Dollo meets Bergmann: morphological evolution in secondary aquatic mammals.

Secondary transitions to aquatic environments are common among vertebrates, and aquatic lineages display several adaptations to this realm, some of which might make these transitions irreversible. At the same time, discussions about secondary transitions often focus only on the marine realm, comparing fully terrestrial with fully aquatic species. This, however, captures only a fraction of land-to-water transitions, and freshwater and semi-aquatic groups are often neglected in macroevolutionary studies. Here, we use phylogenetic comparative methods to unravel the evolution of different levels of aquatic adaptations across all extant mammals, testing if aquatic adaptations are irreversible and if they are related to relative body mass changes. We found irreversible adaptations consistent with Dollo's Law in lineages that rely strongly on aquatic environments, while weaker adaptations in semi-aquatic lineages, which still allow efficient terrestrial movement, are reversible. In lineages transitioning to aquatic realms, including semi-aquatic ones, we found a consistent trend towards an increased relative body mass and a significant association with a more carnivorous diet. We interpret these patterns as the result of thermoregulation constraints associated with the high thermal conductivity of water leading to body mass increase consistently with Bergmann's rule and to a prevalence of more nutritious diets.

Consequences of environmental fluctuations on Taylor's power law and implications for the dynamics and persistence of populations.

Conservation Biologists have found that demographic stochasticity causes the mean time to extinction to increase exponentially with population size. This has proved helpful in analyses determining extinction times and characterizing the pathway to extinction. The aim of this investigation is to explore the possible interactions between environmental/demographic noises and the scaling effect of the mean population size with its variance, which is expected to follow Taylor's power law relationship. We showed that the combined effects of environmental/demographic noises and the scaling of population size variability interact with the population dynamics and affect the mean time to extinction.

Anthropogenic extinctions conceal widespread evolution of flightlessness in birds.

Human-driven extinctions can affect our understanding of evolution, through the nonrandom loss of certain types of species. Here, we explore how knowledge of a major evolutionary transition-the evolution of flightlessness in birds-is biased by anthropogenic extinctions. Adding data on 581 known anthropogenic extinctions to the extant global avifauna increases the number of species by 5%, but quadruples the number of flightless species. The evolution of flightlessness in birds is a widespread phenomenon, occurring in more than half of bird orders and evolving independently at least 150 times. Thus, we estimate that this evolutionary transition occurred at a rate four times higher than it would appear based solely on extant species. Our analysis of preanthropogenic avian diversity shows how anthropogenic effects can conceal the frequency of major evolutionary transitions in life forms and highlights the fact that macroevolutionary studies with only small amounts of missing data can still be highly biased.

The difference between trivial and scientific names: There were never any true cheetahs in North America.

Dobrynin et al. (Genome Biol 16:277, 2015) recently published the complete genome of the cheetah (Acinonyx jubatus) and provided an exhaustive set of analyses supporting the famously low genetic variation in the species, known for several decades. Their genetic analyses represent state-of-the-art and we do not criticize them. However, their interpretation of the results is inconsistent with current knowledge of cheetah evolution. Dobrynin et al. suggest that the causes of the two inferred bottlenecks at ∼ 100,000 and 10,000 years ago were immigration by cheetahs from North America and end-Pleistocene megafauna extinction, respectively, but the first explanation is impossible and the second implausible.

Scaling of the mean and variance of population dynamics under fluctuating regimes.

Theoretical ecologists have long sought to understand how the persistence of populations depends on the interactions between exogenous (biotic and abiotic) and endogenous (e.g., demographic and genetic) drivers of population dynamics. Recent work focuses on the autocorrelation structure of environmental perturbations and its effects on the persistence of populations. Accurate estimation of extinction times and especially determination of the mechanisms affecting extinction times is important for biodiversity conservation. Here we examine the interaction between environmental fluctuations and the scaling effect of the mean population size with its variance. We investigate how interactions between environmental and demographic stochasticity can affect the mean time to extinction, change optimal patch size dynamics, and how it can alter the often-assumed linear relationship between the census size and the effective population size. The importance of the correlation between environmental and demographic variation depends on the relative importance of the two types of variation. We found the correlation to be important when the two types of variation were approximately equal; however, the importance of the correlation diminishes as one source of variation dominates. The implications of these findings are discussed from a conservation and eco-evolutionary point of view.

Temperature and population density effects on locomotor activity of Musca domestica (Diptera: Muscidae).

The behavior of ectotherm organisms is affected by both abiotic and biotic factors. However, a limited number of studies have investigated the synergistic effects on behavioral traits. This study examined the effect of temperature and density on locomotor activity of Musca domestica (L.). Locomotor activity was measured for both sexes and at four densities (with mixed sexes) during a full light and dark (L:D) cycle at temperatures ranging from 10 to 40°C. Locomotor activity during daytime increased with temperature at all densities until reaching 30°C and then decreased. High-density treatments significantly reduced the locomotor activity per fly, except at 15°C. For both sexes, daytime activity also increased with temperature until reaching 30 and 35°C for males and females, respectively, and thereafter decreased. Furthermore, males showed a significantly higher and more predictable locomotor activity than females. During nighttime, locomotor activity was considerably lower for all treatments. Altogether the results of the current study show that there is a significant interaction of temperature and density on daytime locomotor activity of M. domestica and that houseflies are likely to show significant changes in locomotor activity with change in temperature.