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The topic scope and sequence of introductory majors and general education (GE) biology texts correlate with Medical College Admissions Test (MCAT) topic importance ratings. GE texts have higher MCAT term densities than introductory majors texts. Indirect impact of the MCAT on GE texts may detract from scientific literacy goals of GE courses., Most American colleges and universities offer gateway biology courses to meet the needs of three undergraduate audiences: biology and related science majors, many of whom will become biomedical researchers; premedical students meeting medical school requirements and preparing for the Medical College Admissions Test (MCAT); and students completing general education (GE) graduation requirements. Biology textbooks for these three audiences present a topic scope and sequence that correlates with the topic scope and importance ratings of the biology content specifications for the MCAT regardless of the intended audience. Texts for “nonmajors,” GE courses appear derived directly from their publisher's majors text. Topic scope and sequence of GE texts reflect those of “their” majors text and, indirectly, the MCAT. MCAT term density of GE texts equals or exceeds that of their corresponding majors text. Most American universities require a GE curriculum to promote a core level of academic understanding among their graduates. This includes civic scientific literacy, recognized as an essential competence for the development of public policies in an increasingly scientific and technological world. Deriving GE biology and related science texts from majors texts designed to meet very different learning objectives may defeat the scientific literacy goals of most schools’ GE curricula.

We present an inquiry-based, hands-on laboratory exercise on enzyme activity for an introductory college biology course for science majors. We measure student performance on a series of objective and subjective questions before and after completion of this exercise; we also measure performance of a similar cohort of students before and after completion of an existing, standard, “direct” exercise over the same topics. Although student performance on these questions increased significantly after completion of the inquiry exercise, it did not increase after completion of the control, standard exercise. Pressure to “cover” many complex topics as preparation for high-stakes examinations such as the Medical College Admissions Test may account for persistence of highly efficient, yet dubiously effective “cookbook” laboratory exercises in many science classes.

Solitary foragers can balance demands for food and safety by varying their relative use of foraging patches and their level of vigilance. Here, we investigate whether colonies of the ant, Formica perpilosa, can balance these demands by dividing labor among workers. We show that foragers collecting nectar in vegetation near their nest are smaller than are those collecting nectar at sites away from the nest. We then use performance tests to show that smaller workers are more likely to succumb to attack from conspecifics but feed on nectar more efficiently than larger workers, suggesting a size-related trade-off between risk susceptibility and harvesting ability. Because foragers that travel away from the nest are probably more likely to encounter ants from neighboring colonies, this trade-off could explain the benefits of dividing foraging labor among workers. In a laboratory experiment, we show that contact with aggressive workers results in an increase in the mean size of recruits to a foraging site: this increase was not the result of more large recruits, but rather because fewer smaller ants traveled to the site. These results suggest that workers particularly susceptible to risk avoid dangerous sites, and suggest that variation in worker size can allow colonies to exploit profitably both hazardous and resource-poor patches.

Ant colonies should be selected to optimally allocate resources to individual reproductive offspring so as to balance production costs with offspring fitness gains. Different modes of colony founding have different size-dependent fitness functions, and should thus lead to different optimal queen sizes. We tested whether a behavioral transition from solitary colony founding (haplometrosis) to group colony founding (pleometrosis) across the range of the ant Messor pergandei was associated with a difference in queen size or condition. Both winged gynes and founding queens were significantly smaller and lighter at pleometrotic than at haplometrotic sites, with an abrupt shift in these characters across the 8.5 km-wide behavioral transition zone. Both the mutualistic advantages of grouping and among-queen competition within associations are likely to be important in selecting for smaller queen size in pleometrotic populations.

Caste differentiation and reproductive division of labor are the hallmarks of insect societies [1]. In ants and other social Hymenoptera, development of female larvae into queens or workers generally results from environmentally induced differences in gene expression [2–4]. However, several cases in which certain gene combinations may determine reproductive status have been described in bees [5] and ants [6–9]. We investigated experimentally whether genotype directly influences caste determination in two populations of Pogonomyrmex harvester ants in which genotype-caste associations have been observed. Each population contains two genetic lineages [10]. Queens are polyandrous [11, 12] and mate with males of both lineages [6, 7], but in mature colonies, over 95% of daughter queens have a pure-lineage genome, whereas all workers are of F1 interlineage ancestry [6–8]. We found that this pattern is maintained throughout the colony life cycle, even when only a single caste is being produced. Through controlled crosses, we demonstrate that pure-lineage eggs fail to develop into workers even when interlineage brood are not present. Thus, environmental caste determination in these individuals appears to have been lost in favor of a hardwired genetic mechanism. Our results reveal that genetic control of reproductive fate can persist without loss of the eusocial caste structure.

This hypothesis-driven laboratory exercise teaches how DNA evidence can be used to investigate an organism's evolutionary history while providing practical modeling of the fundamental processes of gene transcription and translation. We used an inquiry-based approach to construct a laboratory around a nontrivial, open-ended evolutionary question about the relationship of five species of Drosophila. In the course of answering this question, students at the early college biology level learn how the information in DNA can be extracted and used by both the cell and scientists. This dual proximate-ultimate approach introduces students to the techniques of PCR, DNA sequencing, and phylogenetic sequence analysis while simultaneously providing a concrete pen-and-paper model of the cellular processes of transcription and translation. The laboratory has been successfully employed over 3 years with first-year college students and has proven its versatility by being easily adapted to a "dry lab" form with advanced high school students.

A wide variety of functional domains exist within human genes. Since different domains vary in their roles regarding overall gene function, the ability for a mutation in a gene region to produce disease varies among domains. We tested two hypotheses regarding distributions of mutations among functional domains by using (1) sets of single nucleotide disease mutations for six genes (CFTR, TSC2, G6PD, PAX6, RS1, and PAH) and (2) sets of polymorphic replacement and silent mutations found in two genes (CFTR and TSC2). First, we tested the null hypothesis that sets of mutations are uniformly distributed among functional domains within genes. Second, we tested the null hypothesis that disease mutations are distributed among gene regions according to expectations derived from the distribution of evolutionary conserved and variable amino acid sites throughout each gene. In contrast to the mainly uniform distribution of sets of silent and polymorphic mutations, sets of disease mutations generally rejected the null hypotheses of both uniform and evolutionary-influenced distributions. Although the disease mutation data showed a better agreement with the evolutionary-derived expectations, disease mutations were found to be statistically overabundant in conserved domains, and under-represented in variable regions, even after accounting for amino acid site variability of domains over long-term evolutionary history. This finding suggests that there is a non-additive influence of amino acid site conservation on the observed intragenic distribution of disease mutations, and underscores the importance of understanding the patterns of neutral amino acid substitutions permitted in a gene over long-term evolutionary history.

The process of reproductive caste determination in eusocial insect colonies is generally understood to be mediated by environmental, rather than genetic factors. We present data demonstrating unexpected genetic differences between reproductive castes in a variant of the rough harvester ant, Pogonomyrmex rugosus var. fuscatus. Across multiple loci, queens were consistently more homozygous than expected, while workers were more heterozygous. Adult colony queens were divided into two highly divergent genetic groups, indicating the presence of two cryptic species, rather than a single population. The observed genetic differences between castes reflect differential representation of heterospecific and conspecific patrilines in these offspring groups. All workers were hybrids; by contrast, winged queens were nearly all pure-species. The complete lack of pure-species workers indicates a loss of worker potential in pure-species female offspring. Hybrids appear to be bipotential, but do not normally develop into reproductives because they are displaced by pure-species females in the reproductive pool. Genetic differences between reproductive castes are expected to be rare in non-hybridizing populations, but within hybrid zones they may be evolutionarily stable and thus much more likely to occur.

The degree to which queens and workers control how limiting resources are split between reproductive males and females is central to the study of sex allocation in the eusocial Hymenoptera. We investigated the effect of resource availability on sex allocation decisions by both queens and workers in the ant Messor pergandei. We conducted the following field manipulations of resource availability: food supplementation while queens were laying reproductive brood (early-fed treatment), removal of workers while queens were laying reproductive brood (worker-removal treatment), food supplementation of colonies while workers were tending reproductive brood (late-fed treatment), and unmanipulated colonies (control). Early-fed colonies produced more alates and exhibited more strongly female-biased sex ratios than other treatments. Worker-removal colonies produced the fewest alates and the least female-biased sex ratios. Late-fed colonies yielded individual alates with the heaviest fresh masses (males and females) and dry masses (only females). Aside from worker-removal colonies, the sex and investment ratios of colonies in this study were significantly more female-biased than the relatedness asymmetries hypothesis under worker control would predict. Consistent with the multifaceted parental investment hypothesis, the timing of food supplementation relative to the reproductive cycle of the colony plays a prominent role in influencing sex allocation by both queens and workers. Early food supplements resulted in increased number of females, whereas late food supplements resulted in heavier individual females. Temporal dynamics of food availability may explain part of the tremendous inter-population variation in colony sex ratios seen in this and other ant species. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00265-002-0462-6.

Transitions in behaviour across a continuous distribution of organisms can provide valuable information on how variation in behaviour is maintained. We used analyses developed for interspecific hybrid zones to examine geographic variation in colony founding strategy in the desert seed-harvester ant, Messor pergandei. Newly mated females initiate new colonies either alone (haplometrosis) or cooperatively with other foundresses (pleometrosis). The incidence of these founding strategies were surveyed across the species' range and found to occur in geographically distinct regions joined by a narrow transition zone. Foundresses collected from haplometrotic sites were more likely to display aggression and found solitary nests than foundresses from pleometrotic sites, suggesting that geographical variation in metrosis is due to genotypic divergence. Foundresses from transitional sites were generally not aggressive and tended to co-found nests in the laboratory, yet rarely formed associations in the field. Such an abrupt shift in behaviour indicates that variation in colony founding strategy is maintained by selection rather than the result of secondary contact of neutral characters. Level of aggression displays a wider cline than founding strategy and is likely under selection only when accompanied by active strategy preference. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

Pogonomyrmex colei is a workerless inquiline ant known only from nests ofP. rugosus, its closest relative. Ten of 776 (1.3%) host nests were parasitized at a site in central Arizona, while none of 1499 potential host colonies were parasitized at two other locales. Colonies ofP. colei are perennial, and host alate females in 9 of 10 colonies demonstrates that host queens survive parasitism. Three of 10 colonies died over 19 colony years of observation, while only 1 of 601 colonies became newly parasitized. Mating occurs in morning for up to 2–3 days following summer and fall rains and in afternoon during cool fall days. Mating is intranidal just outside the nest entrance, with males returning to the natal nest. MaleP. colei may be flightless because their wing area is reduced compared to host males. Females fly from the nest and locate potential host colonies by following trunk trails. Workers are the largest barrier to nest establishment, as they removed over 90% ofP. colei females placed in trunk trails or that entered host nests. Males and females ofP. colei andP. anergismus, the only other congeneric inquiline species, are diminutive compared to their hosts, with females 30% lighter than host workers. Fat content is lower and water content is higher inP. colei andP. anergismus females than in their hosts.

During the 1960s and early 1970s, the theory of natural selection as a mechanism for evolution was at its heyday. Other mechanisms of evolution, such as genetic drift, were regarded as being of minor importance relative to natural selection. Textbooks of the time echoed that sentiment, and genetic drift received little more than a passing mention that it could conceivably be a factor in evolution in populations of extremely small size.

Speciation of two social parasites from their respective hosts is tested using a molecular phylogeny. Alignment of 711 DNA base pairs of mitochondrial cytochrome b gene was used to assess phylogenetic relationships of inquiline species to their hosts and to other members of the genus. We show that the inquiline social parasites of the North American seed harvester ants are monophyletic, descending from one of the known hosts (Pogonomyrmex barbatus) in the recent past and shifting hosts in a pattern similar to that observed in other Hymenopteran social parasites. In addition, the host populations unexpectedly were found to be polyphyletic. Populations of Pogonomyrmex rugosus from an area east of the Chiricahua Mountains in Southern Arizona belong to a mitochondrial clade separate from the more western clade of P. rugosus from the Sonoran and Chihuahuan Deserts. Evidence of mitochondrial DNA introgression between P. rugosus and P. barbatus was also observed. We conclude that Emery's rule does not strictly hold for this system, but that the hosts and parasites are very closely related, supporting a loose definition of Emery's rule.

Because workers in colonies of eusocial Hymenoptera are more closely related to sisters than to brothers, theory predicts workers should bias investment in reproductive broods to favour reproductive females over males. However, conflict between queens and workers is predicted. Queens are equally related to daughters and sons, and should act to prevent workers from biasing investment. Previous study of the ant Pheidole desertorum showed that workers are nearly three times more closely related to reproductive females than males; however, the investment sex ratio is very near equal, consistent with substantial queen control of workers. Near-equal investment is produced by an equal frequency of colonies whose reproductive broods consist of only females (female specialists) and colonies whose reproductive broods consist of only males or whose sex ratios are extremely male biased (male specialists). Because natural selection should act on P. desertorum workers to bias investment in favour of reproductive females, why do workers in male-specialist colonies rear only (or mostly) males? We tested the hypothesis that queens prevent workers from rearing reproductive females by experimentally providing workers with immature reproductive broods of both sexes. Workers reared available reproductive females, while failing to rear available males. Worker preference for rearing reproductive females is consistent with queens preventing their occurrence in colonies of male specialists. These results provide evidence that queens and workers will act in opposition to determine the sex ratio, a fundamental prediction of queen-worker conflict theory. Copyright 2000 The Association for the Study of Animal Behaviour.

Etude, chez Messor pergandei, des mecanismes de formation des fondations par une serie d'experimentations realisees en laboratoire

Cofoundresses of the desert fungus garden ant Acromyrmex versicolor exhibit a forager specialist who subsumes all foraging risk prior to first worker eclosion (Rissing et al. 1989). In an experiment designed to mimic a "cheater" who refuses foraging assignment when her lot, cofoundresses delayed/failed to replace their forager, often leading to demise of their garden (Rissing et al. 1996). The cheater on task assignment is harmed, but so too is the punisher, as all will die without a healthy garden. In this paper we study through simulation the cofoundress interaction with haploid, asexual genotypes which either replace a cheater or not (punishment), under both foundress viscosity (likely for A. versicolor) and random assortment. We find replacement superior to punishment only when there is no foraging risk and cheating is not costly to group survival. Generally, punishment is evolutionarily superior, especially as forager risk increases, under both forms of dispersal.

Diets of desert seed-harvester ants Veromessor pergandei and Pogonomyrmex rugosus were studied for 3 years at two habitats where they are common and sympatric. Diets of the two species were similar, consisting mainly (87% of 23,913 seeds) of three annual plant species (Schismus arabicus, Plantago insularis, and Pectocarya recurvata). Diets converged following a drought in Winter/Spring 1984 which reduced seed production during this time. Foraging range of P. rugosus almost doubled following the drought while foraging range of V. pergandei remained constant. Neither ant species move their nests once established rendering them effectively sessile granivores. This limits the dietary options of a given colony and may explain interspecific dietary convergence.

Of 36 plant species surveyed, 6 were significantly associated with nests of the desert seed-harvester ant Veromessor pergandei or Pogonomyrmex rugosus; two other plant species were significantly absent from ant nests. Seeds of two common desert annuals, Schismus arabicus and Plantago insularis, realize a 15.6 and 6.5 fold increase (respectively) in number of fruits or seeds produced per plant growing in ant nest refuse piles compared to nearby controls. Mass of individual S. arabicus seed produced by plants growing in refuse piles also increased significantly. Schismus arabicus, P. insularis and other plants associated with ant nests do not have seeds with obvious appendages attractive to ants. Dispersal and reproductive increase of such seeds may represent a relatively primitive form of ant-plant dispersal devoid of seed morphological specializations. Alternatively, evolution of specialized seed structures for dispersal may be precluded by the assemblage of North American seed-harvester ants whose workers are significantly larger than those ants normally associated with elaiosome-attached seed dispersal. Large worker size may permit consumption of elaiosome and seed.

Desert horned lizards Phrynosoma platyrhinos consumed the solitary-foraging seed- harvester ant, Pogonomyrmex californicus, 10 to 100 times more often than expected based upon its relative abundance in the environment. The group-foraging seed-harvester ants, Pogonomyrmex ru- gosus and Veromessor pergandei, were correspondingly underrepresented in the horned lizard's natural diet. In a series of laboratory prey choice tests, where prey availabilities were held constant and equal, these preferences were confirmed: P. californicus was eaten more often than P. rugosus which was eaten more often than V. pergandei. These preferences correspond to differences in ant aggressive behavior which, in turn, correspond to differences in ant foraging-group size and foraging method. Colonies of solitary-foraging ants have small foraging groups and are generally incapable of mobbing a lizard, but they are also difficult to find. Colonies of group-foraging ants have large to massive foraging groups and vigorously mob lizards. Such aggressiveness is probably effective by increasing the risk of exposure of a lizard to predators of its own; the indirect costs of preying upon these ant species, normally assumed constant over all prey types for most predators, are variable here. Differences in experience with ant aggressive behavior probably account for differences in prey preferences found among adult lizards captured from the same area. Ant-species-specific predation by Phrynosoma may be an important ecological force structuring the Mohave Desert seed-harvesting ant community.

Queens of the pleometrotic seed-harvester ant Veromessor pergandei associate without respect to relatedness during colony foundation in laboratory choice tests. This species may be used as a test case for social competition where kin selection cannot occur. Co-founding queens contribute equally to the initial brood and exist without dominance prior to eclosion of their first workers. Before worker eclosion, claustral founding ants exhibit a closed-energy system. We argue that social competition cannot operate under such circumstances. Among pleometrotic, claustral founding ants, inter-queen aggression should not occur before worker emergence: this is verified for V. pergandei.

As foragers of the harvester ant, Veromessor pergandei, travel further from their nest they spend significantly more time sampling seeds in experimental patches. Although accepted seeds are heavier than offered seeds, mass of accepted seed is not correlated with sampling time. Variably sized V. pergandei workers do not “size-match”; little, if any, variance in size of seed selected can be attributed to body size of forager. The lack of size-matching in V. pergandei suggests individual performance may be an inadequate measure of colony foraging success.

Co-founding Veromessor pergandei queens tended brood equally throughout colony foundation. With the appearance of foragers, however, queens began to fight, resulting in an increase in queen death rate. Worker aggression towards queens occurred only after queen fighting began and was directed only to queens damaged during fights. Starting V. pergandei colonies raided brood from nearby nests; workers exhibited nest fidelity during such raids. Colonies started by multiple queens opened 9 days earlier than those started by single queens and were more successful at brood raiding. Queens and workers of defeated, brood-raided colonies abandoned their nests and joined/invaded victor nests. Brood raiding in this and similar species may be a consequence of territoriality and the clumped distribution of starting nests. Colony foundation by multiple queens, pleometrosis, may be an evolutionary response to brood raiding.

Individual scouts ofFormica oreas are capable of communicating resource availability, location and quality to nest mates. Recruited foragers can perceive and respond to differences in recruitment stimuli of individual scouts. Significantly more workers followed the path of an individual scout from a more rewarding food source than from a less rewarding food source. These findings suggest recruitment in ant colonies is regulated by recruited workers “weighing” recruitment stimuli of scouts returning from numerous areas about the nest.

1. When presented with a patch of 3 differeng grass species' seeds, a Pogonomyrmex rugosus colony harvested a mix of all species available. Individually marked workers, however, specialized on a single species. These individual specializations hold for at least several days but can also be shifted rapidly. Workers of a similar species, Veromessor pergandei, also appear to specialize to seed species, taking larger than average seeds of one species from a mixed seed patch when seeds of a larger species were available and being collected by colony-mates in that same patch. 2. Seed choice in both ants is not a function of worker size; this variable explains

The seed-harvester antVeromessor pergandei Mayr is primitively polymorphic; workers are monophasically allometric. There is a distinct annual cycle in mean worker body size that replicates across colonies and habitats (Fig. 1); this cycle occurs through alteration of the worker size distribution (Fig. 2). There is little, if any, morphspecific task specialization by workers suggesting worker size variance is a colony-level adaptation permitting maintenance of a large and constant worker force during periods of resource fluctuation. Smaller workers appear in the foraging force following the “triple crunch” of reduced seed availability, reduced favorable times to forage, and alate production during winter months. Adult and startingV. pergandei colonies exhibit strong intraspecific territoriality, suggesting the selective advantage for maintenance of a large and constant worker force. Such selective pressures may have provided the initial variance in worker size distributions that led subsequently to specialized castespecific task performance in more distinctly polymorphic ant species.

The possible role of intraspecific territoriality in the evolution of obligate interspecific slavery, dulosis, among ants has been debated by several authors. Recent research on the establishment of colonies in several non-dulotic, intra-specifically territorial ants provides support for and an extension of the territorial hypothesis as a general explanation for dulosis. Several ant species, regardless of dulotic tendencies, have clumped starting nests; adult colonies, nonetheless, are territorial, suggesting that, from each clump, at most a single adult colony will prevail. Territoriality among these starting colonies takes the form of reciprocal brood raiding ("intraspecific slavery" in the sense of Holldobler 1976a); colonies with the most workers, including those acquired from brood raiding, prevail. Truly dulotic species have polydomous hosts; that is, a single colony occupies several nests. Such polydomous host colonies represent a renewable resource that likely permits specialization in their procu...

Nests of the desert seed-harvester ant Pogonomyrmex rugosus are located preferentially near shrubs in some microhabitats at a Mohave Desert site, while nests of the same species are located preferentially away from shrubs at a Sonoran Desert site. At the Mohave site, nearest neighboring shrubs to ant nests show greater mortality than expected at random; this effect is reduced at the Sonoran site. The ants appear to be the cause of shrub mortality; workers defoliate shrubs and make no apparent use of severed leaves or stems. Shrub viability at the Mohave site is dependent upon distance from a P. rugosus nest and size of that nest. In the Mohave Desert, shrubs may initially provide valuable shade to starting colonies, yet later in colony ontogeny represent a significant competitor for water.

During the late glacial and postglacial the productivity of Berry Pond in Berkshire County, Massachusetts, underwent a number of significant oscillations. This is suggested by data on sedimentary chlorophyll degradation products, diatoms, and Cladocera. The productivity changes were. apparently controlled by changes in weathering, terrestrial vegetation in the watershed, litter production, and runoff. There are associated changes in cladoceran community structure.

Velocity of a Veromessor pergandei (Mayr) worker either searching for seeds or returning to the nest with a seed is significantly dependent upon temperature. Velocity of an ant carrying a seed is further influenced by body size and burden ([ant mass + seed mass] / ant mass). Although workers of this species are highly variable in size, body size significantly influences velocity of burdened ants only and does not influence unburdened ones. This may occur because workers do not run at maximum possible velocity while searching for seeds. Velocity of a worker is linear with increasing burden over the range of seed sizes harvested by these ants. Regression equations for velocity of burdened and unburdened ants in the field are presented. On the basis of these regressions, V. pergandei workers appear much larger than necessary to carry burdens normally encountered while foraging.

HYPOTHESES on the evolution of sociality in the Hymenoptera have focused on two non-exclusive selective processes. First, individuals may help relatives to enhance inclusive fitness (kin selection1,2). Second, group living may be so highly advantageous that competitively inferior individuals are forced into subordinate roles through social competition3–7; in this hypothesis, subordinates help dominants in the expectation that they may benefit from the group's resources if the dominants lose status or die. Many social Hymenoptera associate predominantly with close relatives8,9, which precludes an effective comparison of kin selection and social competition. Here we report on the existence of foraging specialists among unrelated co-foundresses of the leaf-cutter ant Acromyrmex versicolor; such task specialization leaves the forager at a relative fitness disadvantage within her foundress association. Contrary to the predictions of social competition theory, individuals specialize independently of competitive ability (as measured by relative body size) or reproductive status (as measured by ovarian condition) and without conflict. The selective basis of foraging specialization may lie in the intense competition that occurs among newly founded colonies engaged in reciprocal brood raiding.