The origin of novelty is a critical subject for evolutionary biologists. Early geneticists speculated about the sudden appearance of new species via special macromutations, epitomized by Goldschmidt’s infamous “hopeful monster”. Although these ideas were easily dismissed by the insights of the Modern Synthesis, a lingering fascination with the possibility of sudden, dramatic change has persisted. Recent work on hybridization and gene exchange suggests an underappreciated mechanism for the sudden appearance of evolutionary novelty that is entirely consistent with the principles of modern population genetics. Genetic recombination in hybrids can produce transgressive phenotypes, “monstrous” phenotypes beyond the range of parental populations. Transgressive phenotypes can be products of epistatic interactions or additive effects of multiple recombined loci. We compare several epistatic and additive models of transgressive segregation in hybrids and find that they are special cases of a general, classic quantitative genetic model. The Dobzhansky-Muller model predicts “hopeless” monsters, sterile and inviable transgressive phenotypes. The Bateson model predicts “hopeful” monsters with fitness greater than either parental population. The complementation model predicts both. Transgressive segregation after hybridization can rapidly produce novel phenotypes by recombining multiple loci simultaneously. Admixed populations will also produce many similar recombinant phenotypes at the same time, increasing the probability that recombinant “hopeful monsters” will establish true-breeding evolutionary lineages. Recombination is not the only (or even most common) process generating evolutionary novelty, but might be the most credible mechanism for sudden appearance of new forms.
Although much of the theory on the success of invasive species has been geared at escape from specialist enemies, the impact of introduced generalist invertebrate herbivores on both native and introduced plant species has been underappreciated. The role of nocturnal invertebrate herbivores in structuring plant communities has been examined extensively in Europe, but less so in North America. Many nocturnal generalists (slugs, snails, and earwigs) have been introduced to North America, and 96% of herbivores found during a night census at our California Central Valley site were introduced generalists. We explored the role of these herbivores in the distribution, survivorship, and growth of 12 native and introduced plant species from six families. We predicted that introduced species sharing an evolutionary history with these generalists might be less vulnerable than native plant species. We quantified plant and herbivore abundances within our heterogeneous site and also established herbivore removal experiments in 160 plots spanning the gamut of microhabitats. As 18 collaborators, we checked 2000 seedling sites every day for three weeks to assess nocturnal seedling predation. Laboratory feeding trials allowed us to quantify the palatability of plant species to the two dominant nocturnal herbivores at the site (slugs and earwigs) and allowed us to account for herbivore microhabitat preferences when analyzing attack rates on seedlings. The relationship between local slug abundance and percent cover of five common plant taxa at the field site was significantly negatively associated with the mean palatability of these taxa to slugs in laboratory trials. Moreover, seedling mortality of 12 species in open-field plots was positively correlated with mean palatability of these taxa to both slugs and earwigs in laboratory trials. Counter to expectations, seedlings of native species were neither more vulnerable nor more palatable to nocturnal generalists than those of introduced species. Growth comparison of plants within and outside herbivore exclosures also revealed no differences between native and introduced plant species, despite large impacts of herbivores on growth. Cryptic nocturnal predation on seedlings was common and had large effects on plant establishment at our site. Without intensive monitoring, such predation could easily be misconstrued as poor seedling emergence.
Although in recent years behavioral syndromes have received a wealth of attention, how traits within syndromes respond to changing environments is not well resolved. Here, we test the effects of temperature on a suite of behavioral traits in the spider Anelosimus studiosus to determine (1) whether there are shifts in individuals’ social tendency, activity level, and foraging behavior in response to temperature, (2) if these traits shift are in the direction predicted by within‐population axes of trait covariance, and (3) whether the effects of temperature differ among individuals. In previous work, we documented a behavioral syndrome in A. studiosus where increased tolerance of conspecifics is correlated with decreased activity level and aggressiveness toward prey. Furthermore, there are distinct among‐population differences in behavior, where individuals from warm sites tend to be more aggressive and active than individuals from cold sites. Our data here reveal that at warmer temperatures A. studiosus exhibit diminished tolerance of conspecifics, increased activity levels, shorter latencies of attack, and increased tendencies to attack multiple prey items. Furthermore, we found that individual differences in behavior were consistent across temperature regimes for the majority of behavioral traits considered here: social tendency, activity level, and latency of attack. These findings are consistent with the hypothesis that these behaviors are linked together by shared genetic underpinnings (e.g., metabolic differences) and shift non‐independently in response to contemporary abiotic environment (i.e., temperature). Furthermore, our data suggest that temperature itself could be responsible for the among‐population variation in social structure in A. studiosus.
Science epistemology is the foundation of how biology constructs knowledge but is often implicit in undergraduate research experiences (UREs). This study describes the development of one student’s ideas about scientific knowledge in a URE in which science epistemology was explicitly discussed in meetings and written reflections.
Graduate teaching assistants (GTAs) are often used as instructors in undergraduate introductory science courses, particularly in laboratory and discussion sections associated with large lectures. These GTAs are often novice teachers with little opportunity to develop their teaching skills through formal professional development. Focused self-reflection about end-of-semester teaching evaluations may be an important informal supplement to teacher training. To inform this practice, we explored the instructional behaviors that undergraduates perceived as most important for GTAs’ teaching effectiveness in laboratory courses. In spring semester 2012, 1159 undergraduates in freshman-level biology lab courses rated their GTAs on 21 instructional behaviors, the GTAs’ teaching effectiveness, the amount the student learned, and their expected grade in the laboratory. Using linear mixed models, we found that instructional behaviors related to the categories of teaching techniques and interpersonal rapport best predicted student ratings of GTAs’ teaching effectiveness. GTAs or other novice teachers can use this information to identify specific areas for instructional improvement when considering student feedback about their teaching.
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