Azevedo, R. B. | bioRxiv Science

bioRxiv2020

Leaf and flower consumption modulate the drinking behavior in a folivorous-frugivorous arboreal mammal

Water is vital for the survival of any species because of its key role in most physiological processes. However, little is known about the non-food-related water sources exploited by arboreal mammals, the seasonality of their drinking behavior and its potential drivers (including diet composition, temperature, and rainfall). We investigated this subject in 14 wild groups of brown howler monkeys (Alouatta guariba clamitans) inhabiting small, medium, and large Atlantic Forest fragments in southern Brazil. We found a wide variation in the mean rate of drinking among groups (range=0-16 records/day). Streams (44% of 1,258 records) and treeholes (26%) were the major types of water sources, followed by bromeliads in the canopy (16%), pools (11%), and rivers (3%). The type of source influenced whether howlers used a hand to access the water or not. Drinking tended to be evenly distributed throughout the year, except for a slightly lower number of records in the spring than in the other seasons, but it was unevenly distributed during the day. It increased in the afternoon in all groups, particularly during temperature peaks around 15:00 and 17:00. We found via generalized linear mixed modelling that the daily frequency of drinking was mainly influenced by flower (negatively) and leaf (positively) consumption, whereas fruit consumption, fragment size, rainfall, and mean ambient temperature played negligible roles. The influence of leaf consumption is compatible with the metabolite detoxification hypothesis, which states that the processing of this fibrous food requires the ingestion of larger volumes of water to help in the detoxification/excretion of its metabolites. In sum, we found that irrespective of habitat size and climatic conditions, brown howlers seem to seek a positive water balance by complementing preformed and metabolic water with drinking water, even when it is associated with a high predation risk in terrestrial sources.

animal behavior and cognition↗

bioRxiv2018

Population structure promotes the evolution of costly sex in artificial gene networks

We build on previous observations that Hill-Robertson interference generates an advantage of sex that, in structured populations, can be large enough to explain the evolutionary maintenance of costly sex. We employed a gene network model that explicitly incorporates interactions between genes. Mutations in the gene networks have variable effects that depend on the genetic background in which they appear. Consequently, our simulations include two costs of sex--recombination and migration loads--that were missing from previous studies of the evolution of costly sex. Our results suggest a critical role for population structure that lies in its ability to align the long- and short-term advantages of sex. We show that the addition of population structure favored the evolution of sex by disproportionately decreasing the equilibrium mean fitness of asexual populations, primarily by increasing the strength of Mullers Ratchet. Population structure also increased the ability of the short-term advantage of sex to counter the primary limit to the evolution of sex in the gene network model--recombination load. On the other hand, highly structured populations experienced migration load in the form of Dobzhansky-Muller incompatibilities, decreasing the effective rate of migration between demes and, consequently, accelerating the accumulation of drift load in the sexual populations.

evolutionary biology↗