Worldwide genetic relationships of pigs as inferred from X chromosome SNPs

The phylogeography of the porcine X chromosome has not been studied despite the unique characteristics of this chromosome. Here, we genotyped 59 single nucleotide polymorphisms (SNPs) in 312 pigs from around the world, representing 39 domestic breeds and wild boars in 30 countries. Overall, widespread commercial breeds showed the highest heterozygosity values, followed by African and American populations. Structuring, as inferred from F_ST and analysis of molecular variance, was consistently larger in the non‐pseudoautosomal (NPAR) than in the pseudoautosomal regions (PAR). Our results show that genetic relationships between populations can vary widely between the NPAR and the PAR, underscoring the fact that their genetic trajectories can be quite different. NPAR showed an increased commercial‐like genetic component relative to the PAR, probably because human selection processes to obtain individuals with high productive parameters were mediated by introgressing boars rather than sows.     

Ecosystem engineering in a high and cold desert: Effect of a subterranean rodent on lizard abundance and behaviour

Subterranean rodents are often considered as ecosystem engineers because they physically modify the surrounding environment due to their burrowing and foraging activities. Understanding the modifications that ecosystem engineering species exert on the environment are of crucial importance in ecology studies, since they may affect the structure and population dynamics of several species, including lizards. Thus, the objective of the present study is to test the effect that Ctenomys mendocinus exert in the abundance of Liolaemus ruibali and its escape behaviour, in a high-elevation desert. Lizard abundance was estimated using observation transects and escape behaviour was studied with an experiment where the observer was considered by lizards as a potential predator and distance before the lizard flees was measured. All the variables were compared between areas disturbed by C. mendocinus and undisturbed ones. We found that L. ruibali was favoured by C. mendocinus activity. By creating burrow systems that serve as refuges for lizards, this rodent species increases the abundance of L. ruibali and reduces its flight distance, thereby improving its escape performance. We may suggest that C. mendocinus, through the construction of burrow systems, would be acting as an ecosystem engineer in Puna desert, affecting L. ruibali ecology.     

Invasion strategies of Cynodon dactylon: Competitive ability under low-nutrient conditions

Cynodon dactylon is one of the five most important invasive alien species worldwide. It is the invasive alien species with the broadest distribution range in Uruguay, and its expansion is frequently associated with disturbances. Since natural grasslands are facing processes of productive intensification, C. dactylon represents a threat as it could displace native species. However, the mechanisms that explain its invasion success remain unclear. The objective of this study was to analyse interspecific interactions under low nutrient conditions between C. dactylon and two species that are native to the Campo grasslands in Uruguay. Specifically, we assessed differences in the components of competitive ability effects and responses (or tolerance) as possible mechanisms involved in C. dactylon invasiveness. We performed a greenhouse experiment in pots with low-nutrient substrate assessing pair-wise interactions between C. dactylon, Mnesithea selloana and Paspalum notatum plus control pots consisting of single individual of each species. The invasive species showed greater competitive ability than both native grasses, as it reduced their below and above-biomass. Conversely, the size of C. dactylon plants interacting with native species was similar to that of single C. dactylon plants growing alone (controls). This reveals that the greater competitive ability of the invasive species was due to a greater tolerance to grow with neighbouring plants. The reason underlying this tolerance was a marked increase in biomass allocation towards stolons and leaves, at the expense of roots. Conversely, native species barely changed their shoot-root allocation pattern when interacting with neighbours. Furthermore, C. dactylon induced reproductive development solely when interacting with neighbours. Along with the fact that the potential growth rate of the invasive and native species was quite similar, these results suggest that sensitive and rapidly triggered shade avoidance responses could be one mechanism involved in the invasion success of C. dactylon.