Delimiting species: comparing methods for Mendelian characters using lizards of the Sceloporus grammicus (Squamata: Phrynosomatidae) complex.

Species form the fundamental units of analysis in many areas of biology and, therefore, rigorous delimitation of this unit is important to a broad array of researchers. Recently, many new empirical methods have been proposed to delimit species in nature, and a large literature exists on the theoretical merit and superiority of each method. However, few empirical studies actually compare the results of these methods applied in the same study system. We used a large allozyme and chromosome dataset to apply a number of genetic-distance, character-based, and tree-based methods to a well-studied, data-rich system: the Sceloporus grammicus lizard complex of central Mexico. We hypothesized species boundaries under a general lineage or evolutionary species conceptual framework in an a priori fashion using mapped restriction-site data (mitochondrial DNA and nuclear rDNA), allozymes, and morphology. We then compared the ability of different methods to recover the "hypothesized evolutionary species" (HES). Highton's genetic-distance method and a tree-based method consistently recovered all four HES, although sometimes with weak support. With two exceptions, other methods recovered the same HES, but additional groups were weakly delimited and nested within the HES. Given the apparent recent divergence of some of the chromosome races and distinct populations in this complex, these are encouraging results. We emphasize the value of specifying testable criteria as clearly as possible and testing these with methods that make use of different properties of a single dataset.

Isolated pelvic perfusion: plasma pharmacokinetics depend primarily on drug dosage and not the type of drug.

PURPOSE: Comparison of the pharmacokinetics of four drugs with the isolated pelvic perfusion protocol showed linear relationships between drug dosage and two isolated pelvic plasma parameters, mean AUC (pelvic exposure, microM min) and the mean maximum pelvic drug level (microM). It appears that the pharmacokinetics are sufficiently defined as to predict plasma distribution curves for an additional drug with this protocol. Recent FDA approval of oxaliplatin allowed an evaluation of this premise. METHODS: Linearity of drug dosage with maximum drug levels and exposure (AUC) in the isolated pelvic plasma yields initial estimates of these parameters for additional drugs. Use of an empirical, four-compartment pharmacokinetic model (Wanebo and Belliveau in Cancer Chemother. Pharmacol. 43:427, 1999) allowed the generation of predictive plasma distribution curves. These curves were established by optimizing the initial estimates of maximum drug levels and exposure along with estimates of two additional parameters (half-life of pelvic clearance and pelvic to systemic exposure ratio) from experimental data of the four drugs pharmacokinetically characterized. RESULTS: Calculated plasma distribution curves for oxaliplatin matched the experimental curves from the first three patients receiving oxaliplatin therapy, given the experimental ranges of pharmacokinetic parameters seen with the initial four drugs. CONCLUSION: These results give an overall picture for the plasma pharmacokinetics during the isolation period for the isolated pelvic perfusion protocol. Enough experimental data have been accumulated for five drugs to establish a simple pharmacokinetic model (Wanebo and Belliveau in Cancer Chemother Pharmacol 43:427, 1999) and interdrug relationships (i.e., this report) which can be used to predict reasonable plasma distribution curves for additional drugs with this protocol.

Can cuticular lipids provide sufficient information for within-colony nepotism in wasps?

Inclusive fitness theory predicts that members of non-clonal societies will gain by directing altruistic acts towards their closest relatives. Multiple mating by queens and multiple queens creates distinct full-sister groups in many hymenopteran societies within which nepotism might occur. However, the weight of empirical data suggests that nepotism within full-sister groups is absent. It has been suggested that a lack of reliable recognition markers is responsible. In this paper, we investigated whether epicuticular lipids could provide reliable cues for intracolony kin recognition in two species of social wasps, the paper wasp Polistes dominulus and the hornet Vespa crabro. Epicuticular lipids have previously been shown to be central to kin recognition at the nest level, making them excellent candidates for within-nest discrimination. We genotyped individuals using DNA microsatellites and analysed surface chemistry by gas chromatography-mass spectrometry. We find that in both species epicuticular lipids typically could provide enough information to distinguish related nest-mates from unrelated nest-mates, a difference that occurs in colonies with multiple queens. However, in V. crabro, where colonies may be composed by different patrilines, information for discrimination between full sisters and half-sisters is weaker and prone to errors. Our data suggest that epicuticular lipids at best provide reliable information for intracolony nepotistic discrimination in multiple-queen colonies composed of unrelated lines.

The phylogeny of the social wasp subfamily Polistinae: evidence from microsatellite flanking sequences, mitochondrial COI sequence, and morphological characters.

BACKGROUND: Social wasps in the subfamily Polistinae (Hymenoptera: Vespidae) have been important in studies of the evolution of sociality, kin selection, and within colony conflicts of interest. These studies have generally been conducted within species, because a resolved phylogeny among species is lacking. We used nuclear DNA microsatellite flanking sequences, mitochondrial COI sequence, and morphological characters to generate a phylogeny for the Polistinae (Hymenoptera) using 69 species. RESULTS: Our phylogeny is largely concordant with previous phylogenies at higher levels, and is more resolved at the species level. Our results support the monophyly of the New World subgenera of Polistini, while the Old World subgenera are a paraphyletic group. All genera for which we had more than one exemplar were supported as monophyletic except Polybia which is not resolved, and may be paraphyletic. CONCLUSION: The combination of DNA sequences from flanks of microsatellite repeats with mtCOI sequences and morphological characters proved to be useful characters establishing relationships among the different subgenera and species of the Polistini. This is the first detailed hypothesis for the species of this important group.

CONFLICTS OF INTEREST IN SOCIAL INSECTS: MALE PRODUCTION IN TWO SPECIES OF POLISTES.

In social insects, reproduction is often monopolized by queens even though in many species are workers capable of laying male eggs. Because it is difficult to see how one or a few queens can suppress the much more numerous workers, collective worker control, or policing, offers an attractive solution. When workers are less related to other workers than they are to queens, workers should be selected to suppress each other in favor of the queen's male offspring, if other things are equal. Otherwise, they should allow each other to lay male eggs. For two species of Polistes, we used DNA microsatellites to estimate these two relatednesses, to determine the sex of brood, and to determine whether male brood was produced by queens or workers. Workers were significantly more related to each other (0.63 and 0.73 for P. bellicosus and P. dorsalis, respectively) than they were to queens (0.40 and 0.54, respectively) so they were predicted to allow each other to lay the male eggs. However, workers did not lay male-destined eggs in either species, so the results do not support collective worker control. There are two possible explanations for this result. Queens may be able to physically dominate in these small colonies. Alternatively, this may be a conventional settlement that minimizes conflict and the attendant costs.