Phylogeography and Sex-Biased Dispersal across Riverine Manatee Populations (Trichechus inunguis and Trichechus manatus) in South America

Abstract

Phylogeographic patterns and sex-biased dispersal were studied in riverine populations of West Indian (Trichechus manatus) and Amazonian manatees (T. inunguis) in South America, using 410bp D-loop (Control Region, Mitochondrial DNA) sequences and 15 nuclear microsatellite loci. This multi-locus approach was key to disentangle complex patterns of gene flow among populations. D-loop analyses revealed population structuring among all Colombian rivers for T. manatus, while microsatellite data suggested no structure. Two main populations of T. inunguis separating the Colombian and Peruvian Amazon were supported by analysis of the D-loop and microsatellite data. Overall, we provide molecular evidence for differences in dispersal patterns between sexes, demonstrating male-biased gene flow dispersal in riverine manatees. These results are in contrast with previously reported levels of population structure shown by microsatellite data in marine manatee populations, revealing low habitat restrictions to gene flow in riverine habitats, and more significant dispersal limitations for males in marine environments.

Cranial and chromosomal geographic variation in manatees (Mammalia: Sirenia: Trichechidae) with the description of the Antillean manatee karyotype in Brazil

“…The pattern observed for the Amazonian manatee, which lacks geographic differentiation in skull shape among the populations studied, agrees with the results obtained by mtDNA control region sequences, which reported no geographic structure of this species in Brazilian rivers of the Amazon Basin, with this species most likely behaving as a panmictic population, constituting a single expanding population cluster (Cantanhede et al 2005;Vianna et al 2006). However, differences among T. inunguis populations were supported by analysis using D-loop sequences and microsatellite data, which demonstrated structure between the Peruvian and Colombian Amazon populations (Satiz abal et al 2012). Unfortunately, more precise information on specimens' collection localities was unavailable for testing additional hypotheses, such as differences between populations from different rivers.…”

Genetic Connectivity of the West Indian Manatee in the Southern Range and Limited Evidence of Hybridization With Amazonian Manatees

“…As threats continue and geographically fragmented populations persist in low numbers (Luna et al, 2018), the Brazilian Antillean manatees are vulnerable to genetic effects that can encumber recovery and population resiliency. In previously studied West Indian manatee populations, low levels of nuclear diversity and small population sizes have been generally observed (Bradley et al, 1993;García-Rodríguez et al, 1998;Hunter M. E. et al, 2010;Hunter et al, 2012;Nourisson, 2011;Nourisson et al, 2011;Tucker et al, 2012;Satizábal et al, 2012). Isolated populations with these characteristics can be vulnerable to disease outbreaks or demographic and stochastic events, compounding negative genetic effects and risking local extinction (Frankham et al, 2002).…”

Data_Sheet_1.docx

“…Conversely, the nuclear genetic diversity of the Brazilian Antillean manatee was low, containing the lowest number of private alleles among the three clusters (N P = 5) and the largest sample sizes. Furthermore, the number of alleles in Brazilian manatees (N A = 3) was similar to those in Belize (N A = 3.4), but lower than studies of manatee populations in Puerto Rico (N A = 3.9), Florida (N A = 4.8), and Colombia (N A = 3.5 to 7) (Hunter M. E. et al, 2010;Hunter et al, 2012;Satizábal et al, 2012;Tucker et al, 2012). In fact, the Brazilian diversity values were lower than other mammalian populations which were demographically challenged through pollution, harvesting, or habitat fragmentation (Garner et al, 2005;DiBattista, 2007;Torres-Florez et al, 2014).…”