies in age- and stage-structured populations. [ABSTRACT FROM AUTHOR]

Environmental change, if severe, can drive a population extinct unless the population succeeds in adapting to the new conditions. How likely is a population to win the race between population decline and adaptive evolution? Assuming that environmental degradation progresses across a habitat, we analyze the impact of several ecological factors on the probability of evolutionary rescue. Specifically, we study the influence of population structure and density- dependent competition as well as the speed and severity of environmental change. We also determine the relative contribution of standing genetic variation and new mutations to evolutionary rescue. To describe population structure, we use a generalized island model, where islands are affected by environmental deterioration one after the other. Our analysis is based on the mathematical theory of timeinhomogeneous branching processes and complemented by computer simulations. We find that in the interplay of various, partially antagonistic effects, the probability of evolutionary rescue can show nontrivial and unexpected dependence on ecological characteristics. In particular, we generally observe a nonmonotonic dependence on the migration rate between islands. Counterintuitively, under some circumstances, evolutionary rescue can occur more readily in the face of harsher environmental shifts, because of the reduced competition experienced by mutant individuals. Similarly, rescue sometimes occurs more readily when the entire habitat degrades rapidly, rather than progressively over time, particularly when migration is high and competition strong. [ABSTRACT FROM AUTHOR]