Pelage variation and morphometrics of closely related Callithrix marmoset species and their hybrids.

BACKGROUND: Hybrids are expected to show greater phenotypic variation than their parental species, yet how hybrid phenotype expression varies with genetic distances in closely-related parental species remains surprisingly understudied. Here, we investigate pelage and morphometric trait variation in anthropogenic hybrids between four species of Brazilian Callithrix marmosets, a relatively recent primate radiation. Marmoset species are distinguishable by pelage phenotype and morphological specializations for eating tree exudates. In this work, we (1) describe qualitative phenotypic pelage differences between parental species and hybrids; (2) test whether significant quantitative differences exist between parental and hybrid morphometric phenotypes; and (3) determine which hybrid morphometic traits show heterosis, dysgenesis, trangression, or intermediacy relative to the parental trait. We investigated cranial and post-cranial morphometric traits, as most hybrid morphological studies focus on the former instead of the latter. Finally, we estimate mitogenomic distances between marmoset species from previously published data. RESULTS: Marmoset hybrid facial and overall body pelage variation reflected novel combinations of coloration and patterns present in parental species. In morphometric traits, C. jacchus and C. penicillata were the most similar, while C. aurita was the most distinct, and C. geoffroyi trait measures fell between these species. Only three traits in C. jacchus x C. penicillata hybrids showed heterosis. We observed heterosis and dysgenesis in several traits of C. penicillata x C. geoffroyi hybrids. Transgressive segregation was observed in hybrids of C. aurita and the other species. These hybrids were also C. aurita-like for a number of traits, including body length. Genetic distance was closest between C. jacchus and C. penicillata and farthest between C. aurita and the other species. CONCLUSION: We attributed significant morphometric differences between marmoset species to variable levels of morphological specialization for exudivory in these species. Our results suggest that intermediate or parental species-like hybrid traits relative to the parental trait values are more likely in crosses between species with relatively lesser genetic distance. More extreme phenotypic variation is more likely in parental species with greater genetic distance, with transgressive traits appearing in hybrids of the most genetically distant parental species. We further suggest that fewer developmental disturbances can be expected in hybrids of more recently diverged parental species, and that future studies of hybrid phenotypic variation should investigate selective pressures on Callithrix cranial and post-cranial morphological traits.

Ticks (Acari: Ixodidae) on wild raptors in Brazil

This research reports ticks on wild raptors in Brazil. Between the years 1936 and 2019, 127 larvae, 230 nymphs and 34 adult ticks were collected on 92 raptors (among 27 different species) from 35 localities in distinct Brazilian biomes. Additionally, an extensive literature review on ticks on wild raptors has been carried out, demonstrating that from 1993 to 2016, 29 larvae, 81 nymphs, 29 adults and 186 indeterminate immature ticks (larvae or nymphs) were collected on 41 raptors (16 different species) in 17 distinct localities in the Brazilian territory. The following tick species were identified on wild raptors in the country: Amblyomma aureolatum (Pallas, 1772), Amblyomma auricularium (Conil, 1878), Amblyomma brasiliense Aragão, 1908, Amblyomma cajennense (Fabricius, 1787) sensu stricto, Amblyomma calcaratum Neumann, 1899, Amblyomma coelebs Neumann, 1899, Amblyomma dubitatum Neumann, 1899, Amblyomma longirostre (Koch, 1844), Amblyomma nodosum Neumann, 1899, Amblyomma ovale Koch, 1844, Amblyomma parkeri Fonseca & Aragão, 1952, Amblyomma sculptum Berlese, 1888, Haemaphysalis juxtakochi Cooley, 1946, Rhipicephalus microplus (Canestrini, 1888), and Rhipicephalus sanguineus (Latreille, 1806) sensu lato. This study is therefore a significant contribution to our knowledge of the ticks associated with Brazilian raptors.