Patterns of genome size diversity in bats (order Chiroptera)

Despite being a group of particular interest in considering relationships between genome size and metabolic parameters, bats have not been well studied from this perspective. This study presents new estimates for 121 "microbat" species from 12 families and complements a previous study on members of the family Pteropodidae ("megabats"). The results confirm that diversity in genome size in bats is very limited even compared with other mammals, varying approximately 2-fold from 1.63 pg in Lophostoma carrikeri to 3.17 pg in Rhinopoma hardwickii and averaging only 2.35 pg ± 0.02 SE (versus 3.5 pg overall for mammals). However, contrary to some other vertebrate groups, and perhaps owing to the narrow range observed, genome size correlations were not apparent with any chromosomal, physiological, flight-related, developmental, or ecological characteristics within the order Chiroptera. Genome size is positively correlated with measures of body size in bats, though the strength of the relationships differs between pteropodids ("megabats") and nonpteropodids ("microbats").

Hunted woolly monkeys (Lagothrix poeppigii) show threat-sensitive responses to human presence

Responding only to individuals of a predator species which display threatening behaviour allows prey species to minimise energy expenditure and other costs of predator avoidance, such as disruption of feeding. The threat sensitivity hypothesis predicts such behaviour in prey species. If hunted animals are unable to distinguish dangerous humans from non-dangerous humans, human hunting is likely to have a greater effect on prey populations as all human encounters should lead to predator avoidance, increasing stress and creating opportunity costs for exploited populations. We test the threat sensitivity hypothesis in wild Poeppigi's woolly monkeys (Lagothrix poeppigii) in Yasuní National Park, Ecuador, by presenting human models engaging in one of three behaviours “hunting”, “gathering” or “researching”. These experiments were conducted at two sites with differing hunting pressures. Visibility, movement and vocalisations were recorded and results from two sites showed that groups changed their behaviours after being exposed to humans, and did so in different ways depending on the behaviour of the human model. Results at the site with higher hunting pressure were consistent with predictions based on the threat sensitivity hypothesis. Although results at the site with lower hunting pressure were not consistent with the results at the site with higher hunting pressure, groups at this site also showed differential responses to different human behaviours. These results provide evidence of threat-sensitive predator avoidance in hunted primates, which may allow them to conserve both time and energy when encountering humans which pose no threat.

Genome size of two cebus species (primates: platyrrhini) with a fertile hybrid and their quantitative genomic differences

Genome size or C-value is defined as the total amount of DNA contained within a haploid chromosome set and is regarded as a species-specific constant. Speciation among neotropical primates seems to be accompanied by marked quantitative changes in DNA content. A direct correlation between genome size and the presence of heterochromatin has also been proposed. In this work, we analyzed the genome of a female fertile hybrid between Cebus libidinosus and C. nigritus using interspecies comparative genomic hybridization (iCGH), in order to detect quantitative differences between the hybrid and the parental genomes. We also estimated the genome sizes of C. libidinosus and C. nigritus. Both species, considered subspecies of C. apella until 2001, have a highly homologous karyotype but are easily distinguishable at the chromosomal level due to the noncentromeric heterochromatin block on C. libidinosus chromosome 11. Our findings on C-value quantification support the species status for C. libidinosus and C. nigritus, each having a different genome size. The iCGH analysis of the hybrid revealed quantitative differences in comparison to both parental species. The hybrid genome contains a greater amount of DNA in the heterochromatic blocks related to those in the genomes of both parental species. In view of observations in previous and the present work, some hypotheses about genome dynamics of neotropical primates are proposed and discussed.

Primate comparative genomics: lemur biology and evolution

Comparative genome sequencing projects are providing insight into aspects of genome biology that raise new questions and challenge existing paradigms. Placement in the phylogenetic tree can often be a major determinant of which organism to choose for study. Lemurs hold a key position at the base of the primate evolutionary tree and will be highly informative for the genomics community by offering comparisons of primate-specific characteristics and processes. Combining research in chromosome evolution, genome evolution and behavior with lemur comparative genomic sequencing will offer insights into many levels of primate evolution. We discuss the current state of lemur cytogenetic and phylogenetic analyses, and suggest how focusing more genomic efforts on lemurs will be beneficial to understanding human and primate evolution, as well as disease, and will contribute to conservation efforts.