The effects of restrictions of available character space on the mean morphological distance between living members of evolutionary phylads are examined by Monte Carlo simulation. The approach involves specifying the degree to which ancestor-descendant species may differ and limiting the range of attainable character states within a phylad. Morphological evolution is modeled as a Markovian process involving quantitative multistate characters. States for a given character are allowed to evolve at time-dependent or speciation-dependent rates. The final distributions of morphological distance for a given trait among members of a phylad depend on the number of species in the phylad, the rate and pattern of evolution of new character states, and the existence of boundary conditions indicating possible selective constraints on the trait. When morphological change is proportional to time, increasing restrictions on character evolution tend to (a) lower mean distance between species and (b) leave the ratio of mean distances ( DR Dp) in species-rich vs. species-poor phylads of comparable evolutionary age near one. When change is proportional to rate of speciation, similar restrictions tend to (a) limit mean distance only in phylads in which the number of speciations exceeds the range of attainable character states and (b) permit DR Dp to be considerably greater than one, except in extreme cases. Implications of these results for the current phyletic gradualism-rectangular evolution controversy are considered. © 1979.

Statistical methods for estimating genetic parentage are increasingly applied to accommodate limited marker polymorphism and the incomplete sampling of individuals. Neff et al. (2000a, Mol. Ecol. 9, 515-528; 2000b, Mol. Ecol. 9, 529-539) published a method (Pat) that estimates the proportion of next-generation individuals sired by a focal male, taking into account that the male may be genetically compatible, by random chance, with offspring that are not his own. Here we employ this method to reestimate paternity of 68 nest-guarding males from several fish species. The difference between the conventional exclusion-based estimate and Pat was >0.05 in only four of the 68 (5.9%) fish nests analyzed. An analytical formula shows that the difference between the two estimates is expected to be negligible if the focal male is consistent with a large proportion of the genotyped offspring, or if marker polymorphism is high. In addition, computer simulations illustrate how numbers of marker loci and their levels of genetic polymorphism, as well as the mating system of the organism under study, can influence estimates of paternity derived from exclusion-based estimates and Pat. Finally, we discuss various applications of these estimators including cases where additional biological information is present in the form of behavioral observations on parental care.

Supplemental breeding is an intensive population management strategy wherein adults are captured from nature and spawned in controlled settings, and the resulting offspring are later released into the wild. To be effective, supplemental breeding programs require crossing strategies that maximize offspring production while maintaining genetic diversity within each supplemental year class. We used computer simulations to assess the efficacy of different mating designs to jointly maximize offspring production and maintain high levels of genetic diversity (as measured by the effective population size) under a variety of biological conditions particularly relevant to species with high fecundity and external fertilization, such as many fishes. We investigated four basic supplemental breeding designs involving either monogamous pairings or complete factorial designs (in which every female is mated to every male and vice versa), each with or without the added stipulation that all breeders contribute equally to the tolal reproductive output. In general, complete factorial designs that did not equalize parental contributions came closest to the goal of maximizing offspring production while still maintaining relatively large effective population sizes. Next, we estimated the effective population size of 10 different supplemental year classes within the breeding program of the robust redhorse (Moxostoma robustum). Two year classes failed to produce progeny, whereas successful year classes used partial factorial designs to realize effective sizes ranging from 2 to 26 individuals. On average, a complete factorial design could increase the effective size of each robust redhorse supplemental year class by 19%.