EARLY LIFE HISTORIES,OCEAN CURRENTS,AND THE POPULATION GENETICS OF CARIBBEAN REEF FISHES

Tropical reef fishes, along with many benthic invertebrates, have a life cycle that includes a sedentary, bottom-dwelling reproductive phase and a planktonic stage that occurs early in development. The adult benthic populations occupy disjunct, patchy habitats; the extent of gene flow due to dispersal of the planktonic life stage is generally unknown.     

Get Rad! The Evolution of the Skateboard Deck

Today there is growing interest in material culture studies among a wide range of social and biological scientists. Researchers recognize that some concepts drawn from biology can be useful in understanding aspects of material culture evolution. Indeed, recent research has demonstrated that material culture can evolve in a branching manner (vertical transmission) similar to that of biological species. However, there are many complicating factors as well, particularly the human penchant for borrowing and resurrecting old ideas resulting in extensive blending and hybridization (lateral transmission). But blending and hybridization occurs in biology as well depending upon the nature and scale of interacting organisms. There is far more lateral information transfer between populations within species than between species (although there are always exceptions). History can also be expected to play a role in the degree to which evolution is affected by vertical versus lateral transmission processes. All things equal, we should expect branching to be most important early in the history of a cultural system since blending could not become significant without the early development of distinct lineages. This is different from most biological systems in the sense that the development of distinct lineages would significantly reduce (or prevent) opportunities for blending. We explore these ideas with an analysis of skateboard decks spanning the history of professional skateboards since 1963. We apply cladistic and networking models in order to develop an understanding of the degree by which skateboard evolution was affected by branching and blending/hybridization processes. The study is enhanced by a historical record that provides significant insight into the actual innovation and borrowing processes associated with skateboard evolution. Results confirm that both branching and blending played important roles and that branching was most critical early in professional skateboard history. The study offers the important implication that while cultural systems will typically incorporate far more horizontal transmission in the evolutionary process (particularly in later stages) than many biological systems, general principles governing early stage branching and disparity may apply to both.     

Pairing dynamics and the origin of species

Whether sexual selection alone can drive the evolution of assortative mating in the presence of gene flow is a long-standing question in evolutionary biology. Here, we report a role for pairing dynamics of individuals when mate choice is mutual, which is sufficient for the evolution of assortative mating by sexual selection alone in the presence of gene flow. Through behavioural observation, individual-based simulation and population genetic analysis, we evaluate the pairing dynamics of coral reef fish in the genus Hypoplectrus (Serranidae), and the role these dynamics can play for the evolution of assortative mating. When mate choice is mutual and the stability of mating pairs is critical for reproductive success, the evolution of assortative mating in the presence of gene flow is not only possible, but is also a robust evolutionary outcome.     

Photic niche invasions: phylogenetic history of the dim-light foraging augochlorine bees (Halictidae)

Most bees rely on flowering plants and hence are diurnal foragers. From this ancestral state, dim-light foraging in bees requires significant adaptations to a new photic environment. We used DNA sequences to evaluate the phylogenetic history of the most diverse clade of Apoidea that is adapted to dim-light environments (Augochlorini: Megalopta, Megaloptidia and Megommation). The most speciose lineage, Megalopta, is distal to the remaining dim-light genera, and its closest diurnal relative (Xenochlora) is recovered as a lineage that has secondarily reverted to diurnal foraging. Tests for adaptive protein evolution indicate that long-wavelength opsin shows strong evidence of stabilizing selection, with no more than five codons (2%) under positive selection, depending on analytical procedure. In the branch leading to Megalopta, the amino acid of the single positively selected codon is conserved among ancestral Halictidae examined, and is homologous to codons known to influence molecular structure at the chromophore-binding pocket. Theoretically, such mutations can shift photopigment λ(max) sensitivity and enable visual transduction in alternate photic environments. Results are discussed in light of the available evidence on photopigment structure, morphological specialization and biogeographic distributions over geological time.     

Tropical Understory Piper Shrubs Maintain High Levels of Genotypic Diversity Despite Frequent Asexual Recruitment

Many plant species have the capacity to regenerate asexually by resprouting from stem and leaf fragments. In the pan‐tropical shrub genus Piper, this tendency is thought to be higher in shade‐tolerant than light‐demanding species, and to represent a trade‐off with annual seed production. Here we use molecular markers to identify clones in five Piper species varying in light requirements. We test predictions that (i) asexual recruitment success is highest in shade‐tolerant species, and (ii) that consequently, shade‐tolerant species are characterized by lower genotypic diversity than light‐demanding Piper. We found that two shade‐tolerant Piper species recruited asexually more frequently (36–42% of sampled shoots were of asexual origin) than, two light‐demanding and one shade‐tolerant species (0–26%). Furthermore, as predicted, genotypic diversity was negatively correlated with the frequency of asexual recruitment in the population. Nonetheless, genotypic diversity of Piper was high compared with other clonal plants. The proportion of unique genotypes found per population ranged from 0.58 to 1.0 and the genotypic Simpson's diversity ranged from 0.93 to 1.0 for all five species. Our results suggest that even though asexual reproduction plays an important role in maintaining local populations of Piper in the understory, it does not seem to reduce genotypic diversity to levels that will threaten these species ability to respond to environmental change. Abstract in Spanish is available in the online version of this article.