Low genetic variation and evidence of limited dispersal in the regionally important Belize manatee

Abstract

The Antillean subspecies of the West Indian manatee Trichechus manatus is found throughout Central and South America and the Caribbean. Because of severe hunting pressure during the 17th through 19th centuries, only small populations of the once widespread aquatic mammal remain. Fortunately, protections in Belize reduced hunting in the 1930s and allowed the country's manatee population to become the largest breeding population in the Wider Caribbean. However, increasing and emerging anthropogenic threats such as coastal development, pollution, watercraft collision and net entanglement represent challenges to this ecologically important population. To inform conservation and management decisions, a comprehensive molecular investigation of the genetic diversity, relatedness and population structure of the Belize manatee population was conducted using mitochondrial and microsatellite DNA. Compared with other mammal populations, a low degree of genetic diversity was detected (H E = 0.455; N A = 3.4), corresponding to the small population size and long-term exploitation. Manatees from the Belize City Cayes and Southern Lagoon system were genetically different, with microsatellite and mitochondrial F ST values of 0.029 and 0.078, respectively (P 0.05). This, along with the distinct habitats and threats, indicates that separate protection of these two groups would best preserve the region's diversity. The Belize population and Florida subspecies appear to be unrelated with microsatellite and mitochondrial F ST values of 0.141 and 0.63, respectively (P 0.001), supporting the subspecies designations and suggesting low vagility throughout the northern Caribbean habitat. Further monitoring and protection may allow an increase in the Belize manatee genetic diversity and population size. A large and expanding Belize population could potentially assist in the recovery of other threatened or functionally extinct Central American Antillean manatee populations.

Genetic population structure of Peninsular bighorn sheep (Ovis canadensis nelsoni) indicates substantial gene flow across US–Mexico border

“…The presence of such genetic diversity in PBS contradicts both theoretical predictions and several empirical studies of endangered mammals which experienced significant demographic declines (Houlden et al, 1996;Hunter et al, 2010;Le Page et al, 2000). There are multiple explanations for this observation.…”

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

“…However, marine West Indian manatees presented population structure contrasting with gene flow in riverine populations [19], [20], [21] We suggest that habitat differences between marine and riverine environments impose different barriers to male dispersal, on which marine T. manatus male migrations are limited by freshwater resources to avoid osmoregulation stressors [67], strong currents, and presence of seagrass beds which restricts them from dispersing across deep waters [68], [69], while riverine males are mostly limited by strong currents and water levels [8], [10], being able to move for longer distances, relying more on behavioral, acoustic or chemical signals to pursue females [4].…”

“…Microsatellite data supported population division between Florida and Puerto Rican populations [21], the wetlands systems of the Gulf of Mexico and the Caribbean coast of Mexico [20], as well as between Belize City Cayes and the Southern Lagoon system in Belize [19].…”

“…Using multiple unlinked loci for populations with smaller sampling sizes improves accuracy in population genetics estimates [13], [14], [15], and provides a solution to study population dynamics in manatee populations. Primers for amplification of highly polymorphic bi-parentally inherited nuclear microsatellite loci have been developed for the Florida manatee [16], [17], [18], and effectively used to study manatee population structure in Florida, Puerto Rico, Belize and Mexico [19], [20], [21].…”

Evidence of two genetic clusters of manatees with low genetic diversity in Mexico and implications for their conservation

“…The Belize population shows a stronger separation from Florida (F ST = 0.141) (Hunter et al 2010) than the Mexican populations, with F ST = 0.096 between the Mexican Caribbean coast and Florida and F ST = 0.106 between the GMx population and Florida. Belize and the Caribbean coast show a different pattern of haplotype distribution with two haplotypes in common and one private haplotype.…”